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The effect of multiple-step thermal ageing treatment (MSTAT) on the corrosion characteristics of A356.0-type Al-Si-Mg alloy in simulated seawater has been studied. The MSTAT treatment also consists of Double Thermal Ageing (DTAT-T7), Single Thermal Ageing (STAT-T6), Step-Quenching and Ageing (SQA). The corrosion of the thermal treated samples was characterized by electrochemical Potentiodynamics polarization techniques consisting of linear polarization and chronopotentiometric method using the fit Tafel plot. Generally, from the linear polarization, the corrosion rate decreases at all temperatures with the ageing time. The corrosion behavior of the DTAT and SQA Al-Si-Mg alloy in the simulated seawater showed better resistance than the STAT Al-Si-Mg alloy. Samples in the SQA-STAT have improved corrosion resistance than the SQA-DTAT one. The chronopotentiometric corrosion study of some selected samples indicates a decrease in the corrosion resistance with open circuit potential exposure time. Consequently, the form of corrosion in the studied Al-Si-Mg alloy are slightly uniform and predominantly pitting corrosion as obtained from the SEM study. The pits diameter were found to range from 30-50µm.

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Aluminium is one of the lightweight materials that have a major contribution in numerous applications globally and it is also considered less expensive compared with other lightweight metals such as titanium and magnesium. As a result of some engineering applications’ requirements of better hardness and strength of material with lesser weight, researchers’ attention is drawn to the enhancement of the mechanical properties of accessible aluminium alloys. This study was conducted to study the microstructure and mechanical properties of a composite Al-Mg-Si matrix with varying weight percentages (0, 4, 6 and 8 wt. %) of palm kernel ash (PKSA) reinforcement, which were denoted correspondingly as C1–C4. The PKSA was obtained at a calcination temperature of 850 °C, XRD and XRF analyses were conducted to characterize it. The formulated samples were then ball-milled using two roll mills for about 60 hours to achieve a near homogeneity of the composites. The SEM image of the reinforced samples (C2 and C3) revealed that there were many networks of coalesced or necked particles while individual particles are hardly found, which is an indication of a high degree of densification ratio percentage of PKSA. The results also showed that there was an increase in hardness (44.4%), modulus of rupture (37.4%) and impact strength (252.03%) of Al-Mg-Si matrix composites (C3) in comparison with the unreinforced matrix material.

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