Inhibition of Corrosion and Hydrogen Permeation into Carbon Steel in the Chloride Media Containing H2s and CO2

Inhibiting action of compositions on base of the technological mixture of the polyaminoamides and polyaminoimidazolines dissolved in the specific organic protonic solvent (IC-1) and aprotonic one (IC-2) has been studied against steel corrosion and hydrogen diffusion through the steel membrane. Investigations were conducted in the HCl solutions (pH = 2 – 6) containing 0.25 – 25 g/l NaCl and saturated by CO₂ (P = 1 – 2 atm) and H₂S (5 – 1000 mg/L) separately and together by the methods of gravimetrical corrosion tests, potentiodinamic polarization measurements, electrochemical impedance spectroscopy. Electrochemical diffusion method has been used too.

Protective efficiency (Z, %) of the inhibitors increases with decreasing pH value and at the insertion of hydrogen sulfide. Its value reaches 96 % in the solutions with pH=2 containing 500 mg/L H₂S and 200 mg/L of IC-1 or IC-2. At the inhibitor concentration equal to 50 mg/L, efficiencies of first and second inhibitors are near 93% and 85% respectively.  Z increases with increasing C_H2S up to 500 mg/l, further growth of the H₂S concentration does not practically influence on the protective action.

The inhibitors slow down both partial electrode reactions of the corrosion process simultaneously. Their adsorption proceeds according to the Temkin isotherm in the wide range of the cathodic and anodic potentials. Both inhibitors decrease the hydrogen permeation into the steel membrane at the corrosion potential and under the anodic and cathodic polarization too in the presence of CO₂ and H₂S separately and together.