Influence of sulfide on the passive film of stainless steel in simulated cooling water

The impedance of 316 stainless steel electrode in simulated cooling water increases in the course of immersion, but decreases sharply with the addition of sulfide. Polarization curves show that the sulfide causes the passivity current of the electrode to increase. The Mott-Schottky plots indicate that, the slope of the straight line that reflects the properties of chromium oxide in passive film decreases or even almost disappears, and the acceptor density N-A increases when raising the sulfide concentration, showing the influence of sulfide to the properties of the stainless steel passive film.