Experimental and quantum chemical studies of carboxylates as corrosion inhibitors for AM50 alloy in pH neutral NaCl solution

Sodium salts of mono- and di- carboxylic acids (glycolic, fumaric and benzoic acid) were studied as corrosion inhibitors for AM50 alloy in pH neutral aqueous NaCl environment. Hydrogen evolution, electrochemical and surface characterization techniques were employed to reveal their corrosion inhibition mechanism, whilst the molecular features of inhibitors were investigated by quantum chemical calculation. All inhibitors reduced anodic dissolution of AM50 and their efficiency generally increased with time and concentration from 5 mM to 100 mM. The inhibition mechanism can be described as physisorption of inhibitive molecules on the surface of the intrinsic oxide layer followed by chemisorption with Mg2+ and Al3+, and the difference in inhibition action among these inhibitors was explained on the molecular scale.