Mesoscopic transformation at initial corrosion stage of 20# steel in aqueous solution under gas–liquid two-phase stratified flow condition

Abstract

Purpose This study aims to investigate the initial corrosion behavior in aqueous solution of 20# seamless steel under (CO2/aqueous solution) gas–liquid two-phase stratified flow conditions. Design/methodology/approach The initial corrosion behavior was studied through the weight loss methods, scanning electron microscopy with energy-dispersive x-ray spectroscopy and x-ray diffraction. Findings The corrosion rate of 20# steel obviously increases with the increasing gas pressure at different corrosion time when the CO2 pressure is less than 0.11 MPa, and the increase of corrosion rate tends to be steady when the pressure exceeds 0.11 MPa. With the increase of CO2 pressure, the corrosion products changed from flocculent to acicular, granular and scaly. A four-stage model for the growth of the corrosion product layer was proposed, namely, the diffusion reaction stage, the local film formation stage, the complete film formation stage and the densification stage of the product film. Originality/value A four-stage model for the growth of the corrosion product layer on the pipe wall surface under this condition was proposed, namely, the diffusion reaction stage, the local film formation stage, the complete film formation stage and the densification stage of the product film. The growing process and densification mechanism of corrosion products layer were discussed.

The Initial Corrosion Behavior of 20# Steel under the CO2/Aqueous Solution Gas–Liquid Two-Phase Bubble Flow Condition

“…The experimental material, the sample size, and its treating process are same as those in references [20,21]. The corrosive medium is the same as that in references [20,21].…”

“…The experimental material, the sample size, and its treating process are same as those in references [20,21]. The corrosive medium is the same as that in references [20,21]. The experimental condition was a gas-liquid two-phase (CO 2 /aqueous solution) bubbly flow at room temperature.…”

“…The samples in this study were divided into ten groups; the corresponding test time of each group was 10 min, 20 min, 40 min, 2 h, 3 h, 4 h, 5 h, 7 h, and 9 h, respectively. The treatment and analysis of the samples after the corrosion are the same as those in references [20,21]. The method for the observation of the surface morphology and composition analysis of the corrosion products is the same as that in references [20,21].…”

“…The treatment and analysis of the samples after the corrosion are the same as those in references [20,21]. The method for the observation of the surface morphology and composition analysis of the corrosion products is the same as that in references [20,21].…”