The seawater pumped storage power plant uses seawater directly as the operational source. The relevant metallic materials were suffered from corrosion induced by high pressure and high speed seawater. Research on the corrosion mechanism and corrosion control of metallic structures and material selection for seawater pumped storage power plant is in urgent need. This article discusses the related marine environmental factors and their impact on the corrosion of metallic materials in service conditions of seawater pumped storage power plant. The common types of metal corrosion in the marine environment are introduced and the corrosion mechanisms of metal materials in the marine environment are analyzed. The possible corrosion problems encountered of the main structural workpieces during service of the seawater pumped storage power plant are briefly introduced. Finally, corrosion-resistant materials that can apply to seawater pumped storage power plant and their anticorrosion properties in marine environment are also described.

Microbiologically influenced corrosion (MIC) of pipeline steels has been recognized as an important form of pipeline failures. It has been reported that more than 20% of pipeline system failures was related to microorganisms. It is therefore important to improve our understanding of MIC and take countermeasures for controlling the MIC. In this paper, the MIC of pipeline steels and the related hazards are reviewed, the MIC failure cases of pipeline steels in recent years are analyzed, and the state-of-the-art of research on the MIC of pipeline steels, as well as the relevant countermeasures are summarized. From the material aspect, the research progress of MIC-resistant pipeline steels is elaborated, and the research and development direction of MIC-resistant pipeline steels is proposed.

The evolution characteristics of corrosion-kinetics,-morphology and -products for X80 steel in a simulated acidic soil solution was acquired by means of weight loss measurement, SEM and XRD. Besides, the long-term corrosion-kinetics of X80 steel, which outdoor burried in real red soil at Nanchang district, was monitored in-situ by using a precise electrical resistance (ER) test system. The relevance between the simulated corrosion experiment and the outdoor soil exposure test were evaluated by using qualitative comparison and grey quantitative analysis. The results show that the corrosion weight loss of X80 steel in the simulated solution as a function of exposure time could be calculated using power function (△W=Atⁿ). For the outdoor exposure in red soil, the corrosion kinetics of X80 steel was similar to that of the simulated test. It had good relevance between the indoor corrosion experiment and the outdoor soil exposure test, regardless of the corrosion kinetics, corrosion morphology and the composition of corrosion products. The correlation degree in the corrosion kinetics for the two methods was about 0.6233. Besides, GM(1,1) corrosion kinetic data prediction model had been established basing on indoor immersing experiment. After verification, the relative error of GM(1,1) prediction model was less than 20%, which indicated that GM(1,1) model could be used to predict the outdoor soil exposure test result.

Corrosion behavior of high nickel weathering steel and conventional weathering steel was contrastively studied in a harsh marine atmosphere environment at Maldives through one-year field exposure tests. Then the corrosion products and the surface morphology of the steels after exposure were characterized by means of scanning electron microscope (SEM), laser scanning confocal microscope (LSCM) and X-ray diffractometer (XRD), while the corrosion resistance of corrosion products formed on the steels was also assessed by electrochemical impedance spectroscopy (EIS). Results indicated that a compact rust scale composed of Fe₃O₄, α-FeOOH, γ-FeOOH and β-FeOOH formed on these two steels. However, the high nickel weathering steel exhibited better weather resistance due to the addition of Ni, which presented the following peculiar features: a denser rust scale with stronger resistance to Cl^- attack and higher α/γ ratio. EIS results confirmed that the corrosion product film of high nickel weathering steel had higher corrosion resistance, thus slowing down its corrosion rate in the harsh marine atmosphere.

Fe₂O₃/TiO₂ nanocomposites were fabricated by chemical bath deposition on the surface of the TiO₂ nanotubes, which had been prepared on titanium foil via anodic oxidation method. Their morphology, phase constituent, composition, and light response were characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible diffuse reflection spectrum (UV-vis DRS). Photoelectric properties of the nanocomposites were assessed by measuring open circuit potential (OCP) under intermittent illumination and photocurrent density versus time (i-t), as well as electrochemical impedance spectroscopy (EIS). Results indicate that the incorporation of Fe₂O₃ increases the utilization efficiency of visible light and strengthens the cathodic protection performance of the TiO₂ nanotubes. In visible light, the open circuit potential of Fe₂O₃/TiO₂ nanocomposite prepared in the bath of 0.05 mol/L Fe(NO₃)₃ is -740 mV, about 300 mV lower than that of the ordinary TiO₂ nanotubes, a better cathodic protection effect for 304 stainless steel.

The crevice corrosion of 316, 904L, 254sMo and 2507 stainless steels in a liquid of the so called green death at 70 ℃, which aims to simulate the corrosive environment of flue gas desulfurization process, was comparatively investigated by means of electrochemical cyclic polarization test and SEM. The results showed that 254sMo and 2507 stainless steel have excellent resistance to crevice corrosion, while the crevice corrosion induced damage of SS316 and SS904L is serious. The "lace cover" structures were observed on the edges of the gap of SS316 and SS904L, but not on that of SS254sMo and SS2507. At the bottom of crevice corrosion pit, duplex super stainless steel 2507 exhibits galvanic corrosion characteristics.

The corrosion behavior of 304 and 316H stainless steels in molten LiF-NaF-KF(FLiNaK) salt at 700 ℃ was studied by static immersion test, followed by SEM/EDS and EPMA analyses. Results show that the corrosion characteristics of the two stainless steels in molten FLiNaK salt are mainly selective depletion of Cr from the surface and grain boundaries underneath the surface. The corrosion depth and weight loss of 316H stainless steel are lower than those of 304 stainless steel, which may be ascribed to the Mo addition in 316H steel. After corrosion, the two steels show surface corrosion layers enriched in Ni and Fe, as well as nano-sized precipitates in the steel matrix near the surface. EDS analyses suggest these precipitates to be Cr and Al nitrides or carbonitrides. The formation of these precipitates significantly increases the hardness of the materials.

A nanocrystalline coating of DD98M was firstly deposited on the surface of high temperature alloy DD98M via magnetron sputtering, then a thin layer of Al-5.2Si (mass fraction, %) was next deposited via multi-arc ion plating on top of the nanocrystalline coating, which was further subjected to vacuum diffusion treatment at 870 ℃ for 3 h, finally a two-layered aluminide coating composed of an outer β-NiAl layer and an inner γ'-Ni₃Al layer was obtained on the DD98M alloy. The isothermal oxidation behavior at 1050 ℃ in air and hot corrosion performance in molten salts Na₂SO₄+25%K₂SO₄ at 900 ℃ of the plain DD98M alloy, the nanocrystalline coating or the two-layered aluminide coating coated DD98M alloy were comparatively investigated. Results revealed that after isothermal oxidation at 1050 ℃, mixed oxides of NiO, α-Al₂O₃, Ta_0.8O₂, CrTaO₄ and NiAl₂O₄ formed on the surface of DD98M alloy, and the oxide scale cracked and spalled seriously. An oxide scale composed of α-Al₂O₃ with a small amount of NiAl₂O₄ formed on the surface of the nanocrystalline coating of DD98M alloy. A dense oxide scale of simplex α-Al₂O₃ formed on the surface of the two-layered aluminide coating. It seems that the bilayered aluminide coating prepared with tri-step process can significantly enhance the oxidation resistance of the DD98M alloy. In molten salts Na₂SO₄+25%K₂SO₄ at 900 ℃, catastrophic corrosion occurred for the plain DD98M alloy only after 20 h corrosion. The as-deposited and pre-oxidation nanocrystalline coating can improved the corrosion resistance of the alloy to certain extent. However, the two-layered aluminide coating can apparently improve the corrosion resistance of the DD98M alloy.

The oxidation behavior of four Ni-Fe-xCr based alloys with different contents of Al/Si was studied in supercritical water at 700 ℃ under 25 MPa. Oxidation kinetics of the alloys was obtained after 200 h exposure. The surface oxide scales were characterized by SEM/EDS and XRD. The results showed that a protective chromia scale formed as the content of Cr increased up to 25% (mass fraction), which was stable during the test. The strengthening phase element-Si was beneficial to the quick formation of protective chromia scale, meanwhile the Al showed little effect on the stability of protective chromia scale.

The thermal barrier coating (TBC) of ZrO₂-7%Y₂O₃ (mass fraction) was firstly prepared on high temperature alloy GH4169 and then remelted via CO₂ laser glazing technique. The hot corrosion behavior of the ordinary and the laser as-remelted TBCs are assessed in 75%Na₂SO₄+25%NaCl (mass fraction) molten salt for different time. The morphologies and phase composition of the two TBCs were characterized by means of scanning electron microscope and X-Ray Diffractometer. The results indicated that the ordinary TBC experienced mass gain in the first period of 50 h, hereafter, mass loss in the rest period of test. The total mass loss was about 6.8 mg/cm² after 100 h test. In the meanwhile spallation of the top surface of the coating did occur and phases of ZrO₂ and Y₂(SO₄)₃ could be detected by XRD on the coating surface. The mass gain versus time curve for the laser remelted TBC rose up gradually in the first stage, and then turned to be stable in the later stage. The total mass gain reached about 3.7 mg/cm² after 100 h test. It is noted that only ZrO₂ phase could be detected on the coating surface. It illustrated that the hot corrosion resistance of the TBCs has been further improved by laser remelted technique.

The iso-thermal oxidation behavior of Co-20Re-20Cr, Co-20Re-25Cr, and Co-20Re-30Cr alloys in 3.04×10^-5 Pa oxygen at 1000 and 1100 ℃ for 24 h was investigated. The three alloys show continuous mass loss due to the evaporation of Re element in the form of ReO₃. The mass loss is more obvious at 1100 ℃ for Co-20Re-20Cr and Co-20Re-25Cr alloys. The oxidation kinetics at 1000 and 1100 ℃ of Co-20Re-20Cr and Co-20Re-25Cr obeys parabolic law, while that of Co-20Re-25Cr is irregular. Correspondingly, the scales formed on the three alloys with different Cr content have a stratified structure. The outermost layer is composed of CoO, while the inner layer, which is very thick and porous, is composed of CoCr₂O₄. However, the very thin innermost layer composed of Cr₂O₃ is not very continuous and complete, accounting for its limited role for protection. With the increase of Cr content, the oxidation resistance of Co-20Re-xCr alloys is enhanced to a certain extent due to the formation of a Cr₂O₃ layer with better continuity and integrity. Furthermore, when the Cr content reaches up to 30%, the oxidation resistance of the alloy was improved greatly.