Inhibition of mild steel corrosion in sulphuric acid using alizarin yellow GG dye and synergistic iodide additive

The corrosion inhibition of mild steel in 2 M H₂SO₄ using Alizarin yellow GG (AYGG) (an azo dye) in the presence of iodide ions was studied at 30 - 60°C using weight loss and hydrogen evolution methods. Results obtained showed that inhibition efficiency increased with increase in concentration of AYGG and decreased with increase in temperature. The inhibition efficiency of AYGG synergistically increased on addition of KI. The adsorption of AYGG alone and in combination with iodide ions on the metal surface is found to obey Temkin adsorption isotherm at all temperatures studied. Phenomenon of physical adsorption is proposed from the values of E_a and δG^̊ _ads obtained. Synergism parameter evaluated is found to be greater than unity for all concentrations of AYGG indicating that the enhanced inhibition efficiency of AYGG caused by addition of iodide ion is only due to synergism. Experimental results obtained indicate that the adsorption of AYGG and AYGG + KI onto mild steel surface is spontaneous.