Surface Response Methodology for Mildsteel Corrosion Inhibition by Ethyl Esters of Castor and Rubber Seed Oils

Surface Response Methodology was conducted for Mildsteel Corrosion Inhibition by Ethyl esters of Castor and Rubber Seed Oils. Inhibitor concentration-in-acid medium, temperature and time were considered as the independent variables, in order to know the effect of the response (dependent) variable, which is the weight loss. The design matrix was constructed on the basis of different conditions of the independent variables at varying coded levels of design consideration (-α, -1, 0, +1 and +α), upon which corrosion inhibition experiments were conducted. Contour plots were used to show the combined effects of the factors (concentration, temperature and time) on the inhibition rate of the two study samples: Castor Seed Oil (CSO) and Rubber Seed Oil, RSO. Weight loss for CSO at combined effects of temperature-concentration, time-concentration and time-temperature were found to be 33.01g, 41.11g and 43.30g respectively, while those of RSO are 30.99g 38.16g and 40.15g respectively. This indicates that the time of the corrosion reaction is the most significant factor among the three factors considered in this study, while reaction temperature is more significant, and the inhibitor concentration is least significant. This high significance of reaction time was eventually manifested at the point of optimization, which indicated the highest response value of 44.52g and 43.89g for CSO and RSO respectively. The results, therefore, identifies RSO (with least weight loss, Z=30.99g) as possessing a better inhibition efficiency, when compared to CSO, and the model equations for both samples are of second order (Pure Quadratic)