When two different metals are placed in a fused alkali or alkaline-earth chloride bath, the more readily corrodible metal will deposit on the less corrodible one. Many such systems were studied, including Ti-Cu, Ti-Fe, Cr-Fe, Cr-Mo, Al-Fe, Si-Fe, Si-Mo, etc. The metals listed first would deposit on the immediately following ones. The resulting coatings belong to the category of diffusion coatings and impart to the substrate metal useful surface properties such as resistance to corrosion, high temperature oxidation, or wear, Chemical exchange reactions contribute only to a very small extent to the mechanism of coating, while disproportionation may play some important part at high temperatures. When cathodic current is applied to the corroding metal, corrosion stops while coating is discontinued in the meantime. On the contrary, coating will be accelerated if anodic current is applied to the metal while the sample being coated is connected as cathode of the electrolytic cell. The coating mechanism is, therefore, electrochemical in nature. Metals readily corrodible in fused salt, such as titanium, can be heat treated in fused salt bath under cathodic protection.

The hysteric ring formed on triangle waveform galvanodynamic polarization curve was investigated under the condition that the surface impedance may be represented by a polarization resistance R_p connected parallelly with a boundary capacitance C. Equations for polarization curve, the height of hysteric ring, the difference between the heights of two terminals of the diagonal, and the difference between the heights of the maximum and minimum on hysteric ring were derived and examined. The way to estimate the value of R_p and C from the parameters of hysteric ring was discussed. Using the method proposed, the R_p and C of Fe in distilled water were determined.

The hysteric ring formed on sine waveform galvanodynamic polarization curve was investigated under the condition that the surface impedance may be represented by a polarization resistance R_p connected parallelly with a boundary capacitance C. Equations for polarization curve and the height of hysteric ring were derived and examined. It was found that R_p and C may be determined simultaneously from the height of hysteric ring. Because the height of hysteric ring was measured at i=0, the measurements were unaffected by solution resistance and thus this method may be used for high resistance system R_p and C of Fe in distilled water and in the tap water in Changchun were determined by the method proposed.

Ionizing radiation can affect the characteristics of the electrode processes and disturb their kinetic equilibria. The effect of radiation on pitting corrosion of aluminium in solutions with cupric and chloride ions are studied. It is shown that pitting corrosion is inhibited as a result of radiation exposure while general corrosion is enhanced, and that the harmful effect of radiation expo sure on metal corrosion will be remarkably decreased if the water quality is restricted. The effects of various kinds of radiation on galvanic corrosion due to metal couples are also studied. Polarization curves and corrosion currents versus time are determined for these couples. The experiments show that both heavy and light radiation accelerate the electrochemical processes of galvanic corrosion due to metal couples, A tentative mechanism of radiation corrosion is presented.

A study of the rust layers fomed on low-alloy steels in sea water was made by using Mossbauer spectroscopy, X-ray diffraction, infrared absorption spectroscopy and DTA. The influences of alloying elements on the morphology of rust layers, the effect of enrichment of various alloying elements in the inner rust layer on corrosion resistance, and the crystallography of Jrust layers were discussed.

Nickel-base alloy, especially Hastelloy N, is a highly corrosion-resistant material developed for fused salt reactor . The experimental results as. reiorted in last literature were obtained in highly pure fused fluoride fuels with dechromisation as the main reaction. The present work is conducted in ordinary fused fluorides or nitrates in static state. The structure of surface. corrosion layer, the influence of Mo on dealloying corrosion at crystal boundaries and the process of stress corrosion cracking have been studied. It is shown that there is selective precipitation of Mo in addition to Cr. The effect of Mo is twofold. On the one hand, as the Mo content in the alloy is increased, the relative speeds of dealloying of Mo and Cr along crystal boundaries and within the crystals are changed accordingly, thus intercrystalline corrosion is restrained. On the other hand,the surface layer is essentially a loose, porous layer of pure Ni owing to dealloying of Mo and Cr, and, despite of rather low speed of general corrosion of Hastelloy, the. dealloying corrosion at crystal boundaries will be accelerated under tensile stress, thus the selective dealloying of Mo and Cr along crystal boundaries will in turn promote the initiation and growth of crack and will lead to. intercrystalline stress corrosion cracking.

The scanning electron fractographs of stress corrosion cracking of Al—Zn—Cu—Mg and Al—Cu—Mg in aqueous solution containing chloride were stutied. Stress corrosion cracking was produced by slow strain rate method. It was found that on the stress corrosion cracking surfaces of the two alloys there was a corrosion product layer which showed various different scanning electron fractographs, such as smooth flat feature resembling cleavage fracture, or "mud-crack pattern" and so on. These, howerer,are not the inherent and real morphologic features of stress corrosion cracking which are actually the same for both alloys under all testing conditions and have typical intergranular cracking feature. The morphology of the corrosion product layer depends on pH of the environment and on potential. The inherent and real scanning electron fractographs of stress corrosion cracking of aluminium alloys can be visualized after removal of the corrosion product layers by chemical method.

Through the curve fitting method for the corroding systems controlled by activation polarization, the experimental data of polarization curves in the weak polarization region and golvanostatic charging curves are analysed mathematically. The computer programs are worked out by applying iterative least squares technique with FORTRAN language. By means of the computer analysis of the polarization data determined by electrochemical method, the corrosion rates and other electrochemical parameters can be obtained. Examples of above-mentioned approach are shown and experimental technique is introduced. The reliability of above-mentioned methods, the field of application, as well as the factors which influence measurement are also analysed and discussed.

A report of the tour of the Chinese delegation group to Federal Republic of Germany to attend the 8th International Congress on Metallic Corrosion held in Mainz from September 6 to 10, 1981,