Potentiodynamic study and microstructural evaluation of the corrosion behavior of mill scale and alumina reinforced aluminium metal matrix composites

The current study reports the corrosion behavior of aluminium metal matrix composites (AMMCs) reinforced with mill scale (MS) and alumina (Al2O3) in a simulated marine environment (3.5 % NaCl solution). Electrochemical technique and optical microscopy were used to evaluate the corrosion behavior of the composites developed at varying weight ratios of MS (0, 2, 4, 6, 8) and Al2O3 (0, 2, 4, 6, 8) respectively. From the results obtained, the average grain size of the composites after exposure to the marine environment varies significantly. Sample A showed an average grain size of 55.02 µm, B - 26.85 µm, C - 28.12 µm, D - 27.03 µm, E - 32.31 µm and F (control) - 37.02 µm. The contributory influence of the reinforcing materials is evident in the variation noted in the average grain sizes. Their presence acts as active sites for corrosion initiation. The oxidation of metal ions causes severe pitting with sample C having the optimum corrosion rate of 0.9532 mm/yr and sample D showing the least corrosion rate of 0.6188 mm/yr. The morphology of the corroded surfaces confirms the presence of pitting corrosion on the composites developed.