Weight loss and microstructural studies of stressed mild steel in apple juice

This study investigated the effect of internal stress of mild steel on its corrosion behaviour in apple juice by weight loss and microstructural analyses. The stress in the mild steel samples was induced by heat treatment at three different austenitic temperatures of 800, 850 and 900°C, followed by rapid quenching in cold water. The analyses of the results obtained showed that the heat treatment of mild steel at different temperatures followed by cold water quenching, changed the microstructure of the mild steel. The weight loss measurements obtained were at the highest of 0.009894 g/cm² for the non-heat treated mild steel, 0.007831 g/cm² for 900°C heat treated mild steel, 0.006394 g/cm² for the sample heat treated at 850°C, and 0.005287 g/cm² for the sample heat treated at 800°C. The analyses of these results showed that the sample heat treated at 800°C was more resistant in apple juice having the lowest average corrosion rate of 53.23 μm/y. The resistance of mild steel to corrosion in this medium decreased with the increase in austenitic temperature, which is observed from corrosion rate of 53.23 μm/y for sample heat treated at 800°C, 65.05 μm/y for sample heat treated at 850°C, and 80.630 μm/y for sample heat treated at 900°C, while 99.83 μm/y is recorded for the control sample. Intergranular corrosion with traces of pitting was observed in the heat treated samples immersed in the apple juice and the acidity of the medium increased with increase in exposure time.