Corrosion Inhibition Performance of Scent Leaf (Ocimum gratissimum) and Cassava Leaf (Manihot esculenta) extracts on Mild Steel C-1026 in Zinc Sulphate Medium

In oil and gas-producing sectors, corrosion of Mild Steel pipelines poses persistent engineering challenges owing to the aggressive nature of industrial and soil-interrelated corrosive media. This research examined the corrosion-inhibitory performance of some environmentally benign plant extracts, Scent Leaf and Cassava Leaf, on Mild Steel C-1026, which were submerged in Zinc Sulphate (ZnSO₄) solution. Pineapple juice was incorporated into inhibitor formulations as an adhesion promoter agent to enhance adsorption onto the steel surface. Corrosion response was evaluated using gravimetric weight loss analysis, corrosion rate, inhibition efficiency calculations, Brinell hardness testing, Surface roughness analysis, Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). The experimental results demonstrated that the uninhibited ZnSO₄ medium produced the greatest material degradation, whereas both plant extracts considerably reduced metal dissolution. Weight loss values decreased from 0.0328g in the uninhibited ZnSO₄ concentration to 0.0266g and 0.0295g in the presence of SL and CL electrolytes, respectively. Corrosion rate values also reduced from 1.32 × 10⁻⁵ mpy in the ZnSO₄ to 1.02 × 10⁻⁵ mpy and 1.14 × 10⁻⁵ mpy for Scent Leaf and Cassava Leaf inhibited samples. Scent Leaf inhibitor exhibited an inhibition efficiency of 22.73%, while Cassava Leaf exhibited 13.64%. The mechanical and surface analyses revealed enhanced hardness retention, lower surface roughness, and smoother microstructures in inhibited specimens. FTIR investigation confirmed the existence of adsorption active functional groups like aromatic, hydroxyl, amine groups and carbonyl actively responsible for inhibitor molecules onto the steel surface. Moreover, SEM micrographs illustrated the formation of protective films that minimized pitting and localized corrosion. The study concluded that plant extracts functions as effective green inhibitors on Mild Steel C-1026 in ZnSO₄ corrosive medium. Their inhibitive efficiencies, low toxicity, availability, biodegradability, cost-effectiveness, and environmental friendliness make them pertinent alternatives to conventional synthetic corrosion inhibitors for pipeline protection in aggressive industrial surroundings.