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Author(s): |
Huan-fang Gao, College of Chemistry and Chemical Engineering, Chongqing University of technology, Chongqing, China
Shengtao Zhang, College of Chemistry and Chemical Engineering, Chongqing University, Chongqing, China
Cheng-long Liu, College of Materials and Engineering, Chongqing University of technology, Chongqing, China
Jun-qiang Xu, College of Chemistry and Chemical Engineering, Chongqing University of technology, Chongqing, China
Jun Li, College of Chemistry and Chemical Engineering, Chongqing University of technology, Chongqing, China
Yu Li, College of Chemistry and Chemical Engineering, Chongqing University of technology, Chongqing, China |
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Abstract: |
The influences of pH on the formation process, corrosion resistance and microstructure, chemical state of the phytic acid conversion coatings on AZ31B magnesium alloy were investigated by electrochemical measurements, hydrogen evolution method, scanning electron microscopy (SEM) and the energy dispersive X-ray spectroscopy (EDS), respectively. The results show that the reaction rate of magnesium alloy with phytic acid was fastest under pH=1, followed by pH=2 and pH=6 during the formation process of the conversion coatings. The coating surface formed under pH=1 was fragmentized and had some big cracks. Some cracks were also on the surface of the coating formed under pH=2 and the cracks were small and uniform. The sample was entirely covered under pH=6 and the conversion coating was thin. The conversion coating mainly consisted of the compounds of magnesium, aluminum, zinc, oxygen and phosphorus. The conversion coating formed under pH=2 had higher corrosion resistance than that of the conversion coatings formed under pH=1 and 6 and the treated samples with phytic acid has better corrosion resistance than untreated sample.
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