Abstract
Ceramic coatings were fabricated on 7A85 aluminum alloy by unipolar positive pulsed micro-arc oxidation (MAO) treatment for enhancing corrosion resistance. A bi-layer coating was formed with large pores between the layers. The outer layer contained several micro pores and cracks. Therefore, cerium nitrate, potash bichromate and SiO2 sol were adopted to seal the MAO coatings. Scanning electron microscope, X-ray diffraction and electrochemistry instrument were used to investigate the effect of sealing treatments on the surface morphology, coating structure and corrosion resistance of MAO coatings. Results show that the MAO coating can not protect aluminum alloy from acid NaCl solution for the existing of defects. The defects can be sealed by precipitations produced by cerium nitrate and potash bichromate sealing treatment, and corrosion resistance of the MAO coating is improved. However, the sealed coatings also fail in the acid NaCl solution for dissolution of the precipitation. After sealing with SiO2 sol, the MAO coating is covered with a SiO2 gel layer has become a compact barrier layer to protect aluminum substrate from corrosion in acid NaCl solution.
| Original language | English |
|---|---|
| Pages (from-to) | 627-632 |
| Number of pages | 6 |
| Journal | Wuji Cailiao Xuebao/Journal of Inorganic Materials |
| Volume | 30 |
| Issue number | 6 |
| DOIs | |
| State | Published - 1 Jun 2015 |
Keywords
- Aluminum alloy
- Corrosion resistance
- Electrochemistry
- Micro-arc oxidation
- Seal treatment
- SiO sol