The protective value of the flame sprayed plastic coating is studied. Tests were made during one month at room temperature. For epoxy resin, high temperature test was also made at 70-80°C. The coatings of polyethylen, polyvinyl-buttylal and epoxy resin were found to be anti-corrosive for strong acids, alkalies and a few organic chemicals.
An excellent curing agent for epoxy resin spraying was found and the mixing ratio was also determined.

View full abstract

This report deals with the investigation of properties of the steels treated by various ways of case-hardening.
The steels tested are low-carbon steel, boron-treated low-carbon steel, chromium steel, and boron-treated chromium steel.
The results are as follows:
By any treating way, the hardness increases in the lower-carbon part of the case, but is almost unchanged in the higher-carbon part.
Moreover, by carbonitriding, the hardenability of the case obtained by diffusions of carbon and nitrogen generally has the similar tendency to that of the hardenability of the boron-treated steel affected by carbon and nitrogen in the steel making.
The mechanism of carbonitriding reaction, however, is considered to be different from that of reactions at high temperature as in the steel making.

View full abstract

From our experimental study of the behavior of electrodes in cadmium plating, it has been found that the current density must be controled from 1.5A to 2A for relatively wide range of concentration of plating solution.
The defect usually found on the surface of cadmium layer kept in wet air for several days after plating, is that many little black stains by electro-chemical corrosion appear in the neighbourhood of local cell which consists of pits on the surface.
The peeling of the cadmium deposited layer from the base metal is one of the main troubles in the plating process.
This study leads to the conclusion that the poor adhesion of plated cadmium layer to the metal is occurred by the hydrogen gas diffused from the plating solution into the boundary of both metals through the cadmium layer.

View full abstract