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目的：研究无溶剂环氧煤焦沥青涂层在饱和水含量土壤中的电化学行为。方法将无溶剂环氧煤焦沥青涂层涂覆在Q235碳钢上,测试不同厚度和不同埋设时间涂层的开路电位和交流阻抗谱图,探索涂层厚度和埋设时间对涂层电化学行为的影响。利用SEM分析基体表面腐蚀产物的元素组成,探索侵蚀性物质是否到达基体表面参与腐蚀历程。结果涂覆200μm厚涂层的Q235碳钢的稳定开路电位约为-0.37 V,与裸Q235钢相比,自腐蚀电位正移了0.28 V。随着涂层厚度的增加,开路电位呈上升趋势,容抗弧半径增大,涂层对侵蚀性溶液的屏蔽阻挡能力提高。随着在土壤中埋设时间的延长,容抗弧半径减小,吸水率增大,涂层的防护性能有所下降,但低频阻抗模值仍高达8.8×107Ω·cm2。能谱分析显示,Q235碳钢表面未出现Cl-等侵蚀性物质。结论无溶剂环氧煤焦沥青涂层在土壤环境中是有效的屏蔽层,可对Q235碳钢基体起到有效的防护作用。

ABSTRACT:Objective The electrochemical behavior of the solvent-free epoxy coal tar coating was investigated in the soil solution of saturated water content. Methods The solvent-free epoxy coal tar coating was applied on Q235 steel, the open circuit potential and electrochemical impedance spectroscopy of the coatings at different thicknesses and different buried time were tested, and the effects of coating thickness and buried time on the electrochemical behavior of the coating were explored. SEM analysis of the ele-mental composition of corrosion products on the substrate surface were used to explore whether the aggressive substances reached the substrate surface and was involved in the corrosion. Results The stable open circuit potential of Q235 steel with a coating thick-ness of 200μm was about-0. 37 V, and the corrosion potential shifted positively by about 0. 28 V as compared to that of the Q235 bare steel. With the increase of coating thickness, the open circuit potential showed a rising tendency, the capacitance arc radius
increased, and the shielded blocking ability of the coating in aggressive solutions was improved. The protective performance of the coating declined, the capacitance arc radius reduced and water absorption increased with the prolonging buried time in soil, but the low-frequency impedance modulus value still reached up to 8. 8×107 Ω·cm2. The energy spectrum analysis showed that no corro-sive substances such as Cl-appeared on the surface of Q235 steel. Conclusion The solvent-free coal tar epoxy coating in soil solu-tion could effectively form a shielding layer and provided an effective protection for Q235 carbon steel.