Abstract
The influence of diffusion coating temperature, materials used, and the addition of Mo on the polaization behavior of austenitic stainless steels, SUS 304 and SUS 304L, diffusion-coated with Cr, was investigated by measuring anodic polarization curves of the steels in 1N-HCl and 1N-H2SO4 solutions. In an 1N-HCl solution, specimens diffusion-coated with Cr exhibited well defined critical current densities and passive range. Increase in the treatment temperature made the surface of the diffusion coating layer more rough and increased the amount of impurities (such as Fe, Ni, C) diffused from the base metal into the diffusion coating layer. This caused the critical current density and the passive current density to increase. SUS 304L diffusion-coated with Cr had a wider passive range and exhibited a better polarization behavior than SUS 304, although the treated SUS 304L had a higher critical current density. Mo added in the Cr diffusion coating treatment decreased the critical current density and passive current density.
