Effect of NaOH on plasma electrolytic oxidation of A356 aluminium alloy in moderately concentrated aluminate electrolyte
(1. College of Materials Science and Engineering, Hunan University, Changsha 410082, China;
2. AECC Zhongchuan Transmission Machinery Co., Ltd., Changsha 410200, China;
3. College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China)
2. AECC Zhongchuan Transmission Machinery Co., Ltd., Changsha 410200, China;
3. College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China)
Abstract: Plasma electrolytic oxidation (PEO) of cast A356 aluminum alloy was carried out in 32 g/L NaAlO2 with the addition of different concentrations of NaOH. The stability of the aluminate solution is greatly enhanced by increasing the concentration of NaOH. However, corresponding changes in the PEO behaviour occur due to the increment of NaOH concentration. Thicker precursor coatings are required for the PEO treatment in a more concentrated NaOH electrolyte. The results show that the optimal NaOH concentration is 5 g/L, which improves the stability of storage electrolyte to about 35 days, and leads to dense coatings with high wear performance (wear rate: 4.1×10-7 mm3·N-1·m-1).
Key words: plasma electrolytic oxidation; wear resistance; sodium aluminate; sodium hydroxide; A356 alloy