Corrosion behavior of AA5052 aluminum alloy in the presence of heavy metal ions in 3.5 % NaCl solution under negative pressure

Abstract

Aluminum alloy heat exchange tube is attractive for the Low Temperature-Multi Effect Distillation (LT-MED) desalination device, for its low cost and excellent mechanical property. However, it is prone to galvanic coupling corrosion in presence of heavy metal ions. In this paper, the effect of Cu2+ and Fe3+ ions on the corrosion of aluminum alloy in 3.5 wt% NaCl solution under negative pressure is investigated by the weight-loss method and the electrochemical measurements. It shows that the operation pressure affects significantly the corrosion behavior of AA5052 aluminum alloy in presence of heavy metal ions. As the pressure decreases, the resistance of the aluminum alloy to corrosion increases markedly. The corrosion products formed under different operation pressure are detected by SEM, XRD analysis. It is found that the diffusion process of corrosion products from the aluminum alloy surface into the solution is prevented as the decrease of pressure, resulting in the formation of the passivation layer on the aluminum alloy surface. The decrease of pressure can effectively restrain the heavy metal ions to be adsorbed on the defects of the oxide layer and mitigate the corrosion of aluminum during the LT-MED desalination process.