The Influence of HCO₃⁻ Concentration on the Corrosion Resistance of 6061 Aluminum Alloy in NaCl Solution

This work investigated the influence of different HCO₃⁻ concentrations (0, 0.01, 0.05, 0.1 M) on the corrosion behavior of 6061 aluminum alloy in 3.5 wt.% NaCl solution by various tests. The results show that the destructive effect of HCO₃⁻ on the corrosion resistance of 6061 alloy is mainly reflected in the H⁺ produced by HCO₃⁻ ionization. This leads to the passivation state indicated by the anode part of polarization curve evolving into an activated state, enhancing the corrosion of the alloy. In addition, as the HCO₃⁻ concentration increases, the corrosion form changes from slight pit to pitting fusion and grooving corrosion. The corrosion resistance of 6061 alloy is correlated to surface film status. Moreover, the micro-galvanic corrosion between the alloy substrate and AlFeSi phase is accelerated by HCO₃⁻, resulting in the initiation and growth of dense pits.