Universalism of inhibitors against hydrogen sulfide and carbon dioxide corrosion of steel

摘要

The universality of inhibitors is understood as their ability to inhibit several types of corrosionattack or to counteract the negative effects of several different corrosion stimulants at the sametime. Criteria of universal inhibitors:Suppression of the general corrosion of steel under the conditions of variouscorrosion stimulants present individually or jointly (H_2S, CO_2).Bactericidal activity in relation to sulfate-reducing and other types ofbacteria.Suppression of hydrogen diffusion into metal. Preservation of mechanical properties of metalstructural materials.Indicators of universalism of inhibitors "INCORGAZ-11TNT" (a composition based on imidazolinesand amidoamines obtained by the interaction of triethylenetetramine and a mixture of naphthenicand ethylhexanoic acids) and "INCORGAZ-11TD" (a composition also based on imidazolines andamidoamines, products of the reaction of diethylenetriamine and mixtures of the same acids ) havebeen studied. The effectiveness of the action of the inhibitors in the concentration of 25 -200 mg/Lhas been studied with respect to carbon steel in a highly mineralized medium (50 mg/L NaCl, pH=6) and NACE medium (5 g/L NaCl, 0.25 g/L CH_3COOH, pH =3.5) containing H_2S (50-400 mg/L) andCO_2 (1at) separately and together. The bactericidal properties of the compounds were studied withrespect to sulfate-reducing bacteria in the Postgate medium "B". The investigations were carriedout by linear polarization resistance, electrochemical impedance spectroscopy, and gravimetrically.A number of studies were carried out in a two-phase system of the hydrocarbon phase(HPh)/electrolyte solution under agitation conditions. As the HPh, diesel fuel (10% by volume) wasused. An increase in the concentration of hydrogen sulfide increases the protective efficacy of theinhibitors up to 80%. It is shown that the protective effect is determined by the joint effect of thesulfide film of corrosion products and the inhibitor. In the presence of diesel fuel, the protectiveeffect of inhibitors increases to 98%. Both inhibitors at a concentration of 100 mg/L repeatedlyreduce the number of sulfate-reducing bacteria and the production of hydrogen sulfide. The studiedinhibitors repeatedly inhibit the diffusion of hydrogen into steel. Thus, INCORGAZ-11TNT andINCORGAZ-11TD inhibitors correspond practically all the requirements for universal inhibitors ofhydrogen sulfide and carbon dioxide corrosion.