Modelling of Corrosion Inhibition of Cucumber Plant Extracts on AISI 1007 Steel in Seawater

Abstract

Adsorption Models with the application of corrosion experimental data is a very popular mechanism to predict various inhibitive systems. The effective modelling and interpretation of adsorption isotherms reliably determine the level of accuracy of adsorption processes. This study aims to apply the adsorption models and inhibitive mechanism of Cucumber Peel Extract (CPE) and Cucumber Seed Oil (CSO) to corrosion of AISI 1007 steel grade in the saline medium using both the electrochemical (Tafel Polarisation) and non-electrochemical (Weight Loss) techniques. The chemical composition of AISI 1007 and the phytochemical properties of studied extracts were determined. Consideration was given to Langmuir and Dubinin-Radushkevich Isotherm models (D-RIM) to study the inhibitive properties of CPE and CSO on AISI 1007 steel in an aggressive medium. The result of inhibition efficiency from weight loss measurement showed maximum inhibitions of  94.44 % and 95.44 % with 1.0 g/L concentration of CPE and CSO respectively in sea water medium. The result of the studied extract at 25 ℃ in seawater showed that the corrosion current density of AISI 1007 steel decreased and increased in the inhibition efficiency with 87.33% and 94.67% for CPE and CSO respectively. The negative value of ΔGads was greater than 20 kJ/mol and was obtained as a result of electrostatic interaction between the adsorbed inhibitor molecules and the  ions/atoms on the metal surface. The studied inhibitors were confirmed to be mixed organic corrosion inhibitors type. The values of E and maximum surface coverage (θmax) for the two measurements are satisfactorily in acceptable agreement  as similar to the range of value obtained for inhibition efficiency.