Effect of Gravity on Pitting Behavior of 304 Stainless Steel

Potentiostatic polarization, EIS and three-dimensional video microscopy were used to study the pitting behavior of 304 stainless steels placed horizontally and vertically respectively in 3.5% NaCl solution. The results indicated that the specimen in vertical position generated pits easily than that in horizontal position. The gravity let the corrosion products in pits of the specimen in vertical position diffuse out of the pits more easily, which could accelerate the nucleation of pits and the transition rate of metastable pits to stable growth. The results of element parameters of the equivalent circuit analysis showed the localized corrosion on the surface of the specimen in vertical position was more serious than that in horizontal position.