ADSORPTION AND THERMODYNAMIC STUDY OF CORROSION INHIBITION EFFECT OF AMINOTRIMETHYLENE PHOSPHONIC ACID (ATMP) – AL3+ SYSTEM ON CARBON STEEL IN GROUND WATER

The synergistic inhibitor effect of 150ppm of TriMethylene Phophonic acid (ATMP) with 50 ppm of Al3+ ion has 98% inhibition efficiency on controlling corrosion of steel immersed in ground water. Effect of temperature on Corrosion rate was studied and shows that the inhibition efficiency decreases with increase in temperature. Also, the inhibition efficiency of the inhibitor increases with increasing concentration of the inhibitor which offered the inhibition efficiency of 98%. The adsorption of the inhibitor on the surface of mild steel in the corrosive environment followed the Langmuir and Frumkin adsorption isotherm. Inhibition occurred through adsorption of the ATMP+Al3+ ion molecules on the metal surface. The apparent activation energies, enthalpies and entropies of the dissolution process and the free energies and enthalpies for the adsorption process were determined and discussed. The fundamental thermodynamic functions were used to evaluate important inhibitive properties of ATMP+Al3+