Study On The Corrosion Resistance Of Phytic Acid Conversion Layer On AZ31B Magnesium Alloy

Magnesium alloys have a number of desirable features, including low density, high strength-to-weight ratio, excellent casting capability, good mechanism and damping characteristics, and they are now increasingly used in aerospace industry, automobile industry, mechanical engineering, commodities and portable communication equipment. However, poor corrosion resistance has often prevented them from further exploitation. Due to some problems existed in the traditional treatment; scholars have paid much attention to the methods of green treatments for magnesium alloys. Such as Phytic acid, but it is rarely reported about the application in magnesium. In this paper, phytic acid was used as chemical conversion treatment solution, the performance and forming mechanism of the conversion layer would be discussed.During the study of phytic acid conversion processing treatment, influencing factors of phytic acid processing treatment were predicted. (The concentration of phytic acid, pH value of treatment solution, the processing time span and temperature, drying). Orthogonal test was used to determine the primary and secondary subsequence of influencing factors. The morphology and the composition of the treated specimens were analyzed by using PHilips-XL30 scanning electron microscopy (SEM) equipment with the EDS. And the thickness of the film has been studied by SEM and optical microscope. The results show that the thickness is about 15～20um, and the composition of the layer are mainly Mg, Al, and P. Besides, the organic elements such as C and 0 maybe also existed. The best quality of the conversion layer have gotten in the treatment solution containing 0.7 wt.% phytic acid at 60℃ under pH=2 for 60min.The test results of corrosion resistance of chemical conversion film by using the immersion test and CH1660B type electrochemistry workstation show that phytic acid conversion film could strengthen the capability of the corrosion resistance of magnesium alloys. An analytical and reasonable explanation to the formation and anti-corrosion mechanisms of phytic chemical conversion film for AZ31B magnesium alloy is put forward accordingly.This paper not only has studied the formation mechanisms of phytic acid...