Rust Layer Formation Behavior of Carbon Steel with the Surface Physically Deposited or Implanted by Alloying Elements of Weathering Steel under Accelerated Corrosion Condition
Jun Itoh, Hiroo Nagano
Effects of alloying elements of weathering steel such as Cr, Cu, Ni, Ti and Nb on the corrosion behavior of carbon steel, especially the rust layer formation, were investigated. The alloying elements were physically deposited or implanted onto the surface of carbon steel coupons in order to elucidate roles of alloying elements that present near/on the surface. The coupons were exposed at accelerated atmospheric corrosion condition, thereafter the weight losses were determined and the rust layers were microscopically or physically analyzed. It was found that alloying elements are present in rust layers and influenced forms of rust layers. In the corrosion test condition excluding chlorides, microscopic observation of the rust layer using polarized reflected light revealed that continuous optically isotropic layer was established on the coupons deposited/implanted with Cu. As for coupons deposited/implanted with Cr or Ti, significant effects of doping process on the corrosion rates were recognized. In the corrosion test condition including chlorides, adhesive rust layer with fewer voids was formed. On the other hand, on the coupons with other elements deposition/implantation, less adhesive rust layers with voids were observed.