To find out the difference between the adhesive property of electro-plating and of organic coating to metal surface, the acetyl cellulose films as organic are coated on the anodized aluminum plates under various anodizing conditions, and each adhesive strength is measured. The results of the measurment are as follows. 1) The adhesive strength of the coating on aluminum plate anodized in phosphoric acid bath at room temperature is several times greater than the others. However, the strength falls with anodizing temperature rise. 2) The coatings on the aluminium plates anodized in sulphuric or oxalic acid bath and etched by sodium hydroxide have almost the same or slightly less adhesive strength as the above. 3) Such tendency of the adhesive property of organic coating is the same as that in the case of electro-plating of anodized aluminum.
Quenching curves of the test pieces of silver, carbon steel and stainless steel in the 150# spindle oil were investigated, and the effects of quenching were compared. The results are as follows. The silver method is most accurate, and most suitable of all oils in the comparison of quenching properties. The carbon steel method is practical, but less accurate. By the above two methods the quenching properties only of the surface of the specimen can be measured. However, it is characteristic that by stainless steel method the quenching propeties of the whole body can be measured.
The quenching curves of the test pieces of silver, carbon steel and stainless steel in all kinds of lubricating oils, paraffine and naphthene series ranging from light oil to superheated cylinder oil were investigated. The results are as follows: The quenching curves consist of vapour film stage (I), nucleus boiling film part (II) and convectio stage (III). The quenching properties become characteristic at the point of vapour film collapse temperature (T1) on the boundary between (I) and (II), time (τ1), and convection begining temperature (T2). The best result is obtained when the time of (I) is short, the width of (II) large and (III) low. The range of quenching chracteristics of mineral oils is from 350° to 750°C of T1, τ1 from 8 to 0.5 seconds, and T2 from 200° to 500°C. T1 and T2 of heavy oils are higher than those of light oils, consequently, the former is better in the begining, and the latter at the lower temperature than the initial boiling point. With the same viscosity and temperature, paraffinic oils are better in the begining, and naphthenic oils later. With the same viscosity and different temperature, oils of the bigger molecular weight are better. The quenching curve take the same tendency even though the initial temperature of test pieces is changed.
We made experiments on the durability of various sprayed metal coatings and on the effect of several sealing materials in order to make up for the poor durability of coatings due to their porosity. Sprayed metals and sealing materials used for this experiment were as follows: (1) Sprayed metals: Zinc, aluminum, copper, brass, tin, lead, and 18-8 stainless steel. (2) Sealing materials: Phenol resin paint, and epoxy resin paint (heat curing type) Polyvinylchloride paint, and chlorinated rubber paint (air drying type) As a result of the experiments zinc and aluminum were suitable for preventing steel from corrosion, while other metals had no rust-preventive effect because of their porosity of coatings. Though zinc and aluminum were excellent in that effect, sufficient effect could not be expected from them without suitable sealing materials because of the high dissolubility of coatings. Heat curing paints were the best sealing materials. If only complete coating was obtained, even air drying paints would form ideal rust-preventive layers with their sealing effect and the characteristics of sprayed coatings. The coatings treated by silicate treatment, when compared with non-treated coatings, showed considerable sealing effect. The practical application of this treatment, however, will be limited, since the treated coating are essentially inferior to paint films.
In measuring the adhesiveness of sprayed metal coatings to steel we improved the ASTM jig used for measuring the adhesiveness of rubber sheets to metals. We could obtain so far the reasonable data by means of measuring tensile strength of sprayed coatings adhered to the jig with Araldite. On zinc coatings, for instance, the sprayed coating by powder spraying method showed far superior adhesiveness to the ones sprayed by arc and flame spraying methods. It was found that steel grit blasting was the best pre-treatment method, and sand blasting and emery blasting werg inferior to the former. But if the grit blasting was incomplete, the coating showed rather lower adhesiveness. Aluminum, brass, copper, etc. showed comparatively good adhesiveness, from the viewpoint of which they were superior to soft metals such as lead and tin. Molybdenum coatings, when used for an undercoat of ferrous sprayed coatings, took an excellent effect as a bonding coat. Being able to increase the adhesiveness of ferrous coatings at least 1.5 to 2.0 time as much, this treatment is the most suitable for pre-treating a repair part required firm adhesiveness.