Abstract
When alumina is produced by the Bayer process with high-sulfur bauxite, the sulfur would strongly corrode the 12Cr1MoV steel made heat exchanger. This study investigated the initial corrosion behavior of the 12Cr1MoV steel exposed to a thiosulfate-containing sodium aluminate (TCSA) solution under the evaporation conditions of alumina production. The obtained corrosion rate equation is V = 6.306·t·exp(−0.71). As corrosion progressed, with the corrosion product film growing, the corrosion current density declines slowly, and the corrosion resistance of the steel is increased. At 1–3 days, the corrosion product film consisted of FeO, Fe2O3, and FeOOH. S2O32− lead to corrosion in local areas of the steel and pits appeared. AlO2− is transformed into Al(OH)3 and filled in the corrosion pits. At 4 and 5 days, Fe3O4 is generated in the outermost layer, and Al(OH)3 is shed from the corrosion pits. The corrosion mechanism of 12Cr1MoV steel in a TCSA solution is proposed based on the experimental results.
Highlights
IntroductionHigh-sulfur bauxite is used for the industrial production of alumina, where sulfur, in the form of pyrite (FeS2 ), is converted into S2− , S2 O3 2− and other ions in a sodium aluminate solution [1,2,3]
High-sulfur bauxite is used for the industrial production of alumina, where sulfur, in the form of pyrite (FeS2 ), is converted into S2−, S2 O3 2− and other ions in a sodium aluminate solution [1,2,3].The accumulation of sulfur in the solution causes a series of hazards, such as the loss of alkalinity and the reduction of the alumina dissolution rate [4]
The purpose of this study is to investigate the corrosion behavior of the 12Cr1MoV steel in a thiosulfate-containing sodium aluminate (TCSA)
Summary
High-sulfur bauxite is used for the industrial production of alumina, where sulfur, in the form of pyrite (FeS2 ), is converted into S2− , S2 O3 2− and other ions in a sodium aluminate solution [1,2,3]. The accumulation of sulfur in the solution causes a series of hazards, such as the loss of alkalinity and the reduction of the alumina dissolution rate [4]. During the evaporation of the sodium aluminate solution, the sulfur strongly corrodes the heat exchanger made from 12Cr1MoV steel [5]. The corrosion behavior of 12Cr1MoV steel in the sodium aluminate solution has become an important problem to study. The mechanism of 12Cr1MoV steel corrosion, especially in solutions containing thiosulfate (S2 O3 2− ), remains unclear.
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