By using alternating current (AC) modulated passivation technique, the formation process of stannate conversion coating could be controlled. The microstructure morphology of the conversion coating was observed by scanning electron microscopy. Polarization curves and electrochemical impedance spectra (EIS) were examined to understand the effect of the AC passivation on the corrosion resistance of the conversion coating. The experimental results revealed that the surface of AZ91D magnesium alloy after the AC passivation was covered by the hemispherical particles whth larger size than that for traditional immersion conversion coating (imm-CC). The corrosion resistance of the conversion coating was significantly improved as a result of the AC passivation.

The stress corrosion cracking (SCC) behaviors of as-cast AZ91 magnesium alloy in CO₃^2-/HCO₃^- solutions were investigated by electrochemical test, immersion test and slow strain rate test (SSRT) respectively. The results showed that the stress corrosion cracking sensitivity of as-cast AZ91 alloy in CO₃^2-/HCO₃^- solutions decreased with the increase of pH values of the solutions. The surface was covered by a film mainly composed of Mg(OH)₂ and Al(OH)₃. Al(OH)₃ could be dissolved in alkaline solutions and AlO₂^- engendered. Pitting was the main crack source of AZ91 alloy in such solutions. The cracking of β phase also resulted in microcracks in the matrix. Microcracks initiating at the bottom of pitting combined into a main crack. The main crack propagated by coalescence of the existing microcracks ahead until the SCC fracture occurred.

By using density functional theory (DFT) method of quantum chemistry, 6 quantum chemistry parameters for 20 kinds of benzimidazole and its derivatives were calculated at B3LYP/6-31*G basis set levels. The quantitative structure-activity relationship (QSAR) of 16 derivatives was studied using regression analysis methods. Via a stepwise regression analysis, some main independent factors affecting the activity of the compounds were selected out, and the QSAR model was established. One-leave-one test and prediction set test were used to examine the relative equation. It has been found that energy of highest occupied molecular orbital (E_HOMO), total negative charge on moleculars (TNC), as well as lipophilicity index (LogP) are main independent factors contributing to corrosion inhibition. The regression coefficient adjusted by freedom is 0.977 and the QSAR model has a good stability and predictive ability for such corrosion inhibitors. We also analysed the inhibition mechanism of the benzimidazole derivatives.

In this work, the single effect of microbe on the corrosion behaviors of 25 carbon steel is studied by comparing the average corrosion depth of the carbon steel in natural seawater and in sterile seawater in tropic condition. Through examining the strength and Charpy impact absorbed energy after different corrosion periods, the effects of microbiologically influenced corrosion (MIC) process on mechanical properties of 25 steel are illustrated. The results show that the bacterial activity at the interface accelerates the corrosion of 25 steel. When the corrosion time is 365 d, the average corrosion depth of 25 steel in natural seawater is 2.6 times higher than that in sterile seawater. Localized attack is also observed on the specimens immersed in natural seawater for 365 d. The corrosion of 25 steel in natural seawater and sterile seawater reduces the ultimate tensile strength of 25 steel, and this effect is more notable during the corrosion in natural seawater than in the sterile seawater. The analysis reveals that the decrease of the ultimate tensile strength is related to the increase of average corrosion depth. MIC does not decrease the elongation and Charpy impact absorbed energy of the annealed 25 steel, and MIC induced hydrogen embrittlement is not found.

Grain boundary segregation, hydrogen embrittlement susceptibility and Mg-H interaction of 7075 aluminum alloys with double-peak aged were studied by means of cathodic H-permeation, hydrogen determinator, electronic tensile machine， energy dispersive X-ray spectrometer (EDS) and scanning electron microscopy (SEM). The results showed that both before and after hydrogen charging, the strength and etc. all had double peaks; the decline of second peak strength was smaller than the first peak, also it had excellent performance like high-strength and low- HE-susceptibility at the second peak; there may exist Mg-H interaction during the hydrogen charging process. Finally, the Mg-H interaction mechanism is discussed.

The autocatalytic plating nickel-phosphorus coatings with different phosphorus content on different substrates were exposed in marine atmospheric environment of South China Sea. During exposure time, the corrosion behaviors were researched and compared. The testing results showed that the corrosion resistance of coatings with high phosphorus content was better than those coatings with medium phosphorus. The corrosion resistance of coatings on Q195 steel substrate was better than those coatings on aluminum substrate. The coatings on LF6M substrate were better than those coatings on LF21M substrate and the coatings on LY12-CZ substrate were the worst; The Cl^- is the primary factor for the nickel-phosphorus cathode coating in marine atmospheric environment.

The effect of hydrostatic pressures of 3.5%NaCl solution on the corrosion resistance of the epoxy coating was studied by using electrochemical impedance spectroscopy (EIS). The results revealed that the hydrostatic pressure greatly affected the failure process of the coating. The diffusion rate of the electrolyte solution through the coatings was accelerated in the solution under high hydrostatic pressure. Compared with the case under atmospheric pressure, the coating resistance was reduced; the charge-transfer resistance was decreased, metal corrosion reaction was more accelerated; the protection properties of the coating was deteriorated.

The Ni-P and Ni-P-PTFE coatings were experimentally electroless deposited on the surface of carbon steel in the present study. The key preparing process was explored and the as-prepared coatings of Ni-P and Ni-P-PTFE were then characterized using SEM, EDS and XRD. The electrochemical polarization curves and the weight increases of the coated samples in the seawater were conducted to assess the anti-corrosion behaviors of the two coatings. The results indicated that the Ni-P and Ni-P-PTFE coatings have been successfully electroless deposited on the surface of carbon steel. The surface microstructure observations showed that the Ni-P coating was smooth and compact rather than the Ni-P-PTFE coating. Although the results from polarization curves and weight gains indicated that the Ni-P-PTFE coating had anti-corrosion behavior slightly poorer than the Ni-P coating due to the presence of the composite interface in the Ni-P-PTFE coating, the two coatings prepared in this study could provide carbon steel with valuable protection from seawater attack.

Steel corrosion occurs in concrete structures when proper environmental conditions are provided. After steel corrosion initiates, the corrosion products first accumulate at the steel surface, then induce an internal pressure on the surrounding confining concrete, and slowly apply stress to the concrete cover until cracks are initiated at the steel surface spreading towards to the concrete surface. Therefore, corrosion product is the most influential factor during the concrete cracking process due to corrosion. Natural rust and electrochemical steel corrosion were investigated by X-ray diffraction (XRD) and digital optical microscope to differentiate the physical characters of two types of rusts. The oedometer tests were used to analyze the mechanical behavior of the powder rust samples, the modulus of these two types of rusts were then deduced according to Hertz contact theory. It was observed that the modulus of rust increased with the load increasing. By quantitative analysis of the inner damage constitutive model of natural corrosion products, the scale effect was accounted into the rust modulus model. The mechanical behavior of ideal natural rust was then described.

Two kinds of carbon steels of different microstructures（ferrite-pearlite and martensite） with the same chemical composition were obtained by different heat treatment processes. The difference in corrosion resistance of the steels with these two kinds of microstructures was investigated by cyclic immersion corrosion test as well as scanning electron microscopy (SEM) observation, electrochemical measurement, and X-ray diffraction (XRD) analysis. The results showed that the martensitic steel exhibited a higher corrosion resistance than the steel with the microstructure consisting of ferrite and pearlite. Martensitic steel had a higher self-corrosion potential and a lower anodic corrosion current. The rust layer of martensitic steel was more compact and mainly composed of α-FeOOH.

The microstructures of friction stir welded (FSW) joint of 2024 aluminum alloy were examined by using optical microscope and transmission electron microscope. The corrosion behaviors of the joint were investigated by method of acid salt spray. The analysis results of microstructure show that the arc stripe is the main feature on the surface of the weld seam due to the extrusion action of the shoulder of the stir tool. The grain and second phase particles are also refined. The second phase particles are mainly composed of Al₂CuMg(S phase) and CuAl₂(θ phase). The corrosion test shows that the resistance to corrosion of FSW seam is lower than that of base metal pure aluminum layer. There exists an unevenness for the corrosion of the FSW seam. The corrosion initially results from pitting corrosion and finally develops to exfoliation.

The pitting susceptibility of 1Cr18Ni9Ti、304 and 316 austenitic stainless steel in 3.5 %NaCl solution was monitored by potential dynamic polarization and electrochemical impedance spectroscope. The pitting induction time (τ) and in-situ changes of electrode surface for the three types of materials in 3.5 %NaCl solution were monitered by electronic speckle pattern interferometry (ESPI) and the chrono amperometry. The results indicated that, bright speckles in ESPI images show pitting corrosion occurring on metal surface. The speckles in ESPI were caused by the pitting corrosion products. The value of pitting induction time (τ) for 1Cr18Ni9Ti and 304 steel were 1 s and 9 s. The value of pitting induction time (τ) for 316 steel was more than 50 s. The results of ESPI showed that, in the 3.5 %NaCl solution, the pitting susceptibility of 1Cr18Ni9Ti was the worst of the three types of materials, and the 316 steel was the best. The result of ESPI was in agreement with that of potential dynamic polarization and electrochemical impedance spectroscope. ESPI can be used as a laboratory technique to monitor the initial pitting susceptibility of metals.

Current research was held to check the influence of the fluorine ion injection on the corrosion rate of the API P110 steel in the high-mineralized solution simulating Puguang process water. Different concentrations of the fluoride can increase or suppress the corrosion rate in this media.

Cracking of Ω loop of high pressure hydrogenation heat exchanger was analyzed by means of morphology and microstructure analysis, chemical composition analysis, SEM micro-morphology analysis and EDS analysis. The results showed that the cracking of the sample was to be hydrogen sulfide stress corrosion cracking. The high working stress and a few of hydrogen sulfide in shell side induced the cracking of the Ω loop jointly.

This paper reviewed the status of the recent researches on galvanic corrosion in marine environment in the fields of bimetal coupling system and multimetal coupling system. Corrosion prediction model of galvanic corrosion is briefly introduced, and progress in research on factor of galvanic corrosion such as galvanic potential, cathode/anode area ratio and temperature is discussed in more detail. Problems existed were summarized and the future development trend was outlined in the researches field.