Effect of Sodium Tungstate on the Microstructure and Properties of Micro-Arc Oxidized Coatings Formed on 2A12 Aluminum Alloy

• DOI: 10.1007/s11665-021-05967-y
• Publication Date: 2021-06-21T15:03:21Z
• Authors: Huanyuan Yan; Wensheng Liu; Zhaoji Yu; Bing Liu; Chao Liu; Tao Wang; Yang Liu; Lei Wu; Yunzhu Ma
• Keywords: Sodium tungstate; Tungstate; Micro arc oxidation

In the current work, micro-arc oxidized coatings were fabricated on 2A12 aluminum alloy with different concentrations of Na2WO4. The microstructure, mechanical properties and wear properties of the micro-arc oxidation (MAO) coatings formed on 2A12 aluminum alloy were investigated. The results show that the thickness and the surface roughness of the coating increased with the increase in Na2WO4 concentration. The thickness increased from 21 μm without sodium tungstate to 43.5 μm with 16 g·L−1 sodium tungstate, and the roughness from 3.2 to 5.5 μm. The hardness and wear resistance of the MAO coatings were also significantly influenced by the Na2WO4 concentration. During MAO, Na2WO4 as a passivator and WO4 ions participated in the coating reaction, which can promote the phase transition from amorphous alumina to γ-Al2O3 phase. The mechanism of action of sodium tungstate in the oxidation process was also elucidated.