Investigating inclusively the beginning curves for all kinds of mineral oils, the approximate calculation method of quenching properties was explained without measuring the quenching curves. Addition of the oil soluble substances of high molecular weight and surfactant agents particularly improved the quenching properties.
When the initial temperature of test pieces is T°C, the later temperature t°C, and the time τsec., the formula of quenching curves are as follows:
At (I) t+T-T₁/τ₁τ=T
At (II), (III) (τ-τ₁) tk₁=k₂
or (t-t_e)τn₁=n₂
but k₁, k₂, n₁ and n₂ are constant, and t_e is the temperature when the oil temperature is idential with the metal temperature.

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In the nickel plating bath the electrode potentials of aluminium plates anodized in the phosphoric acid bath, oxalic acid bath and sulphuric acid bath, are measured.
The results are as follows:
i) The electrode potential is enhanced slightly by the anodizing and is always negative disregarding of the electrolyte used in the anodizing.
ii) The highest potential is obtained by using the phosphoric acid bath for anodizing.
iii) The electrode potential of the plate anodized in the phosphoric acid bath is lowered markedly by immersing into the nickel plating bath. This phenomenon is probably originated from the inherent action of the active layer produced by anodizing, which seems to be effective to improve the adhesive property of the electro-deposite.
iv) The potential-current density curve bends near the 20mA/dm², such bend is most marked in that anodized in the sulphuric acid bath.

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Conductmetric method in testing of soft film type rust preventive oil used at a temporary coating to protect metal surface against corrosion and its standardization as a testing method was studied here. For this test, 21cm×3mm×0.05mm copper ribbon specimens coated with test oils were immersed in 1-N or 0.1-N of HCl aqua solution. Good and effective oil film protects the corrosion by HCl, so that the electrical conductance of ribbon specimen was not changed easily, but it was soon changed when bad one coated on the ribbon which cannot protect corrosion by HCl. Electrical conductance was measured by a double bridge and it is necessary to control the technical factors such as temperature of corrosive solution, concentrations of HCl, test period which is adequate to evaluate oil, oil amount, etc. to standardize of this rusting test.

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We investigated the influence of cold drawing, heat treatment, presence of oxidizing agents and cathodic protection on the susceptibility to stress corrosion of austenitic stainless steel wires. As the corrosive solution, boiling 42% MgCl₂ solution (154°C) was used in this test. The specimens were stressed in tention and measured the time to fracture. The results are as follows:
1) Influence of cold drawing; When 70% of the 0.2% proof stress are applied, the life to failure of stainless steel wires (0.5mm) decreases with the increase in degree of cold working up to 20% reduction, then increases with the increase in degree of cold working up to 40% or 95% redustion.
2) Effect of heat treatment; The specimens cooled rapidly after heating at 900°C in cracked NH₃ gas atmosphere or 1000°C in air, were relatively immune from susceptibility to stress corrosion, but the specimens cooled rapidly after heating at 1150°C in cracked NH₃ atmosphere, became remarkably susceptibile to stress corrosion. The times to fracture by stress corrosion of specimens annealed for one hour at 380°C after cold drawing were shorter than those of “as-cold drawn” specimens. The cold drawn specimens annealed at 650°C for 1.5 hours showed chromium carbide precipitation, but these specimens showed an improvement in stress corrosion resistance because of the stress relief by those heat treatment.
3) Effect of oxidizing agent; When a small quantity of KNO₃ as oxidizing agent was added to the corrosive solution, the fracture of these wires by stress corrosion did not occur.
4) Effect of cathodic protection; The cathodically protected specimens did not fail for 24 hours in the corrosive solution, when the current density exceeded 30μA/cm². The unprotected specimens failed within one hour.

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