Al-Ti-Si-RE涂层在模拟深海压力下的耐蚀机理

通过电化学测试技术与微观分析等手段研究了高速电弧喷涂Al-Ti-Si-RE涂层在模拟深海压力下的耐蚀机理。结果表明:Al-Ti-Si-RE涂层在静水压力条件下具有良好的耐蚀性能。电化学分析表明,在3 MPa浸泡480 h后动电位极化曲线阳极区上出现了1个类似钝化区间的"平台",主要是由于腐蚀产物阻塞腐蚀通道的原因;电化学阻抗谱(EIS)分析则表明,在高压下涂层Al钝化膜在浸泡6 h左右后已溶解,12 h后逐步趋于稳定,300~480 h区间几乎无变化;电化学噪声(EN)测试对比了涂层在常压和高压条件下0~64 ks的腐蚀情况,定量描述了涂层"钝化膜溶解-腐蚀产物快速形成-进入稳定阶段"的腐蚀过程。最后通过微观形貌观察和XRD等测试手段分析,Al-Ti-Si-RE涂层中的富Ti相(主要成分为TiAl、TiAl3等金属间化合物)具有良好的耐蚀特性,且呈现为多孔结构,Al在高压下快速腐蚀溶解填充富Ti相"骨架"孔隙,形成的涂层表面致密,其结构能够有效阻塞腐蚀通道,抑制腐蚀进行。

Anti-corrosion Mechanism of Al-Ti-Si-RE Coating in the Pressure Environment of Simulated Deep Sea

In this paper, the anticorrosion mechanism of Al-Ti-Si-RE coating in the environment of simulated deep sea was investigated using electrochemical measurement and micro-analysis. The result showed that Al-Ti-Si-RE coating performed better corrosion resistance at hydrostatic pressure than that at atmospheric pressure. After 480 h of immersion at 3 MPa, the anode of potentiodynamic polarization curve represented a linear because corrosion products blocked the corrosion channels. At the same time, at hydrostatic pressure, electrochemical impedance spectroscopy (EIS) indicated that Al passive film dissolved in the 6 h of immersion, then the coating tended to be stable, was hardly changed between 300 h and 480 h. To further analyze the original corrosion process, electrochemical noise (EN) of 0~64 ks at 0.1 MPa and 3 MPa was measured, which quantificationally represented the corrosion process from passive film dissolving to corrosion product fast-forming to stabilization. From morphology observation and X-Ray diffraction (XRD) analysis, the rich Ti phase (Ti-Al intermetallics etc.) of the coating with good corrosion resistance was cellular, whose construction could fix the Al oxide inside the coating, and made the coating thick in order to inhibit the corrosion.