P7412陶瓷涂层的制备与腐蚀机理的研究

利用等离子喷涂技术制备NiCr作为粘接层的P7412陶瓷涂层。采用失重法研究了P7412涂层在3.5%NaCl溶液中的腐蚀速率。采用SEM观察涂层腐蚀前后的表面形貌,并用动电位极化曲线和电化学阻抗谱(EIS)技术研究涂层腐蚀过程中的电化学特征。根据陶瓷涂层的特殊结构,建立等效电路图并进行拟合分析,同时结合涂层的失重曲线研究涂层的腐蚀机理。失重曲线显示陶瓷涂层质量在3.5%NaCl溶液中出现周期性增减变化。电化学研究结果表明,基体表面腐蚀钝化膜以及腐蚀产物等都会影响涂层失重。氧化膜的生长与溶解以及腐蚀二次产物的积累共同导致了涂层质量出现增减交替的变化。

Preparation of P7412 Ceramic Coatings and Study of Its Corrosion Mechanism

P7412 ceramic coatings with a NiCr bonding layer were prepared by air plasma spraying(APS).The weight loss method was used to measure the corrosion rate of P7412 ceramic coatings in 3.5% NaCl solution.The surface morphologies of the coatings in corroded and original condition were studied comparatively by scanning electron microscope(SEM).The electrochemical characteristics of P7412 ceramic coatings were analyzed by electrochemical impedance spectroscopy(EIS) and the potentiodynamic polarization curves were used to research the coating corrosion mechanism.According to the special structure of the coatings,equivalent circuit was set up for fitting analysis.The corrosion mechanism of P7412 ceramic coatings were studied based on the weight loss curve and the electrochemical characteristics of the coatings.The weight loss curve showed the weight of coatings occurred periodical loss and growth in 3.5% NaCl solution.Electrochemical study results show that many factors such as the passive film of substrate,corrosion products and so on affected the weight of the coatings.The dissolution of oxide film and the accumulation of secondary corrosion products are the reasons of the alternate changes of the coatings weight.