目的 探索锈层对碳钢腐蚀的影响过程。 方法 通过失重法、表面分析、电化学测试等方法,研究碳钢在稀 NaCl 溶液中的腐蚀行为。 结果 在稀 NaCl 溶液中,初始产物 γ-FeOOH 表现为氧化剂,易还原成 Fe₃O₄。 金属表面将迅速形成黄色薄外层( γ-FeOOH 层) +黑色厚内层( Fe₃O₄ 层) 的双层锈层。 外锈层因 γ-FeOOH 的还原反应而加速阴极过程; 内锈层起大阴极的作用, 溶解氧可以直接在其表面被还原。 结论 锈层将显著加速碳钢的腐蚀,最终腐蚀速率将由溶液中的氧极限扩散速率决定。 防腐措施应能抑制锈层的腐蚀促进作用。

Objective To investigate the influence process of rust layer on iron corrosion. Methods The corrosion behavior of carbon steel in diluted NaCl solution was studied by weight loss method, surface analysis and electrochemical techniques. Results Experimental results showed that the initial product γ-FeOOH worked as an oxidant and was easily reduced to Fe₃O₄. Hence, a double-layer rust, consisted of a thin yellow outer layer ( γ-FeOOH layer) and a thick black inner layer ( Fe₃O₄layer) , emerged rapidly on metal surface. The outer rust layer tended to facilitate the cathodic reaction via reduction of γ-FeOOH. The inner rust layer worked as a large area cathode and dissolved oxygen was directly reduced on its surface. Conclusion Therefore, the corrosion rate of carbon steel was accelerated quickly and was finally determined by the limiting diffusion rate of dissolved oxygen. Anti-corrosion measures for iron should be aimed to reduce the promotional effect of the rust layer on metal corrosion.