Characterization and Corrosion Behaviours of Aluminium Alloy/Aquaculture Shell Powder Particulates in Acidic Environment

Abstract

The corrosion and surface characterizations of aluminium alloys reinforced with mussel shell powder (MSP) were studied. Different weight percentages of 3, 6, 9, 12 and 15 wt% MSP were used to develop metal matrix composites for the investigations. The (MSP) was characterized by X-ray fluorescent (XRF). The alloy and the composites were subjected to corrosive medium at various concentrations (1, 1.5, 2, 2.5 and 3 M) of HCl using gravimetric-weight loss and potentiodynamics polarization techniques. Characterizations of the alloy/composites by scanning electron microscopy (SEM) and Energy-dispersive X-ray (EDS) were used to show the degree of attack of acidic solutions on their surfaces. The temperature and time were varied in the range of 30–60 °C at 10 °C interval, and 24 to 144 h at 24-h interval, respectively. The corrosion rate of the composites increases with increase in the reinforcement of mussel shell powder, temperature and the acid concentrations and was in the sequence of 333 K > 323 K > 313 K > 303 K. The unreinforced alloy exhibited slightly superior corrosion resistance when compared to composites in HCl at various concentrations. This was due to the reinforcements that constitute different compounds such as CaO, SiO and FeO, which may become anodic/cathodic to the matrix, thereby increasing the corrosion rate of the composites. The icorr of the composites increase with increase in the reinforcements. Pits formations were seen on the coupons which indicated intergranular corrosion attack by the acidic medium and increase as the acid concentrations increase. The results of weight loss were in good agreement with those of characterizations and electrochemical techniques. The result of the work lead to the following conclusion that the composite cannot be used either for holding HCl solution or as a structural material where HCl solution is found. This is because it will selectively dissolve the composite, leaving behind an altered residual structure based on the results of weight loss, and the potentiodynamics polarization.