In order to look into the mechanism by which alloyed chromium and molybdenum improve the pitting corrosion resistance of high purity ferritic stainless steel to a quantitative XPS technique was employed to study the composition and thickness of the passive film and transient layer as well, Some twelve materials with various Cr and Mo contents were studied in 1N Cl~--containing neutral solution. The results showed that Mo can rather effecetivly retard the depletion of Cr in the transient layer and improve the stability of the passive film itself. The resistance to pitting of the materials containing Mo was thus bettered up because of the enhancement of repassivity of the transient layer.

Layer structure and thickness of two-layer homogeneous thin film can be investigated by ellipsometric measurements starting from the film-free surface. A break observed on the experimental δΔ-δφ loci seems to suggest the presence of two layers on the substrate. The Drude equation modified for the two-layer film was presented. To determine the film growth and optical constants of the individual layers, the best fit approach was used between calculated Δ_c, φ_c for the proposed complex refractive indexes and the experimental ellipsometric data. Obviously, the second layer may be for reed either as inner layer or as outer layer related to the initially formed layer. These two possible mechanisms of film formation can be judged with ellipsometric computation. Examples of computation were given of passive films on cobalt as well as on stainless steel.

Cathodic protection is generally recommended to control the external corrosion of pipe. Sometimes, however, internal cathodic protection is required. The impressed current protection is usually provided by using discrete inert anodes placed at intervals along the pipe. The characteristics of potential distribution under this condition is perhaps the most importan, aspect because of the limited space inside pipe. Corresponding mathematical expressions were derived. The potential is evaluated as a hyperbolic function of the distance from anode. The relationship has been verified experimentally. The dependence of potential on electrolyte resistivity, polarization resistance of inner surface, pipe diameter and length of pipe is illustrated. The protection current demand was also evaIuated on the basis of non-unlform distribution. Both laboratory investigation and operation experience showed the time-dependence of potential, which could be ascribed to the increase of polarization resistance of the pipe surface. The theoretical consideration presented here would be useful for the design of internal cathodic protection system of pipe in general and for the selection of the inter-anode spaceing in particular.

The fatigue crack growth rate (FCGR) of 08PVXt, 16Mn, 440C and 4340 steels in distilled water anb NaClaqueous solution has been investigated, and the experimental results have been compared with those of corrosion fatigue in the literature. The fatigue life (FL) of of ordinary steels in distilled water is higher then that in NaCl aqueous solution. The FCGR of 08PVXt, 440C and 4340 steels in distilled water is higher than those in NaCl aqueous solution. However, contrary result is observed for the 16Mn steel. The authors are inclined to think that the function of the Cl~- is different in the crack initiation and in the macroscopic crack propagation.

The sulfide stress corrosion cracking(SSCC) resistance of 12Cr2AlMoV low alloy steels with different microstructure and quantity of inclusions was investigated by means of electrochemical hydrogen permeation technique and constant load SSCC test, etc. Experimental results showed that the resistance of the steel to SSCC increased with increase of tempering temperature. The time to fracture, t_f, for normallzed and tempered steel was longer than that of quenched and tempered one, although the heating temperature were identical, For 12Cr2AlMoV steel, the resistance to SSCC was mainly dependent upon themicrostxucture of the steels. The microstructure was closely related to the diffusion coefficient of hydrogen in the steel. The more quantity of sulfur and inclusion in the steel, the lower the resistance of the steel to SSCC . It was found that besides mangness sulphide, other kinds of inclusion would also cause hydrogen induced eracking(HIC)and SSCC.

The permeability, diffusivity and solubility of hydrogen in 21-6-9 aust. enitic stainless steel are determined over the temperature range 230℃ to 430℃ using a gas-phase UHV technique. The temperatures dependence of these properties are given by Φ=2.52×10~(-4)exp(-61.29KJ/mol/RT)mol./m、 s·MPa1/2 D=2.49×10~(-7)exp (-51.15KJ/mol/RT)m~2/s S=1.01×10~3exp(-10.14KJ/mol/RT) mol·/m~3·MPa~(1/2) The effect of surface oxidation can be eliminated by eleetroplating Pd on both sides of sample. The treatment conditions(cold-worked or heat treated) of 21-6-9 steel have no obvious influence on hydrogen permeation.

Six chemical etchants have been selected for reveating the defects in InP crystals. The choice of etchant composition and the optimum etching temperature for each etehant is based on experimental results for obtaining the dislocation patterns with clear etched pits. Finally, an etchant of (H_3PO_4+HBr)has been found which successfully reveals dislocations in VPE InP.

Characteristics of pit growth on aluminium were investigated in seawater by methods of electrochemical kinetics, analysis of solution in localized corrosion region, metallography and scanning electron microscope. The changes in pH value and the concentration of chloride ion inside pits were measured, the pitting processes were traced by television microscope. Results showed that the composition of anodic solution within a pit changed a great deal from the bulk solution, and that pits developed along a certain orientation and hydrogen was released in the pit, the rate of pit growth increased with the increase of applied potential or temperature. The cause of escaping hydrogen and its effect were discussed. It was thought that the pit growth were characterized by selfcatalysis and gradually decreased in the later stage.

Multiple ion implantation is used to improve the resistance of 410 stainless steel(SS)to localized corrosion. Potentiodynamic polarization curves show that the passivity of P~+-B~+ implanted 410 SS is better than that of unimplanted 304 SS in 0.1NH_2SO_4 solution at 30℃; the pitting potential(E_h=E_(10)μA/cm~2)of P~+-B~+ implanted 410 SS is about 500mV more noble than that of unimplanted 304 and 316L (urea grade)SS in 1NHAc/NaAc+0.5％/NaCl solution at 30℃. The passivity of P~+-B~+-Mo~+-N~+ implanted 410 SS is better than that of unimplanted 316L(U.G.)and 25Cr-22Ni-2Mo-N SS, and the pitting potential of P~+-B~+-Mo~+-N~+ implanted 410 SS is about 600mV more noble than that of unimplanted 316L (U. G. )and 25Cr-22Ni-2Mo-N SS, both in HAc/NaAc+0.1 NNaCl solution with pH 4 at 30℃. All those results illustrate that the multiple ion implantation improves the passivity and pitting resistance notably. This conclusion is supported by the results of corrosion weight loss test in 0.1NH_2SO_4 solution at 45℃ for72 hours and the results of pitting corrosion test in 0.1N NaCl+0.07％H_2O_2 solution at 20℃ for 24 hours. Both electron diffraction and micromorphology observation demonstrate that surface layers of 410 SS modified by multiple ion implantation are amorphous. Therefore it is thought that notable improvement of corrosion resistance of implanted 410 SS results from amorphous surface layer containing such benificial elements as Cr, Mo, N and so on.

The type, distribution and size of inclusions in stainless steel 00Cr11Ni10 Mo2Ti were studied by a combination of techniques with scanning electron microscopy, electron probe analyses and metallography. The site susceptible to pit initiation was observed on the surfaces of electrochemically polarized specimens under the long focus microscope. The results indicate that pits initiate at the edge of nonmetallic inclusions. Under the experimental condition, TiN is more susceptible to pitting initiation than Al_2O_3; geometric factors such as size, shape and distribution of the inclusions also affect the pitting susceptibility obviously.

The effect of different deposition temperature (1173-1333K) on thickness, hole ratio, phase componets, morphology of surface and corrosion resistance of deposited tantalum layer on low carbon steel was investigated by means of metallographical technique, microhardness testing, X-ray diffraction analysis, scanning electron microscope analysis and corrosion weight loss test. The experimental results showed that the tantalum coating of steel was composed of Ta and Fe_5Ta_3 phases, and with the increase of deposition temperature from 1173K to 1333K, the grain size as well as the thickness of coating layer increased notably. Under 1283-1333K, a denser, thicker tantalum coating could be obtained. The corrosion rate of Ta-coated steel in 37%HCl solution is 2-3 orders lower than that of uncoated steel.