Amino acids as corrosion inhibitors for copper in acidic medium: Experimental and theoretical study

Abstract

Experimental electrochemical methods combined with quantum chemical calculations and molecular dynamics simulations were used to investigate the possibility of use various amino acids as ?green? corrosion inhibitors for copper in 0.5 M HCl solution. Among eleven amino acids studied, cysteine achieved the highest inhibitor effectiveness reaching 52% at 10 mM concentration. Other amino acids reached achieved effectiveness less than 25%, some of them even acted as corrosion accelerators. Based on the experimental results, theoretical calculations and simulations were focused on cysteine and alanine. The electronic and reactivity parameters of their protonated forms in electrical double layer were evaluated by density functional calculations. In addition, molecular dynamic simulations were introduced to follow the adsorption behaviour of these two amino acids at the Cu(111) surface in the electrolyte solution. The results indicate that the orientation of both molecules is nearly parallel to the surface except of ammonium group which is directed away from the surface. Therefore, as the orientation of the cysteine and alanine molecules at the surface is similar, thiol functional group is responsible for superior inhibition efficiency of cysteine.

Cysteine Duality Effect on the Corrosion Inhibition and Acceleration of 3003 Aluminium Alloy in a 2% NaCl Solution

“…In an aqueous solution, the ionization of this amino acid depends on the solution's pH [18][19][20]. Based on the presence of three different heteroatoms (i.e., S, N and O) in its molecular structure, cysteine has the potential to become a good corrosion inhibitor [21][22][23].…”

The Study of Inhibitory Effect of Some Amino acids on Corrosion of 60/40 Brass in Nitric Acid

“…The general molecular formula for amino acid can be written as, In acidic medium the aminoacids generally exist as protonated species 34 , the amino acid in this form can be attracted to the cathodic sites on the metal surface and decrease the cathodic reduction reaction. The amino acids are also able to be adsorbed on anodic site of metal through unprotonated nitrogen atom and the 'O' of carboxyl group , wich have lone pair of electron.…”

Glutamic Acid as Corrosion Inhibitor for Aluminium in Acidic Medium

“…Unfortunately, most of the inhibitors available in the markets are not only expensive but also toxic to living beings. Again, the safety of environmental issues of corrosion inhibitors which may arise industry has always been a global concern [5]. To avoid toxicity of numerous compounds tested as inhibitors [5,6], natural compounds, regarded as environmentally friendly inhibitors.…”

“…Again, the safety of environmental issues of corrosion inhibitors which may arise industry has always been a global concern [5]. To avoid toxicity of numerous compounds tested as inhibitors [5,6], natural compounds, regarded as environmentally friendly inhibitors. Amino acids have been tested as inhibitors of corrosion of a variety of metals, for example copper, aluminium and steel corrosion in acid media.…”