Ni-P and Ni-W-P coatings were prepared on AZ91D magnesium alloy by a direct electroless plating processing. The microstructure, phases and corrosion resistance of the prepared and post-annealed coatings were studied by using scanning electron microscopy, X-ray diffraction technique and electrochemical test. The results show that the Ni-P coating is of amorphous structure while the Ni-W-P coating is of nanocrystalline structure with a grain size of about 7 nm, and they have similar corrosion resistance against 3.5%NaCl aqueous solution. The corrosion potential of the Ni-W-P coating after annealing at 250℃ for 50 min positively shifts by 150 mV as compared to that of as-prepared Ni-W-P or Ni-P coating, implying the corrosion resistance of the annealed Ni-W-P coatings has been much improved.

Corrosion behavior of steel in concrete with different chloride ion concentration was studied by means of galvanostatic pulse, which is introduced as a new type of non-destructive technique nowadays. Potential transient technique galvanostatically induced is used to determine the corrosion rate with two data analysis methods, followed by comparing to that of the traditional linear polarization method. It is shown that the choice of perturbation magnitude of signal to be applied depends strongly on the corrosion state of steel. Too small current makes it difficult to separate the potential signal from background noise, whereas higher current results in intensive polarization. Thus, neither of two is beneficial for the data processing. Anodic current conversion method is fast and efficient in analyzing the galvanostatic pulse curves; however, this approach has some limitations in case of large applied current.

AZ91D magnesium alloy was treated by alternating voltage (AV) modulated passivation technique. Atomic force microscopy (AFM), First ten angstroms (FTA) contact angle-meter and X-ray photoelectron spectroscopy (XPS) were employed to investigate the influence of AV-modulated passivation on the surface properties of the films formed on the AZ91D magnesium alloy after AV-modulated passivation. The results showed that a uniform and stable film was formed after AV-modulated passivation. The surface films on the samples after AV-modulated passivation consist of an inner layer rich in MgO, with a little Al₂O₃，and an outer layer of Mg(OH)₂，MgO with a little Al(OH)₃.

Water soluble chitosan was modified by phosphonation. The inhibitive properties of chitosan and phosphonic chitosan for Q235 mild steel in seawater were studied by mass loss method and electrochemical measurement, and the inhibitive mechanism was analyzed. The results showed that chitosan had corrosion inhibitive effect for mild steel, and with the increasing of dosage of chitosan the inhibition efficiency was increased. The inhibition efficiency of phosphonic chitosan reached to 88.71 % when the concentration was 300 mg/L, and it had good inhibition effect at high temperature and inhibition efficiency kept high for long period of time. Polarization curves indicated that phosphonic chitosan is a cathodic corrosion inhibitor.

Salt fog spray test is used to accelerate the corrosion of 7B04 aluminum alloy. The pitting corrosion of this alloy was investigated by using metallographic method and localized electrochemical impedance spectroscopy (LEIS). It was concluded that the corrosion rate of the alloy increased sharply, but was retarded at the middle stage of exposure. The maximum depth of the pitting was linearly growing in the whole process. The pitting mechanism was mainly attributed to the dissolving the surrounding matrix of cathode-phase particles, dissolving aluminum itself or secondary pitting of Cu particles which is the corrosion residues. While the cathode phase of AlCu or AlCuMg second-phase particles was the main initiation cause. Localized electrochemical impedance spectroscopy (LEIS) which is suitable to follow changes in the dissolution kinetics during pit growth, could provide valuable information on the changes of the impedance on a small area.

Electrochemical corrosion behavior of TRIP steel in 3.5%NaCl solution was investigated by salt spray test and potentiodynamic polarization curves. The results indicated that large corrosion products were obtained on the specimen surface. Their potentiodynamic polarizations were all activated. The corrosion rate of steel A was significantly higher than that of steel B containing alloying elements. The corrosion potential and current density of steel B were increased and decreased, respectively. The rust layer of steel B was compact and densified compared to steel A. A satisfactory corrosion resistant effect was obtained for steel B. This is attributed to the additions of alloying elements, such as Al，Cu，Cr，Mo，Ni, etc. The enrichment of these alloying elements within the rust layer contributes to the improvement of electrochemical characteristic of TRIP steel.

Self-assembled monolayers (SAMs) of n-and t-dodecyl mercaptan were prepared on iron surface by self-assembly methods. From the results of FT-IR, it can be found that both the n-and t-dodecyl mercaptan can self-assemble on the surface of iron. Then the electrochemical impedance spectroscopy (EIS) and the Tafel polarization curves were performed to characterize the anticorrosion capability of the SAMs in 0.5 mol/L NaCl solution. The general equivalent circuits for the n-and t-dodecyl mercaptan SAMs were established. Based on the results of the EIS, proper equivalent circuit was chosen to fit the Nyquist impedance plots. The inhibition efficiency (IE) of the SAMs on iron corrosion have been calculated according to the fitted results and the Tafel polarization curves. When the iron electrode self-assembled in the n-and t-dodecyl mercaptan for 3h, the IE of the SAMs can reach about 89% and 80% respectively. Comparing with the SAMs of the t-dodecyl mercaptan, the SAMs of n-dodecyl mercaptan have more effective corrosion inhibition for iron as indicated by the high charge-transfer resistance shown in EIS and the positive corrosion potential in the Tafel polarization curves. It is quite possible that the steric hindrance of t-dodecyl mercaptan is bigger than that of n-dodecyl mercaptan. Therefore, it is easy to understand that the quality of the n-dodecyl mercaptan SAMs is better than that of the t-dodecyl mercaptan.

The constant load tensile test, with combination of electrochemical corrosion technology and SEM analysis method, were performed to study sulfide stress corrosion cracking (SSCC) of P110 steel in H₂S/CO₂ NACE standard solution. The results show that, with the increase H₂S content, the corrosion E_corr of P110 steel dropped sharply and increaseed slowly again after reaching minimum point. Then the corrosion E_corr increased to constant point about five hours until fracture phenomenon occurring, and the sample appear brittle cleavage fracture. With the content of CO₂ increasing in the solution, the E_corr potentials of steel P110 increased, the corrosion current decreased, the time of fracture extended and the brittle cleavage fracture transformed to toughness dimples. The generation of this phenomenon has the relevant combination of competitive adsorption of H₂S/CO₂ in steel surface and tensile breakdown and regeneration of P110 surface membrance in stress corrosion environmental.

Corrosion performance of carbon steel under 10 mmol/L Na₂SO₄ liquid layer is investigated by inductive resistance probe(IRP) and electrochemistry techniques. Average corrosion rate in wet period, named by IFACR, is calculated based on integration filter algorithm (IFA) with controlled environment factors including time of immersion (TOI), temperature and relative humidity (RH). A data-standardization approach is proposed in order to improve the accuracy of IFACR correlation with the control factors modeled by a linear equation. Two sets of corrosion kinetics parameters, corrosion current density I_corr, polarization resistance R_p and corrosion rate, of Q235 steel in 10 mmol/L Na₂SO₄ is measured by dynamic potential scan and potential step with an intension to benefit the understanding of corrosion under thin liquid layer. The results indicate that temperature has positive influence on IFACR, while TOI and RH show negative correlation with IFACR. A changed contribution of the factors to IFACR is specified around 24℃ and RH=70% called threshold. This threshold is consistent with that from previous TOW (Time of wetness) measurements. The contribution of TOI to IFACR is minor. However, the domination of temperature and RH on IFACR is strongly dependent on TOI. A detailed discussion on the dependence of IFACR and total corrosion loss on TOI, temperatures and RH is presented with the help of electrochemical measurements.

The morphology of micro-arc oxidation coatings on AZ91D alloy was analyzed by scanning electron microscopy. The tensile strength and fatigue property of AZ91D magnesium alloy treated with micro-arc oxidation was investigated by static tensile test and fatigue test. And the fatigue fractograph was analyzed by stereomicroscopy and scanning electron microscopy. The results show that the inner layer of micro-arc oxidation coating was imporous and compact, the compact layer had good ductility and good bonding to the substrates. The bonding strength was high. Micro-arc oxidation treatment had no influence upon the tensile strength of AZ91D. The fatigue test condition was as follows, mean value S_m was 4.72 kN, amplitude value S_a was 3.15 kN, stress ratio R was 0.2, load was constant amplitude spectrum and frequency was 10 Hz. The average fatigue life of AZ91D treated by micro-arc oxidation was 54148 cycles, corresponded to that with chemical oxidation.

On the basis of improved hyperbolic tangent sigmoid transfer function, a cause-factors evaluation BP neural network model for estimating the atmospheric corrosion of steels was proposed. Using the zero mean stand method to preprocess the input data, Bayesian regularization arithmetic was introduced to solve the generalization problem on sparse data. The simulated results showed that the model provided good evaluation for atmospheric corrosion cause-factors without any prior knowledge.

Using a self-developed ASTM test system of contact material electrical properties of small-capacity and the current-frequency changed，the performance comparison trials and material weighing of AgC，AgCdO， AgNi and AgW contact materials were completed under low voltage、 resistive load and small current at 400 Hz and 50 Hz. The surface profiles and constituents of Ag-graphite contact material were observed and analyzed by SEM and EDAX. Researches indicated: the form of the contact material arc burnout at 400 Hz is stasis, not an eddy flow style at 50 Hz; meanwhile，the area of the contact burnout is less than that of 50 Hz，the ablation on the surface layer at 400 Hz is more serious. Comparing the capacities of arc erosion resistance of the silver-based alloy contact material with different second element at 400  Hz，it can be known that the capacity of the silver/graphite material is the weakest.

The microstructure of friction stir welded (FSW) joint of 7075 aluminum alloy were examined by using of optical microscope and transmission electron microscope. The corrosion behaviors of the joint were investigated by method of natural salt spray. The macroscopical and microscopical appearances of the weld seam were observed by using of scanning electron microscope after corrosion test. The results show that the size of the grain and the second phase particles in the weld zone has been obviously refined. The distribution of the second phase particles are not homogeneous on the weld seam surface. The resistance to corrosion of FSW seam is lower than that of base metal enveloped with pure aluminum layer. The corrosion styles during the initial stage are mainly local pitting and intergranular corrosion and develop to exfoliation corrosion after long time corrosion.

The passive behavior and electrochemical characterization of passive film formed under different potential on X70 pipeline steel in NaHCO₃ solution were discussed by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and capacitance measurements. It is shown that the X70 pipeline steel has a wide passive anodic region between -50 mV to 900 mV. EIS result indicates that the passive film is much denser and uniform with the increasing potential. Mott-Schottky analysis presents that the passive films on X70 pipeline steel in 0.5 mol?L^-1 NaHCO₃ solution exhibits n-type semiconductive character in potential region of -0.2 V to 0.8 V. The donor density of the passive film decreases and the thickness of the space-charge layers increases with the increasing potential. The corrosion resistance of the passive film increases with the forming potential.

The corrosion behavior of 316L stainless steel in H₂S-HCl-H₂O environment at 80℃ was investigated by potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN). The parameters derived from shot noise theory combined stochastic theory had been employed to analyze the corrosion mechanism of 316L stainless steel in H₂S-HCl-H₂O environment at 80℃. The polarization curves of 316L stainless steel indicated that there existed an obvious passivation characteristic without H₂S, and active dissolution with saturated H₂S. The corrosion process of 316L stainless steel was promoted greatly with addition of saturated H₂S. An analysis of the electrochemical noise data based upon the combined stochastic theory and shot-noise theory showed that the characteristic frequency of corrosion of 316L stainless steel were increased and the development of corrosion of 316L stainless steel became much easy with addition of saturated H₂S.

In order to improve the reliability of PWR steam generators, alloy 690TT has been developed and verified as the optimum steam generators (SGs) tubing material at present, based on wide operating and laboratorial experience. Alloy 690TT is and will be one of most popular tube material of present and future commercial nuclear plants. Alloy 690TT is usually insusceptible both under acidic and alkaline conditions, but the corrosion is unavoidable under special corrosive environment in time. Dealloying (Cr depletion), lead stress corrosion cracking (PbSCC), low-valence sulfur stress corrosion cracking (S^y-CC) are considered being potential damage to Alloy 690TT and will be described in detail in this article.