浸泡时间对两种涂层电化学腐蚀行为的影响

目的研究浸泡时间对两种涂层电化学腐蚀行为的影响。方法在质量分数为3.5%的Na Cl溶液中通入饱和CO_2气体,采用电化学方法、SEM形貌检测方法测量两种涂层在该溶液中不同浸泡时间下的动电位扫描极化曲线和表面形貌,对比分析两种涂层的电化学特征和防蚀性能。结果随着涂层浸泡时间的延长,自腐蚀电位E_(corr)逐渐降低,而电流密度逐渐增大;在浸泡时间相同的情况下,涂层A的自腐蚀电位E_(corr)比涂层B高,而电流密度比涂层B低,说明涂层A的耐蚀性能明显优于涂层B。结论涂层短时间浸泡(≤72 h)时,电化学阻抗谱为吸氧过程的单容抗弧,长时间浸泡(≥120 h)时则为析氢过程的2个容抗弧,其耐蚀性下降。

Effect of Soaking Time on Electrochemical Corrosion Behavior of Two Kinds of Coatings

Objective To analyze the effect of soaking time on electrochemical corrosion behavior of two kinds of coatings. Methods The electrochemical method and SEM were used to obtain the polarization curves and surface morphologies of the two coatings in 3.5% NaCl solution with the saturation of CO2 gas during the test at different soaking time. Results The results showed that the corrosion potential Ecorr of the same kind of coating decreased and its current density increased with the soaking time under the same condition. The corrosion potential Ecorr of coating A was higher than that of the coating B and the current density was lower than that of the coating B with the same soaking time, which showed that the corrosion resistance of the coating A was significantly superior to that of the coating B. Conclusion When the soaking time of the coating was short (≤72 h), there was a single capacitive arc with absorbing oxygen process in EIS, but when the soaking time was long (≥120 h), there were two capacitive arcs with hydrogen evolution process in EIS, which showed that the corrosion resistance of the coating decreased in the latter case.