Corrosion behavior of high-nickel and chromium alloys in natural Baltic seawater

Effect of Cl- ion concentration (0 M sodium chloride [NaCl] to 2 M NaCl) an d temperature (25 degrees C to 75 degrees C) on stability of the passive st ate of high-Ni and Cr alloys: NI-1 (similar to 16% Mo), CR-2 (similar to 6. 2% Mo), and NI-3 (3.5% Mo) were investigated in acidic and neutral electrol ytes in strictly controlled electrochemical conditions. The anodic behavior of the alloys appeared to depend mostly upon Mo content in the alloy. Thus , the NI-1 was the most stable alloy under the applied experimental conditi ons, The other alloys were also quite resistant, undergoing pitting only at elevated temperatures, at high anodic potentials, and at a chloride concen tration not lower than 1 M, In natural Baltic seawater, these alloys did no t exhibit any tendency to pitting, in qualitative agreement with the accele rated electrochemical tests. Complementary microscopic and surface analytic al (AES) investigations were tarried our to correlate the anodic and corros ion behavior of these materials with their composition and structure, and t he composition of the passivating films formed at their surfaces.