Under this condition, even the corrosion rate of 13Cr stainless steel obviously increased. The results indicated that constant O 2 concentrations in supercritical CO 2, even trace of O 2 (1.50×10 - 6), could enhance the corrosion rate of carbon steels tremendously (more than 100 mm/a). The decay kinetics of small starting O 2 concentrations were investigated and used for the experiments with continuous replenishment of used-up O 2. In this study, corrosion experiments of supercritical CO 2 with various amounts of O 2 were carried out to study the effect of small concentrations of O 2 on the corrosion rate of two kinds of carbon steels C75 and X65 and three kinds of stainless steels 13Cr, 2205 and 904L in aqueous supercritical CO 2 at 80 ℃ under 12 MPa. In the presence of a water phase, these trace gases can contribute to the corrosiveness of high pressure-high temperature CO 2 (supercritical CO 2) systems. Generally, the purity of captured CO 2 is only about 95% and can contain trace gases such as O 2, CO, SO x and NO x. The carbon capture and storage (CCS) in geological reservoirs is now considered to be one of the main options for achieving deep reductions in CO 2 emissions. The stress corrosion cracking mechanism was ascribed to anodic dissolution-brittle fracture of grain boundary oxides by the applied stress. The cracks were propagated by the brittle fracture of grain boundary oxides rich in Fe and Ni under the external stress. EBSD and fracture morphology observation showed that the steel suffered mainly from intergranular cracking and the fractured surface exhibitedmainly rock candy-like patternwith partly river-like pattern and quasi-cleavage steps. The formed surface oxide film consisted of an inner layer rich in Fe, a middle layer rich in Ni and an outmost layer of oxide particles rich in Fe and Ni, which could not protect the base metal from further corrosion. The results showed that, after immersion for 720 h, obvious stress corrosion cracks were found on the sample surfaces. It can also attack pipe-wells and tubing bundles.The stress corrosion cracking behavior of forged 316L stainless steel used for the main pipe of pressured water reactors was investigated in sodium hydroxide solution at 330 oC using U-bent samples. Materials with little or no nickel (duplex stainless steels and ferritic stainless steels) and those with high nickel content (superaustenitics and nickel-base alloys) have significantly better resistance to stress cracking.Ĭhloride stress corrosion cracking particularly concerns the nuclear industry because of the wide use of austenitic stainless steel, and the inherent presence of high tensile stresses associated with pressurization. Nickel controls susceptibility to chloride stress corrosion cracking. Environments containing dissolved oxygen and chloride ions can readily be created in auxiliary water systems. This pattern of corrosion occurs because the corrosion tends to follow the direction of highest residual tensile stress, but the actual cracking tends to locally relieve that stress.ĬSCC can be controlled by maintaining low chloride ion and oxygen content in the environment and the use of low-carbon steels. In extreme cases, cracking is so pervasive that the metal can be broken off by hand. This can be minimized considerably by proper annealing processes.Ī stainless steel that has been attacked by CSCC often has a web-like array of tiny surface cracks. It has been found that this is closely associated with certain heat treatments resulting from welding. In the formation of the steel, a chromium-rich carbide precipitates at the grain boundaries, leaving these areas low in protective chromium, and thereby, susceptible to attack. It requires a susceptible material and, depending on the material, sufficient levels of:ĬSCC can attack highly resistant austenitic stainless steel. Corrosionpedia Explains Chloride Stress Corrosion Cracking (CSCC)Ĭhloride stress corrosion cracking is a localized corrosion mechanism like pitting and crevice corrosion.
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