Author: Dustov, Aziz Yusufovich

Annotation: Corrosion of carbon-steel equipment in open recirculating (cooling-tower) water systems is one of the most persistent technological and economic problems of the oil-and-gas, chemical and power industries, shortening the service life of pipelines, heat exchangers and pumps and forcing premature capital expenditure. This paper reports the development, laboratory characterization and industrial-scale validation of a family of low-molecular-weight amine-based composite inhibitors (designated AD-1, AD-2 and AD-3) intended for the simultaneous suppression of electrochemical corrosion and mineral scaling in the recirculating cooling-water system of the Shortan Oil and Gas Production Department (Kashqadarya region, Uzbekistan). The inhibitors were synthesized from locally available amine raw materials; the influence of temperature, reaction time and reagent mass ratios on the reaction yield was established. Inhibition efficiency was quantified gravimetrically on St3 steel coupons in accordance with GOST 9.905-82 across fourteen aggressive model media (cooling-tower water, Na2SO4, Na2S, NaHCO3, NaClO, Na2CO3, KCl, MgSO4, CaCl2, CaCO3, CaSO4 and mixed salts) at inhibitor dosages of 1-3 %. Surface films were characterized by scanning electron microscopy (SEM, Zeiss EVO MA 10) coupled with energy-dispersive X-ray spectroscopy (EDS). In aqueous medium the protection degree of AD-1 reached 98.6 %, and values of 91-98 % were recorded across the sulphate, sulphide and chloride media; the minimum corrosion rate fell to 0.004 g·cm-2·h-1 and the maximum protection degree across all media reached 97.6 %. An integrated corrosion-risk coefficient (Kk) was formulated to describe the combined action of ionic composition, dissolved gases, temperature and hydrodynamics of the Shortan water, predicting corrosivity with 15-20 % accuracy where the classical Langelier and Ryznar indices proved insufficient. Under industrial trials the optimized composite reduced the corrosion rate by 85-97 % and mineral scaling by 60-75 % at an optimal dosage of about 1 %, extending equipment service life by 8-12 % and yielding an economic effect of approximately 19 % through import substitution based on local raw materials.

Keywords: recirculating water system; carbon-steel corrosion; amine-based composite inhibitor; protection degree; gravimetric method; scanning electron microscopy; corrosion-risk coefficient; Shortan oil and gas enterprise.

Pages in journal: 5 - 15