ISSN: 1003-6326
CN: 43-1239/TG

Vol. 27    No. 2    February 2017

Wear and corrosion resistant coatings on surface of cast A356 aluminum alloy by plasma electrolytic oxidation in moderately concentrated aluminate electrolytes
Huan-jun XIE, Ying-liang CHENG, Shao-xian LI, Jin-hui CAO, Li CAO
(College of Materials Science and Engineering, Hunan University, Changsha 410082, China)
Abstract: Plasma electrolytic oxidation of a cast A356 aluminum alloy was carried out in aluminate electrolytes to develop wear and corrosion resistant coatings. Different concentrations of 2, 16 and 24 g/L NaAlO2 solutions and a silicate electrolyte (for comparison) were employed for the investigation. Wear performance and corrosion resistance of the coatings were evaluated by WC (tungsten carbide) ball-on-flat dry sliding tests and electrochemical methods, respectively. The results show that the coating formed for a short duration of 480 s in 24 g/L NaAlO2 solution generated the best protection. The coating sustained 30 N load for sliding time of 1800 s, showing very low wear rate of ~4.5×10-7 mm3/(N·m). A low corrosion current density of ~8.81×10-9 A/cm2 was also recorded. Despite low α-Al2O3 content of the coating, the compact and nearly single layer nature of the coating guaranteed the excellent performances.
Key words: A356 aluminium alloy; sodium aluminate; plasma electrolytic oxidation; wear; corrosion
Superintended by The China Association for Science and Technology (CAST)
Sponsored by The Nonferrous Metals Society of China (NFSOC)
Managed by Central South University (CSU)