The solubiliities of the potential thermal barrier oxide components CeO_2, HfO_2 HfO_2 and Y_2O_3 were measured as a function of solvent basicity for fused Na_2SO_4-30m/0 NaVO_3 at 900℃ and Ⅰ atm O_2, The solubility of Y_2O_3 was higher than those for CeO_2 or HfO_2. For comparison, the solubility of CeO_2 was measured in pure Na_2SO_4. In the mixed sulfate-metavanadate melts, the oxides formed orthovanadate acidic solutes with a solubility much higher than the corresponding acidic sulfates for the pure Na_2SO_4 melt. The results point to a revised mechanism for hot corrosion of alloys by acidic fluxing.

Some technical problems concerning the analysis of qarrier anodic films on aluminium by AES were discussed. By ion implantation of Xe marker, composition profiling along with direct observation of ultramicrotomed film sections, it has been proved that the barrier film is usually composed of two layers. The outer layer is formed by outwardly migrating aluminium ions at the film/solution interface. The inner layer, on the other hand, is formed by inwardly migrating oxygen-containing ions at the film/substrate interface. Ions characterizing the electrolyte may be incorporated into the film and migrate under the high electric field within the film. The average migration rate under the experimental conditions was measured.

In the present paper, a study of degradation of aluminide coatings on Ni, Ni-20％Cr and K3 superalloy(Cr10～12％, Co4.5～6.0％, Al5.3～5.9％, Mo3.8～4.5％, W 4.8～5.5％, Ti 2.3～2.9％, Ni Bal.) has been conducted by two test methods at 900℃, one is the burner rig test with 20ppm NaCl injected,and the other is the modified crucible test with evaporation of a mixture of 25％ NaCl+75％Na_2SO_4. Oxidation test at the same temperature was carried out for comparison. The tested samples were analyzed by SEM, X-ray diffraction,and EPMA. It was found that alumina whiskers appeared on the surface of the samples in the burner rig test. The zones having the alumina whiskers became the initiation of pits. The number and size of pits increased with time. When the pits reached the interface between coating andsubstrate,the coating cracked and became unprotective. In the modified crucible test,β-NiAl phase disappeared earlier than in the burner rig test due to stripping of oxide scale and depletion of Al. Then pits appeared and the coatings cracked. The results indicated that Cr greatly increased the resistance of coating to hot corrosion. However, the extent of the improvement is different in both tests. The effect is more pronounced in the burner rig test than in the modified crucible test. This is probably because the higher NaCl concentration in the modified crucible test offsets the beneficial effect of Cr.

The electrochemical behaviour of chromized layer on 45 and T_(10) steels was investigated with cyclic potentiodynamic anode polarization and other methods in 3％ NaCl solution. Similar investigations were carried out on some stainless steels for the purpose of comparison. A precedence phenomenon was observed in all chromized layer.s polarization curves in contrast to the hysteresis loops observed in the case of stainless steels. This indicated that there existed a specific state of passivation ensuring the very high resistance of the chromized layer to pitting and crevice corrosion in all concentrations and pH range of sodium chloride solution. Layer-by-layer electrochemical studies showed that the corrosion resistance was excellent on the chromium-rich outmost layer and decreased gradually on inner layers due to the lower chromium concentrations. Besides, galvanic cell could be formed between the outermost layer and inner layers as well as between chromized layer and substrate to induce the final deterioration of substrate steels when exposed.

In the present work, the effect of prior austenite graiain size upon the stress corrosion cracking(SCC) and corrosion fatigue (CF)of 40CrNiMoA steel in distllied water was studied. The impurity segregations at grain boundaries of various prior austenite grain sizes resulted from different heat treatments were analysed by using Auger electron spectroscopy. The initial crack areas of fracture surfaces after either SCC or CF tests were observed under SEM. It was concluded that the behavior of both SCC and CF of 40CrNiMoA high strength steel in distilled water, in terms of its crack initiation as well as crack propagation, was mainly associated with the grain size, and the cracking modes were dependent upon the interactive relation between the grain size and the plastic zone ahead of the crack tips under tri-axial tensile stressing condition, thus determining the susceptibility to cracking.

The induction time for pitting corrosion of the 18-8 stainless steel in neutral chloride solution is determined by potentiostatio technique. By experimental data analysis, the random change of the reciprocal induction time as well as the induction time is in conformity to logarithmic normal distribution. The effect of the chloride ion concentration on distribution parameter is discussed.

Sulfate-induced accelerated corrosion of nickel has been studied at 750℃ both with the method of Na_2SO_4-eoating test in O_2-0.45％(SO_2+SO_3) (1atm), and with the crucible-test in air in which the specimens are tatally inmersed in the molten NiSO_4-Na_2SO_4 salts mixture. Nickel is rapidly corroded under both circumstances, and an intermixed(NiO+Ni_3S_2)layer is formed as the major corrosion product. The islands of Ni_3S_2 in the intermixed layer are found to be inter-connected with each other. The NiSO_4-Na_2SO_4 melt may act as an oxidant by liberating corrosive gas (SO_3) and cause rapid corrosion of nickel.

B~+ implantations to pure iron, pure nickel and S. S. 316L and ion-mixing with Fe-Ti system are conducted at low temperature in a liquid nitrogen cooled chamber. Electron diffraction and polarization curves are made from the implanted and mixed surfaces. Results show that the electrochemical behavior of the ion-implanted and ion-mlxed surfaces prevails substantially over that of their matrixes. Multi-polarization curves of the same specimen are used to study the corrosion behavior of the ion-implanted and ion-mixed surfaces, it is found that corrosion resistance correlates well with concentration-depth profile of ions.

The corrosion-inhibiting abilities of a series of ringsubstituted benzonitriles were investigated. As in the case of benzene-acetonitriles, chemisorption is probably the mechanism of the corrosion-inhibiting effects.Introducing electtondonating groups in the para-position increases the corrosion-inhibiting ability, while introducing of electron-withdrown groups in the para-position decreases the corrosion inhibiting ability, when a substituent is positioned in o, m or P positions,both elec tronic and steric effects of the substituent affect the corrosioninhibiting ability. Besides, synergistic effect was observed when P-chlorobenzonitrile was used together with anionic or cationic dispersion agents.

The corrosive wear behaviour of pure Ni, Ti-6Al-4V, Al alloy, medium carbon-steel and 304 stainless steel was examined by means of pin-plate wear device and potentiostat in 1 N H_2SO_4 and 1％ NaCl solution. The effect of load and slide speed on polarized curves and scratch traces were measured. It was found that the formation of a passive film on the alloy surface such as stainless steel could retard or promote the corrosive wear, while wear rate was enhanced on fresh surface of carbon steel in corrosive medium.