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Extruded Mg alloy plates of 6 mm thick of AZ61A grade were butt welded using advanced welding process and friction stir welding (FSW) processes. The specimens were exposed to salt spray conditions and immersion conditions to characterize their corrosion rates on the effect of pH value, chloride ion concentration, and corrosion time. In addition, an attempt was made to develop an empirical relationship to predict the corrosion rate of FSW welds in salt spray corrosion test and galvanic corrosion test using design of experiments. The corrosion morphology and the pit morphology were analyzed by optical microscopy, and the corrosion products were examined using scanning electron microscope and X-ray diffraction analysis. From this research work, it is found that, in both corrosion tests, the corrosion rate decreases with the increase in pH value, the decrease in chloride ion concentration, and a higher corrosion time. The results show the usage of the magnesium alloy for best environments and suitable applications from the aforementioned conditions. Also, it is found that AZ61A magnesium alloy welds possess low-corrosion rate and higher-corrosion resistance in the galvanic corrosion test than in the salt spray corrosion test.

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Extruded AZ61A Mg alloy plates of 6 mm thickness were friction stir welded. The effect of pH values, chloride ion concentration and exposure time on the pitting corrosion rate of magnesium alloy welds was investigated in NaCl solution using potentiodynamic polarisation tests. In addition, an attempt was made to develop an empirical relationship to predict the pitting corrosion rate of Mg alloy welds by incorporating the effect of pH values, chloride ion concentration and exposure time using response surface methodology. Microstructural characterisation of the corroded specimens was analysed under light optical microscopy. The corrosion products were analysed using SEM and X-ray diffraction.

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The present research devoted to the investigation of the corrosion behavior of AZ61A FSW welds in accelerated conditions, including the influence of salt fog environmental parameters such as chloride ion concentration, pH, and duration of exposure. Significant numbers of tests were carried out that make possible to create the regression model (empirical equation) of influence of selected environmental parameters on corrosion rate. The corrosion products were analyzed by SEM and XRD analysis. This research demonstrates the effect of chloride ion concentrations, spraying time and pH values on corrosion rate, and it show the corrosion activity decelerates with the increasing pH value and spraying time respectively. It was found that the increase in chloride ion concentration accelerates the corrosion of AZ61A weldments. The corrosion morphology was predominantly influenced by the distribution of β-phase (e.g. Mg17Al12 intermetallic).