The development and research progress of sacrificial aluminum alloy anode was inspected; the influence of alloying elements and microstructure on the electrochemical performance of sacrificial aluminum alloy anode and the latest research results of dissolving activation mechanism were summarized; in addition, the existing problem and the future trend of development were brought out.

The mechanism, feature and influence factors on AC interference corrosion of oil and gas pipelines are introduced; the relevant new claaasification criteria of risks and the advanced monitoring and protection methods for AC interference corrosion are given. Meanwhile, the latest study on the criteria of cathodic protection in the presence of AC interference corrosion is also stated with views of the author. In the end, several suggestions on testing methods, evaluation and protection strategies about AC corrosion are postulated.

The research on corrosion metallic materials beneath insulation (CUI) coat is summarized in this paper. The mechanism and influential factors about CUI are discussed in detail. The recent research progress of CUI is emphasized, including the main research results, experimental simulation and detection technology about CUI.

The commonly used equivalent circuits for electrochemical impedance spectroscopy (EIS) testing in reinforcing steel corrosion in concrete have been reviewed, and the advantages and disadvantages of different equivalent circuits were discussed. Appropriate equivalent circuits were selected and analysed for EIS fitting according to the three stages of reinforcing steel corrosion proces, i.e. passivation, corrosion initiation and corrosion propagation. The results indicated that additional time constants may be required with the evolution of reinforcing steel corrosion; moreover, constant phase element (CPE) and Warburg diffusion element were also demanded for best EIS fittings.

Understandings of the physical significance of elements in equivalent circuit model of rebar corrosion in concrete are not quite similar. In order to give a reasonable explanation, experiments of rebar corrosion in concrete induced by chloride penetration and carbonation were designed, and then the characteristics of electrochemical impedance spectroscopy(EIS) of test specimens were carefully examined. It was found from the test results that, for the rebar corrosion induced by chloride attack, three capacitance arcs were observed in impedance spectroscopy. However, for the rebar corrosion induced by carbonation, there exsited only two capacitance arcs in impedance spectroscopy, which corresponded with characteristics of rebar in passivation state. Low frequency capacitance arc shrank gradually with corrosion going on. As relative humidity increasing, high frequency and low frequency capacitance arcs both shrank, which meant decreasing of concrete resistivity and polarization resistance of rebar. Finally, a simplified equivalent circuit model was proposed and verified by experiment.

Al-Cr coatings were prepared on Ni-based superalloy K417G by pack cementation method. Hot corrosion resistance of the coatings beneath deposits of 25 NaCl+75 Na₂SO₄ (mass) at 900℃ was investigated. The average Cr content of the formed two layered Al-Cr coating prepared by two step process was ca. 20 mass, of which the outer zone was com-posed of β-NiAl with a little AlCr₂ phase. In the contrast, a three layered coating was formed for the AlCr coating prepared by one step progress, of which Cr mainly existed in the outer zone (8 mass) and the middle zone (3 mass). The Al-Cr coating with high Cr content possessed much better resistance to hot corrosion at 900℃ beneath deposits of 25 NaCl+75 Na₂SO₄.

Oxidation behavior of DZ406 alloy without and with aluminized coating in air at 1100℃ was studied, and then their surface morphology and cross sectional microstructure were examined by using SEM. The results showed that in the early stage, the oxide scale on the bare alloy was mainly consisted of flake θ-Al₂O₃, while θ-Al₂O₃, and spinel phase consisted of Ni、Co、Cr etc. appeared later. However, for aluminized coating, the small amount of θ-Al₂O₃ formed in the initial stage on the surface and then transformed into α-Al₂O₃.

The influence of applied stress on pitting behavior of LY12CZ aluminum alloy in 3% NaCl aqueous solution was investigated. Experimental results showed that breakdown potential and protection potential of LY12CZ in 3% NaCl aqueous solution showed obvious negative shift, which indicated that applied stress enhanced the pitting susceptibility of LY12CZ and reduced pitting initiation time. It was showed during the growth period that the relationship between the pitting depth and corrosion time accorded with power function and the relationship between the pit depth and applied stress accorded with exponential function.

Three kind of water-soluble substituted pyridine formyl hydrazone Schiff bases was synthesized and their inhibition effect on copper in 3.5% NaCl solution was investigated by mass-loss, electrochemical method and scanning electron microscopy. The results showed that the three kind of compounds acted as mixed inhibitors with cathodic inhibition as dominative action. It was found that pyridine formyl hydrazone Schiff bases with concentration of 75 mg/L had excellent inhibition efficiency for copper at 35℃. All the three kind of inhibitors showed excellent inhibition effect in the studied temperature range.

An Al-coating was deposited on type 310 stainless steel by multi-arc ion plating, followed by annealing treatment to obtain an aluminide coating. Electrochemical impedance spectroscopy (EIS) was employed to study the corrosion behavior of the bare and the coated steel in molten carbonate at 650℃. The experimental results indicated that the electrochemical spectra for the corrosion of 310 stainless steel were composed of double capacitive loops. With extended exposure, the diffusion-controlled reaction was also observed at the low-frequency part. Electrochemical impedance spectra for corrosion of the coated steel also consisted of double capacitive loops, but with significantly large impedance values. The excellent corrosion resistance of the coated steel was related to the formation of a continuous protective LiAlO₂(Al₂O₃) scale.

The inhibition behavior and mechanism of N,N'-diphenyl thiourea(DPH-TU) on the corrosion of Q235 steel in sulphuric acid medium and the synergistic effect of DPH-TU and sodium dodecyl sulfate (SDBS) were studied by using polarization curves measurements, electrochemical impedance spectroscopy (EIS) and quantum chemistry methods. The results showed that DPH-TU was an effective mixing type inhibitor. The two inhibitors showed significant synergistic inhibition effect on the corrosion of steel, which became the most significant when concentration ratio of the two inhibitors was 1:1. It was suggested that the adsorption of DPH-TU and SDBS on Q235 mild steel might be a chemosorption of exothermic processs. The corresponding thermodynamic parameters of the adsorption process for DPH-TU/ SDBS were calculated according to the El-Awady kinetic model.

By means of slow strain rate test (SSRT), the stress corrosion cracking (SCC) susceptibility of 16MnR in complex environment containing carbonate and hydrogen sulfide were investigated. In this environment, the stress corrosion cracking susceptibility indexes of 16MnR were lower than 25%. With the temperature increasing from 25℃ to 57.5℃, the stress corrosion cracking susceptibility indexes increased slightly, and the concentration of hydrogen sulfide and the carbonate affected the susceptibility reciprocally.

The corrosion behavior of four kind of cast irons made according to the composition of several ancient cast irons in 3.5% NaCl solution were investigated by using immersion test and potentiodynamic polarization measurement. The results showed that the corrosion rate of the grey cast irons was higher than that of the white cast irons. The grey iron with low sulfur content showed a higher corrosion rate and poor corrosion resistance in comparison with that with high sulfur; but for the white irons, the sulfur content showed no significant effect on their corrosion properties. XRD spectra analysis indicated that lepidocrocite, magnetite and goethite existed in the corrosion products of all four cast irons, among which the loose, unstable lepidocrocite was predominant. Akaganeite, the most commonly seen corrosion product for ironwares excavated from the sea, however, had not been seen among the examined corrosion products.

The deflection data for the sputtered microcrystalline Ni20Cr coating/Ni20Cr alloy was measured during oxidation by using an apparatus for in-situ measurement of stresses in oxide scales. The results showed that the thermally grown oxide scale formed on the surface of microcrystalline coating was subjected to compressive stress. The growth stress of oxide scales on the Ni20Cr microcrystalline coating was higher than that on the corresponding alloy, which may be the reason responsible to the better interface adherence of the oxide scale/coating. During cooling, the microcrystalline coating was much plastic than the alloy, which might facilitate the partial release of the thermal stress of oxide scales.

The corrosion behavior of a weathering steel 09CuPCrNi-A and a common steel F500L-Z in 3.5% NaCl solution was investigated by open circuit potential and electrochemical impedance spectrum (EIS) measurements. The results showed that the resistance of the steels increased first and then decreased with increasing soak time and tended to be steady after 1272 h. Bode charts indicated that the curves moved to low frequency and phase angle curves decreased gradually. Corrosion resistance of 09CuPCrNi-A was better than that of F500L-Z.

Based on an investigation of the exfoliation corrosion (EFC) evolution around ADF antenna installing holes on aluminum alloy 7150-T77511 keel beam for aircraft B737CL, the effect of axial stress on the EFC was studied by means of finite element analysis and corrosion test in salt fogging environment. The results showed that compressive stress along directions L and LT accelerated EFC, whilst tensile stress along directions L and LT, and compressive stress along direction ST retarded EFC.

Sodium nitrite and thiourea microcapsule corrosion inhibitors were prepared using microcapsule technology. The characters of these two products were characterized by UV-spectrophotometry, polarization curve and electrochemical impedance spectroscopy methods. It was found that the microcapsule technology could suppress the releasing rate of the corrosion inhibitor, and the corrosion inhibitor released by these two products could effectively inhibit the corrosion rate of metal.