Influence of the Molecular Structure on the Inhibitor Properties of Benzimidazole Derivatives on Mild Steel Corrosion in 1 M Hydrochloric Acid

• Published in: Corrosion (Houston, Tex.) Vol. 59; no. 9; pp. 756 - 764
• Main Authors: Popova, A., Christov, M., Deligeorgiev, T.
• Format: Journal Article
• Language: English
• Published: Houston, TX NACE International 01.09.2003; NACE
• Subjects: Adsorption; Applied sciences; Benzimidazoles; Correlation; Corrosion; Corrosion environments; Corrosion inhibitors; Corrosion prevention; Derivatives; Efficiency; Electronic structure; Exact sciences and technology; Gravimetry; Hydrochloric acid; Inhibitors; Ionization; Ionization potentials; Low carbon steels; Metals. Metallurgy; Molecular structure; Parameters; Steel; adsorption; Mild steel; Acid corrosion; Molecular structure; acidic inhibitors; Corrosion inhibition; Experimental study; Corrosion protection; Corrosion inhibitor; benzimidazole derivatives; polarization curve; Corrosion; Benzimidazole; Corrosion test; Ionization potential; Chloric acid; diazoles; hydrochloric acid
• ISSN: 0010-9312; 1938-159X
• DOI: 10.5006/1.3277604

ABSTRACTIt is well known that the heterocyclic compounds are the best corrosion inhibitors on steel in acid media among the group of the nitrogen-containing organic substances.1 Among them relatively few investigations are dedicated to diazoles. Inhibition properties are reported for benzimidazole (BI) and some of its derivatives.2-7 The mechanism of their adsorption and inhibition is not fully understood and the literature on the subject is rather scarce. The data concerning the effect of these compounds on the kinetics of the electrode reactions, which determine the corrosion process, are incomplete. There is no common view on the adsorption type--some authors2-3,5-6 accept chemisorption of the molecules via the lone electron pair above the nitrogen atom in the third position of the benzimidazole ring, while others7 accept physical adsorption of the protonated, cationic form of the compounds. On the other hand, there are numerous investigations proving the existence of relationships between the electronic and/or chemical structure of the molecules and their function as corrosion inhibitors.8-21 The influence of the electronic structure is reflected in the correlation found between the inhibiting properties and Hammet-like substituent constants through the use of linear-free energy relations,8-12 Taft constants and pKa,2,13 ionization potential and electron ability,14-15 highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy,16 and electrondonor properties of different functional groups.17-18 Other parameters, such as molecular area14,19 and position of the substituents and steric factors,20-21 reflect the relation between the chemical structure and the inhibition efficiency. The goal of this paper was to study the inhibition properties on mild steel corrosion in 1 M hydrochlo-