Abstract
This paper investigated the effect of additional sulfide and thiosulfate on Q235 carbon steel corrosion in alkaline solutions. Weight loss method, scanning electron microscopy (SEM) equipped with EDS, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements were used in this study to show the corrosion behavior and electrochemistry of Q235 carbon steel. Results indicate that the synergistic corrosion rate of Q235 carbon steel in alkaline solution containing sulfide and thiosulfate is larger than that of sulfide and thiosulfate alone, which could be due to redox reaction of sulfide and thiosulfate. The surface cracks and pitting characteristics of the specimens after corrosion were carefully examined and the corrosion products film is flake grains and defective. The main corrosion products of specimen induced by S2−and S2O32-are FeS, FeS2, Fe3O4, and FeOOH. The present study shows that the corrosion mechanism of S2−and S2O32-is different for the corrosion of Q235 carbon steel.
Highlights
The use of high-sulfur bauxite makes Bayer solutions contain high content of S2− in recent years
Q235 carbon steel based on weightlessness corrosion experiment in the alkaline solutions with different concentrations oinfcrSe2a−seadnsdigSn2ifOic3a2n−tlyatin32th8eKp. rTesheencceoorrfoSs2ioOn32−raoter of steel S2−, and the corrosion rate much increased when it is synergy corrosion
The results show that the oxidation film is generated at the steel surface mainly in the absence of S2−, and the corrosion products are sulfide in the absence of S2O32−
Summary
The use of high-sulfur bauxite makes Bayer solutions contain high content of S2− in recent years. Bayer liquor of alumina extraction besides Al(OH) and caustic, other substances are impurities, including Na2SO3, Na2SO4, forth [1]. Na2S2O3 and Na2S are corrosion activators to steel corrosion, which remain the most serious forms of metal failure [2, 3]. As an important equipment material, carbon steel has been widely used and plays a significant role in alumina industry which is used to dissolution equipment, dilution tank, Bayer mother liquor evaporation equipment, and so forth. With the progress of production, the corrosion of sulfides has been recognized as a serious problem, which results in a great economic loss and corrosion cracking and pitting of steel equipment has been experienced in different alumina industry. The study on corrosion of steel equipment and control is a very critical issue
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