Influence of Electrolyte Temperature on the Color Values of Black Plasma Electrolytic Oxidation Coatings on AZ31B Mg Alloy

Authors：Yi, Aihua; Liao, Zhongmiao; Zhu, Wen; Zhu, Zhisheng; Li, Wenfang^*; Li, Kang; Chen, Ken; Huang, Shengkai

Source：Coatings, 2020, 10(9): 890.

DOI：10.3390/coatings10090890

• plasma electrolytic oxidation
• electrolyte temperature
• color value

A coating was prepared on an AZ31B Mg alloy substrate via black plasma electrolytic oxidation (PEO). The colorant NH(4)VO(3)was added to Na2SiO3-(NaPO3)(6)electrolyte at different temperatures (5, 15, 25, and 35 degrees C). The influences of electrolyte temperature on the structures, compositions, and color values of black PEO coatings were studied by UV-Visible, XRD, XPS, Raman, and SEM techniques. The results showed that the relative content of V(2)O(3)and V(2)O(5)was the key factor affecting the coating color value. At higher temperatures, more NH(3)escaped from the electrolyte and the NH(3)quantity participating in the reaction decreased, resulting in a decrease of V(2)O(3)content, an increase in color value, and a darker coating. In the PEO process, VO(3-)mainly reacted to form V2O5, and then, the generated V(2)O(5)reacted with NH(3)to form V2O3.

• Institution
  东莞理工学院