Inhibitory Effects of Various Treatment Concentrations of Aloe Vera Extract on Sodium Chloride Brine Corrosion of AIsi-304 Stainless Steel

The AISI 304 stainless steel has wider engineering applications than any other stainless-steel grade. However, like all steels, it corrodes appreciably in chloride brines, and no ideal corrosion inhibitor has been found for it to date. This study investigates the inhibitory effects of 0-30% treatment concentrations of pure aloe vera extract on the steel corrosion in 3.5% NaCl brine. Coupons were sequentially produced from the steel sheet and immersed in the brine under the treatment concentrations for 0-30 days. The inhibitory effects of the treatments on the corrosion of the steel in the brine were determined by analysing the weight loss, corrosion rate, corrosion inhibition efficiency, and surface morphology of the coupons. The results show that coupons exposed to the blank brine exhibited comparatively higher weight losses in the 13-31 mg range and corrosion rates of 0.29726-0.747951 mm/yr after 5-30 exposure days. An increase in the extract’s treatment concentration resulted in an appreciable reduction in weight losses and corrosion rates of the coupons with an increase in corrosion inhibition efficiencies for the same exposure times. In all cases of the 0-30% treatments, the weight losses of the coupons increase gradually with the exposure time, while the corrosion rates decrease. The treatment concentrations of 5%, 10%, and 15% resulted in corrosion inhibition efficiencies of 61.2905–90%. The treatment concentrations of 20%, 25%, and 30% resulted in negligible weight losses and corrosion rates with inhibition efficiencies of 92.7418%–100%. Coupons exposed to the blank chloride brine displayed rough and pitted surface morphologies characterized by localized corroded areas, whereas coupons exposed to the brine treated with 20% aloe vera extract exhibited comparatively smoother surfaces with adsorbed protective films on them, as evidenced by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analyses of their surface morphologies. The overall results demonstrate that the 20 % treatment concentration can be an economical and highly effective concentration for the corrosion inhibition of 304 stainless steel in 3.5% NaCl brine.