Research on Comparative Marine Atmospheric Corrosion Behavior of AZ31 Magnesium Alloy in South China Sea

In this study, the atmospheric corrosion behavior of AZ31 magnesium alloy exposed in Sanya and Nansha for one year was investigated. While existing studies have characterized marine corrosion of magnesium alloys, the synergistic corrosion mechanisms under extreme tropical marine conditions (simultaneous high Cl^-, rainfall, and temperature fluctuations) remain poorly understood-particularly regarding dynamic corrosion-product evolution. The corrosion characteristics and behavior of AZ31 magnesium alloy exposed in Sanya and Nansha were evaluated using X-ray photoelectron spectroscopy, X-ray diffraction, electrochemical measurements, scanning electron microscopy, and weight loss tests. The results showed that the main components of corrosion products were MgCO₃·xH₂O(x = 3, 5), Mg₅(CO₃)₄(OH)₂·4H₂O, Mg₂Cl(OH)₃·4H₂O, and Mg(OH)₂. The corrosion rate exposed in the Nansha was 26.5 μm·y^-1, which was almost two times than that in Sanya. Localized corrosion is the typical corrosion characteristic of AZ31 magnesium alloy in this tropical marine atmosphere. This study exposes the dynamic crack-regeneration mechanism of corrosion products under high-Cl^--rainfall synergy. The corrosion types of AZ31 magnesium alloy in this tropical marine atmosphere were mainly represented by pitting corrosion and filamentous corrosion.