Effects of stress ratio at five levels and loading frequency at four levels on corrosion fatigue crack growth(CFCG) behaviour in 3.5% NaCl solution for GC--4(40CrMnSiMoVA) steel were studied experimentally. Test results about stress ratio effect sLow that there are two plateaus, i.e. PⅠ and PⅡ, in da/dt vs Kmax curve for CFCG as R >0.5 and (da/dt)pⅡ<(da/dt)pⅠ but only one plateau exists as R <0.3. The essential causes for the two Plateau phenomena were tentatively explored, but complete theoretical explanation still needs forther investigation. Test results about frequency effect show that values of stress intensity factor amplitude, △Kp, in onset point of plateau in da/dN vs △K curve for CFCG decrease in a power function manner with the increase of frequency. The corresponding theoretical functional expression of △Kp vs f curve was also derived in this paper, based on comprehensive analysis of three respects of surface electrochemical reaction dynamics, crack tip surface deformation dynamics and hydrogen diffusion dynamics in material interior st crack tip. This expression is well consistent with experimental functional relation shin in test data.

High temperature corrosion behavior of Fe-20Cr-5Al and Fe-20Cr-SAl-0.5Y alloys under thermal cycling condition was studied in pure SO2 atmosphere at 1200 ℃, aug compared to that exhibited under isothermal condition. The corrosion kinatics of the alloys were measured. The morphologies of surfaces, cross sections and fractures of the corrosion product were examined, the elemed distribution in the corrosion scales was analyzed, and the components of the corrosion products were also identified. The results show that the yttrium-free alloy was subject to oxidation/sulfidation attack at a linear rate. In contrast,the yttrium-containing alloy underwent pure oxidation at a parabolic rate without sulfidation in the duration of 500 hrs. The yttrium doping, as a donor, in α-Al2O3 is believed to effectively block the bulk diffusion of Al3+ in the oxide scale due to a decrease in the Ali concentration. As a result, the oxide scale growth would rely entirely upon the oxygen diffusion down through the oxide grain boundaries, thus leading to the development of a fine, edhesive columnar Al2O3 layer with superior cracking and spallation resistance, even under thermal cycling condition. Consequently, the cyclic oxidation resistance of the alloy is remarkably improved.

Based on thje theory of EIS analysis developed by Cao Chunan, a general-purpose equivalent circuit and a corresponding common equation were proposed for an irreversible electrode under electrochemical step control. By this circuit, EIS parameters can be easily calculated without considering different electrochemical processes.

Cathodic process of iron in three typical solutions and anodic process of iron in two typical solutions were studied in the presence of magnetic field of 0.5T (tesla) at 23 ℃ Polarization curves for hydrogen evolution and iron dissolution during magnetization were measured. The experimental results indicate that both hydrogen evolution and iron dissolution were more or less accelerated by additional magnetic overpotential-- △φmag and the phenomenon is more evident in acidic solution. This could be attributed to the reduction of diamagnetic ion hydrate on the iron/solution interface and the adsorption of Fe2+ on the iron surface, which are responsible for the change of electric double layer structure and the increase of activity in the corrosion system.

Epoxy E-51 was improved with 4-Butoxy Carbonyl Amino Tolueme 2-Isocyanate(BCATI, homemade)and Epoxy acrylate or partial epoxy acrylate was improved with 4-Acryloxy Ethoxy Carbonyl Amino Toluene 2-Isocyanate(AECATI, also home-made). These improved epoxy resins were designated by improved resinⅠ, Ⅱ and Ⅲ respectively. They were used as basic materials to prepare the varnish Ⅰ,Ⅱ and Ⅲ. The present study focuses on the dependence of the resistance to aqueous medium (3%NaCI solution, 10%NaOH solution, distilled water) on the structure of the varnish films. The main results are as follows.(1) In accordance with the PRC national standards for paints, corrosion resistance of the varnish I is only fair while that of the varnish 11 and ill are excellent. (2) The polarization resistance RP measured in 2%NaCI by coulostatic perturbation method are 105Ω-cm2 for varnish Ⅰ and 107Ω-cm2 for varnish Ⅱand Ⅲ. (3) The normalized hole densities of the varnish films as, evaluated by TEM are 8-60 for Ⅰ, 1 for Ⅱ and 1.2-2.1 for Ⅲ. (4) The contents of -OH wt% in the varnish films are 8.97, 4.02 and 3.o6 for Ⅰ, Ⅱ and Ⅲ respectively. (5) In general, the higher the normalized hole density and -oH wt% of the varnish films, the poorer their corrosion resistance.

By considering the correlation of the data and using the clustering technique of pattern recognition,the relationship among various corrosive factors of soil has been analyzed. Both the matrix of correlation coefficients and the pedigree of factor clusters show that some factors are correlated closely to each other;while others are relatively independent. The correlation coefficients are very high between the parameters such as volume density and void volume, conductivity and total salts, wier capacity and air capacity etc.However, NO, redox potential,pipe/soil potential etc. indicate much lower correlation coefficients with other parameters. The results of this paper may have certain significance for the further study on soil corrosivity.

The behavior of hydrogen induced delayed cracking(HIDC) of intermetallic compound Ti-24Al-11Nb was investigated with single-edge notched specimens under cathodic charging. It was found that HIDC could occur for all specimens with three different kinds of heat treatment. The threshold values KIH/Kic were 0.43, 0.59 and 0.85 respectively, for specimens solution if eated (ST) at 1000 ℃ and air coooled (KIc=20MPam1/2), those ST at 1150 ℃ and furnace cooled (FC) (KIc=18.4MPam1/2) and those ST at 1000 ℃ FC (KI.=15.7MPam1/2).The experiments also showed that the HIDC of the alloy was induced by atomic hydrogen and not by hydrides. The fractograph of HIDC was dependent on the KI value. Then KI approached KIH, dimples were observed on the fracture surface; when KI became higher, the fractograph of HIDC was cleavage-like,similar to that of overloaded fracture.

In the present work, the hydrogen permeability and diffusivity of GH718 alloy in several conditions of heat treatment were derermined using a gaseous hydrogen permeation technique. Measurements were made over the temperature range of 210 to 430 ℃. It was shown that the dependence of hydrogen permeability and diffusivity. on temperature of GH718 alloy followed Arrhenius relationship over the experimental temperature range and that the characteristics of hydrogen permeation and diffusion were not sensitive to the forostructure variations of this alloy, namely, the pprecipitation- strengthening phases γ'and γ＂in the alley did not have a pronounced effect on the hydrogen permeation and diffusion behaviour.

The corrosion process of zinc in Guiyang and Huitong areas and under the condition of high concentration of SO2 can be described by a formula: △W = Ktn, where △W stands for weight loss, t represents duration of expose, while n and K are constats. The greater the pollution of SO2 and the relative humidity, the more serious the corrosion of zinc. The X-ray diffraction data show that, the corrosion product is mainly composed of sulfates of zinc. The corrosion productproduct formed in SO2-containing environment hinder anodic process of zinc corrosion.

A statistical study on laboratory data of pitting corrosion of 1Cr17 stainless steel in FeCl3 solutions has been carried out by comparing Logistic, Probit and Extroma models. The fitting values for the three models show that the Logistic model is better than the Probit and Extrema models which are being widely used. The Logistic model can be expressed as:The statistical analysis shows that the above formulation fits quite well with the experimental data. In addition, the paper presents an example of predicting perforated pit numbers on a tube coil of a heat exchanger by the Extrema model analysis.

Electrochemical techniques along with scanning electron microscopy(SEM) andX-ray diffraction analysis(XRD) were employed for investigating the effect of Thiobacillus thioparus(T.P.) and Thiobacillus ferrooxidallces(T.f.) bacteria on the mechanism of Microbiologically Induced Corrosion of Cr-Ni-Mo-V steel and 316L SS. Experimental results showed that both bacteria could attach on the surface of these steels and induce localized changes of the costituents, pH and oxygen levels of the electrolyte. These changes can lead to variations in the types and rates of electrochemical reactions of the steels. T.P. could excrete sulfuric acid and form a slime layer. T.f. could oriize Fe2+ into Fe3+ and form tubercles. In the cultiVation of T.P., the pitting resistance of 316L SS was found to be lower, its mas. and Ecorr became hlgher, an active peak was observed and its Passive range was reduced. However, T.f. has no obvious effect on 316L SS.