Corrosion and SCC initiation behavior of low-alloy high-strength steels microalloyed with Nb and Sb in a simulated polluted marine atmosphere

Corrosion and stress corrosion cracking (SCC) behavior of some low-alloy high-strength steels microalloyed with Nb and Sb were in detail studied in a simulated polluted marine atmosphere. The results indicated that the high-strength steel without Nb and Sb was badly damaged by corrosion and very susceptive to SCC in a SO2-containing marine atmosphere, which was characterized by high corrosion rate and a large number of potential initiation sites for SCC cracks. By contrast, Nb addition affected little on atmospheric corrosion rate, but weakened the role of hydrogen at the boundaries of prior austenite grain and lath bainite. Sb addition significantly reduced the corrosion rate by optimizing the properties of rust layer through its synergy with Cu, and inhibited the localized anodic dissolution and acidification effect underneath. Thus, the combined addition of Nb and Sb increased the resistance to atmospheric corrosion and substantially inhibited SCC initiation.