Experimental Design Modelization and Optimization of Pickling Process Parameters for Corrosion Inhibition in Steel Construction

The present study attempted to investigate the best conditions to use 2-(4-chlorophenyle)-1,4,5-triphenyle-H-imidazole as a corrosion inhibitor of mild steel in a 7% HCl and 20% H2SO4 pickling bath mixture, using chemical, electrochemical, and surface response methodologies in a spherical field. For this, a Doehlert matrix and two principal factors of the Pickling Process were examined. An experimental evaluation was carried out using weight loss, electrochemical impedance spectroscopy, and polarization curve measurements. Impedance diagrams and Bode plots for uninhibited and inhibited systems were analyzed and simulated using the Z-view program, the fitted data obtained closely followed the same pattern as the experimental results. This study demonstrates that the 2-(4-chlorophenyle)-1,4,5-triphenyle-H-imidazole compound is an effective inhibitor for mild steel in pickling bath solutions, and corrosion inhibition efficiency increases with increases in inhibitor concentration to attain 93.2% imidazole at 10−3 M. This is due to the absorbability of Cl− and SO42− present in the pickling bath solution and the synergistic effect between both elements. The response used in the exploitation of the design was the determination of inhibitor efficiency. This was assessed through weight loss measurements and electrochemical studies on samples in the absence and presence of 2-(4-chlorophenyle)-1,4,5-triphenyle-H-imidazole. It has been shown that the compound under investigation is an effective cathodic-type inhibitor of mild steel corrosion in pickling bath mixtures. Therefore, the inhibition efficiency was improved with the concentration of the inhibitor, which depended on the molecular structure. The optimal corrosion inhibition efficiency as a function of variation in 2-(4-chlorophenyle)-1,4,5-triphenyle-H-imidazole concentration and pickling bath temperature was simulated and demonstrated using canonical analysis; the obtained efficiency at 324 K for 6 h was 81.3% for the coded variable and 83.4% for the real variable. The experimental results are based on a real-time system and provide much more precise results than the simulated results.