Evaluation of Desmodium Adscendens (Swartz) Extract as Corrosion Inhibitor on Carbon Steel in Hydrochloric Acid Using Response Surfacemethodology (Rsm)

This study focused on developing predictive models and optimizing the process variables for inhibiting corrosion of carbon steel in hydrochloric acid using Desmodium adscendens (Swartz). Gravimetric analysis was used to examine four corrosion inhibition factors such as inhibitor concentration, acid concentration, immersion time, and temperature as well as their correlations with corrosion rate (CR) and inhibition efficiency (IE) as response variables. Data from the analysis was used to determine optimal parameters for inhibiting corrosion and create mathematical models using Response Surface Methodology (RSM) with Design Expert software version 13 central composite design (CCD) tool. The models investigated the corrosion inhibition performance of Desmodium adscendens (Swartz) and were found to demonstrate high accuracy and reliability, with p-values below 0.0001. 3-D response surface plots showed that increasing the acid concentration, immersion time, and temperature led to an increase in CR with decrease in IE and vice versa, while inhibitor concentration had a similar impact only when inversely paired with the others. The study revealed that using 0.8 g/L of Desmodium adscendens (Swartz) in 2 M acidic conditions at a low temperature of 323 K had the greatest impact on corrosion IE, with a CR of 0.0007 g cm ^-2 min ^-1 and inhibitor efficiency of 82.02 % after 135 minutes of exposure. Numerical optimization showed that the best conditions for inhibition occurred at a concentration of 0.800 g/L, a temperature of 323 K, an exposure time of 135.001 minutes, and acid concentration of 2 M resulting in an inhibitor efficiency of 82.38 % and a CR of 0.001 g cm ^-2 min ^-1 .