摘要
目的改善钒酸盐转化膜表面形貌,提高单一钒酸盐转化膜的耐蚀性能。方法使用偏钒酸盐和硅烷通过两步法在镁合金表面制备钒/硅烷复合转化膜,比较不同硅烷制备的复合膜的耐蚀性能,从而确定使用硅烷的种类,采用扫描电子显微镜(SEM)、X射线能谱(EDS)、X射线光电子能谱(XPS)和傅里叶红外光谱(FT-IR)观察转化膜的微观形貌并分析转化膜的组成和结构,通过交流阻抗测试(EIS)、Tafel极化曲线测试和全浸腐蚀实验评价转化膜的耐蚀性能,并采用划格实验和接触角测试评价转化膜的结合力和疏水性。结果确定使用BTEPST(双-[3-(三乙氧基硅)丙基]-四硫化物)作为成膜组分,使用偏钒酸钠和BTESPT在镁合金表面成功制备钒/BTESPT复合膜,复合膜表面均匀平整,致密无裂纹,与基体结合力好,具有疏水性,该复合膜的组成元素为Mg、V、C、O、Si和S,且元素分布较均匀,膜层是包含Si—O—S、Si—O—Mg、Si—O—V等共价键的交联结构。交流阻抗测试结果显示,钒/BTESPT复合转化膜的膜层电阻为1.17×10^(5)Ω·cm^(2),电荷转移电阻为1.076×10^(5)Ω·cm^(2)。极化曲线测试结果表明,复合膜的腐蚀电位为-1.4570V,腐蚀电流密度为1.4980×10^(-7)A·cm^(-2),腐蚀电流密度相较于基体降低约2个数量级,对镁合金的保护效率达到99.6%。复合转化膜在3.5%(质量分数)NaCl溶液中长期浸泡10d未发生明显腐蚀,全浸实验浸泡14d腐蚀速率为0.0580 g/(m^(2)·h),未处理的镁合金腐蚀速率则为0.5186 g/(m^(2)·h)。结论钒/BTESPT复合膜能进一步提高钒酸盐转化膜对AZ31B镁合金的保护性能。
A single vanadate conversion coating can improve the corrosion resistance of magnesium alloy,but there are cracks and holes on the surface of vanadate conversion coating.In order to improve the surface morphology and corrosion resistance of vanadate conversion coating,the work aims to use vanadate and silane to prepare vanadate/silane composite conversion coating on the AZ31B magnesium alloy by two-step method.Firstly,the AZ31B magnesium alloy was used as the substrate,the AZ31B magnesium alloy after processing and pretreatment was immersed in conversion solution(2 g/L NaVO3,pH 2.5)at 30℃for 15 min to obtain vanadate conversion coating(VCC),and then the vanadate/silane composite conversion coating was obtained by secondary coating formation treatment in silane conversion solution.Finally,the sample was dried and solidified in the oven,and taken out for testing.The corrosion resistance of the vanadate/silane composite coatings prepared by BTESPT(bis-[3-(triethoxysilyl)propyl]-tetrasulfide)and KH550 was compared,so as to determine the type of silane used.The morphology of conversion coating was observed by scanning electron microscopy(SEM).X-ray energy dispersive spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS)and Fourier transform infrared spectroscopy(FT-IR)were used to analyze the composition and structure of the conversion coating.The corrosion resistance of the conversion coating was evaluated by electrochemical impedance spectroscopy(EIS),potentiodynamic polarization curve(Tafel)and full immersion corrosion weight loss method.Adhesion force between the conversion coating and the AZ31B magnesium alloy was studied through cross cut test.The hydrophobicity of the conversion coating was measured by performing contact angle test.According to the EIS experimental results,the corrosion resistance of vanadium/BTESPT composite coating was obviously better than that of vanadium/KH550 composite coating,so the vanadium/BTESPT(V/BTESPT)composite conversion coating was prepared on the surface of AZ31B magnesium al
作者
董丽惠
王华
李琳
DONG Lihui;WANG Hua;LI Lin(School of Chemical Engineering,Dalian University of Technology,Liaoning Dalian 116024,China)
出处
《表面技术》
EI
CAS
CSCD
北大核心
2024年第4期34-45,共12页
Surface Technology
基金
国家自然科学基金(21978034)。
关键词
镁合金
表面处理
化学转化膜
钒酸盐
硅烷
耐蚀性
magnesium alloy
surface treatment
chemical conversion coating
vanadate
silane
corrosion resistance
