铝合金表面等离子体电解氧化陶瓷涂层在NaCl溶液中的电化学阻抗谱研究

Electrochemical Impedance Spectroscopy of PEO Coating on Aluminum Alloy in NaCl Solution

通过调整电解液中硅酸钠的浓度。利用等离子体电解氧化(PEO)技术在铝合金LY12表面制备了各种陶瓷涂层,利用光学显微镜、XRD、电化学阻抗谱(EIS)对涂层的形貌、成分和涂层在NaCl溶液中耐腐蚀性能进行了研究.结果表明:提高电解液中硅酸钠的浓度可以使得涂层的总厚度增加,但过高或过低的浓度都会导致致密层厚度的减薄.当浓度为20g/L时,所制备的涂层的成分以氧化铝为主;当浓度为40g/L时,涂层的成分主要是莫来石和氧化铝;当浓度超过60g/L时,涂层的成分主要为非晶相.EIS的研究表明,涂层耐腐蚀性取决于涂层中的致密层,增加致密层的厚度可以提高PEO涂层的耐腐蚀性,在中性、酸性、碱性腐蚀介质中,PEO涂层都显示出对基体良好的保护作用.

Various Plasma Electrolytic Oxidation （PEO） ceramic coatings were prepared on LY12 aluminum alloy by adjusting the concentration of sodium silicate solution. Optical microscope （OM）, XRD and EIS were used to study their morphology, composition and anti corrosion behavior in NaCl solution. Increasing concentration of sodium silicate leads to the increase of the total coating thickness while too high and too low concentration lead to the decrease of inner dense layer. The main composition of PEO coatings prepared in 20, 40 and above 60g/L concentration solution are correspondingly alumina, alumina with mullite, and amorphous phase. The corrosion resistance is determined by the inner dense layer. Increasing the thickness of inner dense layer can improve the anti-corrosion performance. PEO coating＇s corrosion resistance in acidic, alkaline and neutral NaCl solution is proved and the corrosion mechanism involved is also discussed.