Effect of Metal Cations on Corrosion Behavior and Surface Structure of Carbon Steel in Chloride Ion Atmosphere

In order to better understand why the corrosion behavior of carbon steel exposed in Nansha atmospheric environment is very serious, the effect of sodium, potassium and magnesium chlorides deposited on carbon steel surface has been studied under atmosphere conditions by wet/dry accelerated test. The difference of corrosion behavior and surface structure in Na⁺, K⁺, and Mg²⁺ containing atmosphere has been investigated by thickness loss, scanning electron microscope, X-ray diffraction and electrochemical techniques. The results indicate that the thickness loss of carbon steel exposed in different metal cations containing atmospheric environment increases in the order of Na⁺, K⁺, Mg²⁺. The hard metal cation can promote the dissolution of the steel to a certain extent. In Mg²⁺ containing atmosphere, the relative content of β-FeOOH is rather higher and the protective ability index α*/γ* decreases in the order of Na⁺, K⁺, Mg²⁺. The corrosion current density of both bare carbon steel and the rusted carbon steel increases in the order of Na⁺, K⁺, Mg²⁺. The polarization resistance and the charge transfer resistance decreases in the order of Na⁺, K⁺, Mg²⁺.