Nature of Atmospheric Rust on Iron

In order to elucidate the mechanism of self‐protection of weathering steel, the action of atmospheric rust was studied through a discussion of physical, chemical, and electrochemical nature of rust, with special attention to the effect of copper addition. The aggregating state of rust layer is influenced by two factors: the time of exposure and beneficial elements added to steel. Copper addition inhibits the growth of primary colloidal particle. This action of copper has an effect on the properties of rust and serves to increase the protective ability of rust layer.