1997 Volume 46 Issue 4 Pages 230-235
The quantitative evaluation of tarnish of stainless steel was carried out using cyclic corrosion test (CCT) and computer image analysis. Test samples were austenitic stainless steels which contained 10-18wt%Cr and had various roughness of surface. Effect of surface finish on tarnish has been studied, and main results are as follows. Total area of tarnish (AR) after CCT depends on Cr concentration in passive film and roughness of surface. AR increases with decreasing of the former and with increasing of the latter. Among conventional surface finishes such as 2B, HL, BA and Miller of stainless steel Type 304, sample of 2B-finished indicates the worst resistance against tarnish after CCT. Compared with the resistance against tarnish of another sample which has the same Cr concentration in passive film and roughness of surface, sample of 2B-finished indicates worse resistance. This result could be persuaded by the fact that sample of 2B-finished has the intergranular corrosion at the grainboundary on the surface because of the pickling treatment in the surface finish process.
