For the case where the electrode impedance may be represented by a polarization resistance Rp connected in parallel with an interracial capacitance C and where the electrode system is perturbed by a small amplitude sine wave alternating current9 the following equations can be derived: 2i_0/h_0ω=1/R_p~2C+C·ω~2 and 2i_0/h_0λ=πC+λ~2/πR_p~2C In these equations, h_0 is the difference between the polarization values at τ=π/ωand at τ=0, where lr represents time; ω is the angular frequency; λ. is the half length of the period of the sine wave; i, is the amplitude of the sine wave current. Rp and C may be calculated from the values of b and m which are determined by the least square method. To measure the values of h_0, a device which can impose a pulse on the oscillotron at 0-and π-phase is set up. By this device,the fluorescence of the oseillotron is strengthened at τ= 0 and τ=π/ω, and the value of h_0 may be determined from the distance between the two brightening, points on the fluorescent screen of oscilloscope. The impedances of iron electrode dipped in 1 NH_2SO_4 solutions with and without inhibitor have been measured.

The microstructure and compositions of, and phase transformations in aluminide coating on a new Austenitic Fe-Mn-Al heat-resisting steel have been investigated in detail. Two zones were found in the coating. The outer zone is an ordered FeA1 solid solution, while the inner zone consists of FeAI, β-Mn, and V_4C_3. When this coating is oxidized in static air at 450—750℃ for 50—1000hrs, the processes of phase transformations are different in these zones. The sequence of the phase transformation in the outer zone is as follows. FeAl(→Fe_3Al)→α-Fe.→α-Fe+γ→γ, and that of the inner zone is: FeAl+β-Mn(→Fe_3Al+β-Mn)→α-Fe+β-Mn→α-Fe+β-Mn+γ→α-Fe+γ→γ. The phase transformation of the coating is closely related to the degradation of the coating. Formation of the aluminum deficient FeAl phase indicates the initiation of the coating degradation; the emergence of the γ phase means the stage of drastic degradation while the complete conversiott of the coating into γ marks the end of degradation.

The accidental failures of fastening bolt(M33) made of Ultra-high strength steel 3OCrMnSiNi2 were investigated by fraetography. The result showed that it was stress corrosion fracture in water or БФ-2gum. The K_(ISCC) and da/dt of 3OCrMnsiNi2 steel in water and БФ-2 gum were measured by the constant load and constant displacement specimen of L-C and R-C direction. For three low alloy steels, the influence of heat treatment on the K_(ISCC) and da/dt were investigated. The threshold value of stress corrosion cracking of the notch specimen K_(ISCC)(ρ)was measured by modified WOL type notched specimens of various tip radius ρ. The result was as follows where A and B are constants for the speejfje materials. For 3OCrMnSiNi2 (T. S.=158OMPa), the parameters A, B and ρ are 21.7 MPa m~(1/2), 4180 MPa and 0.027 mm respectively. The accidental failures of the fastening bolt with pre-crack or no crack are quantitatively analyzed by linear elastic fracture mechanics. According to these results. preventive measures to avoid failure of the fastening bolt have been suggested.

The effect of yttrium on hot corrosion behaviour of east Ni-base superalloy IN-939 exposed to 75％Na_2SO_4+25％NaCl at 850℃ and 920℃, for 10hrs to 300hrs has been investigated by crucible test method in the present work. The kinetic curves obtained by measuring the weight losses and depths of penetration due to hot corrosion show that the addition of yttrium to IN-939 increases the resistance against hot corrosion of the alloy. The product of hot corrosion is studied by optical microscope, scanning electron microscope, electron microprobe as well as X-ray diffraction techniques. The morphology of corrosion product layer on the surface of IN-939 Y is different from that of IN-939 without yttrium. The corrosion product on the surface of 1N-939 alloys is found to be composed of chromium oxide and sulphide. The region just below is depleted in chromium. The corrosion product on the surface of IN-939 Y alloy consists mainly of Cr_2O_3 with some TiO_2, α-Al_2O_3 and traces of Y_2O_3, YCrO_3 and sulphides. But instead of depletion in Cr, a region depleting in Titanium, with internal oxides along grain boundaries and dispersed oxysulfide particles of yttrium and titanium is observed.

The exoeleetron emission of freshly exposed metal surface arid its initial oxidation are one simultaneous process. The status of the exoeleetron emission is directly connected with the formation of monolayer of oxide. Therefore the oxidation kinetics of scratched aluminum is associated with the exoelectron emission decay of the scratched surface under ordinary temperature and reduced Pressure. The oxidation of freshly exposed aluminum surface obeys the parabolic growth law at the begining, and then shifts to a logarithmic relationship after a few minutes.

The microbes that are able to deteriorate raw rubber and vulcanizates, have been isolated, screened and identified. Among them there are 5 bacterial species(Bacillus lichenformis, Achromobacter liquefaciens, Alcaligenes afaecalis etc), 7 fungi (Aspergillus flavus, Penicillium chrosogenum etc), and9 species of actinomyces. Mixed strains are more resistant toward microbicides than single strain and rubbers are more sensitive to microbial attack of mixed strains than to that of a single strain. The bateria are most resistant to microbicides, with fungi being less and actinomyces the least resistant. The tendency of anti-microbial attack of rubber increases in order of natural rubber, Buna S, butylrubber, neoprene, Buna N, thiokol in raw rubber; and Buna S, neoprene, Buna N in vulcanized rubber. According to microbicidal toxicity, the durability, the reaction with compounding ingredient, the effect of biocides on physical mechanical properties, ageing of rubber, cheap and low toxic, the microbicide Zn-pentachlorophenate(PR2)is selected from more than 40 microbicides. We suggest that PR2 is applied as microbicide for protection from microbial attack of rubber used in waterproof materials underground. The Buna N incorporated with a concentration 2-5％ of PR2 possesses not only excellent anti-microbial potency, but also desirable physical mechanical properties.

An FNA-coated exhaust valve covered with PSR-1 coating(NiCrBSi)has lasted more than 6000hrs in service. The resistance of PSR-1 to wear and corrosion is due to its multiphase structure with Ni-Cr solid solution and boride and carbide particles of high hardness. In the present paper a study of the phase stability of this coating under corrosion fatigue condition in internal combustion engine is described. The analyses of the coated valves before and after service indicate that the composition of the intermediate layer-between coating and base material has changed from a solid solution rich in Ni to one rich in Feo It is found that, the diffusion of Fe results in transformation of chromium boride to iron chromium boride. The superior properties and longer life of the coated valves can be ascribed to the lower diffusion rate of Fe at the service temperature of about 600℃. The redistrubution of Cr in the coating alloy depends on the diffusion of Fe as well. The diffusion of boron has not induced deterioration of mechanical properties. In conclusion, the PSR-1 coating is Sa.tisfactory as to the phase stability after more than 6000hrs service

The corrosion currents of the oxygen concentration cell for more than hundred types of low alloy steel have been measured in sea water by simulated test of oxygen concentration cell. By these measured values in comparison with carbon steel the localized corrosion resistance of low alloy can be divided into three classes, better, good and bad, The relationship between the corrosion current of oxygen concentration cell and the content of the elements in low alloy has been discussed,