The solubilities of α-Fe_2O_3, Fe_3O_4 and Cr_2O_3 in fused Na_2SO_4 have been measured as a function of Na_2SO_4 melt basicity at 1200K and at 1 arm and lower oxygen pressures. Results are in agreement with the thermodynamic expectations. From the solubility measurements, the basic and acidic solutes of the oxides in molten Na_2SO_4 have been derived and their activity coefficients have also been determined. The solubility studies may be of assistance in understanding fluxing and electrochemical mechanisms of hot corrosion.

The growth kinetics of the intermetallic layer formed in 55％ Al-Zn hot-dipping bath has been analysed. A model of the growth kinetics and its calculation method have been presented. Based on the experimental results of A3 steel in the bathes containing various amounts of silicon, the growth relations of the intermetallie layer and the activation energies of diffusion have been found out by curve-fitting method with a computer. Furthermore, the mechanism of the effect of silicon in the bath has also been discussed preliminarily.

Hydrogen induced cracking in Fe-3％ Si single crystals under mode Ⅱ loading was investigated. The results showed that hydrogen could promote cleavage fracture occurring on a(001)plane, no matter what the orientation, of tensile loading axis was, and if it was along a[001] or [T10] direction the normalized threshold stress intensity K_(ⅡH)/K_(ⅡX) had a minimum value while the maximum value was obtained when the tensile loading axis was nearly along [T11]。Some hydrogen induced secondary cracks were found in which there were evident relative displacements normal or/and parallel to the cracking direction on both sides of the secondary crack。This is due to the unequal number of screw and/or edge dislocations slipping out or in both sides of the secondary crack, i. e. severe local plastic deformaton occurs during hydrogen induced cleavage cracking.The reason for hydrogen promoting cleavage cracking was discussde。

A detailed analysis of the course in which bare metal surface is generated is presented. The decay law of true current flowing through fresh metal surface, i(t), is independent of the methods of scratching the oxide film on the metal surface, and of parameters selected in experiment. The true current decay i(t) can be calculated from the measured transient current, Ⅰ(t), by the following relationship.I(t)=integral from t_0 to (t+t_0)(aui(t)dtwhen freshly generated stainless steel surface is passivating in the chloride solution, the true current decay law follows the following equationi(t)=C_1exp (-a_1t)+C_2 exp(-a_2t)The first term in this equation is associated mainly with the growth of MeOH adsorbed film, while the second term is related to the growth of oxide film. At potentials above a critical potential that is well below the pitting potential measured from the surface covered with oxide film, corrosion pit would occur on the freshly generated surface. The film growth on the stainless steel in MgCl_2 solution follows the high field ion conduction mechanism.

The reaction current density on the surface of scratched stainless steel in chloride solution was studied as a function of applied potential. There is a linear relationship between log i and potential E with a slope of about hundreds of millivolts. This rule is followed not only by the stainless steel/electrolyte system studied in this work, but also by other alloy/environment systems. The detailed discussion shows that the ohmic resistance, diffusion and the oxide ifilm formed during generation of fresh metal surface, can not account for the apparent slow current density increase with applied potential. It has been shown, however, that such large slope arises mainly from adsorption of anions on the bare metal surface.

In this paper the fractography and corrosion product analysis of fractured pressure vessels for growth of cultured quartz crystals were analysed, and the behaviour of stress corrosion cracking(SCC), corrosion fatigue(CF) of CrNiMo low alloy steels in NaOH solution were investigated systematically. The results reveal that the fracture of pressure vessels for growth of cultured quartz crystals is caused by CF. For the CrNiMo low alloy steel-NaOH solution system, a platen was observed in the da/dn versus ΔK curves, but the mechanism does not to SCC, the da/dN in the second stage of CF is reduced by SCC in CF process.

The composition and structure of chromate couversion coatings on aluminum and its alloy were investigated by means of ion beam analysis(RBS, ERD), XPS, AES, IR, X-ray diffraction and DTA.The coatings studied in this paper were obtained from the following solutions: 1~#-CrO_3 4.5g/l, NaF 1.1 g/l, K_3Fe(CN)_6 0.6g/l, pH=1.8; 2~#-CrO_3 3.7g/l, NaF 1.2g/l, Na_2Cr_2O_7 3.2g/l, pH=1.9。The test specimens were sheets (L_2-Y and Ly_(12)-C_2).It was found by RBS and ERD that the main components Of the chromate conversion coatings Cr, O'and H were uniformly distrbuted. Depending on the conditions of treatment, the range of the atomic ratio of these elements (Cr: O: H) in the coatings was as follows:N_t~((Cr)):N_t~((O)):N_t~((H))=1:(2.0～2.3):(1.0～1.6).The main part of these coatings possibly consisted of CrOOH·nH_2O.The relative amounts of Cr(Ⅲ), Cr(Ⅵ), F, Fe, and N were determined with x-ray photoelectron spectrometer model ESCALAB (5) and Auger leectron spectroscope model PHI 550.The depth profile indicates that the Cr(Ⅵ) in the coatings can be found only in the outer layer of the surface (200(?)) and sometimes(e.g, if the thickness is thin) Cr (Ⅵ) even not be detected. The total thickness of these coatings is 3000(?) (obtained in sol. 1~#). The ratio of Cr:O in main part of the coatings is about 1:2 and is constant throughout the coating.In the case of sol. 1~#, F, Fe, C and N are found and the reltive amount of these elements is rather constant throughout the coatings. The reduction of Cr(Ⅵ) by x-ray beam does not show up in our experiments.

In this paper the experimental results of electrochemical monitoring of atmospheric corrosion is reported. It is shown that the electrochemical monitoring cell modified by the present method has the advantages for more accurately controlling the working surface area, superior stability of work conditions and longer service life. Two types of cells Fe-Zn and Fe-Cu, which had been widely used, were compared. The Fe-Zn cell showed better reproducibility and sensitivity than Fe-Cu cell in a great mensure. It is considered to be an ideal electrochemical monitoring element. The effects of outdoor environmental factors and indoor experimental conditions inside the laboratory on corrosive processes were also investigated. It is found that the relative humidity is the most important factor to influence corrosion rate and the relationship between relative humidity and corrosion rate may be assumed as an exponential function.

Hot corrosion of GH33 Ni-base superalloy was investigated by conducting creep tests in an environmental chamber circulated with SO_2-air mixed gas. Analyses were carried out on the outer surfaces, longitudinal sections and fracture surfaces of the tested specimens, including specimens tested to rupture or interrupted at various extents of creep strain. The results were compared with those tested in air.It was found that both in air and in SO_2/air environment a Cr-riched oxide scale was formed initially, which protected the grain boundaries and matrix from being attacked by SO_2. Therefore, as long as the protective scale was not ruptured by the creep deformation, SO_2/air and air played the same role in corrosion, i. e. oxidation is the principal process. But after the deformation increased to a certain extent, intergranular cracks initiated on the specimen surface and sulfur attack occurred. Molten Ni-Ni_3S_2 eutectics formed at grain boundaries which led to catastrophic corrosion and premature failure of the specimen.The mechanism of such corrosion process is discussed. It is suggested that the interaction of hot corrosion and creep of superalloy greatly accelerated the failure process and attention should be paid to this problem during engineering design or material application.

By means of slow strain rate tensile test the stress corrosion cracking behavior related to strain rate and corrosion morphology change of low carbon steel at different temperature and in NANO_3 solution of different concentrations have been investigated. With the help of other experimental method it has been shown that at a higher temperature the material still suffered from stress corrosion cracking related to strain rate under the natural corrosion potential.