特殊亜鉛滲透法について（第1報）純鉄上のZn鍍金

Abstract

It was found that the special zinc-cementation method proposed by the present authors has both merits of the so-called galvanizing and sherardizing. The method is to pack the iron in the powder composed of 3∼10%Zn, 97∼90%Al2O3 or MgO and to heat it to above the melting point of zinc, 500∼600°C, for less than an hour. The authors postulate that the coating is formed by the gaseous penetration as well as by the solid diffusion of zinc into the iron. The effects of zinc content in the powder (from 3% to 90%Zn), heating time (from 1 hr to 5 hr), and heating temperature (from 450°C to 850°C) on the nature of coatings were studied : the greater part of the coating, the outer portion, is a layer consisting of zinc solid solution containing a small amount of iron, and the inner layer is ζ phase based on FeZn13, δ1 phase based on FeZn7, or Γ phase based on FeZn3 as the heating temperature is raised. The thickness of the coating is 0.05 mm to 0.1 mm on heating at the temperature range of 450°C∼600°C for an hour. The cohesion of the coating was studied by dropping a 1.3 kg weight from 10 cm height fifty times repeatedly on the coated articles and measuring the weight change. The corrosion of these articles in the NaCl solution and in the air were also examined, and the result was compared with that of the galvanized or the sherardized articles. The durability of the formers were superior to that of the others.Merits in this special method are as follows :— (1) The treating time becomes shorter than that of sherardizing, since heating temperature is at above the melting point of zinc.(2) This method may be applied for the machine articles finished, without seriously changing their dimentions.(3) The uniformity and evenness of the coating were obtained.(4) There is no fear of the powder coking,in spite of heating at above the melting point of zinc,since little zinc is contained in the powder, and can be used repeatedly by adding a small amount of fresh zinc.