Corrosion inhibition of carbon steel in hydrochloric acid solution by self-formation of a Malpighia glabra leaf extract-based organic film

A forming organic film applied onto a metallic surface to resist electrochemical corrosion is demonstrated as a potentially new low-cost, low toxicity solution. In this work, the inhibitory effect of Malpighia glabra leaf extract (MGLE) on the corrosion of mild steel in 0.01, 0.10, and 1.00 M hydrochloric acid (HCl) media and the changes in its inhibitory efficiency were investigated. The analyses indicate that the inhibition performance increases up to 94.87% with an increase in MGLE concentration in the range of 0–2500 ppm when MGLE is added to 0.1 M HCl solution. However, it slightly decreased with MGLE concentrations greater than 3000 ppm owing to a reduction in the mobility and activity of the MGLE species under the investigated conditions. Notably, the inhibition occurs at a higher level (97.07%) when the steel is immersed in a more aggressive solution (1 M HCl). The results also show good inhibition effectiveness as a mixed corrosion inhibitor with more anodic predomination in a less acidic environment (0.01 M HCl). Furthermore, the surface analysis results show that the uninhibited steel surface is severely corroded, while less corrosion is observed on the inhibited surfaces covered by a protective film. The corrosion mitigation of carbon steel could be attributed to the bonding of the MGLE species on the surface to form a protective layer with densely packed organic compounds involving the MGLE species. Therefore, this work could deliver a new inhibitor with high resistance to steel corrosion in an acidic medium through controlled corrosive electrolytes. [Display omitted] •Malpighia glabra leaf extract (MGLE) is a potential eco-friendly effective inhibitor of steel corrosion in a HCl environment.•MGLE acts as a mixed inhibitor with an anodic predominance in less acidic media.•The high inhibition performance is due to the self-forming organic film on the steel surface.•A more active surface could be a good potential for adsorption of the MGLE species.