Corrosion weight loss test, corrosion potential-time curve, polarization curve, scratched electrode technique and colour test with K_3Fe(CN)_6 and NaCl solution etc. have been used to investigate the inhibition effect of borax on carbon steel in deionized water, FeCl_3 and KClO_3 solutions with different conditions of aeration. The chemical composition of the inhibitory film has been analysed by XPS. It is found that the inhibition of borax is independent on the existence of dissolved oxygen in the solutions. As the concentration of dissolved oxygen increase, the inhibition efficiency, the resistance to pitting perforation of Cl~- and the ability to repair the inhibitory films decrease. The inhibitory films formed by borax on the surface of carbon steel in FeCl_3 solution with dissolved oxygen mainly consists of Fe_2O_3, FeO and ferric borate, with occluded Cl~- ions. In this case, the borax acts as an anodic inhibitor. Under fully deaerated condition, however, the inhibitory film consists of FeO, Fe_2O_3 and adsorbed B_4O_7~(2-) ions, and the borax acts as a mixing inhibitor.

β-NiAl type composite coating with dispersive La_2O_3 particles was prepared by electrodeposition of Ni-La_2O_3 composite on M38 superalloy followed by aluminizing. The fine structure of the coating and its oxide scale was studied by means of highresolution electron microscope(HREM) for the first time. It was found that La_2O_3 particles were distributed in β-NiAl phases of the coating, and that after oxidation at 1273K for 25 hours dispersive or agglomerative La_2O_3 particles with a diameter of 10～50nm were incorporated into the α-Al_2O_3 scale. In addition, an intermediate layer located at the α-Al_2O_3/β-NiAl interface was also observed. The superior oxidation resistance of the coating is believed to be related to effect of La_2O_3 dispersoids on growth mechanism of the oxide scale. A sufficient amount of La_2O_3 dispersoids existing in the vicinity of the oxide/coating interface would act as a barrier blocking the bulk diffusion of Al~(3+) ions which tends to reduce the growth rate of the scale and to improve the oxide scale adhesion. The intermediate layer observed may contribute a beneficial effect to stability of the interface.

The influence of nitrogen on pitting and crevice corrosion resistance of the type 256Mo3 duplex stainless steel was evaluated. It was found that the resistance to both pitting and crevice corrosion increased with increasing nitrogen content, and that the critical crevice corrosion temperature was related to the nitrogen content of steel as follows: CCT(℃)=17.3+78.4N％wt. The more the nitrogen content of steel, the higher the enrichment of nitrogen in the surface layers. The maximum nitrogen concentration was about 14 times its bulk level for the steel containing 0.28％N; pitting sites were transferred from γ phase into α phase with the nitrogen content increasing to more than 0.096％. The simulated occluded cell(OC) testing indicated that the more the nitrogen content, the larger the pH value of solution in OC by the end of the test. The ammonium ions in solution were detected with Nessler reagent for material containing 0.28％ nitrogen, proving the inhibiting-effect of nitrogen on the duplex stainless steel. So it is concluded that the role of nitrogen is due to the enrichment of austenitic phase and inhibiting-effect by proton consuming reaction leading to a reduction of local acidification in OC.

When a mild steel electrode in 93％ sulfuic acid was first controlled potentiostatically over 300mV(vs Pt in the same medium) and then galvanostatically at a reduced currentdensity, regular sinusoidal oscillations of potential were observed. Analysis of the experimental results indicated that the periodic phenomenon was caused by alternate active-passive transition on the electrode surface. Their amplitude and period were almost independent on the polarization potential and current. When temperature increased, the period became shorter, and the amplitude smaller. Vigorous stirring could stop the oscillations. Passiveactive alternation of weak sites of the electrode surface caused the potential oscillations.

The protective surface film formed of carbon steel after a treatment in 1.0 mol/L amino-trimethylidenephosphonic acid(ATMP) solution was analysed by XPS, FT-IR and Raman spectrometer. The restlts showed that an anticorrosive coordination compound film was formed on the steel surface. By Ar~+ sputtering, the composition depth profile of the film was determind. The relative atomic percent contents(A. C. ％) of the film, as obtained from the element composition constant region of the profile curves, were 48.4％O; 28.6％P; 7.0％Fe; 4.3％N; 11.7％C. The structure of the coordination compound film was deducted from the above results, as probably [Fe(ATMP)_2]_n.

The composition and structure of anodic oxide films on aluminum formed in sulphuric acid solution and cold sealed with BY02 agent were investigated by means of X-ray diffraction, infrared spectroscopy, thermogravimetry and differential thermal analysis. Anodic oxide films are mainly composed of amorphous alumina, including sulphate, Boehmite AlOOH, nickel hydroxide Ni(OH)_2 and aluminum fluoride AlF_3 are formed in cold sealing. The cold sealing reaction mechanism was also discussed.

Weight gains during cold sealing and dissolution of anodic oxide films on aluminum in sulphuric acid solution were investigated by using gravimetric method, Auger electron spectroscopy and transmission electron microscopy. Two kinds of cold sealing models were put forward. For thin oxide films, the products of sealing reaction which takes place throughout the film, gradually fill all the pores. For thick oxide films, sealing reaction mainly occurs at the outer layer of the film which is sealed, but the inner layer remains unfilled.

In thes paper cubic spline interpolation of equidistant samples is employed for the numerical execution of Fourier transform to perform the transformation from the time domain into the frequency domain, and interracial impedance of electrochemical system can be determined. The interpolation procedure is performed implicitly by weighting discrete Fourier transform(DFT) coefficients with A_3(ω) as follows (?)(ω)=A_3(ω)·(?)(ω)+B_0(ω) (?)(ω) being DFT and B_0(ω) additive terms. In this way the aliasing effect of DFT spectrum and limitation by sampling theorem can be eliminated. So (?)(ω) is nonperiodical as being the Fourier transform of a continuous function, and the frequency range of (?)(ω) is not limited. The approximation error of numerical Fourier transform is only produced by that cubic spline interpolation. So it is one of the most accurate methods to measure the "ac impedance" in time domain at present. As it is proved in another paper, the linear approximation by Laplace transform in literature is only the case of m=1 for the m-th order spline interpolation via DFT.

A sampling system was assembled with microcomputer, A/D & D/A converter and self-made amplifier & potentiostat. Software consisted of assembly and quick BASIC languages. The maximum sampling rate is 32μs/point. The response current to the step voltage perturbation was sampled, then the algorithm in part Ⅰ of this title was employed and interracial impedance in electrochemical systems was determined. Results of impedance measurements of some equivalent circuits and the Pt, Fe (CN)_6~(3-)/Fe(CN)_6~(4-) system agreed well with closed-form solutions or literature data, thus demonstrating the ability of the computerized measurement system. Measurements with CuSO_4+gelatin systems yielded the expected impedance. Nyquist plot exhibited sufficiently the effect of the dope concentration.

In general, Tafel slopes are obtained from polarization curve in which polarization potential values are often greater than ±30mV. In the present paper, a coulostatic technique was applied to obtain Tafel slopes by analyzing ΔE(t)-T attenuation curve under eoulostatic perturbation. Due to the absence of current, this interrupt relaxation method was not affected by solution resistance and would be particularly suitable for the high resistivity medium and coationg systems. The new method was based on the electrochemical fundamental equations and was combined with coulostatie perturbation techniques, i.e. by arranging differential equation groups from Kirchhoff's Law and nodal current formula, then by solving them by fourth Runge-Kutta method. ΔE could be reduced within ±10mV. Some experimental systems have been used to demonstrate the proposed method.

The effect of nitrogen on the pitting resistance of duplex stainless steel was studied with immersion test, electrochemical measurements and surface analysis techniques. The results indicated that the addition of nitrogen into the duplex steel shifts its pitting potential towards more positive direction, favours austenite with higher contents of Cr, Mo and Si, and hence improves the composition partition in the duplex. Nitrogen enhances the enrichment of Cr and Mo in the passive film, especially for the film formed on austenite, so that the stability of passive film is increased.

Push-pull fatigue tests under plastic strain control were carried out with a high-purity ferritic stainless steel Fe-26Cr-1Mo in 1mol/L H_2SO_4 and 1mol/L NaCl solutions. The current transient behaviour during corrosion fatigue was different in these two solutions. Two sharp current peaks corresponding to maximum tensile and compressive strains respectively were observed in 1mol/L H_2SO_4. A sudden current drop or bump occurred as the test started with tension in H_2SO_4 solution. However, only one current peak, which occurred at approximately 50％ of the applied tensile strain, was found in each strain period in NaCl solution. The experimental results were explained in terms of the depassivation-repassivation process induced by strain cycling with the effect of chloride ions taken into account.

Simulated occluded cell(0C) was used to study the chemical and electrochemical changes within stress corrosion cracks for the system sensitized AISI304 steel/Cl~- with addition of different concentrations of I~-. The respective number of equivalents of migrated I~- as well as Cl~- was proportional to the quantity of electricity passing through the occluded cell. The ratio of migration rate of Cl~-/I~- was the same as that of the concentrations of those ions in bulk solution. The pH value inside occluded cell was independent of I~- migration, but the occcluded potential moved more positively than that without I~-. It was shown by potentiostatie weight loss method using simulated occluded solutions with different I~- concentrations that the migation of I~- from outside inhibited the occluded cell corrosion. The inhibition efficiency of 0C was more than 98％ when the concentration of I~- in bulk solution was only 0.01mol/L. So the iodide was an effective inhibitor of stress corrosion cracking for austenitic stainless steel in chloride solutions.

The long and short fatigue crack growth(FCG) of 12CrNi3MoV steel was investigated under cathodic protection(CP) in 3.5％NaCl solution. The results indicated that the long FCG was different from the short one in brine and under cp. In salt water, the short FCG rate increased while the long FCG rate decreased. The short FCG was apparently hindered at appropriate CP potential (—900mV, SCE) and accelerated at over-protection potential (—1200mV, SCE). On the contrary, CP increased the long FCG rate and the more negative the CP potential, the greater was the long FCG rate. The short FCG rate was greater than the long one at the same ΔK and the difference increased in salt water, but decreased under CP. Finally the oxygen trans-portation, the wedging of corrosion products and the hydrogen embrittlement effect in both long and short crack tips were discussed.