MODELING AND OPTIMIZATION OF CISSUS POPULNEA AS CORROSION INHIBITION ON MILD STEEL IN HCL SOLUTION USING BOX–BEHNKEN DESIGN WITH DESIRABILITY FUNCTION

The corrosion rate and inhibitor efficiency of Cissus Populnea was optimized using Box–Behnken response surface design coupled with numerical optimization technique. The individual and interactive effect of process variables (concentration and time) on the corrosion rate and inhibitor efficiency of Cissus Populnea were studied. The results showed that, concentration and time had significant effect on the corrosion rate and inhibitor efficiency of Cissus Populnea on the mild steel in HCl solution. The experimental data obtained were analyzed by Pareto analysis of variance (ANOVA) and second-order polynomial models were developed using multiple regression analysis. The models developed from the experimental design were predictive and good fit with the experimental data with high coefficient of determination (R ²) values (more than 0.95). An optimization study using Derringer’s desired function methodology was performed and the optimal values were found to be concentration 0.986 g/L and time of 56.697 hours. The corrosion rate and inhibitor efficiency of the Cissus Populnea under these optimum conditions was found to be 0.000199 g/h.cm ² and 71.389 % respectively and the experimental value was 0.000167 and 71.240% respectively. The values of the corrosion rate and inhibitor efficiency obtained were compared with the predicted values and indicated the suitability of the developed quadratic models. The percentage deviation of the experimental and theoretical results was found as 0.602% for corrosion rate and −0.149% for inhibitor efficiency this shows good interaction effect between two independent variables (concentration in g/L and time in hours) on the responses (corrosion rate and inhibitor efficiency).