Electrochemical potentiodynamic reactivation(EPR) test , sulphuric acid - sulphate of copper (GB4334.5-90) and scanning electron microscope were utilized in this paper to study the intergranular corrosion susceptibility of 202,304 austenitic stainless steels and 409,430 ferritic stainless steels at different sensitive heat treatment temperatures, at which intergranular corrosion will be induced. The results show that the sensitive temperature of austenitic stainless steels and that of ferritic stainless steels are different. the sensitive temperature of austenitic stainless steel is about 650℃, while that of ferritic stainless steel is around 950℃. The results provide scientific criterion for correctly evaluating the intergranular corrosion susceptibility of stainless steel and optimizing the production technology.

Diffusing behavior of water and chloride ion through acrylic polyurethane coating was studied using water vapor, chloride ion transmission rate technique of organic coatings and electrochemical impedance spectroscopy (EIS) technique in this paper. The results obtained indicate that diffusing behavior of water was suited for Fick diffusion law in early stage, later water percolating capacity was constant, constant water percolating capacity was reduced with the increasing of film thickness .Chloride ion percolating capacity was constant in early stage, later increased linearly，diffusion coefficient of chloride ion through coatings can be obtained by slope coefficient ;with the ihncreasing of film thickness, time of chloride ion concentration keeping balance was prolonged and equilibrium concentration of chloride ion was reduced, diffusing coefficient of chloride ion through coating was also reduced. According to the change of resistance and capacity of coatings and metal, and time of the second time constant appeared, diffusing behavior of electrolyte through coatings and corrosion of metals under the coating could be evaluated by EIS.

Fe-20Cr nanocrystallized coatings (NC) were prepared by magnetron sputtering on a glass substrate.The potentiodynamic polarization of Fe-20Cr cast alloy and NC were measured respectively in 0.05 mol/L H2SO4+0.25 mol/L Na2SO4 and 0.05 mol/L H2SO4+0.5 mol/L NaCl solutions.The results showed that NC has greater trend to be auto-passivated in both solutions and the passive current density increased about 2 order magnitude compared with cast alloy.In solution containing Cl-,the passivity region of NC is 2 times than that of cast alloy.It indicated that the pitting resistance of NC was greatly improved.The semiconducting properties of the passive films formed on NC and cast alloy in both solutions were investigated by capacitance measurements.The results showed that Fe-20Cr cast alloy has poor resistance to pitting corrosion in chloride acidic solution due to its p-type semiconducting passive film.However,the passive film on Fe-20Cr NC was a n-type semiconductor which had a higher transpassivation potential and therefore higher resistance to pitting corrosion.The passive current density of NC was higher because of the higher donor/acceptor density in the passive film.The investigations showed that the type of passive films is responsible for the electrochemical behavior difference between NC and cast alloy.

Make use of available experimental data of LY12CZ aluminum alloy,a probabilistic neural network was developed to classify the maximum corrosion depth ranges based on the material failure mode.The output is in good agreement with experiment result .Statistical study on classified corrosion damage was carried out.The results show that maximum pitting corrosion depth for aluminum alloy conforms to Gumbel distribution.The normal distribution and three parameters Weibull distribution fit well with period of intergranular corrosion and the maximum exfoliation corrosion depth is consistent with the three parameters Weibull distribution law.It may be necessary to use several distribution functions rather than a single distribution to represent corrosion damage characteristics due to the large distribution of maximum corrosion depth on aircraft materials.

The effects of temperature,pH,Cl- and SO2-4 concentration on pitting potential of 321 stainless steel were investigated by using quadrature test design and contrastive test.The results of quadrature test design showed temperature and Cl- (Cl-≥0.014 mol/L) concentration remarkably influenced pitting potential Eb,but pH(6～9) value did not.The results of contrastive test indicated Cl- concentration had no effect on Eb when Cl-≤0.014 mol/L,but Eb enhanced with the increasing of Cl- concentration when Cl->0.014 mol/L.Increasing the temperature shifted the critical potential to more active values.If Cl-=0,SO2-4 concentration had no effect on Eb,but if Cl-=0.028 mol/L,Eb enhanced with the increasing of SO2-4 concentration.

The influence of NaCl on the initial atmospheric corrosion of Q235 steel in simulated atmospheric environment including 5×10-6(volume) SO2 and 1%(volume) CO2 are investigated by mass gain,SEM and X-ray diffraction techniques.The results show that Q235 steel suffer a serious corrosion under the cooperative effect of NaCl,CO2 and SO2 .It proved that the cooperative effect of SO2 and CO2 is important for the corrosion aggravating of Q235 steel when the NaCl is existed.The presence of NaCl accelerated and catalyzed the reaction of initial stage of atmospheric corrosion for carbon steel.The massgain in the presence of NaCl was near decuple higher than that in the absence of NaCl.The corrosion products mainly are Fe3O4,γ－Fe2O3 and γ－FeOOH.

The atmospheric environment was simulated by using environmental scanning electron microscope and the formation process of the water film on the LY12 Al surfaces contaminated by dust,oil and NaCl was observed.The investigation showed that the water film is easier to form on the contaminated samples than on clean samples,which results in atmospheric corrosion.

The effect of coating used to cover airplane on corrosion fatigue behaviour of LY12CZ aluminum alloy has been studied.The corrosion fatigue lives for uncoated and coated specimens in both air and 3.5% NaCl solution were compared,and the evolution of free corrosion potential with cyclic number was measured.The equations of fatigue and corrosion fatigue lives were obtained on some experiment conditions by quantitative analysis.The results showed that the corrosion fatigue life of LY12CZ aluminum alloy was greatly improved by coating.

The effect of coating used to cover airplane on corrosion fatigue behaviour of LY12CZ aluminum alloy has been studied.The corrosion fatigue lives for uncoated and coated specimens in both air and 3.5% NaCl solution were compared,and the evolution of free corrosion potential with cyclic number was measured.The equations of fatigue and corrosion fatigue lives were obtained on some experiment conditions by quantitative analysis.The results showed that the corrosion fatigue life of LY12CZ aluminum alloy was greatly improved by coating.

Fusion-bonded epoxy (FBE) powder coating on steel was selected to investigate the effect of flowing condition on coating degradation in 3% NaCl aqueous solution at 60℃ by EIS.The immersion tests in flowing condition were conduct ed by using a rotating cylinder apparatus.The relative permittivity calculated from the high frequency value of impedance spectra,was used as the index to monitor properties variation with immersion time.The results obtained from EIS measurements and visual examination showed that the flowing immersion condition brought much greater destruction to the coatings than the corresponding static condition.This results can be explained that the introduction of flowing condition accelerated the ions,not water molecules,into the coatings.The present investi gation provides an accelerating test way to evaluate degradation of excellent coating.

The corrosion inhibition behavior and adsorption mechanism of dodecylamine for a copper-nickel alloy in 0.2 mol/L NaCl solutions was studied by electrochemical methods and atomic force microscopy (AFM).The results showed that dodecylamine had both cathodic and anodic inhibition action,but the cathodic effect was dominant.The adsorption behaviour of dodecylamine obeyed Flory-Huggins isotherm model.The adsorbed dodecylamine film changed the structure of the double-electric layer and made the potential of zero charge (PZC) shift to the positive direction.It can be concluded from the AFM phase images that as the inhibitor concentration increased,the adsorbed film of inhibitor tended to become more density and orderly so that corrosion inhibition efficiency increased.AFM force curve measurements were also performed and showed that as a result of the adsorption of dodecylamine on copper-nickel alloy surface,adhesive forces between the tip and the sample surface were detected and the long-range electrostatic repulsive forces between the tip and the sample surface were decreased.

By using a split cell to separate anode and cathode as well as measuring the change of net-electric current between the two electrodes caused by the change of the amount of oxygen in the solution and the addition of CeCl3.The influence of CeCl3 on corrosion behavior of B95 super-strength aluminum alloy in the 0.1 mol/L NaCl solution was studied.Meanwhile,a further discussion about Ce salt inhibition mechanism was carried out by revealing the features of electrode surface with the help of SEM and X-ray energy-dispersive spectrometry (EDS) and resorting to other electric chemical techniques,such as potential-time curve,polarization curve and so on .The results showed that alayer of uneven conversion coatings could appear on the surface of B95 alloy after being dealt with by Ce salt;the dynamics of coating-formation involved two stages:the solution of aluminum alloys and coating-formation fterwards;the cerium conversion coatings were mainly composed of Ce,O and Al elements;the experiment with completely submerging into the solution of 3.5% NaCl showed that the corrosion rate of B95 could be reduced by several hundre d times and the anti-corrosion performance of aluminum alloys improved greatly when CeCl3 were added to the solution.As a result CeCl3 proves to be an excellent coating-formation material and aluminum alloy corrosion inhibitor.

A novel protective surface treatment of metals by silanization is reviewed.Studies on preparation and characterization of silane films,the performance of silanized electrodes was presented.Two fundamental problems—hydrolysis and failure of silane solution,which can help us get insight in the properties of silane film on metal substrates and have crucial effect on optimizing the preparation of it,are discussed as well.The more promising electrodeposition of silane films and prospects are also presented.