LKP Model of the Inhibition Mechanism of Thiourea Compounds

• Published in: Corrosion (Houston, Tex.) Vol. 53; no. 12; pp. 915 - 919
• Main Authors: Lukovits, I., Pálfi, K., Bakó, I., Kálmán, E.
• Format: Journal Article
• Language: English
• Published: Houston, TX NACE International 01.12.1997; NACE
• Subjects: Applied sciences; Correlation coefficient; Correlation coefficients; Corrosion; Corrosion inhibitors; Corrosion mechanisms; Corrosion prevention; Exact sciences and technology; Metal surfaces; Metals; Metals. Metallurgy; Thiourea; Adsorption; Efficiency; Thiourea; Corrosion protection; Acid medium; Modeling; Corrosion inhibitor; Langmuir isotherm; Mechanism; Organic compounds
• ISSN: 0010-9312; 1938-159X
• DOI: 10.5006/1.3290275

ABSTRACTInteraction of corrosion inhibitors with metal surfaces in acidic solutions was investigated using a nonlinear model encompassing the Langmuir adsorption isotherm. A regression equation, with a multiple correlation coefficient equal to 0.95, was derived between the efficiencies of corrosion inhibition and molecular descriptors. INTRODUCTIONCorrosion inhibitors slow the corrosion process on metals by preventing oxidation of the metal or by blocking diffusion of corrosion products from the surface. Similar to biologically active molecules, quantitative structure activity relationships (QSAR) have been derived for various sets of corrosion inhibitors.1-7 Most inhibitors are tested in concentrations at which the amount of adsorbed molecules is already maximal on the metal surface, although inhibition depends upon the concentration of the inhibitor molecule. Therefore, a model encompassing adsorption would be useful in QSAR studies of corrosion inhibitors. Such a method, the Lukovits-Kálmán-Pálinkás (LKP) model, has been proposed. The quality of the regression equations was improved markedly when Free-Wilson type indices (i.e., indicator variables) were combined with an approach taking adsorption into account.8 The objective of the present work was to extend the proposed model for empirical substituent constants and quantum chemical indices. A highly significant multiple correlation coefficient (R = 0.95) has been demonstrated between experimental and predicted efficiencies using the proposed model. Thiourea and its derivatives were used because they are nontoxic compounds, and their use as corrosion inhibitors will not cause any environmental hazard.