NdFeB表面电沉积不同厚度Al-Mn镀层的耐蚀性

Corrosion Resistance of Al-Mn Coatings with Different Thicknesses Deposited on NdFeB

为了研究不同活化表面的NdFeB上不同厚度Al-Mn镀层的耐蚀性,在经过硝酸酸洗和阳极活化前处理的Nd FeB表面,通过离子液体Al Cl3-EMIC(氯化1-乙基-3-甲基咪唑)-MnCl2电沉积得到不同厚度的非晶态AlMn镀层。利用扫描电镜(SEM)和能谱仪(EDS)考察了基体和镀层的形貌及成分;利用拉拔法测试了镀层-基体结合力;采用动电位极化曲线、静态全浸腐蚀试验和中性盐雾试验,研究了不同厚度Al-Mn镀层的耐腐蚀性能。研究表明:经过酸洗和阳极活化处理的NdFeB能够与镀层形成良好结合,结合力超过13.4 MPa; Al-Mn镀层钝化膜存在与否,使镀层对NdFeB基体表现出不同的保护行为,当钝化膜存在时,全浸试验中基体优先发生腐蚀,当钝化膜不存在时,则为镀层优先发生腐蚀; Al-Mn镀层厚度从0增加到4μm时,耐蚀性能显著提高,之后厚度的继续增加对于镀层耐蚀性的提高影响较小;经500 h的盐雾试验后,Nd Fe B基体不产生腐蚀黄锈的最小Al-Mn镀层厚度为6μm。

After being pre - treated by nitric acid pickling and anode activation, amorphous Al - Mn coatings with different thicknesses were obtained on the surface of NdFeB in AlCl3- EMIC- MnCl2 ionic liquid. The microstructure and composition of the NdFeB and coatings were characterized by scanning electron microscope （ SEM ） and energy dispersive spectroscopy （ EDS ）. The adhesion strength of the coating on NdFeB was evaluated by pull-off test. Then, the corrosion performance of Al-Mn coatings with different thicknesses was examined by potentiodynamic polarization, immersion test and neutral salt spray test, respectively. Results showed that NdFeB showed excellent adhesion with Al-Mn coating after pretreatment, with the adhesion strength over 13.4 MPa. The passivation film made Al- Mn coating exhibit different protection behaviors for NdFeB matrix. When the passivation film was present, the substrate preferentially corroded in immersion test; while when the passivation film did not exist, the coating was preferentially corroded. The corrosion resistance of Al-Mn coatings was significantly improved when the thickness was increased from 0 μm to 4 μm, while the subsequent further increase in coating thickness had less effect on corrosion resistance. After salt spray test of 500 h, the minimum thickness of Al-Mn coating was 6 μm, which ensured that no visible NdFeB rust corrosion occurred.