Journal articles: 'Surface pitting'

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Černý, Michal, Josef Filípek, and Roman Požár. "Pitting process visualization." Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 58, no. 5 (2010): 57–66. http://dx.doi.org/10.11118/actaun201058050057.

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The paper describes time-domain simulation of gear pitting damage using animation program. Key frames have been used to create illusion of motion. The animation uses experimental results of high-cycle fatigue of material. The fatigue damage occurs in the nominal creep area on the side of the gear tooth sample loaded with variable-positioned Hertz pressure. By applying the force, the pressure cumulates between two convex surfaces. This phenomenon results in material damage under of curved surfaces in contact. Moreover, further damage has been registered on the surface. This is due to exceeding the elastic-plastic state limit and development of „tabs“. The tabs serve as origin of surface micro cracks powered by shear stress and enclosed grease pressure as well. This deformation and extreme pressures of Pascal law contribute to elongation and growth of the surface micro crack. Non-homogenous parts of material volume support the initialization/development of the micro cracks as well. Resulting visualization of the tooth-side fatigue damage provides clear and easy-to-understand description of the damage development process right from the micro crack initialization to the final fragmentation due to pitting degradation.

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Shen, Gang, Dong Xiang, Ning Xie, Peng Mou, Wei Yang, and Qiang Zhao. "Study on the Influence of Gear Rattling on Pitting Fatigue Failure." Applied Mechanics and Materials 496-500 (January 2014): 634–41. http://dx.doi.org/10.4028/www.scientific.net/amm.496-500.634.

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The pitting fatigue failure is one of the main gear failure modes, and it has extremely important significance in studying on the influence of dynamic characteristics on pitting fatigue failure. The article has set up increasing-speed test-bed, using photoelectric encoder and NI DAS to measure and collect rotational-speed pulse of driving wheel and driven wheel. Arc-length difference and rotational-speed difference of driving wheel and driven wheel are analyzed to verify gear rattling phenomenon under increasing-speed transmission. And then gear surfaces under certain cycles are observed and analyzed utilizing surface mapping microscope to explore the influence of gear rattling on pitting fatigue failure under increasing-speed transmission. It is shown that there is rotational-speed difference between driving wheel and driven wheel, which indicates that gear rattling phenomenon appears in the meshing process, or more precisely, gear rattling phenomenon appears on both surfaces of the tooth because rotational-speed difference fluctuates bilaterally. In addition, tooth surface contact stress is 221.3Mpa, in theory, if actual contact stress is less than fatigue limit, pitting fatigue failure should not occur. However, through gear surface observation, pitting phenomenon authentically appears with the tendency from micro pitting to destructive pitting. In a word, gear pitting fatigue failure is induced by gear rattling to a certain extent.

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Moon, Suk Man, Byung Wook Lee, Tae Wan Kim, and Yong Joo Cho. "The Effect of Oil Quantity Supplied on Micro-Pitting Life for Rolling and Sliding Contact." Advanced Materials Research 433-440 (January 2012): 2149–54. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.2149.

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The influence of oil quantity supplied and contact bulk temperature on micro-pitting lifetime is estimated using two-roller contact machine. The failure criterion is set as 4% micro-pitting on contact surfaces, which is adopted from precedent researches. To quantify the failure rate of damaged surfaces of micro-pitting occurrence, DBR(Dark and Bright Ratio) technique was effectively implemented for observing not a sudden emergence of macro-pitting but the transition of micro-pitting growth. The change of damaged surface area was measured and calculated by the use of dark and bright ratio of test specimen pictures taken by optical microscope. The optimum oil quantity was determined to obtain the minimum oil quantity with no change in bulk temperature despite of increasing the inlet oil quantity. In conclusion, the influence of supplied oil quantity and contact bulk temperature considering film parameter on micro-pitting lifetime and the surface contact strength by the S-N curves of failure rate are quantitatively reported and expressed as empirical formulas.

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Vinogradova, Svetlana S., Anna N. Akhmetova, and Ramilya F. Tazieva. "CALCULATION METHOD OF IMPEDANCE MODULE FOR CORROSION MONITORING OF SURFACE STATE OF CHROMONICKEL STEELS." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 63, no. 3 (March 8, 2020): 60–66. http://dx.doi.org/10.6060/ivkkt.20206303.6092.

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In discussed issue the additional criterion for chromium-nickel steels surface state assessment is proposed. It is used in periodic potentiostatic regime of stainless steels surface state monitoring under the condition of pitting corrosion origin. Electrochemical investigations were carried out with pitting corrosion resistant austenitic (12Х18Н10Т) and austenitic-ferritic chromium-nickel steels 10Х17Н13М2Т in chloride solutions of 0.1 mol/L NaCl and 0.5 mol/l NaCl with the additional oxidant K2Cr2O7. Polarization curves were recorded under potentiostatic mode of polarization in the electrochemical three-electrode cell using the ZIVE SP2 workstation and a personal computer. The fast Fourier transformation method was used for conducting the spectral analysis, as this method is more effective in terms of the algorithmic complexity when processing a large amount of the initial data. It is established that scalar impedance angular coefficient shows the current oscillation frequencies change concerned with the pitting occurrence and passivation process. The scalar impedance angular coefficient allows to estimate the pitting corrosion evaluation processes boundaries: passivity; metal dissolution due to the development of metastable pittings; the metastable nucleation and passivation processes concurred with the stable pitting development. The algorithm based on the statistical method of spectral analyses for scalar impedance angular coefficient calculation is developed. It is established that the decrease in passive film total resistance corresponds to the breakdown process and first metastable, and then stable local surface destructions that reflect on the higher the scalar impedance angular coefficient value. The boundary values of an additional criterion for surface state assessment were proposed, on the basis of which an interval scale was constructed to determine the current state of the surface of chromium-nickel steels. It is shown that the boundary values of the scalar impedance angular coefficient correspond to the metallographic studies of investigated steels.

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Kamran, Muhammad, F. Hussain, R. Ahmad, Tahir Ahmad, and Fahad Riaz. "Investigating the Pitting Resistance of 316 Stainless Steel in Ringer's Solution Using the Cyclic Polarization Technique." Defect and Diffusion Forum 344 (October 2013): 1–7. http://dx.doi.org/10.4028/www.scientific.net/ddf.344.1.

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Corrosion rate, corrosion potential and susceptibility to pitting corrosion of a metal are measured using cyclic polarization Direct Current (DC) electrochemical technique. The aim of the present research is to investigate the pit nucleation resistance of polished, ground and passivated surfaces of 316 stainless steels in Ringers solution. The electrochemical cyclic polarization results showed that polished surface gave better pitting resistance as compared to ground surface. It was also observed that passivation treatment gave better pitting resistance to both polished and ground surface of 316 stainless steels in Ringers solution.

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Han, Yan, Cheng Zheng Li, Hua Li Zhang, Yu Fei Li, and Da Jiang Zhu. "Analysis of Corrosion Behavior on External Surface of 110S Tubing." Materials Science Forum 993 (May 2020): 1242–50. http://dx.doi.org/10.4028/www.scientific.net/msf.993.1242.

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The failure analysis of 110S tubing during acidizing process was addressed. Results showed that serious pitting corrosion occurred on the outer wall of tubing, and there was no obvious pitting on the inner wall. The maximum pitting depth on the outer wall was 1019 μm. According to the results of simulation corrosion test, needle-shaped pitting appeared on the sample surface in the test without inhibitor, the maximum depth of pitting was 158 μm; and no pitting was found on the sample surface in the test within 1.5% TG501 inhibitor; the original pitting were deepened after spent acid test, and the sample with no pitting at the beginning also showed deep pitting corrosion after 96 hours spent acid test. It was indicated that the spent acid accelerated the development of pitting significantly. The external surface corrosion of the 110S tubing was caused by the chemical reaction between the high-concentration acidifying liquid and the outer wall of the tubing. There is a gap between the tubing and coupling threaded connection, which caused the acid solution entered into the thread position, and hence the severe corrosion of the thread and pin end of the tubing happened, the joint strength was continuously reduced with corrosion development till the tripping of the coupling, and then the lower string dropped. Some suggestions were proposed for avoiding or slowing down this kind of failure based on this study.

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Kappel, Frank, Peter Toivonen, Sabina Stan, and Darrell-Lee McKenzie. "Resistance of sweet cherry cultivars to fruit surface pitting." Canadian Journal of Plant Science 86, no. 4 (October 10, 2006): 1197–202. http://dx.doi.org/10.4141/p05-244.

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A recently developed technique was used to determine the susceptibility to fruit surface pitting of new sweet cherry (Prunus avium L.) cultivars and compare them to an industry standard. The cultivars tested included Bing (industry standard), Cristalina, Lapins, Sandra Rose, Santina, Skeena, Sonata, Staccato, and Sweetheart. Fruit were harvested at commercial maturity, injured, held at 1°C for 2 wk and then rated for fruit surface pitting. The cultivars Lapins, Skeena, Staccato, and Sweetheart had less pitting than Bing. Cristalina and Sonata tended to have similar levels of injury to Bing and Sandra Rose and Santina tended to have more severe pitting than Bing. Key words: Sweet cherries, cultivars, simulated pitting injury

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Bergstedt, Edwin, Jiachun Lin, and Ulf Olofsson. "Influence of gear surface roughness on the pitting and micropitting life." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, no. 24 (June 9, 2020): 4953–61. http://dx.doi.org/10.1177/0954406220931541.

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Pitting and micropitting are the two main gear rolling contact fatigue modes. It is widely accepted that micropitting will lead to pitting; however, the relationship between pitting and micropitting life needs further investigation. In this work, micropitting and pitting tests were performed on an FZG back-to-back test rig using standard FZG PT-C and GF-C gears. The gear tooth profile change due to micropitting and pitting damage was measured in situ in the gearbox using a profilometer after each test. The gear surface roughness parameters were calculated from the measured tooth profile. A Gaussian low pass filter with cut off length [Formula: see text] mm was applied to the measured tooth profile to obtain the waviness. The calculated roughness parameters and the obtained tooth profile with waviness for each test were imported into the KISSsoft software to calculate the contact stress and specific film thickness at the corresponding load stage. Experimental results show that smooth gear surface can reduce or even avoid micropitting damage, but could lead to a reduction in pitting life.

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Guan, Xinchun, Lianjuan Miao, Hui Li, and Jinping Ou. "A new approach for describing pitting corrosion of steel bars in concrete." Anti-Corrosion Methods and Materials 64, no. 6 (November 6, 2017): 573–79. http://dx.doi.org/10.1108/acmm-01-2016-1631.

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Purpose The purpose of this study is to quantitively characterize pitting or local corrosion of steel bars. Characterization of pitting or local corrosion is important for steel bar corrosion research in concrete, which is still an unsolved problem for the reason that the pitting on corroded steel is distributed irregularly, besides the varied pitting depths. To solve this problem in a certain degree, two parameters were collectively used to find the pitting distribution and pitting depth distribution of corroded steel bar surface. Design/methodology/approach Corroded reinforcement bars were subjected to two different corrosive conditions to obtain the profile of the surface of corroded steel bar. The arithmetic mean deviation of the profile, Ra, also a roughness parameter, and the fractal dimension, D, were computed using MATLAB software from the data on corroded steel bar profiles scanned by a profile tester. Statistical analysis was performed to determine the parameters distribution of Ra. Findings Ra and D can assist gravimetric technique in defining the degree of pitting corrosion and make further understanding about the characterization of local or pitting corrosion. Originality/value Two parameters were collectively used to find the pitting distribution and pitting depth distribution of corroded steel bar surface, while many studies only study the fractal dimension of pitting corrosion. And, the relationship between these two parameters is studied when using them to describing the non-uniformity of pitting corrosion degree. Using these two parameters can much better describe the non-uniform degree of pitting corrosion.

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Miltenović, Aleksandar, Ivan Rakonjac, Alexandru Oarcea, Marko Perić, and Damjan Rangelov. "Detection and Monitoring of Pitting Progression on Gear Tooth Flank Using Deep Learning." Applied Sciences 12, no. 11 (May 25, 2022): 5327. http://dx.doi.org/10.3390/app12115327.

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Gears are essential machine elements that are exposed to heavy loads. In some cases, gearboxes are critical elements since they serve as machine drivers that must operate almost every day for a more extended period, such as years or even tens of years. Any interruption due to gear failures can cause significant losses, and therefore it is necessary to have a monitoring system that will ensure proper operation. Tooth surface damage is a common occurrence in operating gears. One of the most common types of damage to teeth surfaces is pitting. It is necessary for normal gear operations to regularly determine the occurrence and span of a damaged tooth surface caused by pitting. In this paper, we propose a machine vision system as part of the inspection process for detecting pitting and monitoring its progression. The implemented inspection system uses a faster R-CNN network to identify and position pitting on a specific tooth, which enables monitoring. Prediction confidence values of pitting damage detection are between 99.5–99.9%, while prediction confidence values for teeth recognized as crucial for monitoring are between 97–99%.

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Zhou, Jingzhong, Kuoteng Sun, Songqiang Huang, Xuemin He, Zhaowei Hu, and Wenge Li. "Direct and Indirect Evidence of the Microbially Induced Pitting Corrosion of Steel Structures in Humid Environments." Coatings 10, no. 10 (October 15, 2020): 983. http://dx.doi.org/10.3390/coatings10100983.

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Corrosion is a severe problem for steel structures in humid environments. In particular, humidity usually triggers the surface adhesion of microorganisms, leading to microbiologically induced corrosion. This study aims to explore the effect of bacterial biofilm formation on the pitting corrosion of stainless steel. This research uses electrochemical methods to obtain indirect evidence of the pitting corrosion of steel. In addition, in order to obtain direct evidence of the pitting corrosion of stainless steel, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to characterize the dimensional morphology of the stainless steel after pitting. It was shown that the bacterial adhesion increased with the pH and temperature, which significantly increased the surface roughness of the stainless steel. Electrochemical analysis revealed that the formation of biofilm greatly destroyed the oxide film of 304 SS and accelerated the corrosion of stainless steel by forming an oxygen concentration battery. SEM and AFM analyses showed cracks and dislocations on the surface of stainless steel underneath the attached bacteria, which suggested a direct role of biofilm in corrosion induction. The results presented here show that the bacterial biofilm formation on the steel surfaces significantly accelerated the corrosion and affected the pitting corrosion process of the steel structure.

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Kiremit, Sinan, Julian Cremer, Yannic Stallmeier, Adrian Sonntag, Michaela Klöcker, Dario Anselmetti, Andreas Hütten, and Thomas Kordisch. "Development of an In Situ Micro-Corrosion Cell for the Investigation of Pitting Corrosion on Austenitic and Ferritic Stainless Steels." Corrosion and Materials Degradation 4, no. 1 (January 31, 2023): 104–19. http://dx.doi.org/10.3390/cmd4010007.

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In order to investigate the electrochemical pitting corrosion in more detail, a micro-corrosion cell was developed, allowing real-time in situ optical observations of steel surfaces in direct correlation with electrochemical measurement results. In this study, the austenitic 1.4301–X5CrNi18-10 and the ferritic 1.4016–X6Cr17 stainless steel grades were examined in electrolytes containing chloride ions. The micro-corrosion cell revealed a stable pitting corrosion of the ferritic 1.4016 and metastable pitting corrosion of the austenitic 1.4301. The pits were characterized by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM) in detail. A clear correlation between current peaks in the current density-potential curve and the growth of many small pits on the test surface was established and was identified as metastable pit growth. In general, the pitting corrosion potential increased as the diameter of the test surface decreased for both stainless steels. In contrast to the complex precipitates of 1.4301, chromium precipitates with a significantly higher amount was detected on the entire surface of the 1.4016. The corrosion initiation was identified at the interface between the precipitates and the base material for both stainless steels. By comparing both materials, the ferritic 1.4016 had a lower pitting corrosion potential than the austenitic 1.4301 under all test conditions.

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Subawi, Handoko, and Sutarno. "The Phenomenon of Pitting Corrosion Attack on the Milled Aluminium Alloy Al 2618 Plate during Surface Preparation through Sulphuric Acid Anodising." Advanced Materials Research 896 (February 2014): 596–99. http://dx.doi.org/10.4028/www.scientific.net/amr.896.596.

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This study purposed to investigate corrosion characteristic on aluminium alloy by considering parameters that involved metal preparation, different surface treatment, and alloy types. Through series of the salt spray test, the rolled aluminium sheet revealed higher resistance to surface corrosion rather than milled aluminium plate. However trace elements, as reinforced filler in the metal alloy, may contribute to possible pitting corrosion. By employing sulphuric acid anodising, it revealed higher probability of pitting corrosion to attack the milled aluminium plate surface compared to rolled aluminium sheet. The surface pitting corrosion on the anodised aluminium alloy Al 2618 plate was observed through enlargement of pitting diameter and additional new pitting holes during 500 hours corrosion test. The corrosion propagation grew sharply during 500 hours test and it increased slowly after 750 hours. This study did not evaluate further variables either alloy composition, metal processing, or operation condition in anodising process.

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Yan, Xudong, and Jianlin Sun. "Pitting Corrosion Behavior and Surface Microstructure of Copper Strips When Rolled with Oil-in-Water Emulsions." Materials 14, no. 24 (December 20, 2021): 7911. http://dx.doi.org/10.3390/ma14247911.

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Copper strips experience severe corrosion when rolled with an oil-in-water (O/W) emulsions lubricant. The effects of rolling reduction on the pitting corrosion behavior and surface microstructure of Cu strips were studied in detail using electrochemical measurements and electron back scattered diffraction (EBSD) analysis. It was found that the corrosion current densities of the rolled Cu strips increased with accumulated reduction, which also lowered the pitting potentials and weakened their corrosion resistances. Therefore, the corrosive tendency of Cu strips under different rolling reductions (ε) followed the order of ε0% < ε20.7% < ε50.6% < ε77.3%. The Cu surface easily reacted with chlorine, sulfur, and carbon components from O/W emulsions to generate pitting corrosion. Under the interactive effect of pitting corrosion and stress corrosion, pits expanded along the rolling direction. The aggregation of anions in surface defects, such as dislocations, metastable pits, and microcracks, further accelerated the pitting corrosion of the surface.

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Ma, Yun, Yao Li, Yan Jun He, Xuan Wang, and Hai Tao Bai. "Rapid Pitting Corrosion Failure Analysis of 13Cr Stainless Steel as Thermocouple Protecting Material in Dry Gas Pipeline." Defect and Diffusion Forum 394 (August 2019): 91–96. http://dx.doi.org/10.4028/www.scientific.net/ddf.394.91.

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This paper presents corrosion failure analysis of 13Cr stainless steel (SS) in gas pipeline ingas pipeline, which was used as thermocouple protecting material (TPM). A portion of TMP faileddue to pitting corrosion under unknown circumstances. Scanning electron microscopy (SEM) andX-ray diffraction (XRD) are employed to characterize the scales and/or corrosion products near thefailed portion. Based on visual and microscopic analyses, reviewing the background information andthe thermodynamic calculation, the following rapid pitting corrosion failure sequences wereidentified: Once the pitting appeared, in addition to the gas leakage and expansion, the temperaturedrop should lead a small amount of water in dry gas to condense on the surface of TPM. On one hand,the high salinity produced water will corrode the thermocouple. On the other hand, the high salinityproduced water will pass into the annular space of TPM through the pitting because of the pressuredrop, and the water will stay on inner surface for more time than that of external surface, whichaccelerated pitting of TPM. More and more pitting appeared, and the surface roughness increased.The film-forming property of condensation water will also increase. So, the TPM will be scrappedsoon.

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Maruschak, Pavlo, Igor Konovalenko, Anna Guzanová, Petro Sydor, and Sergey V. Panin. "Defectometry Analysis of Surface Condition Damaged with Corrosion Pitting." Materials Science Forum 818 (May 2015): 153–57. http://dx.doi.org/10.4028/www.scientific.net/msf.818.153.

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The dismantled tubes of the steam-boiler operated by the “Kalush Heat and Power Plant” were investigated. Defects of various nature, pitting of the indefinite shape were found during the examination. Since pitting is a deepening in the material and contains dark products of the corrosion process. It looks like a darkened area that stands out against the light background of the non-damaged surface in the optical images. The efficiency of such processing for identification of the corrosion defects is analyzed. The suitability of the proposed methods for the calculation of Shannon entropy of the surface analyzed was tested, as well as for determining the area and number of pitting defects.

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Makino, Taizo, Masayuki Horimoto, and Hitoshi Matsumoto. "The Effect of Slip Conditions on the Contact Fatigue Strength for Pitting of a Carburized Steel." Solid State Phenomena 118 (December 2006): 521–26. http://dx.doi.org/10.4028/www.scientific.net/ssp.118.521.

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The objective of the present study is to clarify the effect of slip conditions, such as slip ratio, outer surface velocity, and lubricant oil temperature on the contact fatigue strength for pitting (pitting strength) of carburized steels. Rolling contact fatigue (RCF) tests were conducted under oil lubrication on 26mm-diameter specimens made of a carburized steel with various combinations of slip ratio, outer surface velocity, and lubricant oil temperatures. Relationships among those three parameters were also evaluated. The pitting strength decreased with the increase of slip ratio, with the decrease of outer surface velocity, and with the decrease of lubrication oil temperature. It was found that the slip ratio, the outer surface velocity, and the lubricant oil temperature influenced the friction coefficient and the contact surface temperature. The friction coefficient increased when slip ratio increased. The friction coefficient was considered to be the dominant factor which directly affected the pitting strength.

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Mary, N., V. Vignal, R. Oltra, and L. Coudreuse. "Advances in local mechanoelectrochemistry for detecting pitting corrosion in duplex steels." Journal of Materials Research 19, no. 12 (December 1, 2004): 3688–94. http://dx.doi.org/10.1557/jmr.2004.0475.

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The goal of this study was to demonstrate that a relationship exists between surface stress and pitting corrosion. The surface stress field generated by polishing was first calculated using a thermomechanical model and a finite element code. Pitting corrosion tests performed at the microscale along the austenite/ferrite interface using the electrochemical microcell technique were then analyzed considering the microstructure, and the residual surface stress field calculated numerically under the microcapillary. Mechanical criteria are proposed leading to an enhancement of pitting corrosion of duplex steels.

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Aoyama, Takahito, Hiroaki Ogawa, Chiaki Kato, and Fumiyoshi Ueno. "Decrease in Pitting Corrosion Resistance of Extra-High-Purity Type 316 Stainless-Steel by Cu2+ in NaCl." Metals 11, no. 3 (March 19, 2021): 511. http://dx.doi.org/10.3390/met11030511.

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The effect of Cu2+ in bulk solution on pitting corrosion resistance of extra-high-purity type 316 stainless-steel was investigated. Pitting occurred in 0.1 M NaCl-1 mM CuCl2, whereas pitting was not initiated in 0.1 M NaCl. Although deposition of Cu2+ on the surface occurred regardless of a potential region in 0.1 M NaCl-1 mM CuCl2, Cu2+ in bulk solution had no influence on the passive film formation. The decrease in pitting corrosion resistance in 0.1 M NaCl-1 mM CuCl2 resulted from the deposited Cu or Cu compound and continuous supply of Cu2+ on the surface.

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D'Errico, Fabrizio, Marco Boniardi, Silvia Barella, and Silvia Cincera. "Damage Mechanisms of Initiating Micro-Pitting on 42CrMo4 Hardened and Tempered Steel." Key Engineering Materials 348-349 (September 2007): 869–72. http://dx.doi.org/10.4028/www.scientific.net/kem.348-349.869.

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A deep comprehension of the damage mechanisms involved in contact fatigue should optimize material and heat treatment choice for a specific application. In this work rolling disc-on-disc contact fatigue tests have been performed on a hardened and tempered UNI EN 42CrMo4 . The adopted test method creates the best conditions in order to develop micro-pitting on disc surface. Extensive micro-fractographic examinations have been carried out, on the damaged surfaces, through a scanning electronic microscope (SEM). For this steel, loaded with Hertzian pressure of 1000 MPa, the failure mode is always micro-pitting which begins at the surface, and it is not a sub-superficial damaging. If micro-pits develop, they will coalesce in larger craters. By this way, the probability that micropitting will degenerate into sub-superficial destructive pitting is very high.

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Brytan, Z., and J. Niagaj. "Corrosion Resistance and Mechanical Properties of TIG and A-TIG Welded Joints of Lean Duplex Stainless Steel S82441 / 1.4662." Archives of Metallurgy and Materials 61, no. 2 (June 1, 2016): 771–84. http://dx.doi.org/10.1515/amm-2016-0131.

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Abstract This paper presents results of pitting corrosion resistance of TIG (autogenous and with filler metal) and A-TIG welded lean duplex stainless steel S82441/1.4662 evaluated according to ASTM G48 method, where autogenous TIG welding process was applied using different amounts of heat input and shielding gases like pure Ar and Ar+N2 and Ar+He mixtures. The results of pitting corrosion resistance of the welded joints of lean duplex stainless steel S82441 were studied in as weld conditions and after different mechanical surface finish treatments. The results of the critical pitting temperature (CPT) determined according to ASTM G48 at temperatures of 15, 25 and 35°C were presented. Three different surface treatment after welding were applied: etching, milling, brushing + etching. The influence of post weld surface treatment was studied in respect to the pitting corrosion resistance, basing on CPT temperature. Research on TIG welding of lean duplex stainless steel S82441/1.4662 showed a clear influence of the applied shielding gas mixtures, where the addition of 5 to 15% N2 to Ar virtually no effect on the level of resistance to pitting corrosion, only 5% N2 addition has a positive effect, while use of a mixture of 50% Ar + 50% He compared with welding at 100% Ar atmosphere, can significantly reduce the resistance to pitting corrosion. Definite good results were obtained during TIG welding with the participation of activation flux (A-TIG). The weld surface of lean duplex stainless S82441/1.4662 obtained in A-TIG welding without the addition of filler metal has a much lower tendency to pitting corrosion than traditional welds made by TIG method. Pitting corrosion resistance of welds made by A-TIG improved with the increase of the heat input in the tested range of welding current 100-200 A. It was also found that the intensity of the occurrence of pitting does not affect the method of cleaning welds after welding, but the mechanical removal of a thin surface layer of metal significantly reduces their intensity.

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Ren, Zoran, Srecko Glodez, and Joze Flasker. "Influence of inclusion interfaces on surface pitting." Technology, Law and Insurance 4, no. 1-2 (March 1999): 137–44. http://dx.doi.org/10.1080/135993799349243.

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Datsyshyn, O. P., and V. V. Panasyuk. "Pitting of the rolling bodies contact surface." Wear 251, no. 1-12 (October 2001): 1347–55. http://dx.doi.org/10.1016/s0043-1648(01)00771-2.

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Mansfeld, F., S. Lin, K. Kim, and H. Shih. "Pitting and surface modification of SIC/Al." Corrosion Science 27, no. 9 (January 1987): 997–1000. http://dx.doi.org/10.1016/0010-938x(87)90065-5.

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Tang, Yiwei, Nianwei Dai, Jun Wu, Yiming Jiang, and Jin Li. "Effect of Surface Roughness on Pitting Corrosion of 2205 Duplex Stainless Steel Investigated by Electrochemical Noise Measurements." Materials 12, no. 5 (March 4, 2019): 738. http://dx.doi.org/10.3390/ma12050738.

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The influence of surface roughness on the pitting corrosion behaviour of 2205 duplex stainless steel (DSS) in a chloride-containing environment was investigated using electrochemical noise (EN) techniques and morphology observation. A rougher surface condition increased the frequency of pit initiation because of the increase in more occluded pit sites. Rough surface finish also accelerated pit growth by increasing the actual dissolution rate in the pit. Metastable pits on rougher surfaces had longer lifetimes and grew to larger sizes, as their inner chemical environment was more easily maintained. However back-scatter images showed that pitting initiates on DSS 2205 regardless of the roughness condition.

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Blake, J. W., and H. S. Cheng. "A Surface Pitting Life Model for Spur Gears: Part II—Failure Probability Prediction." Journal of Tribology 113, no. 4 (October 1, 1991): 719–24. http://dx.doi.org/10.1115/1.2920684.

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A predictive pitting model for estimating failure probabilities and service lives has been developed. This paper presents the failure probability analysis and a discussion of the model’s application to spur gears. Probability estimates are based on an initial crack size distribution and on possible interaction between cracks and inclusions. Plots of the fraction of components experiencing pitting (percent) versus life show less spread than would be expected. However, trends predicted based on parametric variation are consistent with service behavior. The model is applied by linking the pitting model with a spur gear performance code. Results are compared with AGMA standards.

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Toivonen, Peter M. A., Frank Kappel, Sabina Stan, Darrell-Lee McKenzie, and Rod Hocking. "Firmness, Respiration, and Weight Loss of `Bing', `Lapins' and `Sweetheart' Cherries in Relation to Fruit Maturity and Susceptibility to Surface Pitting." HortScience 39, no. 5 (August 2004): 1066–69. http://dx.doi.org/10.21273/hortsci.39.5.1066.

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A convenient and reliable method that used a specially designed tool to apply a uniform bruising force in situ was developed to assess the relative susceptibility to fruit surface pitting in sweet cherry. Assessment of pitting with a visual scale after 2 weeks of 1 °C storage was found to be in close agreement with measurements of pit diameter. Using this method `Bing' showed the greatest susceptibility to pitting in both years of the study and `Bing', `Lapins', and `Sweetheart' cherries showed a decline in susceptibility as fruit matured. The predictive value of fruit firmness at harvest, fruit respiration at harvest, and weight loss in storage was assessed in relation to the severity of pitting. The model to best describe pitting was found to include all three physiological variables (firmness, respiration, and weight loss). While an acceptable model was obtained when combining all three cultivars, the best models were achieved when each cultivar was considered separately. It was concluded that there are likely unmeasured variables involved in determining susceptibility to pitting. Hence the best approach to predicting pitting susceptibility is the application of the pit-induction method described in this work.

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Karasz, Erin, Timothy Montoya, Jason Taylor, Ryan Katona, Charles Bryan, and Rebecca Filardo Schaller. "Factors Impacting Atmospheric Pitting Morphologies." ECS Meeting Abstracts MA2022-02, no. 12 (October 9, 2022): 774. http://dx.doi.org/10.1149/ma2022-0212774mtgabs.

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Stainless steels exposed to marine and near-marine environments can suffer from localized corrosion due to the appreciable amount of chloride aerosols present. In some cases, this localized corrosion, in the presence of sufficient tensile stress, can lead to stress corrosion cracking (SCC). Spent nuclear fuel (SNF) is currently stored in stainless steel canisters at independent spent fuel storage installation sites (ISFSI), many of which are located in near-marine environments. The possibility of localized corrosion features transitioning to SCC is a potential concern, particularly as the use of the SNF canisters at ISFSIs has been extended beyond their original licensing period. There is evidence that the likelihood of this transition occurring is dependent on the morphology of corrosion damage. Therefore, it is important to examine factors impacting the corrosion morphology. This work focuses on the effects of environment, surface finish, and stress state. 304L stainless steel u-bends of various surface finishes were deposited with fine droplets of magnesium chloride solution or artificial sea water. They were divided among several exposure environments, cyclic or static in nature. Flat coupons of 304H, 304L, or 316L were finished to the same surface roughnesses and exposed in the cyclic environment. Static exposures were 75% or 40% RH at an elevated temperature while the cyclic environment varied both temperature and relative humidity. The cyclic environment is designed to mimic diurnal cycles experienced on a warm SNF canister after an initial storage (or cooling) period. In the flat coupons, the roughest surface finish developed elongated pits and microcracks formed along the edges of the pits, largely running perpendicular to the grind lines. When viewed in cross-section, pits on the roughest surface finish also appeared to have more severe under-cutting and to be more irregularly shaped. The results of the flat coupons will be compared to the u-bends exposed with various salt types and stress states. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2022-4056 A. PNNL-SA-171827

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Krauß, Martin, Ralf Herzog, and Berthold Scholtes. "Influence of Surface Treatment on the Pitting Corrosion Behaviour of High Alloyed Stainless Steels in a Chloride Solution." International Journal of Materials Research 92, no. 8 (August 1, 2001): 910–15. http://dx.doi.org/10.1515/ijmr-2001-0166.

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Abstract The pitting corrosion behaviour of the austenitic stainless steel alloys 31 and A 351 with different surface treatments in a technical MgCl2 solution was investigated. Potentiometric current density-potential measurements were carried out, and critical repassivation temperatures were determined, using a galvanometric method. Pickled, ground, abrasively blast cleaned and shot-peened surfaces, respectively, were analysed concerning roughness, residual stress, work hardening and near-surface structure. The effects of the surface properties on the local corrosion behaviour was investigated. Basically, with increasing roughness, amount of residual stress and work hardening, one can see a tendency to decreasing resistance against pitting corrosion. On the other hand, those effects are superimposed by special properties of the passive layer, e. g., caused by pickling, or from the processing-specific surface texture.

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30

Hwa, Yoon, Christopher S. Kumai, Nancy Yang, Joshua K. Yee, and Thomas M. Devine. "Effect of Microstructural Bands on the Localized Corrosion of Laser Surface-Melted 316L Stainless Steel." Corrosion 77, no. 9 (June 9, 2021): 1014–24. http://dx.doi.org/10.5006/3779.

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The localized corrosion of laser surface melted (LSM) 316L stainless steel is investigated by a combination of potentiodynamic anodic polarization in 0.1 M HCl and microscopic investigation of the initiation and propagation of localized corrosion. The pitting potential of LSM 316L is significantly lower than the pitting potential of wrought 316L. The LSM microstructure is highly banded as a consequence of the high laser power density and high linear energy density. The bands are composed of zones of changing modes of solidification, cycling between very narrow regions of primary austenite solidification and very wide regions of primary ferrite solidification. Pits initiate in the outer edge of each band where the mode of solidification is primary austenite plane front solidification and primary austenite cellular solidification. The primary austenite regions have low chromium concentration (and possibly low molybdenum concentration), which explains their susceptibility to pitting corrosion. The ferrite is enriched in chromium, which explains the absence of pitting in the primary ferrite regions. The presence of the low chromium regions of primary austenite solidification explains the lower pitting resistance of LSM 316L relative to wrought 316L. The influence of banding on localized corrosion is applicable to other rapidly solidified processes such as additive manufacturing.

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Iswanto, Priyo Tri, Viktor Malau, Bambang Hari Priyambodo, Trio Nur Wibowo, and Nur Amin. "Effect of Shot-Peening on Hardness and Pitting Corrosion Rate on Load-Bearing Implant Material AISI 304." Materials Science Forum 901 (July 2017): 91–96. http://dx.doi.org/10.4028/www.scientific.net/msf.901.91.

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AISI 304 is a type of stainless steel used for load bearing implants due to relatively low cost. However, its mechanical properties and corrosion resistance must be improved to the level of AISI 316L, cobalt-based alloys, titanium and titanium alloy properties. Its fatigue characteristic is also one of the most important criteria have to be evaluated to achieve the overall service performance requirements, when this material subjected to dynamic load. High surface hardness may delay fatigue crack initiation and decrease corrosion rate because these two processes initiated at surface layer. The purpose of this research is to investigate the change in mechanical and corrosion characteristics of AISI 304 due to shot peening processes.Surface treatment with shot peening process were done by regulating the variation time for 0, 5, 10, 20, 30 and 40 minutes at the firing pressure of 7 bar; using 0,6 mm steel ball with hardness of 40-50 HRC. Firing distance between the nozzle with the specimen surface is 100 mm. Surface hardness was tested using indentation load of 10 grams for 10 seconds. Pitting corrosion test of treated AISI304 and non treated AISI316L was conducted in intravenous Otsu-RL brands as corrosion media. Pitting corrosion was performed using cyclic polarization methodThe hardness of surface layer increase with increasing shot-peening time. According to increase of length of shot-peening time from 0, 5, 10, 20, 30 and 40 minutes the hardness of these specimen increase to 241, 404, 418, 437, 481 and 496 VHN, respectively. The pitting corrosion rate tend to significantly decrease with increasing of shot peening time. According to increase of length of shot peening time from 0, 5, 10, 20, 30 and 40 minutes the pitting corrosion rate of these specimen also decrease to 0.853, 0.619, 0.086, 0.017, 0.116 and 0.036 mpy, respectively. Pitting corrosion rate of AISI316L is 0.042 mpy. Best pitting corrosion rate of treated AISI304 is 2.5 times smaller than that of non treated AISI316L. Therefore, shot-peening could be used to increase hardness number and reduce pitting corrosion rate, significanly.

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Nahvi, Hamdan Gowhar. "Study for Improvement in the Surface Properties and Wear Behavior of Mild Steel." International Journal for Research in Applied Science and Engineering Technology 9, no. 10 (October 31, 2021): 938–48. http://dx.doi.org/10.22214/ijraset.2021.38538.

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Abstract: Surface of a material can be improved by depositing the filler metal for the enhancement of various properties. Surface should be harder than substrate material for surface improvement. This surface improvement is also known as surfacing. In present research Mild steel specimens of size 140×35×40 were used to deposit surfacing layers and study the feasibility of iron/aluminum with varying compositions on low carbon steel deposited by GTAW process. Specimens for hardness and oxidation resistance were prepared. While studying oxidation of surfaced and un-coated area (base material), oxidation test resulted that the oxidation occurred on surface of base metal (un-coated area) after heating at different temperatures and time intervals. Specimens kept at 500˚C, 700˚C temperatures for 3, 6, 9 hours to get oxidized from un-coated surface but no mark of oxidation and pitting was visible at surfaced area but pitting of un-coated area occurred at 700˚C temperature. Oxidation had no effect to surfaced area. Low temperature oxidation test specimens gave only weight loss from un-coated portion but high temperature oxidation gave high amount of weight reduction due to pitting occurred on un-coated portion. The amount of weight loss of specimens increased with increase in furnace holding time at constant temperature. With increase in temperature oxidation of un-coated area of specimens also increased and pitting action occurred on un-coated area of specimens at high temperature. Further, for the various wear tests the cylindrical pins of 8 mm diameter with spherical tip 4 mm radius was made. Wear tests were carried out on pin on disc sliding wear testing machine. The comparison of wear rate loss was studied with constant sliding distance, varying load and sliding velocity of different compositions of iron/aluminum surfacing and substrate material. Hardness and wear resistance of composition were increased with increase in percentage of Fe element in composition. Composition C1 (Fe:Al/70:30) had high hardness and high wear resistance as compared to composition C2 (Fe:Al/30:70) and C3 (Fe:Al/50:50). Composition C3 (Fe:Al/50:50) had better hardness and wear resistance as compared composition C2 (Fe:Al/70:30). Keywords: Surface improvement, Fe-Al intermetallic, GTAW process, Sliding wear.

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33

Vinogradova, S. S., and Ye V. Pleshkova. "Staged Local Dissolution of Stainless Steel in Chloride Solutions." Solid State Phenomena 299 (January 2020): 711–15. http://dx.doi.org/10.4028/www.scientific.net/ssp.299.711.

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The paper defines galvanostatic polarization parameters (current density and test duration) to simulate self-dissolution conditions; the results are confirmed by potentiostatic tests. It is shown that under the conditions of self-dissolution simulation, increasing the solution concentration reduces the nucleation rate, while prolonging the pitting development time. Spectral analysis of chronopotentiograpms reveals low-frequency potential fluctuations that characterize the nucleation and passivation of pits at the onset of pitting corrosion. The paper describes the basic regularities observed in the alteration of surface electrochemistry by impedance spectroscopy; such alteration corresponds to the transition from the passive area to the pitting area. The researchers propose optimal electric equivalent circuits to reflect the surface conditions in early nucleation of pits. The paper also proposes an additional pitting resistance criterion, that is, cumulative electric-charge density.

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Vinogradova, S. S., and Ye V. Pleshkova. "Staged Local Dissolution of Stainless Steel in Chloride Solutions." Materials Science Forum 989 (May 2020): 74–78. http://dx.doi.org/10.4028/www.scientific.net/msf.989.74.

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The paper defines galvanostatic polarization parameters (current density and test duration), to simulate self-dissolution conditions; the results are confirmed by potentiostatic tests. It is shown that under the conditions of self-dissolution simulation, increasing the solution concentration reduces the nucleation rate, while prolonging the pitting development time. Spectral analysis of chronopotentiograms reveals low-frequency potential fluctuations that characterize the nucleation and passivation of pits at the onset of pitting corrosion. The paper describes the basic regularities, observed in the alteration of surface electrochemistry by impedance spectroscopy; such alteration corresponds to the transition from the passive area to the pitting area. The researchers propose optimal electric equivalent circuits to reflect the surface conditions in early nucleation of pits. The paper also proposes an additional pitting resistance criterion, that is, cumulative electric-charge density.

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35

Koumya, Y., R. Idouhli, M. Khadiri, A. Abouelfida, A. Aityoub, A. Benyaich, and A. Romane. "Pitting corrosion and effect of Euphorbia echinus extract on the corrosion behavior of AISI 321 stainless steel in chlorinated acid." Corrosion Reviews 37, no. 3 (June 26, 2019): 259–71. http://dx.doi.org/10.1515/corrrev-2018-0090.

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AbstractStainless steel (SS) is a very corrosion-resistant alloy used in different industrial plants because of its chemical and mechanical properties. However, the high chloride concentration in sulfuric acid (H2SO4) may promote both general corrosion and pitting corrosion. The pitting corrosion susceptibility in SS in chlorinated H2SO4 and the effect of Euphorbia echinus extract (EEE) on both general corrosion and pitting corrosion have been studied using potentiodynamic polarization, electrochemical impedance spectroscopy, chronoamperometry, cyclic voltammetry, and scanning electron microscopy (SEM). The pitting potential has been found to shift slightly in the presence of chloride ions (Cl−) in H2SO4. Also, pitting corrosion initiation has been demonstrated in the recorded chronoamperograms as a linear straight line having a positive slope. EEE has reduced the general corrosion and the inhibitor adsorption was found to follow the Langmuir isotherm. SEM micrographs showed that the tested inhibitor has efficiently acted on pitting corrosion for different concentrations of Cl−. Also, the kinetic findings were in good agreement with the surface analysis data. Fourier transform infrared spectroscopy and ultraviolet-visible absorption spectrophotometric measurements provided more insights on the interaction between the chemical functional groups of the inhibitor and the SS surface.

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36

Chang, Bao Hua, Dong Du, and Y. Zhou. "Finite Element Analysis of the Formation Mechanism of Electrode Pitting in Resistance Spot Welding of an Aluminum Alloy." Materials Science Forum 580-582 (June 2008): 275–78. http://dx.doi.org/10.4028/www.scientific.net/msf.580-582.275.

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A finite element analysis was conducted to study the roles of temperature and pressure in the formation of electrode pitting in resistance spot welding of an aluminum alloy. The distributions of pressure and temperature were computed at the electrode tip surface. Results showed that the highest temperature is always located at the center of electrode tip surface, while electrode pressure is concentrated mainly at the edge of contact region. The location of the concentrated electrode pressure coincides with that of electrode pitting, which indicates that the pressure concentration plays a more significant role than the temperature in the formation of pitting.

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Ferreira, Mário G. S., Rui Xing Li, J. S. Fernandes, Amélia Almeida, Rui Vilar, Ken G. Watkins, and W. M. Steen. "Pitting Corrosion of Laser Surface Modified Aluminium Alloys." Materials Science Forum 192-194 (August 1995): 421–32. http://dx.doi.org/10.4028/www.scientific.net/msf.192-194.421.

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38

Glodež, Srečko, Zoran Ren, and Jože Flašker. "Simulation of surface pitting due to contact loading." International Journal for Numerical Methods in Engineering 43, no. 1 (September 15, 1998): 33–50. http://dx.doi.org/10.1002/(sici)1097-0207(19980915)43:1<33::aid-nme410>3.0.co;2-z.

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Zhang, Wei, Shengli Lv, Leijiang Yao, and Xiaoyan Tong. "Simulation Investigation on Environment-Induced Pitting Corrosion on the Metal Surface." Science of Advanced Materials 13, no. 5 (May 1, 2021): 820–28. http://dx.doi.org/10.1166/sam.2021.3940.

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The prediction of corrosion damage is one of effective research methods in the safety inspection of aging aircraft structures. A mathematical model for quantifying corrosion damage is used in this paper to predict the onset of corrosion on structural surfaces exposed to aggressive environments. Based on the finite difference technique, the evolution process of local pitting corrosion on the surface of aluminum alloy in the medium is simulated, which can consider the sudden onset and the randomness of pitting corrosion. The effect of local ion concentration and oxide film damage on subsequent pitting nucleation was analyzed. Based on the efficient calculation program, the effectiveness of the mathematical model is verified by the comparison between the corrosion damage morphology and the experimental data in the literature. The results show a more widespread distribution of subsequent pits because of stronger aggressive ions are released during the life cycle of active pits and the higher diffusion coefficient of the aggressive ions. The three dimensional morphology is generated by image processing method based on the gray value of the two dimensional image of pits.

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40

Merola, C., H. W. Cheng, K. Schwenzfeier, K. Kristiansen, Y. J. Chen, H. A. Dobbs, J. N. Israelachvili, and M. Valtiner. "In situ nano- to microscopic imaging and growth mechanism of electrochemical dissolution (e.g., corrosion) of a confined metal surface." Proceedings of the National Academy of Sciences 114, no. 36 (August 21, 2017): 9541–46. http://dx.doi.org/10.1073/pnas.1708205114.

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Reactivity in confinement is central to a wide range of applications and systems, yet it is notoriously difficult to probe reactions in confined spaces in real time. Using a modified electrochemical surface forces apparatus (EC-SFA) on confined metallic surfaces, we observe in situ nano- to microscale dissolution and pit formation (qualitatively similar to previous observation on nonmetallic surfaces, e.g., silica) in well-defined geometries in environments relevant to corrosion processes. We follow “crevice corrosion” processes in real time in different pH-neutral NaCl solutions and applied surface potentials of nickel (vs. Ag|AgCl electrode in solution) for the mica–nickel confined interface of total area ∼0.03 mm2. The initial corrosion proceeds as self-catalyzed pitting, visualized by the sudden appearance of circular pits with uniform diameters of 6–7 μm and depth ∼2–3 nm. At concentrations above 10 mM NaCl, pitting is initiated at the outer rim of the confined zone, while below 10 mM NaCl, pitting is initiated inside the confined zone. We compare statistical analysis of growth kinetics and shape evolution of individual nanoscale deep pits with estimates from macroscopic experiments to study initial pit growth and propagation. Our data and experimental techniques reveal a mechanism that suggests initial corrosion results in formation of an aggressive interfacial electrolyte that rapidly accelerates pitting, similar to crack initiation and propagation within the confined area. These results support a general mechanism for nanoscale material degradation and dissolution (e.g., crevice corrosion) of polycrystalline nonnoble metals, alloys, and inorganic materials within confined interfaces.

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Černý, Michal, Josef Filípek, and Pavel Mazal. "Pitting damage of gears." Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 58, no. 2 (2010): 51–60. http://dx.doi.org/10.11118/actaun201058020051.

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Presented work combines the knowledge presented in literature and own experimental works concerning characteristics of fatigue damage of cog-wheels. Material damage of the cog-wheel tooth sides at their relative movement is demonstrated in terms of microstructure. Development of damage is described with respect to presence of micro-cracks, their connection to another type of structural discontinuities and lubricant influence. The location of pitting damage is exactly determined on the base of experimental results. The conclusion of the work clearly determines the nature of pitting damage of cog-wheels evoked by fatigue loading, presence of under-surface inclusions and effect of lubricant pressure.

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Vasyliev, Georgii S., and Oleg M. Kuzmenko. "Pitting Suppression of AISI 316 Stainless Steel Plates in Conditions of Ultrasonic Vibration." International Journal of Chemical Engineering 2020 (December 4, 2020): 1–7. http://dx.doi.org/10.1155/2020/6697227.

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Plate heat exchangers are widespread type of equipment that suffers from pitting corrosion in chloride containing solutions. Anodic behaviour of AISI 316 stainless steel was tested in 3.5% NaCl solution in conditions of ultrasound vibration (27 kHz, 10 W). The potentiodynamic sweep, potentiostatic technique, and galvanostatic technique were used coupled with surface morphology investigation after polarization. The pitting potential increased from 0.26 ± 0.02 V/SSCE to 0.42 ± 0.05 V/SSCE, and repassivation potential increased from 0.03 ± 0.01 V/SSCE to 0.18 ± 0.04 V/SSCE when vibration was applied. The anodic current at applied potential in pitting region was two orders of magnitude lower in conditions of ultrasound vibration. A possible mechanism of vibration influence on pitting is proposed, which is the elimination of pit covers from the vibrating surface, vibration-induced electrolyte motion in and out of the pits, and repassivation of active metal inside the pits.

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43

Wang, Hao, Xiaoyong Shu, and Jianping Zhao. "Influence of Build Angle and Polishing Roughness on Corrosion Resistance of 316L Stainless Steel Fabricated by SLM Method." Materials 15, no. 11 (June 6, 2022): 4020. http://dx.doi.org/10.3390/ma15114020.

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Metal parts formed by laser additive manufacturing methods usually have large surface roughness, which affects the corrosion resistance of the parts. This study reported the reason for and mechanism of the large surface roughness of 316L stainless steel samples manufactured by selective laser melting (SLM) at different build angles. Through the study, the reason for the large top surface roughness (average surface roughness is 15.3 μm) is due to the molten channel structure formed on the surface. The large side surface roughness (average surface roughness is 19.1 μm) is due to the incomplete fused particles adhering to the surface. Through electrochemical experiments, the influence of the build angle and polishing treatment on the corrosion resistance of the sample was studied. The different roughness of the top and side surfaces results in different corrosion resistances (the top surface pitting potential is 0.317 VAg/AgCl and the side surface pitting potential is 0.148 VAg/AgCl), and polishing can improve the surface corrosion resistance of specimens by reducing the surface roughness, especially for the side surface (from 0.148 to 0.351 VAg/AgCl). Therefore, parts manufactured by SLM can be post-treated to reduce roughness and improve surface corrosion resistance.

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44

Wang, Hao, Xiaoyong Shu, and Jianping Zhao. "Influence of Build Angle and Polishing Roughness on Corrosion Resistance of 316L Stainless Steel Fabricated by SLM Method." Materials 15, no. 11 (June 6, 2022): 4020. http://dx.doi.org/10.3390/ma15114020.

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Metal parts formed by laser additive manufacturing methods usually have large surface roughness, which affects the corrosion resistance of the parts. This study reported the reason for and mechanism of the large surface roughness of 316L stainless steel samples manufactured by selective laser melting (SLM) at different build angles. Through the study, the reason for the large top surface roughness (average surface roughness is 15.3 μm) is due to the molten channel structure formed on the surface. The large side surface roughness (average surface roughness is 19.1 μm) is due to the incomplete fused particles adhering to the surface. Through electrochemical experiments, the influence of the build angle and polishing treatment on the corrosion resistance of the sample was studied. The different roughness of the top and side surfaces results in different corrosion resistances (the top surface pitting potential is 0.317 VAg/AgCl and the side surface pitting potential is 0.148 VAg/AgCl), and polishing can improve the surface corrosion resistance of specimens by reducing the surface roughness, especially for the side surface (from 0.148 to 0.351 VAg/AgCl). Therefore, parts manufactured by SLM can be post-treated to reduce roughness and improve surface corrosion resistance.

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45

Son, In-Joon, Hiroaki Nakano, Satoshi Oue, Shigeo Kobayashi, Hisaaki Fukushima, and Z. Horita. "Effect of Equal-Channel Angular Pressing on the Pitting Corrosion Resistance of Al Alloy." Materials Science Forum 503-504 (January 2006): 487–92. http://dx.doi.org/10.4028/www.scientific.net/msf.503-504.487.

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The effect of equal-channel angular pressing (ECAP) on the pitting corrosion resistance of Al and Al-Mg alloy was investigated by means of polarization curves in solutions containing 300 ppm of Cl- and by surface analysis. The potentials for pitting corrosion of Al and Al-Mg alloy were evidently shifted to the noble direction by using the ECAP process, indicating that this process improves resistance to pitting corrosion. This increase in resistance seems to be attributable to the increase in formation rate of Al oxide films due to the increase in grain boundary with ECAP. The pitting corrosion resistance of Al and Al-Mg alloy anodized galvanostatically in H2SO4 solution after ECAP was also investigated using electrochemical techniques. The pitting corrosion resistance of Al and Al-Mg alloy was remarkably improved by anodizing. However, the pitting corrosion resistance of anodized Al-Mg alloy was better without ECAP than with ECAP.

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Hoi, T. K. N. "CORROSION CHARACTERIZATIONS OF CARBON STEEL IN CAI TAU RIVER WATER SYSTEM - VIET NAM." Vietnam Journal of Science and Technology 55, no. 5B (March 24, 2018): 66. http://dx.doi.org/10.15625/2525-2518/55/5b/12211.

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Corrosion problem happens in Cai Tau river water system; however, the mechanism is still questionable, resulting in unsolved ways. Therefore, this study focuses on the corrosion characterizations of carbon steel in Cai Tau river water system to analyze the corrosion mechanism using advanced electrochemical techniques and surface analysis. Electrochemical results indicated that Cl‾ and SO42- ions shows a significant effect on corrosion of carbon steel, resulting in pitting corrosion. Whereas, carbon steel showed passive behavior when it immersed in solution containing CO32- ion. Furthermore, pH strongly affects the corrosion properties of carbon steel. It indicated that corrosion of carbon steel increased with a decrease of pH. Surface analysis was done to identify the surface area of the pitting corrosion of carbon steel. Corrosion rates, pitting and corrosion products were clearly observed and analyzed by optical microscopy and X-ray diffraction.

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47

Dong, BaoJun, Wei Liu, Fei Wu, JiaQi Zhu, Banthukul Wongpat, Yonggang Zhao, Yueming Fan, and TianYi Zhang. "Determination of critical salinity of pitting and uniform corrosion of X60 under CO2-O2 coexistence environment." Anti-Corrosion Methods and Materials 67, no. 2 (January 20, 2020): 166–77. http://dx.doi.org/10.1108/acmm-06-2019-2147.

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Purpose The salinity of the oilfield produced water has a significant effect on steel corrosion. The purpose of this paper is to study the influence of salinity on corrosion behavior of X60 steel and it also provides basic for material selection of gas wells with high salinity. Design/methodology/approach The weight loss experiment was carried out on steel with high temperature and high pressure autoclave. The surface morphology and composition of corrosion scales were studied by means of scanning electron microscopy, energy dispersive spectroscopy and X-ray diffractometry. Findings The results show that as salinity increases, the corrosion rate of X60 steel will gradually experience a rapid decline stage and then a slow decline stage. X60 steel is mainly exhibiting uniform corrosion in the first rapid decline stage and pitting corrosion in the second slow decline stage. The increase in salinity reduces gas solubility, which, in turn, changes the morphology and density of the corrosion scales of X60 steel. At low salinity, loose iron oxides generated on the surface of the steel, which poorly protects the substrate. At high salinity, surface of the steel gradually forms protective films. Chloride ions in the saline solution mainly affect the structure of the corrosion scales and initiate pitting corrosion. The increased chloride ions lead to more pitting pits on the surface of steel. The recrystallization of FeCO3 in pitting pits causes the corrosion scales to bulge. Originality/value The investigation determined the critical concentration of pitting corrosion and uniform corrosion of X60 steel, and the new corrosion mechanism model was presented.

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Grzeszkowski, Mateusz, Sebastian Nowoisky, Philipp Scholzen, Gregor Kappmeyer, Clemens Gühmann, Jens Brimmers, and Christian Brecher. "Classification of gear pitting damage using vibration measurements." tm - Technisches Messen 88, no. 5 (April 17, 2021): 282–93. http://dx.doi.org/10.1515/teme-2021-0010.

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Abstract In future aero engines, a planetary gearbox is to be integrated between fan and turbine to increase the efficiency and bypass ratio. This gearbox has to be monitored during operation to detect possible gearbox faults such as gear wear or gear pitting at an early stage. This paper presents a method consisting of vibration measurement, sensor-dependent feature extraction and support-vector machine (SVM)-based classification of pitting for gear condition monitoring. Several gears were loaded with a constant torque on a standardized back-to-back test rig to provoke pitting, and the pitting amount was captured during the tests with a camera. Features are extracted from accelerometers and an acoustic emission sensor, and based on the results of the visually recorded pitting surface, SVM classification is applied to identify the pitting defect. In this contribution, two different SVM classification approaches are investigated. One approach uses a Two-Class SVM, where tests from one gearset are used for SVM training and another approach utilizes a One-Class SVM based on outlier detection. Both methods show that single tooth pitting defects with a relative pitting area of less than 1 % can be effectively identified, whereas the One-Class SVM method showed a higher pitting detection accuracy.

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Xu, Wenbo, Hongtao Huang, Yang Gao, Xiaofeng Qin, Taolue Wen, Shufeng Yang, Peng Zhang, Liang Wang, and Ce Guo. "Influence of the Machining Process on the Service Life and Pitting Morphology of Gear-Tooth Surfaces." Metals 12, no. 8 (August 20, 2022): 1382. http://dx.doi.org/10.3390/met12081382.

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Pitting, which results from contact fatigue, is a common failure mode in gear transmission systems and is influenced by the material strength and stress state of the contact area, which is further influenced by lubrication and roughness because of stress fluctuations. In this study, a comparative contact-fatigue test was conducted on two types of gears with different terminal machining processes. The contact stress of the tooth surface considering the microtopography was analyzed using the fractal method based on surface microtopography data measured from the surface formed by the two processes. Test results show that the average service life of gears machined using the barrel-finishing process was approximately 5–7 times that of gears machined using grinding. The pitting morphologies of gears fabricated using different processes exhibited evident differences. The maximum stress level of the gears machined with barrel finishing was approximately twice that of the gears machined through grinding. Different stress levels resulted in different micropitting load-bearing capacities, which could be attributed to the different service lives of gears manufactured through different machining processes. The different presence features of the pitting morphology were due to the different micromorphologies of the surface formed by the different finishing processes. In particular, the randomly distributed pitting morphology of the gear surface machined using the barrel-finishing process was due to its flattening and polishing effect. Optimization of the surface-microgeometry distribution via the finishing process is an effective method for prolonging the service life of gears.

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Han, De Sheng, Di Li, and Tian Liang Zheng. "Influence of SO₂ Concentration on Initial Corrosion of Aluminum in Marine Atmosphere." Advanced Materials Research 15-17 (February 2006): 53–58. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.53.

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Influence of SO2 concentration on initial corrosion of aluminum was studied in simulated marine atmosphere. Variation of initial corrosion morphology, relation between weight gain and time in the course of initial corrosion, corrosion speed (token with maximum pitting depth and weight gain) were analyzed and discussed. Primary results is list below: In marine atmosphere, SO2 sedimentation above 0.1 mg/100cm2 can accelerate Al pitting with low Cl- sedimentation. Both corrosion weight gain and pitting depth increase obviously. For pitting surface of LY12 with SO2 and Cl- sedimentation, corrosion potential change little, Nyquist Graph was single arc of capacitance resist with retractile real part, Rr can’t reflect corrosion degree.

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Journal articles on the topic 'Surface pitting'

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