AZ91, with excellent cast ability and high yield strength, is the most widely used magnesium alloy. Unfortunately, the alloy also has a number of undesirable properties, such as poor corrosion-resistance and heat-resistance, and inflammability during melting, which prevent it from being wide-spreadly used in many fields. Rare earth, as an important alloying element, can improve the performance of AZ91 magnesium alloy significantly. This paper gives a review of the effects of rare earth elements on fire retardant, mechanical properties and corrosion resistance of AZ91 magnesium alloy and a brief summary of the prospect of AZ91 magnesium alloy with rare earth addition.

Based on the summary of the research on AC corrosion of underground pipelines induced by high voltage transmission lines, the judgment principles of AC corrosion of underground pipelines with or without cathodic protection were introduced. The relevant standards for the relationship between the high voltage transmission line and underground pipeline were summarized. Finally the existing problems and the relevant suggestions for improvement were also put forward.

Ellipsometry is a highly-sensitive and non-destructive in  situ characterization method, which is widely applied in researches on corrosion and protection of metals. The measurement theory of ellipsometry is briefly introduced. The traditional applications and the recent developments of the ellipsometry in the field of corrosion and protection of metals are reviewed.

Cavitation corrosion behaviors of aluminum alloys, which were pre-oxidized by anodization and micro arc oxidation respectively, in 3.5% NaCl solution were studied. It was found that the cumulative mass loss rates of anodized and micro arc oxidized Al alloys initially increased with time within the first hour, and then increased slowly until the fourth hour, and subsequently increased rapidly with time. There were no marked effects of oxidation processes on the cavitation corrosion resistance of the oxidized Al alloys if the thicknesses of oxidized films are the same. During cavitation corrosion, the electrochemical corrosion processes of the two oxidized Al alloys in 3.5% NaCl solution were controlled by mixed cathodic and anodic processes. During cavitation corrosion the EIS of the anodized Al alloy was a deformed semicircle with contraction at low frequencies like porous electrodes, however, the EIS of the micro arc oxidized Al alloy was composed of a semicircle at high frequencies and another semicircle and Warburg line at low frequencies.

Potentiodynamic polarization curves and potentiostatic polarization easurements were carried out to study the cathodic polarization ehavior of X70 pipeline steel in low temperature and low dissolved xygen seawater. The formation of the calcareous deposits after CP as analyzed by electrochemical linear polarization resistances and urface analysis techniques, SEM and EDX. The results showed that he hydrogen evolution potential of X70 steel was the most positive n seawater with 1.5 mg/L of dissolved oxygen at 8℃, the evolving ydrogen current density of X70 steel was the smallest in seawater ith 3.0 mg/L of dissolved oxygen at 4℃. In low temperature and low issolved oxygen seawater the formation of calcareous deposits on he steel was with difficulty, in otherwords, higher polarization otential was needed to form the compact calcareous deposits. In low emperature and low dissolved oxygen seawater, it favored the recipitation of Mg(OH)₂, but not the formation of CaCO₃

Corrosion behavior of X60 steel in CO₂ and thermophile sulfate-reducing bacteria (SRB) coexisted sludge and sewage, a submarine pipeline encountered environment, were studied by using weight-loss method and scanning electron microscopy (SEM). The results showed that with the increase of temperature, corrosion rate of X60 steel in sludge and sewage saturated with CO₂ increased, and corrosion rate in CO₂-saturated sludge and sewage with SRB was higher than that without SRB. The morphology of corroded coupon showed characteristics of pitting corrosion. The corrosion rate increased with the increasing CO₂ partial pressure at static state, and the corrosion rate in sludge was always higher than that in sewage; moreover, the corrosion rate increased quickly with the rising CO₂ partial pressure at dynamic state.

The corrosion behavior of three stainless steels, i.e. B2205, B439 and B409 in molten LiCl-5 mass% Li₂O in air at 700℃ was examined by mass-loss measurements as well as XRD and SEM analysis. According to the experimental results, the three steels underwent severe corrosion, and their corrosion followed approximately a linear rate aw. The corrosion rate of the steels decreased with the increase of Cr content. The accelerated corrosion of the steels is related to a cyclic chlorination/oxidation reaction process. Meanwhile, fast lithiation reaction was also observed.

The corrosion behavior of co-continuous SiC/20 steel composite in simulated ocean and industrial atmospheres has been investigated by accelerated salt spray test. The results showed that mass-loss of the SiC/20 steel composite was slightly less than that of pure 20 steel in both 5.0% NaCl and 0.01 mol/L NaHSO₃ salt spray. For the composite, the corrosion effect of NaCl was approximately equal to that of NaHSO₃. The composite presented better anti corrosion performance than the substrate in the two environments. The main reason is the formation of FeOOH phase, which diminishes the corrosion rate of the composite.

The corrosion behavior of co-continuous SiC/steel composites in 3.5% NaCl aqueous solution has been investigated by electrochemical method and immersion test. The results show that the porous SiC foam affected the corrosion resistance of the co-continuous SiC/steel composite in neutral 3.5% NaCl aqueous solution to a certain degree. It was slightly more susceptible to corrosion than the matrix 20 steel. The reason may be that the numerous interfaces of SiC and the matrix reduced its corrosion resistance, while the intermetallic compound formed by the interface reaction improved its corrosion resistance. The SiC reinforcement had a considerable effect on the corrosion of co-continuous SiC/steel composites, which may be due to the galvanic corrosion between the matrix and the reinforcement. Therefore, the composite of 45 steel matrix with compact SiC skeleton framework exhibited much weaker corrosion resistance than the corresponding matrix 45 steel.

Composite films of PANI/PPY were prepared by cyclic voltammetry(CV) method on stainless steel. Its corrosion performance was investigated in 3.5% NaCl solution by Potentiodynarnic polarization curves and electrochemical impedance spectroscopy(EIS). The results show that the composite film of PANI/PPY has well corrosion resistance. The free corrosion potential of the stainless steel with PANI/PPY film was much positive than that without and with PANI film. The corrosion resistance of the steel with composite film are influenced by the concentration of aniline, pyrrole, sulfuric acid of the elctrolytes and electrochemical parameters of the preparation process. The composite film of PANI/PPY has the best corrosion resistance when the concentration ratio of aniline to pyrrole is 7:3, and sulfuric acid is 1.1 mol/L, the scanning segment is 25, the scanning rate is 60 mV/s, scanning voltage is 1.2 V.

Self-repairing coating on rebar steel was damaged artificially and immersed in sea water. Then the free corrosion potential, corrosion area of the steel beneath the coating, adhesion between the coating and steel were measured. The rust product in the damaged area was observed. The inhibiting effect of nitrite in the self-repairing coating and the influence on the nitrite effctiveness of alkaline environment provided by cement were investigated. The result showed that the alkaline environment provided by cement played a positive role; the addition of nitrite in the inner coating can effectively inhibit the corrosion; the higher the nitrite concentration is, the stronger the inhibiting efficiency; the effect of nitrite was stronger than that of alkaline environment, the combined effect of nitrite and cement was superior to that of the two individuals. Finally, the inhibiting mechanism of this self-repairing coating was discussed.

Corrosion characteristics of AA7075 reinforced with nano-SiC particles(SiC\rm _p/7075Al) after T6 treatment were studied in 3.5% NaCl solutions and the corrosion mechanisms were further analyzed. The results show that in comparison with the bare 7075Al, the free corrosion potential of SiC\rm _p/7075Al become much positive and its corrosion rate decreases, therewith its corrosion resistance enhances. The surface microstructure of the sample after corrosion text and then po-lished was analyzed by SEM, two distinct features were found: (1) micropitting corrosion occorred at grain boundary and the adjacent Al matrix in the SiC\rm _p/7075Al-T6; (2) The number and the spread area of pits on the AA7075-T6 are significantly larger than that on the SiC\rm _p/7075Al-T6; intergranular corrosion of AA7075-T6 is very serious, which are consistent with the EIS and immersion test. The SiC\rm _p distributes discontinuously on the grain boundary was observed by TEM, the η (MgZn₂) phase and the active corrosion path resulting from the η phase and their adjacent Al matrix were destroyed by SiC\rm_p, the corrosion resistance was then improved.

Exfoliation depth and mass loss for 2024 and 7075 were measured after long-term field exposure in typical atmospheres of six test sits in China. By gray relation analysis, the relationship between environmental factors and exfoliation depth or mass loss was investigated. The result shows that sea-salt particles, HCl and H₂S are the main pollutants factors for the exfoliation of 2024 and 7075. The time of RH>80%, the time of RH>70% and average RH are the main climatic factors for the exfoliation of them. While for the mass loss of 2024 and 7075, SO₂, sea-salt particles, and HCl are three main pollutants factors. The time of RH>80% is the main climatic factor.

Effects of chloride ion concentration and temperature on the anode performance of aluminum/air batteries were studied by polarization curves, electrochemical impedance spectroscopy(EIS) and galvanostatic potential-time curves. The results showed that the aluminum alloy exhibited the fastest corrosion rate when the chloride ion concentration was 3.5%. The potential shifted to negative direction and polarization became weaker when the chloride ion concentration of the solutions increased. The corrosion rate of aluminum alloy increased when the temperature of the solutions increased. The corrosion rate is slightly lower at 50℃ due to the formation of corrosion products layer. The aluminum alloy exhibited the lowest potential when the temperature was 40℃.

The corrosion rate of superplastic Zn-Al alloys in high temperature and high humidity environments was investigated. With mass fraction of Al in the range of (1~22) mass%, the corrosion resistance of the alloys varies unmonotonously. Annealing is favorable to increasing the corrosion resistance of the alloys. The alloys annealed 300℃ showed the highest increment in corrosion resistance. Intergranular corrosion depth is determined by two factors i.e. the fraction of Al-rich phase and the grain fineness. Al rich phase deteriorates the corrosion resistance while fine grains increase the corrosion resistance. Intergranular corrosion depth is linear to corrosion time.

By using a simulating of water-steam system at 350~560℃, the decomposition of octadecylamine was investigated, and the ODA film formation characteristics were studied for the T22 and P91 heat exchange pipes used in gas fired generating units. It was shown that Octadecylamine had a decomposing equilibrium at high temperature and the decomposition products didn't include harmful organic substances such as low molecular organic acids. Octadecylamine promoted formation on the steels of a good protective film in the range of 350~560℃ with the best film at 480℃. The protection property of the film formed with ODA at 560℃ was much better than that without ODA, which suggested the probability of application of octadecylamine for shutdown protection of heat exchange pipes without cooling in gas fired generating units. The optimal conditions were as follow: 560℃, 80 mg/L ODA, pH 9.5 and 2 h. The surface film was supposed to be a compound of ferroferric oxide and octadecylamine through analysis of X-ray photoelectron spectroscopy.

An BP (back-propagation) aritifical neueal network(ANN) model for the predicting of the corrosion rate of L360 steel in H₂S/CO₂ environment was established, neural network architecture is 5-4-1. After the successive training, the model could be applied to predict the corrosion rate of L360 steel in H₂S/CO₂ environment. The forecast results from the network model are in good agreement with the experimental data, the comparative error is less than 14%. Application of BP aritifical neural network to predict the corrosion rate of gathering and transport pipeline in H₂S/CO₂ environment is feasible.

Samples of rust cast iron were prepared by the electrochemical polarization to simulate anciet relics of iron. Then the samples were dechlorinated by constant current polarization method. The dechlorination treatment was carried out with auxiliary electrodes made of different materials with various shapes and arrangements. The results showed that a cage-like auxiliary anode of low carbon steel net showed effective with a chloride removal rate up to 70.10% and thereby the chlorine content was decreased from 5.26 mass% to 0.32 mass% after 48 h dechlorination. Considering the cost of auxiliary anode material, maneuverability and dechlorination performance, low-carbon steel net is most suitable to be taken as auxiliary anode in electrochemical dechlorination.