Chloride ingression is a major cause of the durability deterioration of reinforced concrete structures in marine environments or exposed to deicing salt. The inevitable cracks in real structure have a significant influence on the transport of chloride ions. The present available methods for artificially inducing concrete cracks in concrete structural parts were introduced, while the relevant advantages and disadvantages of these methods were demonstrated in this paper. On basis of the overview of experimental studies on the chloride ion diffusion in cracked concrete, the geometrical parameters of concrete cracks and their influence on chloride penetration were analyzed, the theory and numerical models of chloride ion transport in cracked concrete were summarized, and some recommendations for further research were given.

Magnesium alloys, as the lightest structural metallic material, have great potential for applications in transportation、electronic and aerospace industries. However, the poor corrosion resistance extremely limits their utilization. Pitting corrosion is the most common localized corrosion form, which is a kind of hidden danger and frequently causes damage to structural parts of Mg-alloys. The effect of corrosive environment and microstructure of alloys on the initiation and propagation of pitting corrosion are summarized based on the recent research progress at home and abroad while the in situ techniques of micro area measurement for pitting corrosion research are introduced. It follows that the combination of in situ techniques and traditional corrosion research methods is the most efficient approach to reveal the pitting corrosion behavior of Mg-alloys. Meantime, the possible methods for declining the pitting corrosion of Mg-alloys are suggested. Eventually, the research focus of pitting corrosion of Mg-alloys in the future is analyzed and forecasted, expecting to give some advices to improve the pitting corrosion-resistant of Mg-alloys.

The effect of Pseudomonas sp. on the decomposition and anticorrosion behavior of polysiloxane varnish coating was investigated by means of microbiological analysis, EIS, SEM and FTIR. Results showed that after 1 d immersion in seawater with Pseudomonas sp. the corrosion resistance of the coating decreased obviously, while which changed little in the sterile seawater, indicating that at the initial immersion stage Pseudomonas sp. could significantly decrease the corrosion resistance of the coating, while decompose the coating. With the extension of immersion time, both in the Pseudomonas sp. inoculated seawater and the sterile seawater, the corrosion resistance of coatings decreased obviously. While for the immersion period of 1~30 d, the decrease of corrosion resistance of coatings was obviously higher in the former seawater, suggesting that Pseudomonas sp. caused damages to the coating. For long term immersion, Pseudomonas sp. exhibits only slight effect on the corrosion resistance of the coating. Additionally, whether seawater with or without Pseudomonas sp., only one time constant could be observed in the EEC obtained by fitting the EIS data. The SEM and FTIR results revealed that the decomposition of coatings could occur to a certain extent for 30 d immersion in the Pseudomonas sp. inoculated seawater.

Q235 carbon steel samples were exposed to tidal- and full immersion-zone at two selected sea waters, namely Qingdao- and Sanya-sea waters for 90, 180 and 270 d months respectively. Then, of which the corrosion morphology, corrosion rate, and the composition of corrosion products were characterized, while the microorganisms in the rust scales were isolated, purified, and identified with the aid of the conventional plate isolation and 16S rDNA sequencing technologies. It was found that the corrosion rate of Q235 carbon steel varied with the location of the test samples and the corrosion rate of the test sample in the tidal zone was always higher than that in the immersion zone. There were variations in the composition of the inner- and outer-layer of corrosion products, and the outer consisted of Fe₃O₄, α-FeOOH, and γ-FeOOH, while Fe₃O₄ dominated in the inner layer. Furthermore, the composition of rust scales was independent on the sea waters. There was a complex microorganism community in the rust scales, which varied with the exposure sea waters and time, as well as the location of test samples. The community was comprised of sulphate-reducing bacteria, iron bacteria, and aerobic bacteria/facultative anaerobes. More species and a larger quantity of isolated bacteria were obtained for the corrosion scales formed in the immersion zone than those in the tidal zone at any exposure time, and it was more facile to detect sulphate-reducing bacteria for the corrosion scales formed in the immersion zone. Aerobic bacteria and facultative anaerobes covered diverse genera, and the dominant bacteria were Vibrio sp., Bacillus sp. and Pseudoalteromonas sp..

The inhibition effect of a new composite organic inhibitor (named IMC-16) on the corrosion of steel rebar in simulated concrete solutions or inside mortar specimens was investigated by means of half-cell corrosion potential measurement, linear polarization measurement and electrochemical impendence spectroscopy respectively. For the comparison, the inhibition effect of a conventional inhibitor Ca(NO₂)₂ was also presented. Results indicate that whether in simulated concrete solutions or inside mortar specimens,for the case of blank, the corrosion potentials of steel rebar electrodes gradually reduced, while the corrosion current densities significantly increased, indicating that the passivity of steel rebar was deteriorated and the localized corrosion initiated on the surface of steel rebar electrodes due to the aggressive effect of chloride ions. However, after the addition of IMC-16 inhibitor, the corrosion potentials and the impedance modulus of steel rebar electrodes were obviously increased, the corrosion current densities and double layer capacitances largely decreased in comparison with those of blank, which reveal that the corrosion of steel rebar was well controlled, the composite organic inhibitor had excellent inhibition effect for the chloride-induced corrosion, and the onset time of steel rebar corrosion was effectively delayed. Dry and wet cycle experiments further show that Ca(NO₂)₂ could retard the steel rebar corrosion at the early stage of tests, but its inhibition performance was gradually decreased with the process of experiments. In comparison with Ca(NO₂)₂, although the inhibition effect of IMC-16 inhibitor was not enough to prevent the steel rebar from corrosion at the early stage of tests, but its inhibition effect and stability were much better than those of Ca(NO₂)₂ at the same concentration for long term.

The severe corrosion of Al-anode is the main barrier preventing the application of Al for air battery with alkaline solution. In this paper, the influence of organic/inorganic compound inhibitor of L-Cysteine/ZnO on the corrosion and electrochemical performance of 3102 Al-alloy were examined in 4 mol/L alkaline solutions. Results show that the corrosion of 3102 Al-alloy is significantly restrained by the L-Cysteine/ZnO compound inhibitor. The dissolution of Al-anode is mainly controlled by the charge-transfer in NaOH and NaOH L-Cysteine solutions, but in NaOH/ZnO and NaOH/L-Cysteine/ZnO solutions, the discharge is mainly controlled by the diffusion of the zincate ions and corrosion products. By adding L-Cysteine/ZnO compound inhibitor in 4 mol/L NaOH alkaline solution, the discharging performance of aluminum air battery with 3102 Al-anode was improved obviously.

The oxidation behavior of three Ni-Fe-Cr alloys with different contents of Cr was studied in supercritical water at 700 ℃ under 25 MPa. Oxidation kinetics was acquired by weighting samples at intervals. After oxidation, the surface and cross-sectional morphologies, and phase compositions of the oxide scales were investigated using SEM/EDS and XRD. The results showed that the high Cr-content enhances the oxidation resistance of Ni-Fe-Cr alloys in supercritical water, i.e. lowering the mass gains and postponing the onset of breakaway oxidation. In supercritical water, the critical concentration of Cr, needed for the formation as well as sustained and steady growth of the protective chromia scale on Ni-Cr-Fe alloys, is higher than that in air. And in supercritical water, the protective Cr-rich oxide scale forms after a short time exposure. However, this protective Cr-rich oxide scale transforms to non-protective scale more easily in the further oxidation process. As exposure time increases, a duplex oxide scale forms on the alloy with low Cr concentration, and Ni-rich oxide exists in between the two oxide layers.

The wet recovery efficiency of superalloy directly depends on its dissolution rate, therefore,the electrochemical dissolution behavior of a Ni-based superalloy N5 in aqua regia was studied by means of potentiondynamic polarization measurement and electrochemical impedance spectroscopy (EIS), as well as galvanostatic- and potentiostaic-electrolysis. While the surface morphology and dissolution products of the treated alloy were characterized by means of SEM, EDS, EPMA and XRD. It was found that during electrolysis a two layered corrosion product formed on the alloy surface, which consisted of an outer layer with loose deposition of oxides and carbides of Ta and W and an inner porous layer consisted of residual matrix and Cr-rich oxides. A qualitative model has been assumed to illustrate the electrochemical dissolution behavior. It follows that the diffusion barrier effect induced by corrosion products on the anode is the main cause responsible for the increase of the electrolytic resistance, hence, stripping off the corrosion products in time can increase the dissolution rate of the superalloy by ca 100%.

A novel protective coating, namely ES150 silicone modified with nano-particulate of metal was prepared by physical blending process, which was further applied on AZ91D Mg-alloy, and then the corrosion resistance of the coated alloy was evaluated by electrochemical impedance spectroscopy (EIS), immersion test in 3.5% (mass fraction) NaCl solution and neutral salt spray exposure. The results indicated that lots of micropores could be observed within the silicone lacquer coating, which deteriorates its protective efficiency. In contrast, the number of micropores decreased greatly for the modified silicone coatings with nano-particulate of metal. The modified ES150 coatings can withstand 6000 h immersion in 3.5%NaCl solution and 5000 h neutral salt spray exposure without blistering, peeling off or corrosion. The impedance of the coatings is larger than 10⁹ Ω·cm² during immersion in 3.5%NaCl solution. The SO₂ accelerated corrosion experiments revealed that the coatings provide sufficient protectiveness for airplane workpieces.

Three polyethylene glycol (400) lauric acid monoester Schiff base surfactants (M1, M2 and M3) were synthesized and characterized. The adsorption behavior and the effect of the group of surfactant molecules on the adsorption properties about M1, M2, M3 on the metal Zn surface were investigated by means of molecular dynamics simulation method. While the corrosion inhibition performance of the three surfactants on alkaline Zn-electrode was assessed by means of mass loss method, electrochemical impedance spectroscopy and scanning electron microscopy. It showed that M3 exhibited the best corrosion inhibition, and the corrosion inhibition efficiency was 92% when the concentration reached 1.0 mmol/L. The Schiff base surfactant molecules adsorbed on Zn surface parallelly to form a dense molecular adsorption film. What's more, the ranking of the adsorption energy of the three surfactants was M3>M2>M1, and that of the adsorption rate was M3>M2>M1. M3 had better corrosion inhibition performance for alkaline zinc electrode, and had better inhibition effect on zinc dendrite.

MgO ceramic coating was prepared firstly on AZ91 Mg-alloy by micro-arc oxidation (MAO),and on which then a Cu-layer was deposited by electroless copper plating. The microstructure, composition, corrosion resistance and electrical conductivity of the composite coating were characterized by means of SEM, XRD, EDS, electrochemical techniques and four-point probe test. The results indicate that the corrosion resistance of Mg-alloy can be effectively improved due to the existence of the ceramic MAO coating, and the 2.5 μm-thick Cu-layer is evenly covered on the surface of MAO coating, while the deposited Cu penetrates and fills the reticular-like pores on the MAO coating and thus to realize a mechanical interlock between the Cu-layer and the MAO coating. The composite coating exhibits well electrical conductivity. Meanwhile, the free corrosion potential of the composite coating increases by 0.2 V, and the corrosion current density is one order of magnitude lower in comparison with the bare Mg-alloy. However, the corrosion resistance of the composite coating is inferior to that of the MAO coating because of the galvanic corrosion between the Cu-layer and the matrix Mg-alloy.

Nantokite hydrolysis is the key reaction in the progression of bronze disease on cupreous objects. This transformation was researched in solutions of 0.15%~4%NaCl with initial pH value 2~7 (adjusted with 0.5 mol/L H₂SO₄). The solution color and the pH change were recorded, while the final products of nantokite hydrolysis were characterized by X-ray diffraction analysis. The solution became Cu ion-containing electrolyte after hydrolysis of nantokite in the solution with pH=2.0. The hydrolysis product is Cu₄SO₄(OH)₆·2H₂O in solutions with pH=2.4~3.0. However the hydrolysis product is Cu₂(OH)₃Cl in solutions with pH=3.3~7.0. The procession varies with the concentration of Cl^-, namely in solutions with low Cl^- cocentration the hydrolysis of nantokite generates cuprite at first and then gradually Cu₂(OH)₃Cl with the increasing Cl^- concentration. In solutions with higher Cl^- concentration, the hydrolysis of nantokite generates directly Cu₂(OH)₃Cl.

The galvanic corrosion for the couple of TA2 Ti-alloy and Cu-Ni alloy, which was adopted typically for seawater pipeline of ship, was numerically simulated by means of the numerical simulation technique based on the boundary element method. In the meanwhile, the measured potentiodynamic polarization curves of Ti-alloy and Cu-alloy in static and flow seawater are used as reference as the boundary conditions for the numerical simulation. The following items are mainly concerned in the numerical simulation, namely the distributions of galvanic corrosion potential and the galvanic corrosion current density corresponding to the given parameters such as varying pipe radius, medium velocity and insulation grade etc. The results showed that the most severe corrosion area emerged in the place, where the two electrodes directly connected for the couple system of TA2 and B10 (area ratio 1:1), with a corrosion severity of about 4 times of that appeared in the case of natural corrosion. The galvanic corrosion rate shows a positive correlation with the pipe diameter and the media velocity.