The effect of marine algae chaetomorpha antennia extract on corrosion inhibition of brass in
phosphoric acid was investigated by weight-loss measurements. The inhibition efficiency is found to increase
with increasing concentration of extract and the inhibition efficiency decreases with rise in temperature. The
activation energy, thermodynamic parameters (free energy, enthalpy and entropy change) and kinetic
parameters (rate constant and half-life) for inhibition process were calculated. These thermodynamic and kinetic
parameters indicate a strong interaction between the inhibitor and the brass surface. The inhibition is assumed
to occur via adsorption of inhibitor molecules on the brass surface, which obeys Temkin adsorption isotherm.
The adsorption of inhibitor on the brass surface is exothermic, physical, and spontaneous and follows first order
kinetics.
