AN ANALYSIS OF CURRENT FLUCTUATIONS DURING PASSIVE FILM BREAKDOWN AND REPASSIVATION IN STAINLESS ALLOYS

To investigate the difference in passive film breakdown and repassivation between crystalline SUS304 stainless steel and an amorphous FeCrSiB steel, the current fluctuations under potentiostatic condition were measured in 3% NaCl solution. Fluctuation in current was separated into individual current waveform, which consisted of a pit growth and repassivation process, and analyzed with respect to the dependence of pit growth and repassivation time on potential, charge amount and peak current of separated single fluctuation. There was a broad distribution in the pit growth and repassivation time, and the charge passing. At the same time, it was found that the pit growth and repassivation time increased with potential increase. How fast the locally broken passive film is repaired is one of the main factors on improving the pitting potential. The high repassivation rate of amorphous alloy contributes to its high corrosion resistance. © 1990.