Corrosion Resistance Mechanism of Silane Zirconium Salt Phytic Acid Composite Conversion Coating on Steel Surface

Corrosion Resistance Mechanism of Silane Zirconium Salt Phytic Acid Composite Conversion Coating on Steel Surface

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In order to improve the corrosion resistance of 40Cr steel surface,bis-[7-(triethoxy silicon)propyl]-tetrasulfide(BTESPT),zirconium nitrate and phytic acid were used to prepare silane zirconium salt composite conversion coating with excellent corrosion resistance on the surface operation igloo white of 40Cr steel.The film forming process conditions of silane zirconium salt composite conversion solution were determined by orthogonal tests.The corrosion resistance,morphology,composition and potential characteristics of the composite coating were analyzed by copper sulfate titration,scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR)and electrochemical tests.Results showed that the optimum process of silane zirconium salt composite coating was as follows:silane concentration was 5(volume fraction),zirconium nitrate concentration was 0.

75%(mass fraction),pH value of solution was 4,hydrolysis temperature was 25 C,and reaction time was 50 s.Through the results of copper sulfate iphone 14 price texas drop test and electrochemical test,it was found that the corrosion resistance of the composite convesion coating doped with phytic acid was significantly improved compared with that of the silane coating and the silane zirconium salt coating.Through the observation of micro morphology,it was indicated that the addition of phytic acid made up for the defects of the coating,hindered the diffusion of corrosive medium,therefore,enhancing the corrosion resistance of the coating.