Synergistic Effect of Potassium Iodide on Corrosion Inhibition of Mild Steel in HCl Medium by Extracts of Nypa Fruticans’ Wurmb

The effect of Nypa Fruticans’ Wurmb extract and the mixture of various concentration of KI and Nypa fruticans’ wurmb extract on corrosion of mild steel in 0.1M and 0.5M HCl have been investigated using weight loss methods. The study revealed that mild steel is more efficiently inhibited by Nypa Fruticans’ Wurmb in the presence of KI than pure extract of Nypa Fruticans’ Wurmb. The inhibition efficiencies increased with increased concentration of the additives. The highest inhibition efficiency of 77.31% was observed with single Nypa Fruticans’ Wurmb extract. An improved inhibition efficiency of 95.36% was observed with the mixture of Nypa Fruticans’ Wurmb extract and KI at 30oC in 0.5M HCl. Inhibition efficiency decreased with increase in temperature from 30-40OC but increased at relatively high temperature of 50°C an effect attributed to synergism between Nypa Fruticans’ Wurmb extract and KI. The adsorption of inhibitor molecules on metal surface followed langmuir isotherm. Thermodynamic parameters such as heat of adsorption, ΔH, free energy of adsorption ΔG and enthropy of adsorption are obtained from experimental temperatures ranging from 30 – 50°C.