Both the E-pH equilibrium diagram and the experimental E-pH diagram were used to investigate the corrosion process and characteristics of 55％ Al-Zn-1.6％Si coating.Chemical analysis was used to trace the total corrosion process of the coating in solutions containing Cl-with different pH values(pH=3～5) The corrosion mechanism was revealed to be selective dissolution of Znrich phase or elementary Zn at the very beginning, but rapidly coming to the propotional dissolution of the Al-Zn alloy.The micrography showed that the coating has diverse characters in four different pHvalue regions, feing coincideut with the conclusions derived from the E-pH equilibrium diagram.

The influence of additive amount of Si on the microstructure and corrosion behaviour of 55％ Al-Zn-1.6％Si alloy hot-dip coating has been investigated. It is shown that small amount of si (1～20％) had little influence on the microstructure and corrosion resistance while amount of Si>2％ would show up free crystals of Si or silicon compounds condensed together with the interdendritic quasi-eutectic Zn-rich phase thereby increasing the electrochemical heterogeneity of the coating and decreasing its corrosion resistance.The corrosion current density of each phase on the multiphase electrode has been calculated by computerizing technique, combined with the simulating phase method. The relation between the corrosion rate of the coating and the additive amount of Si has been founded quantitatively.

Anodic and cathodic processes of Cu-Ni alloy in 3％ NaCl solution have been investigated. Theanodic process is under diffusion controlled. The film Produced on the alloy surface inhibits theanodic process. Cathodic process is the reduction of oxygen on alloy. It is activation controlled near the corrosion potential(φ_c). An equatien for the corrosion kinetics of Cu-Ni alloy was derived and some kinetics parameters were calculated by computer.

The critical conditions and the kinetics of pitting initiation in austenitic stainless steels in chloride solutions have been studied by the method of electrochemistry.The relationship between the critical potential and the concentraion of chloride ion,temperature as well as the content of molybdneum is obtained. The rate of pitting initiation follows she equation: Ⅰ/t=Aexp (-Ea/RT) [C1~-]~α [SO_4~(-2)]~β.It is shown by Electron Microprobe analysis that the chloride ions locally concentrate on the film.A critical nucleus model for pitting initiation has been put forward, by whieh the following could be explained: (1)the existance and nature of critical conditions, (2)localized attack of chloride ions on passive film, (3)the repassivating of pits and the critical size of repassivated pits,(4) the sites susceptible to pitting initiation, (5)the effect of inhibiting anions and (6)the physical meaning of induction period.

Plate specimens of commercially pure iron and cylindrical specimens of low a11oy steel were tested for hydrogen permeation under slow strain rate tensile test condition. Results showed that J/J(?) versus time curves of the evolution of hydrogen for both plate and cylindrcal specimens were similar. Apparent diffusivity D as related to tension is considered as a function of strain from which a mathematical solution of D can be obtained by using Newton'S method to solve the groups of non-linear equations by means of computer.

The electrochemical noise during pitting corrosion of iron in solutions of K_2Cr_2O_7, Na-benzoete, boric acid+borax and NaNO_2 with various concentrations of Cl~- -ion at 30℃ was studide using a FFT analyzer.No electrochemical noise can be detected when the concentration of C1~- -ion is below the critical concentration to induce pitting corrosion for each solution. As the concentration of Cl~- -ion is high enough to cause pitting corrosion, electrochemical noise arises sooner or later after the iron coupon is dipped into solution, and pits are formed correspondingly in most eases. In all cases the electrochemical noise observed is 1/f noise in low frequency range, and the power of noise increases with Cl~- concentration roughly lineraly in each solution. It is considered that the noise observed is similar to the flicker noise in semiconductors and is caused by the increase of aaodic current through the passive film under the action of Cl~- -ion.

The oxidation kinetics of an Fe-Cr-Ni-Ti superalloy, containing 4.43at％ titanium was studied in air over the temperature range of 700～900℃ for period of 10 minutes to 500 hours. The weightgain due to oxidation obeyed the conventional parabolic lair and the values of activation energy were Qp_1=38 kcal/mol and Qp_2=42 kcaI/mol. The depth of penetrating pits obeyed linear iaw. AES/ESCA indicated the initial sclae was rich in Ti, Fe and Cr, Consiting mainly of Fe_2O_3, TiO, and Cr_2O_3. By X-ray analysis the long-term oxides were estimated to be NiTiO_3 and FeCr_2O_4. The cation vacanies generated in oxidition at the alloy-scale inteerface joined up to produce oracks and caused spalling. The selective oxidation of η-Ni_3Ti phases genrated random penetsrating pits. The higher titanium concentration obstructed the formation of Cr_2O_3 protective scale and promoted the formation of NiTiO_3, thus deteriorated the oxidation resistance

This paper serves as a review of the failure mechanism of composites in adverse environments. A brief discussion is presented about the factors which influence the corrosion-resistant properties of composites, such as resin matrix, fiber and resin/fiber interface as well as the diffusion process of liquids into composites and the stress effects on the behaviour of composites in corrosive media.