FACTORS OF CORROSION INHIBITION OF STAINLESS STEELS AND Fe-Ni ALLOYS BY CHLORIDE IN H2SO4.

The effect of chloride ions on the corrosion inhibition was investigated on iron, Ni-Fe alloys and stainless steels in sulfuric acid 1N containing variable concentrations of sodium chloride. The corrosion rate was evaluated by the determination of the charge transfer resistance Rt derived from electrochemical impedance. The inhibition efficiency is found to depend on parameters such as surface activity of the alloy, immersion time, alloy composition and chloride concentration. The more the environment is aggressive against the material, the more the efficiency of the inhibition due to chloride presence is enhanced. For the considered alloys in deaerated solutions, the efficiency of the inhibition by chloride depends essentially on the content of alloying iron. For each alloy, there exists a maximum chloride concentration below which the variation of the coverage fraction of adsorbed C1- obeys the Langmuir isotherm.