Influences of edge effect on microstructure and corrosion behaviour of PEO coating

ABSTRACT

Plasma electrolytic oxidation (PEO) coatings were prepared on AA1060 alloy substrate by a galvanostatic regime in an alkaline sodium hexametaphosphate ((NaPO₃)₆) electrolyte, and the influences of electric field edge effect on the microstructure, surface roughness, semiconducting behaviour and corrosion behaviour of the coatings were investigated by means of scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM), Mott–Schottky analysis and electrochemical impedance spectroscopy (EIS) tests. The results showed that an ordered porous film was formed before the presence of micro-discharges during the PEO treatment. The electric field strength at the specimen edge region was about twice as large as that in the specimen centre region, which resulted in the differences in the microstructure, surface roughness and corrosion behaviour of the specimens at the edge and centre regions. All PEO-coated specimens showed n-type semiconducting behaviour, and the coating at the edge region had a lower carrier concentration.

KEYWORDS:

• Plasma electrolytic oxidation
• edge effect
• semiconductor
• corrosion behaviour

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on the contributors

Dong-Dong Wang is doctoral student at the State Key Laboratory of Metastable Materials Science and Technology (Yanshan University).

Xin-Tong Liu is master student at the State Key Laboratory of Metastable Materials Science and Technology (Yanshan University).

Yu Su is master student at the State Key Laboratory of Metastable Materials Science and Technology (Yanshan University).

Ye-Kang Wu is doctoral student at the State Key Laboratory of Metastable Materials Science and Technology (Yanshan University).

Zhong Yang is master student at the State Key Laboratory of Metastable Materials Science and Technology (Yanshan University).

Hui-Ping Han is master student at the State Key Laboratory of Metastable Materials Science and Technology (Yanshan University).

Xu-Zhen Zhang is master student at the State Key Laboratory of Metastable Materials Science and Technology (Yanshan University).

Guo-Rui Wu is doctoral student at the State Key Laboratory of Metastable Materials Science and Technology (Yanshan University).

De-Jiu Shen is a professor at the State Key Laboratory of Metastable Materials Science and Technology (Yanshan University) and has been engaged in surface modification research for more than 30 years.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (Nos. 51671167 and 51171167) and Hebei Province Natural Science Foundation of China (Nos. A2015203348 and B2015203406).