This paper reviewed the development history of microarc oxidation (MAO) technique and the mechanism related with spark discharge process, with emphasis on the corrosion prevention for Mg-alloys in the past two decades. Various aspects of MAO coating of Mg-alloys and recent progress were summarized in detail, such as power types, operating modes, electrical parameters, electrolyte solutions, post- and pre-treatments. And the problems and suggestions of MAO technique for corrosion prevention of magnesium alloys were presented in the end．

The corrosion types encountered in oil-fired boiler plants were introduced, and the mechanisms related with high- and low-temperature corrosion were elucided. The relevant anticorrosion countermeasures were reviewed with emphasis on cold-end additives, chemical cleaning agents and boiler fuel additives etc., meanwhile, the anticorrosion mechanisms and application characteristics of these additives were also described respectively. The current status of anticorrosion studies for oil-fired boiler in power plant and the necessities of intensive studies on anticorrosion treatment were pointed out, the prospects of anticorrosion treatment were forecasted.

This paper summarizes relevant techniques for enhancing wear resistance of Ti-alloy, with emphases on advantages and disadvantages of the micro arc oxidation technique. The duplex treatments, namely, the combination of micro arc oxidation with other surface modification techniques are described in detail. The application of the duplex treatments significantly improved wear and corrosion resistance of titanium alloy and seems to be the development trend of the titanium alloy surface treatment technology.

The effect of substrate preheating time on the interface bonding of fusion bonded epoxy powder coating/Q345 substrate was investigated by means of tensile test and wet adhesion test. Results showed that the preheating time presents significant effect on the interface bonding of coating/Q345 substrate, and among others, the best bonding performance could be acquired for the substrate being preheated for 6 h at 210 ℃. The surface morphology, roughness and chemical composition of the substrate were characterized by CLSM, AFM, XPS, and the correlation between the surface state of the substrate and the bonding performance of coating/substrate was inquired into. Results revealed that the preheating treatment resulted in the formation of a dense oxide scale on the surface of Q345 substrate, which composed of an outer layer Fe₂O₃ and an inner layer Fe₃O₄. With the prolonging preheating time, the thickness of Fe₂O₃ layer was almost the same and the inner layer Fe₃O₄ became thicker, whilst the surface roughness of the substrate changed gradually. The change of the surface roughness of the substrate affected the bonding performance of the coating/substrate system.

Nano-containers were synthesized via layer by layer (LbL) self-assembly technique with SiO₂ as core and alternative layers of chitosan and polyaspartic acid inhibitor as shell. Then nano-containers modified epoxy coatings were prepared and applied on carbon steel Q235. The nano-containers were characterized by means of Malvern laser particle size analyzer, Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM). In addition, the electrochemical behavior of epoxy coatings/Q235 systems with and without nano-containers in 3.5% (mass fraction) NaCl solution were investigated through electrochemical impendence spectroscopy (EIS). Results indicated that the corrosion resistance of epoxy coatings had been greatly increased by the incorporating nano-containers, which can effectively reduce the diffusion of water in coating matrix and enhance the coating impedance for corrosion reaction. The impedance value of the modified epoxy coating may be maintained by above 10⁵ Ω·cm² even after 120 h immersion, revealing the enhanced anticorrosion performance.

Phytic acid (C₆H₁₈O₂₄P₆, Phy) is the principal storage form of phosphorus in many plant tissues, especially bran, corn and seeds. Herein, high protective and stabile polypyrrole (PPy) films were directly electro-synthesized on Cu from aqueous phytic acid solution. The electrodeposition process was monitored with an electrochemical quartz crystal microbalance (EQCM), while the prepared PPy films were characterized by means of SEM, FT-IR and Raman spectroscopy. It was indicated that the growth of these films was facilitated by the initial oxidation of the Cu-electrode in the phytate solution to generate a Cu-phytate pseudo-passive layer. After that, highly adherent and homogenous polypyrrole was facilitated were electrodeposited on Cu in the phytic acid solution. Corrosion protection property of the PPy films were examined through immersion test in 3.5%(mass fraction)NaCl solution in terms of the amount of Cu ions dissolved from the PPy covered Cu during immersion, which presented the excellent stability and corrosion protective ability of the PPy films. Among others, the PPy film synthesized from the pH=4 phytic acid solution exhibited the best protective performance. EQCM-CV tests indicated that the PPy film doped with phytate anions, acting as cationic perm-selective membrane, can effectively inhibit the diffusion of Cl^- to the substrate and therewith improve the anti-corrosion property.

The electrochemical behavior and corrosion feature of X80 steel in red soil with different moisture contents adjusted by simulated acid rain were studied by means of potentiodynamic polarization curves, EIS, three-dimensional video microscope, SEM and XRD. Results show that the corrosion rate (R_ct^-1), corrosion type and corrosion mechanism of X80 steel in red soil irrigating with simulated acid rain were significantly dependent on the soil water content (SWC). By 15% (mass fraction) SWC, the overall corrosion process was controlled by electrochemical activation reaction, the steel surface underwent pitting and filiform corrosion, and R_ct^-1 was small. With the increase of SWC, R_ct^-1 increased, and the corrosion type of the steel surface varied from the localized pitting to the uniform corrosion. When SWC was 25%, a loose and reddish-brown corrosion product layer was formed by the incorporation of soil particles. In the acid rain-saturated soil, the steel surface underwent severe ulcer-like corrosion, the corrosion mechanism varied upon the exposure time. The corrosion process was mainly controlled by a charge-transfer process at the initial stage, but the subsequent corrosion processes were controlled by a combination of activation control and diffusion control after 15 d. In addition to the soil acidity, the condensation phenomenon should be taken into account to understand the corrosive nature of red soil. When X80 steel was exposed in the soil at Nanchang area, the time with moisture film on the steel surface could account for 98.6% of the total exposure time, which means that the corrosion reaction of X80 steel in the acidic red soil could occur at almost any time.

The electrochemical corrosion behavior of the matrix and weld seam of X70 steel in Na₂CO₃+NaHCO₃ solution was studied by means of potentiodynamic polarization, electrochemical impedance spectroscopy and Mott-Schottky technique. Results showed that the passive film could form on both the matrix and weld seam of X70 steel in solutions with the concentration of Na₂CO₃+NaHCO₃ within a range of 0.1~1.0 mol/L. The stability of passive films increased with the concentration of Na₂CO₃+NaHCO₃. The passive films form on both the matrix and weld seam of X70 steel behave as a n-type semiconductor, the donor density follows the same trend as the passivity current density. There is a notable feature that the Cl^- adsorbed onto the oxygen vacancies on the weld seam in the solution of 1 mol/L carbonate/bicarbonate.

The microstructures of the cold-weld layers on A350 LF2 steel prepared with different process parameters was characterized and then their sulfide stress cracking (SSC)- and hydrogen induced cracking (HIC)-behavior was assessed corresponding to NACE standard experimental conditions. Results show that the welding process with low heat input, short duration and high duty cycle can lead to incomplete fusion, while high influx of Ar is easy to generate bubbles. The cold-weld layer is not sensitive to SSC, however it is easy to produce HIC cracks at welding defects. The cracks initiate in the non-fusion zone and the edge of weld bubbles, and then propagate along welding line. Appropriate parameters can eliminate welding defects, thereby, the prepared cold weld layer may possess good resistance to HIC.

Pseudoalteromonas piscicida was separated and extracted from seafloor sediments located in offshore waters of Zhoushan institute of marine corrosion at Zhoushan islands of the East China Sea. Then the bacterium was inculated to laboratorial bottle that placed in a constant temperature incubator shaker and to an incubator with environment of simulated lowing sea water, respectively. The effect of Pseudoalteromonas piscicida on the corrosion of Q235 carbon steel in the above two bacterial culture systems has been studied by means of electrochemical workstation, scanning electron microscope and Fourier infrared spectrometer. Results showed that this bacterium could inhibit effectively the corrosion of Q235 carbon steel in seawater. The impedance of the carbon steel was enhanced more obviously in laboratorial bottle and its surface was completely covered with an uniform and dense biofilm, while the uneven biofilm formed on the surface of carbon steel in the simulated flowing seawater system, seawater can direct contact the substrate via holes and crevices which were randomly distributed throughout the biofilm, provided conditions for the formation of oxygen concentration cell, therefore weakened the corrosion resistance of carbon steel. FT-IR spectrum showed there were differences in secretory macromolecules for the same bacterium but cultured respectively in the two culture systems after 7 d.

Ingots of four Al-Cu-Li alloys with different amounts of micro-alloying elements of Mg, Zn and Ag respectively were prepared via melt and casting technique, which were successively hot- and cold-rolled to produce sheets of 2 mm in thickness and finally subjected to T6 aging treatment. Further,the intergranular corrosion behavior of the above T6 aged alloys was studied in solution of 57 g /L NaCl+10 mL/L H₂O₂. The result showed that the Al-Cu-Li alloys with micro-alloying element of Mg, Zn, and Mg+Zn respectively present more or less the same evolution tendency of intergranular corrosion behavior, namely, local IGC emerges at the initial aging stage, general IGC at the under peak aging stage, local IGC at the peak aging stage and pitting with slight IGC at the over-peak aging stage with the prolonging T6 heat treatment. But the IGC susceptibility of the Zn- alloyed Al-Cu-Li alloy is weaker than that of the Mg-alloyed one. Intergranular corrosion morphology of Mg+Ag-alloyed Al-Cu-Li alloy was different from that of the above three alloys, showing pitting with IGC at peak aging stage, local IGC or general IGC at other aging stages. The mechanism of intergranular corrosion of Mg+Ag-alloyed Al-Cu-Li Alloy is anodic dissolution derived by the potential-difference between the precipitates free zone (PFZ) and numerous amount of continuous precipitates of T1 phase at grain boundaries.

Due to high protection performance for cut edges, much attention was focused on Zn-Al-Mg coating. Considering hot-dip galvanizing technology was widely applied for the Zn-Al-Mg coating, solidification should strongly influence its microstructure and corrosion properties. In this work, a Zn-Al-Mg alloy was melted in a resistance furnace and then cooled to room temperature with different solidification processes, including water quench, air cooling and furnace cooling. Scanning electron microscopy (SEM) was applied to analyzed the microstructure of the alloys solidified with different processes. Moreover, the effect of solidification on corrosion resistance was studied by electrochemical method. Results show that microstructure of the Zn-Al-Mg alloy consists of Zn-rich primary grains and eutectic of Zn, Al and Mg. It could be found that among others, the furnace cooled Zn-Al-Mg alloy presents the largest size and ratio of the primary grains. With the increasing solidification rate, the primary grains turn to be finer and more eutectic appears, besides, the eutectic transforms from granular-like to lamellar-like. Electrochemical test indicates that the corrosion potentials for all the alloys solidified with different ways are more or less the same level but their corrosion currents and plots of electrochemical impedance spectroscopy (EIS) are remarkable different. The corrosion current of the furnace cooled alloy is the smallest, which means the highest corrosion resistance.

In neutral and acidic solution, Mg reacts with water and release hydrogen, which reduces the utilization rate of electrode and brings difficulties to the assembly of the battery. In the alkaline solution, the Mg-surface would form a dense protective film, which make the electrode passivation and prevents discharging. In order to develop proper Mg-alloy suitable for battery electrolytes, the discharge properties and voltage delay of AZ31B Mg-alloy in compound electrolytes with different volume ratio of Mg(NO₃)₂ to Mg(ClO₄)₂ were studied by means of chronopotentiometry and electrochemical impedance spectroscopy and the corrosion products-films formed on the surface of AZ31B Mg-alloy were examined by means of SEM and infra-red spectrometer. Results show that in solutions with volume ratios of Mg(NO₃)₂ to Mg(ClO₄)₂ are 72:28 and 74:26 respectively, the discharge curves of AZ31B Mg-alloy are smooth and steady with stable potentials about -1.24 V (2.5 and 6 mA·cm^-2) and the delay time 5~8 s. Chemical groups of the corrosion products-film after discharge is the same as before. However, the surface film of corrosion products has been destroyed by discharge process, resulting in continuous beads-like corrosion pits, therewith the film resistance would disappear and the charge transfer resistance decreases to 375 Ω·cm².

The corrosion behavior of Fe-based bulk metallic glass with sulfide inclusions in HCl solution was investigated by electrochemical test technique and immersion test. Results showed that the Fe-based bulk metallic glass presented obvious passivation characteristic in solutions with various amount of HCl at different temperature, however its corrosion resistance gradually decreased with the increasing HCl-concentration and temperature. The as-casted amorphous alloy had just only one capacitive loop, which indicated that the faraday process of the electrode system was controlled by the electrode potential. The SEM corrosion morphology after immersion tests showed that sulfide inclusions presented non-obvious influence on the corrosion behavior of Fe-based bulk metallic glass, whilst non-obvious pitting corrosion was triggered.

T2 Cu and QCr0.5 Cu-alloy were passivated in chromate-free solutions with single molybdate and complex molybdate respectively. The formed passivation films were then characterized by electrochemical method, nitric acid drop test, neutral salt spray test, SEM and XRD etc., taking the passivation film prepared with conventional chromate containing solution as comparison. Results show that the addition of polyaspartic acid (PASP) and H₂O₂ could improve the passivation effect of molybdate, especially the addition of the both simultaneously, which promoted the formation of passive film, the decrease of dissolution of Cu-alloy, and thereby the formation of a passivation film of copper oxide-based, significantly improved the corrosion resistance of T2 Cu and QCr0.5 Cu-alloy. After salt spray test, the surface of passivation treated samples presents metallic lustrousness to certain extent, while with less corrosion pits. In particular, the free-corrosion current density for T2 Cu passivated in molybdate solution with PASP+H₂O₂ is only 3.10×10^-6 A/cm², which is close to that for the chromate passivation film i.e. 9.06×10^-7 A/cm².