Electrochemical monitoring of the degradation of galvanized steel in simulated marine atmosphere

摘要

Galvanized steels with different thicknesses of coatings were exposed to the wet-dry cycles in the presence of NaCl. The degradation of galvanized steels was investigated at different exposure times by electrochemical impedance spectroscopy. Further, the degradation is categorized into four characteristic stages, including tau(1): dissolution of zinc, tau(2): galvanic protection by metallic zinc, tau(3): barrier protection by zinc corrosion products, and tau(4): onset of the underlying steel corrosion, respectively. The underlying steel was protected by the zinc corrosion products for a relatively long time even after the metallic zinc coating was completely corroded (i.e., the tau(3) stage).