In search of functionality for efficient inhibition of mild steel corrosion both in HCl and H 2 SO 4

Abstract

While the organic ammonium compounds are known to be effective against mild steel corrosion in HCl, these cationic salts are not as effective in sulphuric acid media. A new series of tertiary diallylamines containing C₁₂, C₁₄, C₁₆ and C₁₈ alkyl hydrophobes, N-hexadecylpyrrolidine and their corresponding ammonium salts were found to be among a rare class of inhibitors in arresting mild steel corrosion in HCl as well as in H₂SO₄ media effectively. While all the inhibitor molecules exhibited excellent inhibition efficiencies (%IEs) (∼99%) in 1M HCl, ammonium salts containing alkyne moiety at 400 ppm provided 93-97%IE even in 7·7M HCl. The inhibitors (400 ppm) containing diallyl moiety demonstrated the %IEs in the range 80-97% in 0·5M H₂SO₄. The interactions of the π electrons in the diallyl moiety with the low lying vacant d-orbitals of iron help the inhibitor molecules to undergo adsorption and interfere with the anodic dissolution process.