The research progress of the corrosion of structural metal-materials in liquid metals, such as Bi and Sb, the positive electrode materials and Li, the negative electrode material used for the liquid metal energy storage battery is briefly reviewed, while the research results of liquid metal corrosion in the field of atomic energy reactors in recent years were also taken into account. Issues related with this topic, including the corrosion phenomena, corrosion mechanism and corrosion influencing factors of metal materials in liquid Li, Bi and Sb are summarized, and finally proposals to prevent corrosion of liquid metal are put forward.
Scaling is universal phenomenon in the field of industrial water, and the most cost-effective way to control scaling is chemical scale inhibition. In this paper, the synthesis, modification, application progress and technical difficulties are reviewed for the green environment-friendly scale inhibitors, namely, polyepoxysuccinic acid (PESA) and polyaspartic acid (PASP) and their derivatives, plant extracts and their derivatives, as well as other new type of inhibitors such as carbon nanoparticle scale inhibitor in the field of water treatment. Finally, their future development directions are proposed respectively.
The corrosion behavior of X65 pipeline steel, and the galvanic corrosion behavior of dissimilar metal welds of X65/316L stainless steel and X65/Inconel 625 in CO2-containing environments, as well as the inhibition effect of imidazoline oleic acid corrosion inhibitor on the corrosion were assessed. The results show that with the increase of the potential difference of the galvanic couples, the corrosion rate of the weld seams for X65 steel with different metals increases obviously, and which is significantly higher than that of the base metal. The addition of oleic acid imidazoline corrosion inhibitor can reduce the uniform corrosion rate of the weld seams for X65 steel with different metals in CO2-containing environment, but when the corrosion inhibitor concentration is low, serious groove corrosion or dense pitting pits appear on the X65 steel side of the welds for X65 steel with different metals. Further increase of corrosion inhibitor concentration can eliminate the phenomenon of groove corrosion. The electrochemical polarization curves and electrochemical impedance spectroscopy were used to analyze the inhibition mechanism of corrosion inhibitors on galvanic corrosion of dissimilar metal welds. This study can provide a reference for the corrosion protection of welding joints of dissimilar metals.
Cassava starch ternary graft copolymer (CS-SAS-AAGC) was prepared by grafting two monomers of sodium allylsulfonate (SAS) and acryl amide (AA) simultaneously on the plain cassava starch (CS). The inhibition effect of CS-SAS-AAGC on the corrosion of cold rolled steel (CRS) in H2SO4 was studied by mass loss method, electrochemical technique, scanning electron microscope (SEM) and contact angle measurement. The results show that inhibition performance of CS-SAS-AAGC is better than the single CS, AA or SAS, and the maximum inhibition efficiency is higher than 90%. The adsorption of CS-SAS-AAGC on CRS surface obeys Langmuir isotherm. Inhibitive action gradually decreases with the increase of temperature and acid concentration, while almost remains stable along with the increase of immersion time. CS-SAS-AAGC acts as a mixed-type inhibitor while mainly retards the cathodic reaction. With the addition of CS-SAS-AAGC, the charge transfer resistance of CRS electrode surface is drastically increased, the CRS surface becomes hydrophobic, as a result, its corrosion is efficiently mitigated.
Single phase flow induced erosion-corrosion behavior of 90-degree horizontal elbow was investigated via a loop test device designed independently by means of weight loss measurement and surface analysis methods. The results indicate that the erosion-corrosion rates at different locations of the 90-degree horizontal elbow are different, which vary between 2.11 and 8.90 mm/a. The erosion-corrosion is more serious at the inner part of the elbow and the outer part nearby its outlet. The erosion-corrosion rates induced by single phase flow of 3.5% (mass fraction) NaCl solution are much higher than that in static solution for 20# steel, in other word, the fluid flush promotes the corrosion process, therefore, which is responsible to the significant increase of erosion-corrosion rates. As a consequence, pits and grooves emerged on the surface of steel pieces situated around the inner surface of the elbow, while the grooves show clearly preferred orientation, i.e. their longitudinal axis is consistent with the flow direction of local fluid.
Co(OH)2 was deposited firstly on the surface of nanotube TiO2 by successive ionic layer adsorption and reaction method, and then deposited Co(OH)2 was transformed partially into CoOx by post heat treatment, therewith the Co(OH)2/CoOx modified TiO2 nanotube was acquired as high performance photoanode material. By assessing the effect of the times of Co(OH)2 deposition, as well as the temperature and holding time of heat treatment on the performance of the Co(OH)2/CoOx modified TiO2 nanotube, the optimal processing parameters were determined for the preparation of the best photoanode material. Besides, the relevant mechanism was proposed to interpret the role of Co(OH)2/CoO surface modification in the enhancement of photoelectric performance of the TiO2 nanotube.
A novel anodic process was developed for a RE-containing 7000 series Al-alloy Al-Zn-Mg-Cu-Sc. Further, sealing-pore post treatments were carried out to improve the compactness of the anodic film. The results indicate that the precipitated Sc-containing phases on the surface of 7000 series Al-alloy act as micocathodes to accelerate the corrosion of Al matrix, which has a negative effect on the uniformity of the anodic film. In order to solve this trouble, the formula and electric parameters of the electrolyte bath were adjusted, hence, a uniform and smooth anodic film is formed on the surface of the Al-alloy. Meantime, three sealing-pore processes with fluozirconate, cerate and boiling water respectively were carried out to improve the compactness of the anodic film. It is found that after boiling water sealing-pore, the anodic film exhibits a sliver like uniform surface without defects and microcracks, among others, that film presents the best corrosion resistance, and the film can keep intact after salt spray test for 336 h, which can satisfy the requirement for the actual applications.
Functionalized graphene was firstly prepared by controllable chemical oxidation method, thus grafting reaction between graphene and triethylenetetramine could be realized. The results showed that the structure of graphene sheet is smoother after chemical modification. The properties such as compactness and adhesion of the epoxy resin coating were obviously improved due to the proper incorporation of the modified graphene. Chemical modification can also improve the graphene's dispersibility in and compatibility with epoxy resin binder, as a result, internal defects of the coating can be reduced, which makes the coating much compact and thus effectively prevents the inward migration of corrosive medium. In addition, chemically-bonded interfaces between the modified graphene and epoxy resin can be formed, which delays the destruction of the interface by alternating hydrostatic pressure, and thus prolongs the service life of the coating under this condition.
The electrochemical behavior of the extruded dilute Mg-2Sn-1Al-1Zn alloy was examined in simulated body fluid (SBF) by means of electrochemical workstation CS350. While stable open circuit potential, polarization curve and the impedance data after immersion for different time were measured. Results indicate that the stable open circuit potential value was -1.57 VSCE, the polarization corrosion rate was 8.98 mm/a and the corrosion resistance was 1011.21 Ω·cm2. Impedance tests at different time of immersion in simulated body fluids showed that the corrosion resistance first increased and then decreased. Due to the corrosion product layer on the surface of the soaked alloy is the densest after 2 h of immersion, the value of corrosion resistance reached a maximum of 2151.62 Ω·cm2.
The corrosion behavior in artificial seawater of a marine steel plate suitable for extremely cold environments, EH40 steel before and after subzero treatment was studied by means of immersion test, electrochemical polarization curve measurement, electrochemical impedance spectroscopy, X-ray diffractometer and scanning electron microscope. Results showed that uniform corrosion occurred on the steel before subzero treatment, leading to the formation of a dense corrosion product scale on the steel surface. Whereas, pitting corrosion emerged on the steel subjected to subzero treatment at -80 ℃. The mass loss and corrosion current density of the steel before subzero treatment were 1.15 mm/a and 1.244 μA·cm-2, respectively, which increased to 1.33 mm/a and 3.643 μA·cm-2 for the steel after subzero treatment, indicating that the subzero treatment could reduce the corrosion resistance of the steel. The corrosion products for the steels before and after subzero treatment were composed of α-FeOOH, β-FeOOH, and γ-FeOOH. Therefore, low ambient temperature has certain degree of negative impact on the corrosion resistance of marine steel plate in extremely cold environments.
The corrosion behavior of vacuum diffusion welded component of H62 brass and TC4 Ti-alloy in 3.5% (mass fraction) NaCl solution for up to 24 h was investigated by means of immersion test, scanning Kelvin probe test, scanning electron microscopy attached with EDS and X-ray photoelectron spectroscopy. The results demonstrate that the weld seam width of the jointed H62 brass and TC4 Ti-alloy is about 25~30 μm, and the free corrosion potential of H62 brass is slightly higher than that of TC4 Ti-alloy at the initial stage of immersion test. However, with the prolongation of immersion time, the free corrosion potential of TC4 Ti-alloy turns to be higher than that of H62 brass, and the corrosion of the area of H62 brass, where closed to TC4 Ti-alloy is much more severe than that, where far away from the weld seam. The corrosion products of H62 brass after immersion test composed mainly of CuO, Cu2O, CuCl, CuCl2 and Cu(OH)2, while the scale on TC4 Ti-alloy composed mainly of Ti-oxides TiO2 and Ti2O3. The welded couple of H62 brass/TC4 Ti-alloy exhibits galvanic corrosion tendency in 3.5%NaCl solution, and the H62 brass acts as anode in the galvanic couple, which correspondingly underwent accelerated corrosion process.
The corrosion behavior of riveted dissimilar metals TC4-316L in simulated marine atmospheric conditions was investigated by means of mass loss methods, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and confocal laser scanning microscopy. While the corrosion kinetics, rust composition, and corrosion morphology are mainly concerned. The results indicate 316L stainless steel is corroded when riveted parts TC4-316L were immersed in 3.5%NaCl solution periodically for 1200 h, but TC4 Ti-alloy has no obvious corrosion. The corrosion products of 316L stainless steel composed of FeOOH, Fe3O4 and Fe2O3, while the oxide scale formed on the surface of TC4 Ti-alloy is mainly TiO2 and Ti2O3. Compared with the corrosion behavior of the bare 316L stainless steel, the 316L stainless steel with riveted TC4 Ti-alloy was suffered from accelerated corrosion due to the combined effect of galvanic corrosion and crevice corrosion.
The influence of sulfate-reducing bacteria (SRB) on the corrosion behavior of X70 pipeline steel in an artificial solution for simulation of the corrosivity of soil at Daqing area was studied by polarization curves, electrochemical impedance spectroscopy and SEM, EDS and XRD methods. The results showed that the growth cycle of SRB in the simulated solution could be differentiated as three phases: logarithmic growth phase, decay phase and death phase. SRB metabolism had significant effect on the corrosivity of the simulated solution. The pH value decreased in the first 2 d of SRB growth and then increased. Redox potential, Eh, decreased in the logarithmic growth phase, and increased in the decay and death phases. Conductivity of the solution increased in the logarithmic growth phase and decreased in the decay phase and death phases. During SRB logarithmic growth phase, the free SRB reduced sulfate into sulfide through its metabolic product H to promote the pitting corrosion of X70 steel. During the decay phase of SRB, the corrosion products formed as clusters-like, while the film was dense, which slowed down the corrosion. During the death of SRB, the biofilm dropped off and obvious cracks appeared, thereby microscopic corrosion cell formed, leading to intensified corrosion of X70 pipeline steel. Corrosion products of X70 pipeline steel in the simulated solution with SRB were mainly FeS and Fe3O4.
The corrosion behavior of 316L stainless steel (316LSS) in FLiNaK-CrF3/CrF2 redox system has been studied in this paper. The corrosion rate of 316LSS in molten salt was found to be dependent on the salt potential, which can be adjusted by varying the ratio of the ion pairs ([Cr3+]/[Cr2+]) in the molten salt. When the salt potential was controlled below -0.741 V vs Ni/NiF2 at 873 K or -0.703 V vs Ni/NiF2 at 823 K, the corrosion of 316LSS in the molten salt can be effectively inhibited. This conclusion was verified by the immersion corrosion tests. Another important and interesting feature of the redox buffering molten salt is that different metal- or alloy-materials have almost identical potential in the salt. This effect is significant for applying the modified Tafel method in the redox buffering system.
Composites of Cu matrix with reinforcers of graphite, ZrSiO4 and Fe were prepared via powder metallurgy, then their high temperature oxidation behavior and wear performance were assessed in air at 25, 250, 350 and 450 ℃. The results show that the size and distribution of Fe particles in Cu-matrix affect the oxidation resistance and wear resistance of Cu-based friction materials. With the increasing temperature, the formed oxidation product of Cu on the surface of copper-based friction materials is Cu2O, but that of Fe changed from Fe2O3 to Fe3O4, and the thickness of oxide scale increased gradually. When Fe particles of small size distribute uniformly in the Cu-matrix, it is more conducive to improving the overall oxidation resistance of the Cu-matrix, in the range of 350~450 ℃, the formation of stable oxide scale was beneficial to reduce the adhesive wear, demonstrating better high-temperature wear resistance. However, when the Fe particles in the Cu-matrix were of large size, the phenomenon of heterogeneous oxidation can be observed, which is not conducive to improving the high-temperature wear resistance.
Zn(CH3COO)2 injection in PWR primary loop can slow down the corrosion of structural materials. During the running time of PWR, the water-side corrosion of Zr-based alloy, as fuel element cladding material,may result in significant hydrogen uptake, embrittlement and cracking etc. of the Zr-based alloy, and finally the invalidation of cladding material. In this study, the corrosion behavior of ZIRLO alloy was assessed in LiOH and H3BO3 containing aqueous solution at 360 ℃/18.6 MPa with addition of 50 μg/kg Zn(CH3COO)2 via an autoclave test set, as well as weight change measurement, metalloscopy, XPS and TEM with EDS. The results show that the Zn(CH3COO)2 addition has no significant effect on the weight gain and scale thickness, while the type, valence state and distribution of elements in the formed oxide scale of the tested ZIRLO alloy, but can remarkably reduce the Fe content of the deposits on top of the formed oxide scale, and correspondingly restrain the hydrogen absorption of the ZIRLO alloy.