Effect of halide ions on the corrosion inhibition efficiency of different organic species - A review

The influence of halide ions (Cl^-, Br^-, I^-) on the corrosion inhibition efficiencies of various organic-type inhibitors including polymers, natural products of plant origin, organic dyes, surfactants, drugs etc. on metals corrosion in various aqueous aggressive environments and under different experimental conditions has been widely reported in the literature and is discussed in this paper. Most of the available data show that the halide additives synergistically increased the inhibition efficiencies of most organic cation-type molecules in the order Cl^-<Br^-<I^- in the different environments investigated. Such synergistic effects often show sensitivity to various factors including nature and concentration of the additives, temperature as well as nature of the metal and aggressive environments. Mechanisms proposed for the synergistic interactions have been compared and evaluated with respect to the reported experimental data.