Insight into the influence of alloying elements on the secondary corrosion protection of Fe-base alloys by means of atom probe tomography

Breakaway corrosion of Fe-base alloys remains a challenge in applications operated in harsh conditions. The material lifetimes are often determined by the corrosion propagation after breakaway. Nevertheless, detailed microstructural studies, linking the protective properties of the Fe-rich oxides formed after breakaway, are scarce. This study utilizes APT to investigate the Fe-rich oxides formed after breakaway, i.e., the secondary corrosion protection, of four Fe-based model alloys chosen to exhibit good and poor secondary protection at 600 °C. The APT investigation shows that the inward-growing scale is heterogeneous at the nanometer scale and that Fe-enriched regions form on the poorly protective oxides.