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 citrate-phosphate 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.

摘要

除了使用pH值为4的醋酸盐，柠檬酸盐和柠檬酸盐-磷酸盐缓冲液之外，还研究了化学性质（除了缓冲液的pH值以外）对低碳钢（MS）和7004铝合金（AA）的电化学腐蚀行为的影响。在Pt上显示出其阳极和阴极动力学的边际至微不足道的变化，这些缓冲液中MS和AA的阴极电流密度按柠檬酸盐<柠檬酸盐-磷酸盐<乙酸盐的顺序增加。至于阳极电流密度，其增加顺序为：对于MS，乙酸盐<柠檬酸盐<柠檬酸盐磷酸盐，对于AA来说，柠檬酸盐<乙酸盐<柠檬酸盐磷酸盐。基于弱酸的直接还原以及金属离子与缓冲剂物种的络合行为解释了这种变化。