The variation role of ion transport number during the growth of anodic films on aluminium and its effect on film morphology have been studied by using TEM allied with ultramicrotomy sectioning,marker technique and quantitative chemical analyses by ICP-AES.The results show that athe alumin- ium and oxygen-containing ions migrate in opposite directions through the film.In a particular electrolyte,the real transport number of aluminium ions is a constant.When the applied anodic current density exceeds a critical value,a fraction of the aluminium ions acts as film material at the film- electrolyte interface in the form of barrier film.On the other hand,when the applied anodic current density is less than the critical value,all the outwardly migrating aluminium ions enter into the electrolyte and hence the film is entirely formed by oxygen-containing inos at the film-metal interface. The film formed under this condition is porous due to attack of the electrolyte on the outer film surface.Mathematic expressions of film growth efficiency and the relationship between apparent and real transport numbers have been derived.The process of film material formation by aluminium ions at the film-electrolyte interface is explained by a direct dissolution-precipitation theory.

A microcomputer based system for impressed current cathodic protection was developed on the basis of the fact that under steady state condition prot- ection potemtial will not change much if voltage of d.c.supply is maintained.Its operating principle is entirely different from that of available industrial potentiostat,in which closed-loop feedback control is continuously executed. Potential control with the new system is achieved by periodic adjustments of d.c.power output.Potential received periodically from a sensing electrode is compared with a preset control value and their difference is fed into an A/D converter.Then the digital signal goes into microcomputer and a result- isng voltage proportional to potential difference is sent to thyristor circuit to correct the d.c.output voltage.Steady state condition is reached by suc- cessive adjustments.The operation of the system was demonstrated by cathodic protection of mild steel at +0.1V vs zinc reference electrode in portable water.When a sampling period of 0.7second was taken,a potential control accuracy of +10 mV was obtained.The most attractive feature of this new design is that it could be easily extended to multi-anode system.Iu this case each anode is driven by its own d.c.power module and is under computer control periodically.

The growth stresses and thermal stresses developed during oxidation of Nb and Nb-752(Zr 2.5%wt.,W 10%wt.)at 400～500℃ in 1 atm pure oxygen and the effect of oxygen dissolved in metals on the stresses were investigated by the bending strip method.It was found that alloying elem- ents Zr and W had little effect on the stresses until their contents reach 2.5%wt.and 10%wt.respectively.The results of X-ray diffraction anal- ysis also indicated that the composition of oxide film was Nb_2O_5 either on pure Nb or on Nb-752 alloy.

Variable angle XPS studies of the passive films formed on the alloys Fe19Cr9Ni and Fel9Cr9Ni2.5Mo in deaerated 0.1M HCl revealed the bipolar structure of the passive films.Addition of Mo to the alloy enh- anced the bipolarity of the passive film by forming MoO(_4~(2-)) incorporated in the outer region of the film.In neutral solution,it is possible to introduce MoO(_4~(2-))anion to the film from the solution.It plays the same role in enhancing the bipolarity of the film as it does in Mo bearing alloys.

Corrosion behaviour of mild steel buried in clay containing 35% water was studied by means of the potentiodynamic technique,curve fitting method and AC inpedance measurement.The regression equation that describes variation of corrosion rates of the mild steel with time was obtained.Equivalent circuit and mechanism involved in the corrosion processes are proposed.

The results of salt spraying tests indicate that the corrosion resistance of chromate conversion coatings on aluminum and its alloy is dependent on the substrate composition and on the surface pretreatment condition.The coating on L_2-Y is better than that on Ly_(12)-C_2.When an acidic(HNO_3+CrO_3+HF) pretreatment is used in place of alkaline etching,the corrosion resistance of these coatings could be markedly improved.

Polymerized aniline films on pure iron were obtained anodically by electrochemical methods.Electrochemical and surface analysis techniques were employed for measuring the corrosion resistance of polyaniline modified iron (Fe/PA).Experimental results showed that polyaniline films offered good protection for ferrous metals.In comparing polyaniline modified iron specimens with unmodified ones in strongly basic to weakly acidic aqueous solutions it wes found that the corrosion current densities were reduced by three orders of magnitude with Fe/PA,and the trans- passivity potentials remarkably moved toward the positive direction.

PC-602 (A mixture of polyhydric alcohol phosphate ester,phosphate and polyphosphate) is an efficient corrosion inhibitor for cooling water and possesses some antiscaling properties. In this paper,the inhibition mechanism of corrosion inhibitor PC-602 for carbon steel in cooling water were discussed.Potassium ferricyanide colour reaction method,Auger electron spectroscopy(AES)analysis and ellipso- metric measurement were adopted to study the composition and the growth of the inhibi tire film.The results showed that the protective film formed on carbon steel surface by the inhibitor was composed of iron oxide and complex compounds of phosphate ester,The polarization curve measureme- nts showed that PC-602 inhibited both the cathodic and anodic processes of the corrosion reaction.

The effect of some factors on anodic dissolution of carbon steel in man- made pit,the component and action of surface layer inside pit have been researched. It was found that anodic dissolution rate inside the man-made pit increa- ses with polarization potential values and concentration of chloride ions,After the pit getting proper depth,the relationship between its dissolution rate and pH value of solution is not priority,The anodic dissolution rate in the man- made pit with smaller diameter and depth are quicker than that of the pit with biger diameter and depth,but when diffuslon resistance form,its dissolution rate decreases more quickly,There is a resistance layer mainly consist of Fe and Cl in the bottom of the pit.

Electrochemical potentiodynami cpolarization,linear polarization and weight loss methods,were used to study the corrosion behavior of 12Cr2MoAlXt steel in sea water. Experimental results showed that the limiting oxygen diffusion current on 12Cr2MoA1Xt steel was much smaller than that on A3 steel and reached a steady value in a few days.It was supposed to be the main factor for improved corrosion resistance in sea water.

A rotating ring-disk electrode with demountable and interchangeable disk was designed.Collection efficiency was investigated with the reac- tion Fe(CN)_6~(3-)+e~Fe(CN)_6~(4-) to ensure the reliability of the electrode. With no electrolyte leakage this construction can be used in electroche- mical corrosion experiments with many materials.

The paper is intended to correlate the microstructure of rubber modified phenolic resin with results of OsO_4 staining method.The micro forms of this blend material before and after corrosion testing are measured by phasecontrast microscopy and X-ray energy dispersive spectrum(EDS) method. The results of analysis show that this blend system is the form of IPN.This structure is beneficial to improving anti-impact property and anti-permeability.