Adsorption and Corrosion Inhibition Characteristics of Some Thiophene-3-Carbohydrazide Derivatives on Low Carbon Steel in Hydrochloric Acid Solutions

New compounds namely amino-N'-(3-(hydroxyimino)butan-2-ylidene)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbohydrazide (1), amino-N'-(thiophen-2-ylmethylene)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbohydrazide (2) and amino-N'-(1-(pyridin-2-yl)ethylidene)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbohydrazide (3) were synthesized and used as corrosion inhibitors for carbon steel in 1 M hydrochloric acid at 25°C using different monitoring techniques. Potentiodynamic polarization studies showed that these derivatives were mixed type inhibitors. The effect of temperature on the corrosion behavior of carbon steel in 1 M HCl in presence and absence of these compounds at were studied. The adsorption of these inhibitors on carbon steel surface from hydrochloric acid obeyed the Langmuir adsorption isotherm. Quantum chemical method is used to explore the relationship between the inhibitors molecular properties and their inhibition efficiency.