Corrosion inhibition performance of amino acid-based monomer and gemini surfactants for mild steel corrosion in HC1 solution

摘要

The advantages of using surfactants as corrosion inhibitors are their high inhibition efficiency, low cost, low toxicity and easy production. The hydrophilic part of surfactants strongly favours interactions with polar entities such as water, metals and ions, which facilitates surfactant aggregation and adsorption on the metal surfaces, blocks active surface sites, and thereby protects metal from corrosion. The corrosion behavior of mild steel in 1M HC1 solution in the presence of an amino acid-based gemini surfactant derived from cystine, N,N'- dialkyl cystine gemini surfactant 2(CpCys), and its monomeric N-alkyl cysteine counterpart, (C_(12)Cys), was investigated as a function of surfactants concentration and temperature by means of weight loss measurements, potentiodynamic polarization measurements (PDP), electrochemical impedance spectroscopy (HS) scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and atomic force microscopy (AFM). The performance of monomeric surfactant was also compared with gemini surfactant. The compounds exhibited surface active properties and acted as good inhibitors for the mild steel corrosion of in 1 M HC1 solution. The EIS results revealed a higher charge transfer resistance in 2(C_(12)C_(ys)) solution compared to that in (C_(12)C_(ys)) solution at the same concentration. Surface morphological studies (SEM/EDAX and AFM) carried out after being exposed to the acidic test solutions confirmed existence of a protective adsorbed film of the inhibitor on the electrode surface. The reduction of surface roughness in the presence of 2(C_(12)Cys) was more evident than in presence of (C_(12)Cys). In order to study the adsorption of studied inhibitor molecules on mild steel surface the various quantum chemical parameters such as energy of highest occupied molecular orbital (E_(hqmo))> energy of lowest unoccupied molecular orbital (E_(LUMO)), energy gap (E_(L.H) = E_(LUMO) - E_(HOmo))> electron affinity (E=-E_(LUMO)), ionization potential (I=-E_(HOmo))- electronegativity (X = -1/2(E_(HOMO) + E_(LUMO)), hardness (h = 1/2(E_(HOMO) - E_(LUMO)) and softness (σ = 1/h) were obtained and discussed.