An array electrode technique was developed as a novel electrochemical method for studying the interaction between macrocell and microcell in the early corrosion process of reinforcing steel in cement mortar.The corrosion potential and galvanic current of macrocell corrosion of the reinforcing steel in cement mortar were imaged by the array electrode technique during the corrosion initiation and propagation.It was certified that the corrosion macrocell current is closely related with the difference of corrosion potential between the anodic and cathodic areas.The corrosion macrocell and microcell always exist during the corrosion process.The interaction of corrosion macrocell and corrosion microcell of steel in concrete was directly sensed by the array electrode for the first time,and was discussed in terms of corrosion electrochemistry.
LI LanQiang1,DONG ShiGang1,WANG Wei2,HU RongGang1,DU RongGui1,LIN ChangJian1,ZHUO XiangDong1 & WANG Jia2 1 State Key Laboratory of Physical Chemistry of Solid Surfaces,Department of Chemistry,College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361005,China
The effects of cerium nitrite on corrosion behaviors of carbon steel in simulated concrete pore solutions were studied with the methods of linear polarization, electrochemical impedance spectroscopy and surface analysis. In pore solutions in the presence of Ce(NO3)3?6H2O, the corrosion potential, polarization resistance and impedance of carbon steel obviously increased in contrast to the situation in the absence of cerium salts. The pore solution with [NO2-] / [Cl-] = 0.3 and 0.1% Ce(NO3)3?6H2O, carbon steel shows better corrosion resistance than that in the pore solution with [NO2-] / [Cl-] = 0.6, which indicates that a small amount of Ce(NO3)3?6H2O in pore solutions can effectively promote passivation of the steel and reduce the threshold [NO2-] / [Cl-] ratio for corrosion control. The surface layer formed in cerium salt containing pore solutions is more compact and smooth and 1.36%Ce is examined on the sample surface. The addition of 0.1% Ce(NO3)3?6H2O in pore solutions can decrease the corrosion rate of steel in pore solutions and has little influence on pH change of the solutions. However, more cerium nitrate addition above 0.1% may result in pH decrease of the solution.
