6063铝合金中性无铬转化膜制备及膜层性能分析  

Preparation and Performance Analysis of Neutral Chromium-free Conversion Coating on 6063 Aluminum Alloy

作　　者：穆松林[1] 郭加林 欧云才 杜军[1] 樊雨欣 MU Songlin;GUO Jialin;OU Yuncai;DU Jun;FAN Yuxin(School of Materials Science and Engineering,South China University of Technology,Guangzhou 510640,China;Guangdong Huachang Group Co.,Ltd.,Guangdong Foshan 528225,China)

机构地区：[1]华南理工大学材料科学与工程学院,广州510640 [2]广东华昌集团有限公司,广东佛山528225

出　　处：《表面技术》2024年第9期65-74,共10页Surface Technology

基　　金：广东省基础与应用基础研究基金项目(2020A1515010006)。

摘　　要：目的提高铝合金微小器件的耐蚀性,开发一种条件温和可控的转化膜成膜工艺。方法采用中性无铬转化工艺,在6063铝合金表面制备转化膜。通过研究NaF、NH_(4)HF_(2)、KMnO_(4)、十二烷基硫酸钠(SDS)和没食子酸等几种添加剂对转化膜外观与耐蚀性的影响,确定NH_(4)HF_(2)为最佳添加剂。采用电化学方法分析膜层的耐蚀性,用SEM和EDS分析表面形貌及元素组成,并采用XRD和XPS表征膜层晶态结构和化合物组成。基于检测结果,简要分析转化膜的成膜过程。结果最终得到了中性转化处理的最佳成膜工艺为EDTA-2Na8.0g/L,单宁酸1.0g/L,Na_(2)WO_(4)6.0g/L,H_(2)ZrF_(6)4.0g/L,NH_(4)HF_(2)3.0g/L,pH6.6,成膜温度为30℃,成膜时间为15 min。该工艺所制备的转化膜外观致密均匀,颜色为浅黄色。电化学测试结果表明,转化膜具有良好耐蚀性,自腐蚀电流密度由基体铝合金的16.22µA/cm^(2)下降为转化处理后的0.87µA/cm^(2)。EDS能谱分析结果表明,膜层主要由Al、C、F、O、Na、Zr和W元素组成。XRD结果显示,膜层中含有Na_(3)AlF_(6)晶体。XPS分析结果表明,膜层中还含有Al_(2)O_(3)、AlF_(3)、WO_(3)、ZrF_(4)以及金属有机络合物。结论采用中性转化处理工艺,可以在6063铝合金表面制备有色均匀、耐蚀性良好的转化膜,膜层主要由Al的难溶化合物组成。To improve the corrosion resistance of aluminum alloy micro devices,the work aims to develop a mild and controllable preparation process of conversion coating.The neutral chromium-free conversion treatment was used to prepare a conversion coating on the surface of 6063 aluminum alloy.By studying the effects of several additives such as NaF,NH_(4)HF_(2),KMnO_(4),sodium dodecyl sulfate(SDS),and gallic acid on the appearance and corrosion resistance of the conversion coating,NH_(4)HF_(2) was determined as the optimal additive.The electrochemical methods were utilized to analyze the corrosion resistance of the coating,SEM and EDS were applied to analyze the surface morphology and elemental composition,and XRD and XPS were used to characterize the crystalline structure and compound composition of the coating.The optimal coating-forming process for the neutral conversion treatment was obtained as:EDTA-2Na 8.0 g/L,tannic acid 1.0 g/L,Na_(2)WO_(4)6.0 g/L,H_(2)ZrF_(6)4.0 g/L,NH_(4)HF_(2)3.0 g/L,pH 6.6 and treatment at 30℃for 15 minutes.The conversion coating prepared by the process owned the dense and uniform appearance in light yellow.The electrochemical test results showed that the conversion coating had good corrosion resistance,and the self-corrosion current density decreased from 16.22µA/cm^(2) of the bare aluminum alloy to 0.87µA/cm^(2) after conversion treatment.EDS spectroscopy analysis indicated that the coating was mainly composed of Al,C,F,O,and Na elements.The XRD results illustrated that the conversion coating contained Na_(3)AlF_(6) compound crystals.The XPS analysis exhibited that the coating also contained Al_(2)O_(3),AlF_(3),and organic complexes.The formation of the conversion coating might be triggered by the dissolution of aluminum element in the conversion solution.Due to the presence of Fe and Cu elements in 6063 aluminum alloy,the difference of standard electrode potential between these metallic elements and Al,enabled them to form corrosive micro batteries in electrolyte solution.Therefore,Al e

关 键 词：铝合金 中性 无铬转化膜 性能分析 耐蚀性 成膜过程 

分 类 号：TG174.4[金属学及工艺—金属表面处理]