Theoretical Study to Evaluate Experimental Corrosion Inhibition of Ammonium Salt Derivatives for Mild Steel in Acidic Solution

Some new organic triethylammonium salts, with names: triethylammonium 4-((4-(aminomethyl)phenyl)amino)-4-oxobut-2-enoate (B4); triethylammonium5-((4-(aminomethyl)phenyl)amino)-5-oxopentanoate (B5); and triethylammonium 4-((4-(aminomethyl)phenyl)amino)-4-oxobutanoate (B6) were synthesized and identified successfully. They were applied as corrosion organic inhibitors for mild steel in acidic environment. The new organic triethylammonium salts were tested in 1M sulfuric acid for 24 h at room temperature by applying the weight loss measurements. The high efficiency of inhibition values of all triethylammonium salts (B4, B5 & B6) were revealed at the maximum organic triethylammonium salts concentrations. The decreasing of corrosion rates of mild steel were associated with increasing the concentration of organic inhibitors (B4-B6), as well as, the increasing with coverage surface degree. The adsorption free energy values were explained the effects of physisorption for organic salts (B4, B5, and B6). The correlation between experimental results and theoretical data was considered via semi-empirical molecular orbital calculations for the three studied inhibitors. Theoretical calculations were used to understand the nature of interaction among organic corrosion inhibitor molecules and the metal surface of the mild steel.