Eco-friendly biomass from Ziziphus spina-christi for protection of carbon steel in acidic conditions - Parameter effects and corrosion mechanism studies

The eco-friendly plant extract based corrosion inhibitor, synthesized using Ziziphus spina-christi, was investigated for its corrosion control and surface protection potential for carbon steel under acidic conditions. The influence of process parameters, corrosion inhibitor concentration (160-810 ppm), operating temperature (330.15-315.15 K) and immersion time (4-24 h), on inhibition efficiency was evaluated. Based on mass loss experiments, the maximum inhibition efficiency achieved was found to be 91.35% at 810 ppm inhibitor concentration and 300.15 K. Corrosion rate decreased with increase in inhibitor dose which could be due to enhanced surface coverage. The activation energy associated with this process indicated surface interaction as the main mechanism and positive values of enthalpy change confirmed the endothermic nature. The electrochemical parameters, namely corrosion potential (E_corr), anodic and cathodic Tafel constants (β_a and β_c), and corrosion current density (i_corr) were calculated, and the inhibitor was found to be mixed type. Through double-layer capacitance, the increase in corrosion resistance was proved. The active functional groups associated with corrosion inhibitor were identified.