Spirulina platensis – A novel green inhibitor for acid corrosion of mild steel

The inhibition of the corrosion of mild steel in 1 M HCl and 1 M H2SO4 by Spirulina platensis has been studied at different temperatures viz., 303 K, 313 K and 323 K by weight loss method, potentiodynamic polarization method, electrochemical impedance spectroscopy measurements and SEM analysis. The inhibition efficiency increased with increasing concentration of the inhibitor in both HCl and H2SO4 media. The results of weight loss studies correlated well with those of impedance and polarization studies. From the results of weight loss studies at various temperatures, the mode of adsorption is confirmed to be physisorption. Further the adsorption has been found to follow Temkin isotherm. From this isotherm, the free energy of adsorption (ΔG) and entropy (ΔS) are calculated. The study reveals the corrosion inhibition potential of S. platensis in both the acid media, thus bringing to light another facet of this microalga as it has so far been used only to produce antioxidant principles, finding extensive use in medicine especially as neutraceutical.