Abstract
The inhibition of the corrosion of mild steel was studied via the weight loss method over a period of 30 days in an acidic medium formed by 1.0 M HCl and also through potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). In the weight loss approach, the weight loss of the mild steel exposed to the acidic medium, the evaluation of the inhibition efficiency of the (1E,8E)-9-(3-bromo-4-methoxyphenyl)-1,8-bis(2-(2,4-dinitrophenyl)hydrazone)-3,3,6,6-tetramethyl-1,2,3,4,5,6,7,8,9,10-decahydroacridine, a novel hydrazone derivative and the determination of the corrosion rate thereof were carried out. The loss of weight increased with the length of time that the samples were exposed to the acidic medium, with the total weight loss of 12.190 g, 4.208 g, 7.408 g,11.226 g recorded for the corrosive medium that had no inhibitor and those that had 2 ppm, 6 ppm and 10 ppm of the inhibitor respectively. The percent inhibition efficiency was highest in the acidic medium that had 2 ppm concentration and then decreased as the concentration increased. The highest inhibition efficiency value determined was 69.44 % after 15 days exposure to 1.0 M HCl containing just 2 ppm of the inhibitor. The corrosion rate showed same diminishing values with increasing concentration confirming that the inhibitive capacity of the organic inhibitor compound is dose dependent. From the PDP methodology, a very high corrosion rate of 1.416 × 10³ mpy and corrosion current density (icorr) of 3100 µA/cm² were noted for the corrosion test without the inhibitor. With the inhibitor, the corrosion rate and corrosion current density (icorr) significantly reduced to 604.7 mpy and 965 mpy as well as 1320 µA/cm² and 2110 µA/cm², for 2 ppm and 10 ppm inhibitor concentrations respectively. This indicated an effective suppression of the electrochemical reactions responsible for mild steel corrosion. From the EIS methodology, the blank solution exhibited a relatively low Rct value of 36.49 Ω, indicating a highly aggressive environment. However, these values increased significantly to 136.8 Ω and 43.41 Ω in the corrosion medium with 2 ppm and 10 ppm inhibitor concentration respectively, confirming an impeding of corrosion. All the methods used in evaluating C36H36BrN9O9 as an inhibitor of mild steel corrosion confirmed a moderate inhibition efficiency at the concentration of 2 ppm, which diminished in all the cases as the concentration was increased to 10 ppm.