Abstract:The effects of surface preparation on the corrosion resistance of AISI 316L austenitic stainless steel were studied using the cyclic potentiodynamic polarization method. Grinding, mechanical polishing, and electropolishing were considered as the surface modifier methods. Regarding the surface roughness parameters, besides the conventional height parameter (R a), the kurtosis (Rku) as the shape parameter was also considered to rationalize the pitting resistance for the first time. Based on the results of the Ta… Show more
“…The roughness of the surface can affect both uniform and pitting corrosion due to variations in oxide thickness, creating weak points at which pitting can originate. 2,[36][37][38][39] However, the expected decrease in E pit with increase in Ra was not observed (first column in Fig. 6, Table S2).…”
Electropolishing as a surface preparation technique is increasing in popularity in industrial applications and for corrosion studies. Electropolished surfaces have shown better resistance to pitting corrosion over mechanical polishing; however, the fundamental reason governing the change in corrosion behaviour remains unclear. This study examined the corrosion behaviour of 13Cr4Ni stainless steel (UNS S41500) after five surface preparation techniques and shows that sulfate is incorporated in the oxide film when it is present in the electropolishing solution. Even after removal from the sulfate-containing solution, the sulfate incorporation increases the material’s pitting resistance by lowering the number of sites available for chloride to induce pitting. This work also demonstrates that, when used as a counter electrode, Pt can dissolve and reprecipitate on the working electrode surface during electropolishing. The deposits result in a more noble open circuit potential, indicating an artificial increase in passivity. These artificial changes to corrosion behaviour due to surface preparation method may result in erroneous conclusions. To establish fair comparisons between surface preparation methods, the counter electrode and the sulfate effect should be strictly considered.
“…The roughness of the surface can affect both uniform and pitting corrosion due to variations in oxide thickness, creating weak points at which pitting can originate. 2,[36][37][38][39] However, the expected decrease in E pit with increase in Ra was not observed (first column in Fig. 6, Table S2).…”
Electropolishing as a surface preparation technique is increasing in popularity in industrial applications and for corrosion studies. Electropolished surfaces have shown better resistance to pitting corrosion over mechanical polishing; however, the fundamental reason governing the change in corrosion behaviour remains unclear. This study examined the corrosion behaviour of 13Cr4Ni stainless steel (UNS S41500) after five surface preparation techniques and shows that sulfate is incorporated in the oxide film when it is present in the electropolishing solution. Even after removal from the sulfate-containing solution, the sulfate incorporation increases the material’s pitting resistance by lowering the number of sites available for chloride to induce pitting. This work also demonstrates that, when used as a counter electrode, Pt can dissolve and reprecipitate on the working electrode surface during electropolishing. The deposits result in a more noble open circuit potential, indicating an artificial increase in passivity. These artificial changes to corrosion behaviour due to surface preparation method may result in erroneous conclusions. To establish fair comparisons between surface preparation methods, the counter electrode and the sulfate effect should be strictly considered.
“…Correction accounts for the atomic number effect (Z), absorption effect (A), and fluorescence excitation effect (F) may be needed, especially when no standard is available. The automatic ZAF correction may be applied as successfully implemented [34]. Figure 13 (a), (b) SEM images and (c) EDX analysis of the intermetallic phase of Er-containing samples.…”
The effects of erbium on the microstructure of a semisolid A356 alloy for thixoforming were investigated. Semisolid A356 alloys were prepared using the serpentine channel technique. The results demonstrated that a semisolid A356 alloy could be successfully produced. The addition of erbium refined the size of primary α-Al globules; moreover, the eutectic silicon phase was modified. The thermal analysis results showed that the addition of erbium decreased the amount of nucleation sites for eutectic phases, leading to increased undercooling of the melts. Therefore, erbium delays the nucleation of eutectic phases, resulting in refinement of the eutectic silicon phases. Moreover, the addition of erbium increased the rheocast quality index value of the semisolid A356 alloy, which is beneficial for thixoforming.
“…The reason is the presence of a more stable passive layer in this sample, which breakdown at more positive potentials. The larger value of E pit -E corr and the wider passivation range of 750 °C-5 min sample confirm higher resistance of its passive layer against pitting corrosion [59,82]. The existence of a sub-micron grain structure with a high grain boundary volume, as well as the formation of a suitable texture in the 750 °C-5 min sample has led to greater diffusion of the chromium to the surface and improvement of the passive layer properties [22-24, 29, 79].…”
“…While the narrower loop indicates a more repassivation tendency. In this potential range, the new pits cannot nucleate but the initiated pits can grow [59,75,[77][78][79]82].…”
In this study, the evolution of the microstructure and texture during thermomechanical treatment and its effect on corrosion properties of 310s austenitic stainless steel were investigated. This stainless steel was cryo-rolled at 50 and 90% thickness reductions, and then the 90% cryo-rolled sample was annealed at 750 °C for 5 and 30 minutes. SEM and optical microscope images were used to examine the microstructure of the samples. Fritoscopy test was also used to calculate the volume fraction of the martensite phase. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and cyclic potentiodynamic polarization tests were performed in the 3.5 wt. % NaCl solution to investigate the corrosion behavior of the studied steel. The results showed that the cryo-rolling process caused the reduction of grain size, texture strengthening and transformation of austenite to strain-induced αʹ-martensite phase. Decreasing grain size and increasing texture components containing dense planes are beneficial factors and the formation of the αʹ-martensite phase is a harmful factor for corrosion resistance. It was observed that annealing at 750 °C for 30 min caused the grain growth and texture weakening, while a favorable condition is developed in the annealed sample for 5 min. After 90% cryo-rolling and subsequent annealing at 750 °C for 5 min, the corrosion resistance was significantly improved compared to the as-received sample and reached 37 kΩ.cm2. Formation of the sub-micron microstructure along with the high volume fraction of Brass and Goss texture components were the main reasons for improving corrosion resistance at 750 °C-5 min.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
