磷酸盐浓度对5083铝合金微弧氧化膜组织与耐腐蚀性能的影响

为研究电解液浓度对微弧氧化的影响规律,在磷酸钠电解液中采用恒压模式对5083铝合金进行微弧氧化,采用场发射扫描电镜、划痕仪以及电化学工作站等研究了电解质浓度对膜层生长速率、组织成分、膜基结合强度以及耐腐蚀性能的影响。结果表明:随着磷酸钠浓度的增大,氧化膜厚度线性增加,膜层表面的"火山堆积"状形貌特征愈发明显,但浓度过大时氧化膜出现局部不均匀堆积及较大孔洞,其对氧化膜成分影响不明显;氧化膜与基体结合良好,且随着浓度增加结合强度出现先增后减的趋势。当磷酸钠浓度为10 g/L时,氧化膜的自腐蚀电流最低,为2.96×10~(–8) A/cm~2,比铝合金基体降低了1个数量级,表现出良好的耐腐蚀性能。

Effects of Na5P3O10 Concentration on Microstructure and Corrosion Resistance of Micro-arc Oxidation Coating on 5083 Aluminum Alloy

In order to study the effects of electrolyte on micro-arc oxidation (MAO), 5083 alloy was treated by MAO in a solution containing phosphate at a constant applied voltage. The effects of phosphate concentration on thickness, microstructure and element content, bonding strength between matrix and MAO coatings, as well as corrosion resistance were investigated by field emission scan electron microscope (FESEM), scratch tester and electrochemical workshop. The results show that : the coating thickness increases linearly with increasing phosphate concentration, while "volcano deposit" characteristic is gradually significant. However, excess piles and unclosed pores are observed in the coating at phosphate concentration of beyond 20 g/L, and the element content has rather obvious difference. Additionally the bonding strength between the matrix and the MAO coatings first increases and then decreases with increasing phosphate concentration. The corrosion current density of the ceramic coating is 2.96×10^-8 A/cm², lower one order of magnitude compared with the matrix, when the phosphate concentration is 10 g/L.