An-Najah Staff

The inhibition of ethyl 2-(4-(2-ethoxy-2-oxoethyl)-2-p-tolylquinoxalin-1(4H)-yl) acetate (Q3) on the corrosion of carbon steel in 1.0 M HCl at 308-343 K was studied by gravimetric method. Results obtained show that Q3 acts as inhibitor for carbon steel in hydrochloric solution. The inhibition efficiency was found to increase with increase in Q3 but decreased with temperature, which is suggestive of physical adsorption mechanism although chemisorption may play a part. The adsorption of Q3 onto the carbon steel surface was found to follow the Langmuir adsorption isotherm. Both kinetic parameters (activation energy, pre-exponential factor, enthalpy of activation and entropy of activation) and thermodynamics of adsorption (enthalpy of adsorption, entropy of adsorption and Gibbs free energy) were calculated and discussed.

N-1-Naphthylethylenediamine dihydrochloride monomethanolate (N-NEDHME) was tested as a corrosion inhibitor for copper in 2 M HNO3 solution using the standard gravimetric technique at 303–343 K. N-NEDHME acts as an inhibitor for copper in an acidic medium. Inhibition efficiency increases with increase in concentration of N-NEDHME but decreases with a rise in temperature. Thermodynamic parameters such as adsorption heat ( \UpdeltaH∘ads ), adsorption entropy ( \UpdeltaS∘ads ) and adsorption free energy (\UpdeltaG∘ads) were obtained from experimental data of the temperature studies of the inhibition process at five temperatures ranging from 303 to 343 K. Kinetic parameters activation such as Ea , \UpdeltaH∘a , \UpdeltaS∘a and pre-exponential factors have been calculated and are discussed. Adsorption of N-NEDHME on the copper surface in 2 M HNO3 follows the Langmuir isotherm model.