Enhanced corrosion resistance of mild steel in molar hydrochloric acid solution by 1,4-bis(2-pyridyl)-5H-pyridazino[4,5-b]indole: Electrochemical, theoretical and XPS studies

The inhibition effect of the new pyridazine derivative, namely 1,4-bis(2-pyridyl)-5H-pyridazino[4,5-b]indole (PPI) against mild steel corrosion in 1 M HCl solutions was evaluated using weigh loss and electrochemical techniques (potentiodynamic polarisation curves and impedance spectroscopy). The experimental results suggest that PPI is a good corrosion inhibitor and the inhibition efficiency increased with the increase of PPI concentration, while the adsorption followed the Langmuir isotherm. X-ray photoelectron spectroscopy (XPS) and theoretical calculation of electronic density were carried out to establish the mechanism of corrosion inhibition of mild steel with PPI in 1 M HCl medium. The inhibition action of this compound was, assumed to occur via adsorption on the steel surface through the active centres contained of the molecule. The corrosion inhibition is due to the formation of a chemisorbed film on the steel surface.     

Experimental and theoretical study for corrosion inhibition of mild steel in hydrochloric acid solution by some new hydrazine carbodithioic acid derivatives

The corrosion inhibition of mild steel in 0.5 M hydrochloric acid solutions by some new hydrazine carbodithioic acid derivatives namely N′-furan-2-yl-methylene-hydrazine carbodithioic acid (A), N′-(4-dimethylamino-benzylidene)-hydrazine carbodithioic acid (B) and N′-(3-nitro-benzylidene)-hydrazine carbodithioic (C) was studied using chemical (weight loss) and electrochemical (potentiodynamic and electrochemical impedance spectroscopy, EIS) measurements. These measurements show that the inhibition efficiency obtained by these compounds increased by increasing their concentration. The inhibition efficiency follow the order C > B > A. Polarization studies show that these compounds act as mixed type inhibitors in 0.5 M HCl solutions. These inhibitors function through adsorption following Langmuir isotherm. The electronic properties of these inhibitors, obtained using PM3 semi-empirical self-consistence field method, have been correlated with their experimental efficiencies using non-linear regression method.