Failure accidents by SCC in chemical plant are mainly caused by the residual tensile stresses which are under plane stress states.
Therefore, it is considered to be important to make clear the effect of biaxiality of surface stresses on the stress corrosion cracking.
A series of SCC tests under combined stress states were carried out in order to establish the stress criteria for stress corrosion cracking in service.
This first paper is concerning with the test results of chloride-SCC of austenitic stainless steel SUS304 under combined tensile and torsional loading where the maximum and the minimum principle stresses are tensile and compressive, respectively.
Test results obtained are summarized as follows;
1) A SCC test apparatus for appling combined tensile and torsional loading was newly developed, which enabled the direct microscopic observation of any cracks on the specimen surface in the corrodent.
2) Threshold stresses for the emergence of slip steps well agree with the equivalent stress by Von-Mises shear strain energy theory.
3) Threshold stresses of SCC under combined tensile and torsional loading could be evaluated by the equivalent stress by total strain energy theory.
4) There exists some deviation of threshold stresses between the elastic failure (shear strain energy theory) and SCC (total strain energy theory) in the region of m(=σ/τ)≤1. Direct observation of cracks revealed that so-called pool-river type SCC initiated by the locallized corrosion of (100) plane was the due cause of this disagreement.
5) It was found that the grain boundary played an important roles in the initiation stage of SCC. Fractographic examination showed that there existed clear intergranular cracking in the initiation area of SCC with the increase of shear stress component (m>1).

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A low temperature cure epoxy paint has been developed for the purpose of protecting offshore steel structures in cold areas from corrosion.
This paint is composed of epoxyacrylate resin, epoxy resin, hardener and so on, and is available as a finish coating material on an inorganic zinc-rich primer.
Properties of paint and coated film, applicability with airless machine and accelerated corrosion test results are discussed in detail herein.
The field test and its durability results are also described herein.
These results showed that this new low temperature cure epoxy paint could be field applied and even when coated at low temperatures, had good corrosion resistance on sea area.

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Titanium is one of the candidate materials for solidification process equipment of high level liquid waste produced in reprocessing of spent nuclear fuel from Light Water Reactors.
The high level liquid waste is a nitric acid solution containing various kinds of oxidizing agents such as Cr₂O₇^2-, Fe³⁺ and Ce⁴⁺ ions and is very corrosive to metallic materials. Therefore, effect of oxidizing agents on corrosion resistance of commercially pure titanium in nitric acid solution was investigated using gravimetric and electrochemical techniques.
As a result, it was clarified that corrosion resistance of titanium was markedly improved by adding oxidizing agents having high redox potentials. The peak height ratio of O 1s/Ti 2P obtained from ESCA spectra for the specimens revealed that the passive film formed in Cr₂O₇^2- free nitric acid solution consisted of Ti₂O₃ but it formed in the solution with Cr₂O₇^2- consisted of TiO₂ which was more stable thermodynamically. This is the reason why Cr₂O₇^2- inhibits titanium to corrode. Cr₂O₇^2- seems to oxidize dissolved Ti³⁺ in the solution to Ti⁴⁺ and TiO₂ would form by following reaction; Ti⁴⁺+2H₂O→TiO₂+4H⁺.
Furthermore, titanium showed an excellent corrosion resistance in the simulated high level liquid waste even at high temperature.
From these results, it is considered that titanium is a suitable material for the solidification process equipment.

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In our previous paper, it was showed that sprayed and fused coatings of some Ni-Cr-Mo alloys can effectively prevent crevice corrosion of austenitic stainless steel in sea water and that addition of B, which is essential to fused coatings, might cause considerable depletion of Mo in the matrix of fused layer. Such matrix containing insufficient amount of Mo is not preferred to crevice corrosion resistance, and this depletion of Mo might be attributed to the very little solubility of B in Ni. So we replaced Ni to Co, which is so similar in corrosion property and is able to make solid solution up to about 1% (at eutectic temperature) with B, and studied the effect of Cr and Mo on corrosion resistance of Co-base ternary cast alloys for fused coating by cyclic polarization method in 3% NaCl solution.
The following results were obtained.
(1) Based on cyclic polarization measurements of thirty five varieties of Co-Cr-Mo alloys, the satisfactory region of Cr and Mo contents to prevent crevice corrosion in 3% NaCl solution was defined.
(2) From this region, Co-30%Cr-10%Mo and Co-35%Cr-20%Mo alloys were selected and to each alloy 2%B and 2%Si were added in order to obtain good preformance of the fused coating layer easily. Fused coating layers with powder of both alloys containing B and Si revealed good cyclic polarization behavior.
(3) However fused layer might substantially contain a certain extent of Fe with dilution from base metal, in the case of Co-30%Cr-10%Mo alloy, up to 30%Fe the dilution of fused layer could not have detrimental effect on its resistance to crevice corrosion.

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The latest surface analytical data are reviewed on the relationships between the surface structure of galvanized steel sheets and their qualities such as performances to chemical treatment, paint adhesion, corrosion resistance and weldability.
It has been found that the surface structure varies depending on the production conditions and the subsequent working treatment conditions even if the galvanized steel sheets are produced with the same galvanizing bath and, as a result, the performance which is sensitive to the surface structure changes remarkably. Furthermore, the desirable surface structure to obtain the high quality of the products has been and will be disclosed gradually and quantitatively.
In the future, the relationship will be made clearer between the production conditions and practical performance.

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