INVESTIGATIONS OF THE PITTING CORROSION BEHAVIOR OF PASSIVE FILM ON REBAR ELECTRODES CONTAINING ARTIFICIAL PIT IN SIMULATED CEMENT SOLUTIONS

In this paper, in-situ photoelectrochemical microscopic method has bee n used to characterize the spatial variations of the passive film on ' artificial pit'-containing REBAR electrodes in simulated cement pore s olution. It is clearly shown that the photocurrent at the artificial p it region was larger than that at other normal regions under suitable conditions. This was attributed to a thicker and more porous passive f ilm formed potentiostatically at the artificial pit. With the help of 'line-scan' technique, we have provided a first example of in-situ mon itoring the changes of local photocurrent in the artificial pit region on REBAR electrode surface. It was found that the photocurrent at the pit reduced gradually during the incubation time of pitting corrosion . It is thought that this phenomenon was correlated to the dissolution of the passive film in the artificial pit region which caused by the penetration of chloride ions, and the changes of photocurrent may refl ect the accumulation and diffusion of corrosion products.