With the solid oxide fuel cells (SOFC) operation temperature reduced from 1000℃ to 600~800℃,\linebreak Fe-based ferritic stainless steels was the best candidate for SOFC interconnect applications. However, rapid scale growth and the volatility of Cr led to significant SOFC performance degradation. Two solutions were suggested to solve the problem, i.e. applying surface protective coating and bulk material modification, and the former one was considered as potential remedy due to its low cost and easy fabrication. The focus of this paper was to categorize the current coatings for interconnects, as well as the characteristics and prospects of coatings.

Ta modified layer was obtained on Q235 steel by double glow plasma surface metallurgy and its microstructure, composition and corrosion resistance were investigated by XRD, SEM, EDS, polarization curve, electrochemical impedance spectroscopy(EIS) and neutral salt spray test(NSS). The results indicated that the Ta modified layer adhered strongly to substrate and its thickness was about 32μm. Ta element distributed gradiently from the surface to substrate and the modified layer was mainly consisted of α-Ta phase. The results of polarization curves, electrochemical impedance spectroscopy and neutral salt spray test revealed that the Ta modified layer exhibited better corrosion resistance than Q235 steel.

Potential and current distributions in a cathodically polarized crevice between a simulated disbonded coating and segmented Q345 steels were measured in this paper. The effects of agitation, oxygen concentration and pH value of initial solution on cathodic polarization behavior were studied. The results showed that agitation forced the oxygen in bulk solution to enter the crevice, thus degrading cathodic polarization level of Q345 steels in crevice. In low conductivity solution, agitation caused oxygen concentration cells in crevice, and aggravated corrosion at the rear of crevice. The oxygen concentration and initial solution pH had little influence on the final cathodic polarization level of Q345 steels beneath the simulated disbonded coating.

The corrosion behavior of super-austenitic stainless steel AL-6XN exposed to supercritical water (SCW) at 500℃, 550℃, 600℃/25 MPa respectively was investigated by means of mass loss method, scanning electron microscope/energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. A dual-layered oxide scale formed on AL-6XN, which was mainly composed of Fe₃O₄, Cr₂O₃, Fe₂O₃ and FeCr₂O₄. The oxide scale had a tendency to spall, which increased with the increase of exposure temperature.

The corrosion behavior of austenite stainless steel Al-6XN exposed in high temperature high pressure water for different periods was investigated. The results showed that compact oxide scale could form on unirradiation sample in sub- and supercritical water. The oxide scale formed on irradiation sample exhibited obvious dissolution in sub-critical water and oxide scale exfoliated in supercritical water. Proton irradiation could not alter the chemical elements and phase structure of the oxide film. The oxide scale exfoliation model for the protons irradiated austenitic stainless steel exposed in high temperature water was proposed.

Black ceramic coating was obtained by micro-arc oxidation on 6063 aluminum alloy in an electrolyte containing silicate-phosphate. SEM, EDS, XRD, spectrophotometer, 3D morphology instrument were used to characterize the morphology, composition, microstructure, blackness, surface roughness and corrosion resistance of the ceramic coating. The results showed that the additive not only improved the blackness, homogeneity and adhesion strength of ceramic coating, but also reduced the surface roughness. The constituent phase in coatings from electrolyte with or without additive were the same, i.e. γ-Al₂O₃ and Al$_{86}V₁₄. The corrosion current density of coating treated in electrolyte containing additive was much lower than that of the coating fabricated without additive, indicating significantly improved corrosion resistance.

Polyaniline-SiO₂ was in situ synthesized and doped by p-toluenesulfonic acid (p-TSA). The composites were characterized by FTIR, SEM and TEM. The corrosion performance of polyaniline-SiO2 pigmented waterborne coating on carbon steel was studied by electrochemical testing technique in 3.5% NaCl solution. The tested results showed that a passivation effect and a positive shift of corrosion potential occurred due to the application of coating on metals and the anticorrosion property was enhanced.

The effect of urea (0.05 mass %) on the microbial corrosion of Q235 steel in soil with humidity at 10 % was investigated by electrochemical impendence spectroscopy(EIS), polarization curve, scanning electron microscopy (SEM) and EDX. The results showed that urea accelerated carbon steel corrosion in soil with SRB yet prevented the corrosion of steel in sterile soil. The results of EIS showed that in inoculated soil only one time constant appeared in primary experimental period, two time constants appeared after 5 d and corrosion product formed on the steel surface. Warburg impedance was found at the later stage, which indicated that the process was controlled by concentration polarization. Sulfur element was detected in corrosion product of carbon steel in soil with SRB by EDX, which confirmed the effects of SRB on the corrosion.

Magnesium sacrificial anodes with different Mn contents, i.e. 0.08%, 0.2%, 0.3%, 0.4%, 0.5% and the Mg-1Mn (0.6% and 0.7% Mn), which was used mainly in engineering applications  were prepared by highly purified magnesium. The effects of Mn content on diminishing the Fe content, the microstructure and the electrochemical properties of Mg-Mn anodes were investigated. In addition, the availability of decreasing the Mn content of the Mg-Mn high potential sacrificial anode was proved and the proper Mn addition scale was also determined.

The micro developed and passivated process of corrosion pits of Al-Zn-Sn-Ga alloy were investigated by SEM, and the function relationship between pH value and pits depth in corrosion pits was also calculated in order to explain the expanded and passivated mechanism of pitting corrosion under the condition of neutral NaCl solution. The result showed that pH value increased along with the expanding of the depth of corrosion pits. However in the range of 0~10^-4 cm, the pH variation was minimal. The cathodic reaction, which could lead to passivation of corrosion pits, gradually became faster because of the activation of Ga amalgam. The passivation depth of corrosion pits was about 10^-5 cm.

The corrosion behavior of Q235 steel in seawater reverse osmosis permeate(RO) was investigated by rotation coupon method, SEM, IR and XRD, and electrochemical tests were used for studying the control step and electrode process of corrosion reaction. Experimental results showed that the corrosion rate was speeded up in first 48 h and maintained at 1.4 mm/a afterwards. Initial rust layer was formed by a thin layer of\linebreak γ-FeOOH, and with time passing by, it transformed to a double-layer structure with inner thick Fe₃O₄ layer and outer α-FeOOH/γ-FeOOH layer. Corrosion process was controlled by cathodic reaction, resistance of which reached peak in initial stage, then reduced rapidly because of conversion of γ-FeOOH to Fe₃O₄, which provided no inhibition of corrosion and caused high corrosion rate of Q235 steel. As the generation and conversion of γ-FeOOH reached equilibrium on the surface of Q235 steel, corrosion resistance and corrosion rate kept steady.

In order to investigate the fracture properties of low carbon steel after seawater immersion and reloading, Q235 steel were made into a series of rectangle cross-section beams with prefabricated crack, and the specimens were divided a few group according to the history of its loading or reloading before and after soaking in room temperature seawater. The fracture behavior of specimen was analyzed in different test conditions, and their bearing capacity was compared with each other for loading before and after soaking. The length of plastic zone of specimen which was soaked in seawater for short-term after loaded into plastic zone became shorter and the material was more brittle.

The initial pitting behavior of 15-5PH stainless steel immersed in 6% FeCl$_{3}$ solution was investigated by electrochemical impedance spectroscopy (EIS) and scanning Kelvin probe (SKP). The results showed that the electrochemical impedance magnitude and the impedance module declined with the immersion time. One time constant appeared in EIS spectrum first then two time constant as the immersion continued. The SKP results indicated that the anodic and cathodic areas alternated constantly with distinct character of localized corrosion. When the corrosion process continued, the surface potential of 15-5PH stainless steel increased, while anodic and cathodic area distinguished evidently from each other.

In order to give an exact evaluation of pitting resistance of 1Cr13 stainless steels, the discrete data of breaking potential was analyzed. By the relationship of the pitting occurrence probability, threshold value and electrode potential, a new parameter called the ultimate zero probability breaking potential was obtained. It could be used for evaluating the pitting corrosion resistance of the stainless steel.

The polarization curves of 304 stainless steel in 3.5% NaCl solution at different potential scanning speed was measured by dynamic potential scanning method, and its pitting potential in NaCl solution with different concentration, temperature and pH value was investigated by electronic speckle pattern interferometer (ESPI) and dynamic potential scan technique. The result indicated that the influence of potential scanning speed on corrosion potential, pitting potential and the size of the hysteresis loop of 304 stainless steel was little when it was 0.3~6 mV/s. The pitting corrosion sensitivity of 304 stainless steel increased with solution concentration and temperature rising and reduced with pH value rising.