Effect of amino acids containing sulfur on the corrosion of mild steel in phosphoric acid solutions containing Cl−, F− and Fe3+ ions: Behavior under polarization conditions

Abstract

The effect of cysteine (RSH), methionine (CH 3 SR), cystine (RSSR) and N-acetylcysteine (ACC) on the corrosion behavior of mild steel in 40% H 3 PO 4 solution without and with Cl ) , F ) , Fe 3+ and their ternary mixtures was studied using both potentiostatic and electrochemical impedance (EIS) techniques under anodic and cathodic polarization conditions. The inorganic additives stimulate the overall corrosion reaction while the amino acids inhibit it with a predominant effect on the dissolution of iron. Both RSH and ACC are adsorbed according to Temkin's isotherm while adsorption of RSSR and CH 3 SR follows Frumkin and Langmuir isotherms respectively. The standard free energy of adsorption (DG o ads ) was found to be in the order: RSSR > RSH @ ACC > CH 3 SR. The binary mixtures of Cl ) or F ) with RSH or CH 3 SR are the best inhibitors (IE > 90%) while those containing ferric ions or blend I and amino acids are not good corrosion inhibitors. EIS measurements showed that the cathodic reaction, hydrogen evolution, is charge transfer controlled while the anodic one, iron dissolution, is a complex process.

Corrosion inhibition of mild steel in sulfamic acid solution by S-containing amino acids

“…In the pure solution, values of b a and b c amount to 56 and -166 mV decade -1 , respectively. These values are close to those obtained for mild steel corrosion in mineral acids [7,[20][21][22]. In the presence of 10 lM RSH, RSSR, ACC and BzC, values of b a and b c obtained in blank solution are significantly decreased and by increasing the inhibitor concentration, they again increase.…”

“…Regardless of the inductive loop that appeared in the pure solution, the experimental data were found to fit well the equivalent circuit R s (R ct Q dl ) proposed in previous studies on steel corrosion in acid media [7,8,[13][14][15]. This consists of a solution resistance R s , a charge transfer resistance R ct and a constant phase element cpe, which is related to the capacity of the double layer C dl .…”

“…Our previous investigations showed that amino acids containing sulfur are effective inhibitors for many corrosion systems [3][4][5][6][7][8][9]. In this study, five amino acids containing sulfur were tested as inhibitors for mild steel corrosion in 5% sulfamic acid solution at 40°C.…”

Evaluation of the best corrosion inhibitors used with copper artifacts to protect the silver artifacts

“…Some recently laboratory studies were presented Met. as good corrosion inhibitor of copper [16] and steel [23][24][25][26][27][28] at different environments. It has important been suggested especially after comparing it with BTA and give best result but its use in museums not yet documented.…”

Inhibition of copper corrosion by modifying cysteine self‐assembled film with alkylamine/alkylacid compounds

“…They have two functional groups of carboxyl and amino in their molecular structure. The number of publications about the corrosion inhibition effect of amino acids increases [14][15][16]. It is generally agreed that their inhibition was based on the interaction between their N, O heteroatom and metal surface [17,18].…”