Inhibition effect of 3,5 bis (2-pyridil) 4-amino 1,2,4 triazole and 1-10 phenantrolin on corrosion of mild steel in acid solutions

The inhibition effects of 3,5 bis (2-pyridil) 4-amino 1,2,4 triazole (NBTA) and 1-10 phenantrolin (PHEN) , on corrosion of mild steel in acid solutions, (sulphuric acid and hydrochloric acid) were studied. The Tafel polarisation and ac impedance techniques were employed. Results obtained reveal that both compounds are relatively good inhibitors. The inhibition efficiencies of NBTA are higher in hydrochloric acid than in sulphuric acid. This has been attributed to the synergistic effect of chloride ions present in hydrochloric acid. The mechanism of inhibition of PHEN is believed to be owing to the formation of insoluble chelates between the organic molecules and atom/ion on the metal surface. The adsorption of NBTA is believed to occur through the formation of an iron-nitrogen coordinate bond. The adsorption isotherms were also determined and found to be of the Langmuir type.