Researches into the corrosion fatigue in last decade have shown that the following three steps should be involved in the mechanico-chemical interaction: 1)medium transportation,2)surfaee adsorption and reaction, 3)hydrogen diffusion in the solid inducing the embrittelment. Moreover, the slowest step is the rate governing process in the mechanico-chemical interaction. The process of the mechanico-chemieal interaction in corrosion fatigue is very complicated and can be influenced by many factors. Therefore, the models on the mechanico-chemical interaction developed up to now are generally restricted to bear the relationship with one or two steps. In the present paper, a review is made on the mechanico-chemieal models in corrosion fatigue developed in recent years from the view point of interaction process. The physical image and the mathematical descriptions of various models are analyzed, and spheres and limitations of application of these models on the mechanico-chemical interaetiort are pointed out. Finally, the research trends on the mechanico-chemical model in corrosion fatigue are outlined.

The transient response of passivated metallic electrode system under potential step is analysed with the aid of a linear model, and a technique for calculating the parameters characterizing the growth and dissolution of passive film is proposed. It is believed that the information which is expected from impedance measurement can be obtained by this technique and that this technique is superior to the former as it is much more rapid.

The spalling processes of the oxide scales formed on 5621S alloy(Ti-5Al-6Sn-2Zr-1Mo-0. 25Si)and 5621S alloy containing 1％Nd during cooling from 700℃, 800℃,850℃ were studied by using acoustic emission technique. The effect of composite oxide 'pegs' composed mainly of Nd_2O_3 on the adherence of oxide scales was analyzed. The 'pegs' can extend the distance between cracks and retard their movement in the oxide. The results indicate that the adherence of the oxide scale is improved due to the addition of Nd. However,the oxide scale still cracks easily. This is because that the 'pegs' suffer high compressive stress during cooling of specimen. If the 'pegs' are large enough, some of them can serve as centers of crack initiation. The mechanism of crack formation caused by the 'pegs' is also discussed.

Simulated occluded solutions were used to study inhibition effect and its mechanism of NO_3~!-on 0Crl8Ni9Ti occluded cell in 0.5M NaCl solution. It was found that the corrosion rate of 0Crl8Ni9Ti in occluded solution decreased and that the open-circuit potentials moved in the positive direction with increase of [NO_3~-]_(bulk). When [NO_3~-]_(bulk)≥0.025M(50℃) or [NO_3~-]_(bulk)≥0.2M(90℃),a state of active-passive transition occurred inside occluded cell. When [NO_3~-]_(bulk)≥0.3M(50℃)or[NO_3~-]_(bulk)0. 5M(90℃),the passivating effect was greatly improved, namely, the passive region becoming larger, the critical anodie current density for passivity and passive dissolution rate decreased. The inhibition efficiency inside O. C. was more than 90％at the above-stated NO_3~- concentration. The addition of sufficient NO_3~- cancause the steel in occluded cell to become passive, so that O. C. C. can be retarded.

An investigation of the effect of preoxidation treatment and preoxidation with surface-applied CeO_2 on the hot corrosion behavior of HK40 alloy was electrochemically carried out in 75％ Na_2SO_4+25％NaCl melt at 800℃. The free corrosion potential (F_(corr)) and polarization resistance (R_p) were measured, and the corrosion current density (I_(corr))was calculated by polarization curve fitting technique. The results show that the surface-applied CeO_2 promotes the formation of the more adherent and protective Cr_2O_3 scale, and therefore markedly decreases the corrosion rates of the alloys and improves their hot corrosion resistance. With the aid of SEM, EPMA and XRD analysis results of the corrosion products, the observed beneficial effect of surface-applied CeO_2 was discussed.

A new method——bubble method is used to study the scale inhibition of four methylenephosphonic acids (MP) with (HO)_2OPCH_2——N[CH_2PO(OH)_2]_2 structure (n=0,1,2,3)——ATMP (Aminotrimethylenephosphonic acid), EDTMP (Ethylenediaminetetramethyleneposphonie acid), DETPMP (Diethylenetriaminepentamethylenephosphonic acid) and TETHMP (Triethylenetetraaminehexamethylenephosphonic acid). Results show that all these metb.ylenephosphonicacids have significant scale inhibition ability and threshold effect. The scale inhibition ability of methylenephosphonie acids increases with the number of functional group—CH_2PO(OH)_2 in their molecules (m). According to their scale inhibition ability,these methylenephosphonic acids may be arranged in the following order: TETHMP>DETPMP>EDTMP>ATMP m=6 m=5 m=4 m=3 The contribution of every—CH_2PO(OH)_2 group in these methylenephosphonic acid molecules to scale inhibition is about the same.

Electrochemical modification of surface films on metals is an effective means for anti-corrosion brought forward recently. The modification of aniline and its derivatives on iron-based alloy was investigated in this work. The anti-corrosion performance of modified films was studied in various solutions under different modification conditions by using some electrochemical techniques, such as polarization resistance method, polarization carve and impedance measurements. The surface morphology, composition and structure of modified films were analysed by modern physical analysis techniques, such as AES, XPS, SEM, etc. The results show that the modified films of aniline and its derivatives on iron-based metal surface have good anti-corrosion performance,and pitting resistance and passivity of modified films on 18-8SS are greatly improved. The protection mechanism of modified films and the effect of both structure of modification substances and substitute group position on corrosion resistance were discussed.

High temperature sulfidation of FeCrNi base alloys containing different contents of Cr,Ni,Al, Y was studied in sulfur vapor under 600℃C with Ps_2=64×10~2Pa,Po_2=0.53×10~(-2)pa. Sulfidation kenetics of studied materials have been examined and compared. The structure and morphological features of sulfide scales have been investigated using metallographical, X-ray diffraction and EMPA techniques. The addition of Cr was shown to be beneficial in reducing corrosion rate. Increase in addition of Ni was shown to be detrimental. The beneficial effect of Al, Y minor additions on the sulfidation restistance was distinguished. Based on analyses of the structure and composition of sulfide scales,the sulfidation mechanisms of the alloys with different additions have been proposed.

Due to the electrochemical nature of atmospheric corrosion of metals, it is reasonable to evaluate the effectiveness of temporary rust preventive oil by electrochemical measurements. In the past, almost all such measurements were performed with the oil coated metal specimen being totally immersed in aqueous solution. Obviously such an experimental arrangement is quite different from the practical condition,under which the rust preventive oil is commonly used. In this paper a new method for evaluation of rust preventive oil is proposed, which allows electrochemical measurements to be done under thin water film. An electrode assembly similar to the morfitor initially designed for atmospheric corrosion study is constructed by alternate stacking of rectangular mild steel plates and placed in humid environment. However, moisture condensation on oily surface has been found to produce beads of water and has lead to unstable data readings. To obtain an uniform,reproducible and appropriately thick water layer on metal surface,a piece of lens paper is used to cover the surface of electrode assembly. By means of the proposed approach polarization resistance, polarization curves and ac impedance can be successively measured for both rust preventive oil and uninhibited oil in water vapor saturated atmosphere at 50℃.

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An investigation of electrochemical behavior of N, N-dipropynoxy methyl alkyl amine compounds was carried out by potentiodynamic and A. C. impedance measurements. It was found that the feature of anodic polarization curves of the compounds reflected desorption transition phenomena of the inhibitors. This type of inhibitors possesses high inhibition efficiency and is more effective in hydrochloric acid than in sulfuric acid. Inhibition action is a mixed type retarding both anodic and cathodic reactions. The inhibition mechanism is discussed.

The relationship between friction coefficient and potential, the polarization curves during sliding and the change of potential with sliding speed of 1045 steel were determined in dilute H_2SO_4 or NaCl solution with various types of additives such as K_2Cr_2O_7, SDBS, IMC-5 (trade name of an inhibitor with salt of quaternary amine as main component)and (CH_2)_6N_4 by means of a pin on disc device. The recovery rate of surface film formed by additive during sliding was measured by a transient corrosive wear device. Experimental results show that the ability of the additives to control corrosive wear is dependent on the antifriction behavior,the corrosive inhibition,the load carrying capacity and the recovery rate of surface film.

The influence of cathodic protection in atmosphere on corrosion fatigue behavior of weathering steel has been investigated. The results show that the cathodic protection can inhibit the initiation of pitting and uniform corrosion on surface,and can prolong service life of the steel more than 10 times.