Development of Electropolishing-Based Corrosion Resistance Technique for Ferritic Stainless Steel 2016-01-0354

One issue raised by the use of austenitic stainless steels in commercial vehicles is the increase in material costs. To reduce those material costs, a nitric acid electropolishing treatment was applied to SUS436L (18 Cr - 1.5 Mo - 0.4 Nb) and corrosion tests were conducted to compare its corrosion resistance to that of SUS316L(16 Cr - 12 Ni - 2 Mo). Compared to SUS316L, SUS436L subjected to nitric acid electropolishing indicated superior corrosion resistance. In addition, XPS and TEM analyses showed that while the SUS436L passivation film layer contained approximately twice as much chromium, its thickness was also generally reduced by approximately half, to 2 nm. These results suggest that electropolishing with nitric acid, which is highly oxidative, formed a fine passivation film.