Surface Response Methodology for Mild Steel Corrosion Control Using Udara Bark Extract as Inhibitor

This study employed factorial design (Random) experiments to generate surface responses of three factors – Extract Concentration, Time and Inhibition Efficiency. This is aimed at evaluating the effect of the independent variables (Concentration and Time) on the response variable (Inhibition Efficiency). The use of Udara Bark Extract as inhibitor in the control of acid corrosion of mild steel was examined during the study. In the bid to realize the research objectives, the design matrix for the two variables was varied at two levels (high and low) in accordance with the Yates Analogy. Experimental data generated were analyzed using the Design Expert Software, whereas Analysis of Variance and Regression Analysis were employed to assess the correlation efficiency of design factors. Surface plots of the interaction effects of the factors were also used to evaluate optimum conditions for the inhibition efficiency, and the correlation between the experimental process variables and the inhibition efficiency, which was evaluated using the central composite modeling technique. Inhibition Efficiency in 1M HCl medium was found to 30%, while that in 0.5M H₂SO₄ was 20%. The result of the ANOVA showed zero values for Coefficient Estimate and Sum of Square, indicating that the quadratic model suits the experimental data and the interaction of the factors were within acceptable level of significance. The even distribution of data points around the straight line in the plot of Experimental versus Predicted values demonstrates that there is good relationship between plot variables, and the underlying assumptions of the analysis were appropriate. The result, generally, suggests that the selected quadratic model was adequate in predicting the response variables for the experimental data.