Corrosion Behavior of Zinc-Aluminum-Magnesium Coated Steel in Simulated Marine Atmosphere

Abstract

The corrosion behavior of zinc-aluminum-magnesium (ZAM) coated steel in a simulated marine atmosphere was investigated using compositional, morphological, electrochemical, and mass loss analyses. The results revealed that the corrosion rate of ZAM coated steel fluctuated because of the corrosion products formed during its exposure to the marine atmosphere, and the mass loss after 1848 h of exposure was 27.37 g.m-2 after 1848 hours' exposure. The corrosion preferentially occurred in the eutectic phases, especially in the eutectic phases near the primary zinc phase and with an area smaller than the primary zinc phase. As the exposure time increased, some of the corrosion products flaked off from the coating, leading to the aggravation of local corrosion and the formation of corrosion pits. Moreover, the corrosion products in the corrosion pits were dissolved, which can be attributed to the decrease in pH caused by the consumption of hydroxides during the chemical reactions of the corrosion process.