不锈钢局部腐蚀过程中的氢去极化反应研究

HYDROGEN DEPOLARIZATION REACTION DURING LOCALIZED CORROSION OF STAINLESS STEELS IN SODIUM CHLORIDE SOLUTION

用恒电位失重法和Ｔａｆｅｌ外推法绘制了１Ｃｒ１３和０Ｃｒ１８Ｎｉ９两种不锈钢在各自模拟闭塞区溶液中的极化图，并叠加了外表面极化的影响．得到了闭塞电池在开路状态下以及在外表面极化作用下的放氢速度和腐蚀速度．进一步阐明闭塞电池加速腐蚀的原因是在临界ｐＨ值处发生了钝态／活态转变，从根本上改变了阳极过程，同时使内外电位差扩大，外表面的极化作用增大．

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.