镁合金表面植酸转化膜研究Ⅱ.pH值对镁合金植酸转化膜的影响

通过SEM观察、AES元素深度分析、成膜增重实验、动电位极化曲线和EIS电化学测试，研究了植酸处理液的pH值对AZ91D镁合金转化膜生长速度及耐蚀性的影响.结果表明：溶液在pH=8时，转化膜生长速度最快，膜层较厚，且完整，无碎裂；pH=12时，转化膜生长速度较慢，膜层较薄；pH=5时，转化膜生长速度最慢，有碎裂.当植酸溶液的pH值在5～12时，镁合金表面形成的转化膜均可提高其耐蚀性，且pH=8时形成的膜耐蚀性最好.

STUDY ON PHYTIC ACID CONVERSION COATINGS FOR MAGNESIUM ALLOY Ⅱ. Influence of pH on Phytic Acid Conversion Coating on Magnesium Alloy

The influence of pH on the microstructure and corrosion resistance of phytic acid conversion coatings on AZ91D alloy was investigated by SEM ,AES ,potentiodynamic polarization curves and EIS. Resuits show that the microstructure of the phytic acid conversion coating formed at pH 8 is integrated, uniform and no fragmentized. The coating gained at pH 5 is fragmentized for its high dissolution rate and that at pH 12 is thin for its low deposition rate. The coatings deposited at pH of 5 - 12 can all improve the corrosion resistance of magnesium alloy, and among which the one formed at pH of 8 has the best corrosion resistance.