Study on potential distribution of atmospheric corrosion using a scanning Kelvin probe

A scanning Kelvin probe setup was developed for potential map measurements, and the characteristic of a potential distribution for atmospheric corrosion of metal with salt particle deposition was investigated using this setup. It was found that as the relative humidity increased to a level higher than that over the saturated solution of the salt, the potential map changed from homogeneity into heterogeneity, which formed initially a valley, then a volcano shape. As a result, atmospheric corrosion was initiated due to the heterogeneity shown by the potential distribution, which led to the formation of anodes and cathodes on the metal surface. It also indicated that ambient relative humidity and dry-and-wet cycles played an important role in accelerating the corrosion process shown by the changing potential map. In addition, the potential map had a close relationship with the chemical maps of the corrosion products. Based on the above findings, a model was proposed and discussed for describing the initiation of atmospheric corrosion resulting from salt particle deposition. Copyright OCCA 2005.