In the CO2 separation and recovery process of CCS, high concentration alkanolamine (amine) solutions are widely used. However there exists a basic chemical structure difference between primary and tertiary amines. Therefore, corrosion tests were carried out on CO2-saturated DGA (primary amine) and CO2-saturated MDEA (tertiary amine). There was no distinct difference in corrosivity between DGA and MDEA at their low concentrations. However, remarkable difference was confirmed at their high concentrations. MDEA absorbs CO2 as bicarbonate, whereas DGA absorbs CO2 mainly as carbamate at high concentrations. It was concluded that DGA carbamate produces a stable water-soluble five-membered chelate ring with Fe2+, resulting in the high corrosivity. Carbamates, which do not produce a five-membered chelate ring with Fe2+ do not show very high corrosivity as DGA carbamate.
In this paper, the effect of supercritical CO2 on corrosion behavior of stainless steels, mainly 13%Cr steels, was reviewed. Corrosion rate of 13%Cr steels in supercritical CO2 was similar to or less than that in gas CO2. When the pressure of supercritical CO2 became higher than 20MPa, pitting corrosion was more likely to occur in the steels. Under the supercritical CO2 including 45kPa oxygen, crevice corrosion of 13%Cr steels was recognized. When oxygen partial pressure reduced to 4.5kPa in supercritical CO2, no crevice corrosion was recognized in Steel B which was a low C steel with Mo addition. Steel B showed better corrosion resistance than Steel A which did not contain Mo, in all tested conditions, not only CO2 gas conditions but also critical CO2 conditions. Published papers related to effects of impurities such as NO2, SO2 and etc. on corrosion resistance of stainless steels and estimation of phase behavior of supercritical CO2 were reviewed and summarized.
We outlined the notes on the structure and material selection of the CO2 injection pump to be used in transport and injection in the CCS. The effect of CO2 density changes in the inside of pump is taken into account in structural design. As CO2 has a low viscosity, it is necessary to note selection and surface modification of the wearing parts. Since the increase in corrosion resistance becomes important if water or impurities are contained more than some level, it is necessary to pay attention to the selection of material used for the pump parts. We also introduce our supply experiences to the actual plants.
Regarding the geological storage of CO2 in CCS, the stability of the casing steel tube and the cement plug in the abandoned well is important in order to investigate the potential for CO2 leakage. Recent studies on chemical reaction (corrosion) of the casing steel and cement with stored CO2 are introduced on the assumption that the CO2 in the reservoir reaches the abandoned well.
In 2014, a cast iron lump was excavated from the precinct of Tōdaiji temple. We investigated the similarity of the excavated cast iron lump and cast iron bathtub in the Ōyuya (bath house), Tōdaiji temple. Cu concentration and the ratio of Cu/Fe were used to compare their similarity. On the basis of the Cu/Fe ratio, we have estimated that both cast iron materials have different compositions. Moreover, XRD analysis showed that the rust piece of the cast iron bathtub contained a considerable amount of β-FeOOH (Akaganeite), which is only formed in the presence of Cl‒. β-FeOOH was also found in the metallic parts of the bathtub sample.
Authors have developed anti-corrosive method using porous sintered Al-Zn plate and fiber sheet in atmospheric environment. In addition to this, reductive reaction mechanism of the corrosion product due to electrons supplied from the sacrificial anode was investigated. The purpose of this research is to clarify the validity of the anticorrosive method using the Al-Zn alloy casting plate instead of the porous sintered plate. Laboratory tests and atmospheric exposure tests in a corrosive environment by airborne sea salt were conducted on the model specimens with different Al-Zn alloy casting plates.