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采用电化学技术结合XRD分析,研究了A3碳钢在海水中的阴极电化学行为,探讨了锈层在阴极过程中的作用。碳钢表面生成的锈层由内锈层和外锈层组成,内锈层主要组成相为γ-FeOOH,α-FeOOH,β-FeOOH以及Fe_3O_4与γ-Fe_2O_3的混合物。浸泡126 d时,外锈层主要由γ-FeOOH组成;浸泡364 d由γ-FeOOH,α-FeOOH,Fe_3O_4和γ-Fe_2O_3组成。不同锈层在阴极过程中所起的作用不同。外锈层主要作用是阻碍溶解氧到达金属表面,内锈层除此之外还可以参与还原反应,加速阴极反应。提出了一个评价锈层参与还原反应程度的参数α,在浸泡不同时期锈层参与还原反应的比例不同,浸泡前7d,α值上升比较明显,随后增加比较缓慢,浸泡168 d后基本稳定。探讨了内、外锈层组分的变化以及锈层各组分间的相互作用。
The electrochemical behavior of A3 carbon steel in seawater was studied by electrochemical technique combined with XRD analysis. The effect of rust layer on cathodic process was also discussed. The rust layer formed on the surface of carbon steel is composed of inner rust layer and outer rust layer. The main components of the inner rust layer are γ-FeOOH, α-FeOOH, β-FeOOH and mixtures of Fe 3 O 4 and γ-Fe 2 O 3. After soaking for 126 d, the outer rust layer mainly consisted of γ-FeOOH. The soaked 364 d was composed of γ-FeOOH, α-FeOOH, Fe 3 O 4 and γ-Fe 2 O 3. Different rust layers play different roles in the cathode process. The main function of the outer rust layer is to prevent the dissolved oxygen from reaching the metal surface. In addition, the inner rust layer can also participate in the reduction reaction and accelerate the cathode reaction. A parameter α was proposed to evaluate the degree of rust participation in the reduction reaction. The proportions of the rust layer participating in the reduction reaction were different at different stages of soaking. The value of α increased more obviously at 7 d before soaking, then increased slowly and remained stable after 168 d. The changes of the inner and outer rust layers and the interaction between the components of the rust layer were discussed.