Performance Evolution of Phytic Acid Conversion Film in the Forming Process

To improve conversion film techniques, control film properties and improve quality of following techniques, in this study, the environment-friendly phytic conversion films were deposited on AZ91D magnesium alloy. The performance evolution of the film during the forming process such as mechanical property, residual stress, corrosion resistance, micromorphology, composition, and roughness was investigated by nanomechanical testing system, electrochemical workstation, scanning electron microscope, Auger electron spectroscopy, and atomic force microscope. The results indicate that, in the forming process, the changes of micromorphology, roughness, mechanical property, and corrosion property are closely related to the variation of elements and residual stress. With the prolonging of film formation time, the difference between film elements and substrate elements gradually increases, and the residual stress first increases then decreases. When the film formation time is about 30 min, the film begins to crack and the residual stress is released, which leads to the decrease of mechanical property and corrosion resistance of the film.