Anti-corrosion properties of the symbiotic effect of Rosmarinus officinalis and trypsin complex on medium carbon steel

The synergistic reaction of Rosmarinus officinalis and trypsin complex on the susceptibility of medium carbon steel to interfacial deterioration in 2 M H2SO4 and HCl solution was studied using potentiodynamic polarization method, weight loss evaluation, open circuit potential analysis, optical microscopy and ATR-FTIR spectroscopy. Experimental outcome confirmed the effective performance of the admixture with highest inhibition values of 79.72% and 80.85% in H2SO4 with anodic type inhibition, 78.88% and 94.17% in HCl with cathodic type inhibition from the electrochemical tests. The inhibiting compound significantly influenced the thermodynamic behaviour of the steel, shifting the corrosion potential of the steels due to its passivation characteristics. Chemisorption adsorption mechanism was observed with respect to Langmuir and Frumkin adsorption isotherms, and correlation coefficients of 0.8359 and 0.9559 in H2SO4 solution, and 0.9900 and 0.9991 in HCl solution respectively. Identified functional groups from ATR-FTIR spectroscopic analysis partially adsorbed onto the carbon steel in H2SO4 and completely in HCl. Micro-analytical images of the admixture protected steel contrast the uninhibited.