HYDROGEN DEPOLARIZATION REACTION DURING LOCALIZED CORROSION OF STAINLESS STEELS IN SODIUM CHLORIDE SOLUTION
不锈钢局部腐蚀过程中的氢去极化反应研究

Potentiostatic weight loss tests and cathodic Tafel extrapolations were carried out to establish the polarization curves of 1Cr13 and 0Cr18Ni9 stainless steels in simulated occluded solutions.The effects of external surface on the potential of occluded cell (O. C.) were also superimposed on above diagrams from which the hydrogen evolution rate and corrosion rate of O.C. were clear. It was found that hydrogen depolarization occurred within O. C. as the pH value of occluded solution decreased below the critical pH value, but the velocity of hydrogen depolarization was only 0.057% and 2.3% of corrosion rate inside O.C. for 1Cr13 and 0Cr18Ni9 stainless steels respectively. It was shown that the "accelerating corrosion effect" of O.C. was caused by the passive active transition accompanied with the sudden increase in the potential difference between O.C. and external surface.