硼酸对7050铝合金硼酸-硫酸阳极氧化膜结构及耐蚀性的影响

摘要

通过AFM、交流阻抗谱及扫描Kelvin探针技术,研究硼酸对7050铝合金硼酸-硫酸阳极氧化膜结构及耐蚀性的影响.结果表明,在硼酸-硫酸阳极氧化体系中,硼酸不会改变氧化膜阻挡层的结构,但会显著影响氧化膜多孔层的结构形式,进而影响氧化膜的耐蚀性.在0～8 g/L的范围内,随着电解液中硼酸含量的增加,氧化膜的多孔层电阻增大,电容减小,表面势正移,孔径缩小,耐蚀性变好.在高于8gL时,随着硼酸含量的增加,氧化膜的孔隙变大,阻抗变小,电子逸出功降低,耐蚀性变差.%The microstructure and corrosion resistance of different boric/sulfuric acid anodic (BSAA) films on 7050 aluminum alloy were studied by atomic force microscopy (AFM),electrochemical impedance spectroscopy (EIS) and scanning Kelvin probe (SKP).The results show that boric acid does not change the structure of barrier layer of anodic film,but will significantly affect the structure of porous layer,consequently affect the corrosion resistance of anodic film.As the content of boric acid in electrolyte increases from 0 to 8 g/L,the resistance of porous layer (Rp) of BSAA film increases,the capacitance of porous layer (CPEp) decreases,the surface potential moves positively,the pore size lessens,and the corrosion resistance improves.However,the Rp,CPEp and surface potential will change towards opposite direction when the content of boric acid is over 8 g/L.