Fabrication and analysis of anti-corrosion coatings on in-situ TiB2p reinforced aluminum matrix composite

Anodizing and rare earth sealing were combined to investigate the feasibility of in-situ TiB2p/A356 composite for corrosion protection. Optical microscope observation found that the thickness of anodic film was non-uniform. Scanning electron microscope analysis showed that anodic film of the composite mainly presented porous structures and had many cavities, micro-pores and micro-cracks. Ce sealing treatment was proposed to remedy the surface defects in order to further enhance the corrosion resistance of the composite surface. The sealing layer was composed of spherical deposits and main compositions were cerium oxide and cerium hydroxide. These deposits completely sealed the porous structures as well as covered most defects of anodic film. The salt spray corrosion test and electrochemical corrosion test were used to evaluate the corrosion resistance of the coatings. The results indicated that the synergism effect of anodized film and Ce sealing layer resulted in a higher degree of protection in a chloride-containing environment than a single anodized coating for TiB2p/A356 composite. The cerium sealed anodized film effectively held back corrosive intermediate and protected the composite matrix.