The influence of Nickel on the corrosion protection of FeCrNi alloys after breakaway corrosion at 600 °C

Breakaway corrosion of stainless steels remains a challenge for many industrial applications operating in harsh conditions. The lifetimes of metallic components are often determined by the corrosion propagation after breakaway. Nevertheless, studies on the protective properties of the Fe-rich oxides formed after breakaway are scarce. This study investigates the influence of Ni on the protection after breakaway on a broad range of Fe18CrxNi model alloys, by systematically inducing breakaway of the initially formed protective, Cr-rich oxides. The results clearly demonstrate an improved protection after breakaway for higher Ni-contents, explained by the alloys’ ability to avoid internal oxidation involving Fe-rich BCC and spinel. • Increased amount of Ni in FeCrNi-alloys reduces the oxide growth rate after breakaway. • Avoiding internal oxidation including BCC+spinel is suggested to explain the reduction. • Ni shifts the range of stability for this type of internal oxidation to lower Cr content. • Thus, reduced oxide growth rates are expected by increased amounts of Ni and/or Cr.