The inhibiting action of alkyltriphenylphosphonium iodine salt ((C8H17)Ph3P+,I-) towards the corrosion behaviour of nickel in 1 M H2SO4 solution has been studied. This compound was found to retard both anodic and cathodic reactions of nickel corrosion. At constant temperature, the corrosion rate decreases with increasing inhibitor concentration. On the other hand, the increase in temperature leads to an increase in the corrosion rate. The activation energy, Delta E (a), were calculated. They were found 19.3 kJ mol(-1) and 71.1 kJ mol(-1), respectively for the uninhibited solution and in the presence of 10(-3) M of phosphonium salt. The inhibitor adsorption was identified to occur according to Langmuir isotherm. The equilibrium constant, k, as well as the free energy of adsorption, Delta(ads)G degrees, for inhibitor process were then calculated. Phosphonium iodine exhibited a singular behaviour for T >= 318 K where inhibitor desorption increases.