摘要
仅以单宁酸作为成膜剂,使用化学转化法在AZ91D镁合金表面制备环境友好转化膜,以提升耐蚀性。采用对比实验筛选合适的酸调节转化液pH值;利用响应面(Box-Behnken)法对转化工艺中的pH值、反应温度、转化时间进行优化,得到最佳工艺条件,并探讨了pH值对转化膜性能的影响。使用CuSO_(4)点滴实验、动电位极化曲线和电化学阻抗谱评价膜层耐蚀性;利用SEM、EDS对AZ91D镁合金表面形貌及元素组成进行表征。结果表明,单宁酸转化膜的最佳工艺为单宁酸10 g/L、pH值2.7(盐酸调节)、反应温度41℃、转化时间15 min,所得转化膜具有良好的耐蚀性,膜层均匀致密,且覆盖完整,主要由单宁酸的水解产物和与Mg2+生成的螯合物组成。响应面法实验结果显示,pH值对转化膜耐蚀性的影响较大:pH值过低,膜层粗糙,致密性较差;pH值过高,膜层较薄,缺乏连续性,无法完整覆盖镁合金表面。
An environmentally friendly conversion coating is prepared on AZ91D magnesium alloy surface by chemical conversion method using tannic acid as the coating forming agent to improve corrosion resistance.The acid regulating the pH value of the conversion solution is selected by contrast experiment.The pH value,reaction temperature,and conversion time are optimized by the Box-Behnken test,and the optimum process conditions are obtained.The effect of pH value on the corrosion resistance of the conversion coating is also discussed.CuSO_(4) pitting time and electrochemical experiments are used to judge the corrosion resistance,SEM and EDS are used to characterize the coating surface morphology and element composition of AZ91D magnesium alloy.The results show that the optimum process of tannic acid conversion coating is as follows:tannic acid content 10 g/L,pH value 2.7(hydrochloric acid regulation),reaction temperature 41℃,conversion time 15 min.The conversion coating has good corrosion resistance,uniform density,and the covering is complete.The coating is mainly composed of tannic acid hydrolysate and Mg2+chelate.Box-Behnken test result shows that the pH value has a great influence on the corrosion resistance of the conversion coating.When the pH value is too low,the coating is rough and poorly compacted;while when the pH value is too high,the coating is thin and lacks continuity,which cannot completely cover the surface of the magnesium alloy.
作者
张书弟
许宇恒
何欢欢
刘琳坤
雷全达
ZHANG Shudi;XU Yuheng;HE Huanhuan;LIU Linkun;LEI Quanda(School of Environmental and Chemical Engineering,Shenyang Ligong University,Shenyang 110159,China)
出处
《材料工程》
北大核心
2025年第10期115-123,共9页
Journal of Materials Engineering
基金
国家自然科学基金项目(51771050)。
关键词
镁合金
单宁酸
转化膜
工艺条件
响应面法
magnesium alloy
tannic acid
conversion coating
process condition
Box-Behnken
