Corrosion Behavior of Aluminum Composite Coatings

Abstract The corrosion behavior of metal-matrix composite (MMC) coatings (3 mm to 5 mm [0.12 in. to 0.2 in.] thick) fabricated by the plasma-transferred arc (PTA) surfacing process was investigated by potentiostatic and immersion techniques. The test electrolyte was a 3.5 wt% sodium chloride (NaCl) solution. Composites were reinforced with angular particles of aluminum oxide (Al2O3), silicon carbide (SiC), or titanium carbide (TiC) of varying volume fractions (Vf≈2.5% to 40%) and of two sizes (70 μm and 140 μm). The matrix was predominantly aluminium with 2 wt% Ni, which was added to enhance the matrix's wear resistance. The reinforcement type significantly influenced corrosion behavior of the MMC coatings. The immersion study showed the corrosion rate increased in the following order of reinforcement addition: Al2O3 < SiC < TiC. Al2O3 particles appeared to play no role in the corrosion process, whereas SiC and TiC particles participated actively. Reinforcement surface area appeared to be a significant pa...