No abstract

The harm of salt expansion of saline soil in arid areas has always been a major problem to be solved urgently. According to the conversion rule between sodium sulfate and sodium sulfate decahydrate, sodium sulfate decahydrate crystals can be precipitated from sodium sulfate solution by cooling. Besides, when the relative humidity (RH) exceeds the critical relative humidity (CRH), sodium sulfate decahydrate can be formed by the combination of sodium sulfate and vaporous water, resulting in the salt volume expansion. However, at present, in the salt expansion mechanism of sulfate saline soil, only the influence of liquid water is considered while vaporous water is not involved. To study the effects of temperature, salinity, and ARH on salt expansion, the salt expansion test of dry sulfate saline soil under the action of vaporous water was conducted, and its composition was analyzed by X-ray diffraction (XRD) technology. Experimental results showed that sodium sulfate decahydrate crystals were produced in the sulfate saline soil if the relative humidity (RH) of pore gas exceeded the critical one so that salt expansion occurred. Salt expansion and salt expansion rate of sulfate saline soil increased with the increase of RH and salinity but decreased with the increase of temperature. Therefore, the new salt expansion mechanism of sulfate saline soil under vaporous water is verified. The experimental results further perfected the original salt expansion mechanism of sulfate saline soil under the action of liquid water and guided the study of new treatment methods of sulfate saline soil.

No abstract

The corrosion behavior of L360 pipeline steel coated with or without elemental sulfur (S8) in CO2–Cl− medium at different pH was studied. An autoclave was used to simulate the working conditions for forming the corrosion scale, and an electrochemical workstation with a three-electrode cell was used to analyze the electrochemical characterization of the corrosion scale. A wire beam electrode was used to determine the potential and current distribution, and scanning electron microscopy and X-ray diffraction were used to characterize the morphology and composition of the corrosion scale. The results showed that the deposition of S8 on the surface of the electrodes caused serious localized corrosion, especially under acidic conditions. The morphology and localized corrosion intensity index further proved that the deposition of S8 significantly promoted corrosion, especially pitting corrosion. Finally, a novel corrosion mechanism of L360 pipeline steel coated with S8 in a CO2-Cl− environment under acidic conditions was proposed, and we then modeled the theoretical mechanisms that explained the experimental results.

No abstract