Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： none
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： none
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： The corrosion behaviour of low alloy steel containing Ni and Cu was studied because it is a promising candidate canister material for the disposal of high-level radioactive waste (HLW) in China. Due to the intensely radioactive nature of HLW, the waste has to be prevented from reaching the biosphere for many tens of thousands of years. Deep geological disposal is now considered to be the most preferable option for isolating HLW and it relies on series of natural and engineered barriers, e.g. a metallic canister. However, as soon as the waste package is settled, groundwater would seep back slowly through the outer barriers and ultimately arrive at the surface of the canister. Accordingly, there comes the groundwater-induced dissolution of the canister and subsequent transport of radionuclides through the barriers. That is to say, the effectiveness of radionuclide retention and isolation depends mostly and finally on the corrosion resistance of metallic canisters in deep groundwater environments. In this work, the test solution is deaerated 0.1 mol/L NaHCO3+0.1 mol/L NaCl, simulating the deep groundwater environment. The evolution of corrosion of NiCu low alloy steel in the test solution was investigated by electrochemical measurments. XRD was used to illustrate the composition of formed corrosion products. SEM was used to observe the electrode surface morphology and the cross section of the rust layer. The electrochemical results showed that low alloy steel has a lower corrosion rate and is less prone to localized corrosion than low carbon steel. In order to understand the mechanism of alloying elements, EDS and EPMA were used to analyse the distribution of alloying elements cross-sectional. XPS and E-pH diagram were used to estimate the possible existence form of alloying elements. By means of EDS and EPMA, it was founded that Ni is concentrated in the inner rust layer while the enrichment of Cu is not so obvious. XRD, XPS and E-pH results indicated that Ni and Cu are existed in the form of NiFe2O4 and CuFeO2 respectively.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： The atmosphere in many cities along the coastal lines such as Qingdao in China has been polluted with SO2 due to the development of industry, and the atmosphere therefore has been changed to coastal-industrial atmosphere. The corrosion behavior and mechanism of steels in coastal-industrial atmosphere with the co-existence of SO2 and Cl- are different from that in the coastal atmosphere containing only Cl- or the industrial atmosphere containing only SO2. In addition, pH value is diverse in different coastal-industrial atmosphere. However, there are only few researches on the effect of pH value on the corrosion evolution of steels in the coastal-industrial atmosphere. Almost all the atmospheric corrosion data of steels were obtained by the field exposure test, which could not reflect the dependence of the atmospheric corrosion evolution of steels on pH value due to the difficulties in controlling the field conditions. In this work, the effect of pH value on the corrosion evolution of Q235B steel in the simulated coastal-industrial atmospheres has been investigated by the dry/wet cyclic corrosion test (CCT), XRD and EIS. The results indicate that, when the content of SO2 is lower, changing pH value has no effect on the corrosion of the steel. When the content of SO2 is higher, the corrosion rate of Q235B steel influenced by changing pH value shows an extreme phenomenon, that is, when the pH value being a certain value between the "higher" and the "lower", the corrosion rate of Q235B steel reaches the maximum value. When the SO2 content is certain, changing pH value almost has no effect on the rust composition. To some extent, the existence of SO2 inhibits the formation of b-FeOOH. With the increasing of SO2 content, the relative contents of b-FeOOH and g-FeOOH are decreasing, and g-FeOOH maybe reduced back to Fe3O4 or transform to a-FeOOH. With the corrosion process prolongs, the rust evolution shows almost the same trend. In addition, when the content of SO2 in the simulated coastal-industrial atmosphere is lower, the Q235B steel mainly follows Cl- corrosion mechanism, and the influence of pH value on corrosion behavior of the steel is not obvious. When the content of SO2 is higher, the Q235B steel also follows Cl- corrosion mechanism in the early stage; with prolonging the dry/wet cyclic corrosion test number, H2SO4 regeneration mechanism accelerates corrosion of the steel as the effect of SO2 on corrosion increasing significantly.
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