7075铝合金表面钼/钛/钒复合转化膜的制备与性能表征

Preparation and performance characterization of Mo/Ti/V composite coating on 7075 aluminum alloy

采用钼酸盐和钛酸盐为主盐,以偏钒酸钠为成膜促进剂,植酸钠为有机添加剂,在7075铝合金表面制备了钼/钛/钒复合转化膜。借助扫描电子显微镜(SEM)、能谱仪(EDS)和X射线光电子能谱仪(XPS)分析了膜层的微观形貌、元素组成和化学成分,采用电化学工作站考察了基体和膜层的耐蚀性。实验结果表明:最佳转化液配方为2 g·L^(-1)植酸钠、1.5 g·L^(-1)偏钒酸钠、1.5 g·L^(-1)六氟钛酸及25 g·L^(-1)钼酸铵,最佳成膜条件为15 min和35℃。膜层主要成分为Al_(2)O_(3)、MoO_(2)、MoO_(3)、V_(2)O_(5)和TiO_(2)。钼/钛/钒复合转化膜使7075铝合金的腐蚀电位正移了206.401 mV,腐蚀电流密度降低了9.912μA·cm^(-2),有效提高了基体的耐蚀性。

Molybdenum/titanium/vanadium composite conversion coatings were prepared on the surface of 7075 aluminum alloy using molybdate and titanate as the main salts,sodium metavanadate as the film-forming promoter and sodium phytate as the organic additive.The microscopic morphology,elemental composition and chemical composition of the film layer were analysed with the aid of scanning electron microscope(SEM),energy spectrometer(EDS)and X-ray photoelectron spectroscopy(XPS),and the corrosion resistance of the substrate and the film layer were investigated using an electrochemical workstation.The experimental results showed that the optimum formulation of conversion solution was 2 g·L^(-1)sodium phytate solution,1.5 g·L^(-1)sodium metavanadate solution,1.5 g·L^(-1)hexafluoro titanate solution and 25 g·L^(-1)ammonium molybdate solution,and the optimum film formation conditions were 15 minutes and 35℃.The main components of the coating were Al_(2)O_(3),MoO_(2),MoO_(3),V_(2)O_(5) and TiO_(2).Mo/Ti/V conversion coating positively shifted the corrosion potential of the 7075 aluminum alloy by 260.401 mV and reduced the self-corrosion current density by 9.912μA·cm^(-2),which effectively improved the corrosion resistance of the substrate.