Optimization of the preparing process for the phytic acid based conversion coating on AZ91D magnesium alloy by orthogonal experiment
CHEN Dongchu 1,2,WU Jianfeng1,GONG Weihui2,LI Wenfang2,XU Dongming1 (1.Foshan University,Foshan 528000,China;2.South China University of Technology,Guangzhou 510640,China)
In order to prepare a conversion coating on AZ91D magnesium alloy with phytic acid, the process parameter was optimized through an orthogonal experiment. The coating corrosion resistance was studied with the electrochemistry technology of polarization curve and E-t curve, and the coating micro-morphology was observed with metalloscope. To the corrosion resistance, the most important factor in orthogonal experiment is the immersing time period, and the second is solution temperature, as well as the third and the fourth are solution concentration and solution pH value. The result shows that the phytic acid treated conversion coating has good corrosion resistance, whose corrosion current density is smaller than that treated in chromate solution, so phytic acid surface treatment technology is a promising alternative to the harmful chromate treatment.