Effect of buffer chemistries on the electrochemical corrosion behaviour of three metallic materials

Abstract

The influence of chemistry apart from the pH of buffers on the electrochemical corrosion behaviours of mild steel (MS) and 7004 aluminium alloy (AA) was studied using acetate, citrate, and citratephosphate buffers having an identical pH of 4. While the buffers showed marginal to insignificant variations in their anodic and cathodic kinetics on Pt, the cathodic current density for MS and AA in these buffers increased in the order citrate < citrate-phosphate < acetate. As for the anodic current density, it increased in the order: acetate < citrate < citrate-phosphate for MS and citrate < acetate < citrate-phosphate for AA. Such variations were explained based on the direct reduction of the weak acids and the complexing behaviour of the metal ions with the buffer species. The study suggests the importance of considering buffer chemistries while studying the influence of pH on electrochemical corrosion including localized corrosion behaviour of metals.