The protective effect of Schiff and Mannich bases on steel corrosion in neutral media

Abstract

The protective effect of Schiff and Mannich basesmorpholine and benzotriazole derivativeson steel corrosion in neutral media has been studied. These substances were previously investigated as inhibitors of atmospheric corrosion. Protective properties were calculated by the effect of the inhibitors on the anodic dissolution rate. The electrochemical measurement was carried out in a mixed electrolyte of 70 mg/dm 3 NaCl + 80 mg/dm 3 Na 2 SO 4 , containing 10% isopropyl alcohol to ensure the solubility of the inhibitors. It has been found that all studied inhibitorsderivatives of morpholine and benzotriazole are more effective than unsubstituted starting compounds. The paper analyzes the dependencies of corrosion inhibitors of this class on a complex of physicochemical properties, such as saturated vapor pressure, electron density on heteroatoms, ionization potentials (PI) of inhibitors, and Hansch hydrophobic constants. Based on literature and experimental data, the protective effect of the morpholine and benzotriazole derivatives investigated in the present work is due to the hydrophobicity effect of the molecules. The decrease in the rate of anodic dissolution in the presence of inhibitors is due to a decrease in the dielectric constant of the electrode layer during the adsorption of inhibitors.