Inhibition of steel corrosion in model stratum water containing acetic acid and saturated with H2S and CO2

The inhibitory composition, which is a solution of the reaction products of polyamines with carboxylic acids in an organic solvent was shown to have a high efficiency against corrosion of carbon steel in model stratum water containing CH 3 COOH and saturated with H 2 S and CO 2 .The research was carried out using the methods of gravimetry, potentiodynamic polarization, impedance spectroscopy, and electrochemical diffusion techniques.At a concentration of 200 mg/L, the inhibitory composition reaches a protective efficiency of 87% in the presence of H 2 S (400 mg/L) and CO 2 (1 excess atmosphere) in the model stratum water.With the introduction of 5-10% hydrocarbon phase into this medium under dynamic conditions, the protective effectiveness increases up to 97%.The analysis of polarization curves in the media studied showed that the inhibitory composition slows down the cathodic process.The values of the protective effectiveness of the inhibitor calculated on the basis of polarization curves and impedance spectroscopy are in satisfactory agreement with the results obtained from gravimetric data.The inhibitory composition effectively reduces the diffusion of hydrogen into the metal.Impedance spectroscopy data made it possible to evaluate the adsorption of the inhibitory composition, to calculate the degree of coverage of the steel surface, to establish the type of adsorption isotherm and to calculate the value of 0 ads G  .The experiment under autoclave conditions confirmed the high protective effectiveness of the inhibitory composition.