2020 Volume 69 Issue 3 Pages 77-82
Protective rust formed on Cr-Cu-Ni-P and Cr-Cu weathering steels （WSs） exposed for 44 years were analyzed to compare with previous studies for exposure test results for weathering steels. The formation of a typical protective rust composed of a polarizing layer （crystalline α-FeOOH and γ-FeOOH） and an insulation layer （fine α-FeOOH） was observed on both the weathering steels. Alloy elements were distributed in the protective rust layer. Cr enrichment was observed in the insulation layer. It was similar to previous studies and indicated that Cr contributed to form fine rust. Cu was present in the insulation layer, P was present in the insulation layer and the top of the polarizing layer, and Ni was present in the entire rust layer. Structure of the rust layers and the distribution of Cr and Ni were consistent in the results of previous studies, the exposure tests for less than 32 years, however there was a difference in the distribution of Cu and P.
