Abstract
When various types of rust powder coexist on the process of rust occurrence, the feature of the formed rust was investigated. As a result, the rust of the same crystalline morphology as the coexisted rust was formed preferentially. Moreover, the protective rust was formed by coexistence of rust homogeneous as the protective rust formed on weathering steel. Furthermore, by surface treatment of resin mixing the rust which promotes protective rust formation on weathering steel, the protective rust layer was formed under the surface treatment film from the corrosion early stage, and the suppression of corrosion dissolution reaction or the noble of corrosion potential was checked.