APPLICATION OF SILK PROTEIN HYDROLYSATE AS A POTENT ANTI-CORROSIVE AGENT FOR MILD STEEL IN HCl SOLUTION

The study focuses on broadening the application of Silk Protein Hydrolysate (SPH) towards conventional metal protection of metallic materials. The inhibitory potentials of SPH against corrosion of mild steel in 1 N HCl media are analyzed through weight loss, electrochemical, and surface morphological techniques. The assessment of the inhibitor effectiveness, kinetic and thermodynamic variables was done at the temperature of 303 – 333 K. The studies exhibited superior anti-corrosion efficacy of 93 % for 10 ppm SPH at 303 K and good maintenance in corrosion control is seen with temperature rise. The SPH assimilation at the metal surface follows the Langmuir adsorption model with free energy values lower than -20 KJ/mol. Potentiodynamic polarization studies evince the mode of corrosion protection to be mixed overall with cathodic predominance. Electrochemical impedance spectroscopy describes the resistive and capacitive behavior through Rct and Cdl values signifying the physical barrier prevailing on the metal surface. Surface monitoring through SEM-EDS reveals the firm adherence of SPH to the metallic surface, XRD study characterizes the corrosion products formed in the process. The roughness variables derived from AFM imaging remark the stable protective layer formed by the SPH molecules. The defensive film formed smoothes the metal surface leading to an enhanced water contact angle.