Abstract
The quality of lead film coated on steel seems to very depending upon the treatment applied in hot dipping. Various experiments in this respect were carried out and the following result was obtained.
(1) Lead coating can be obtained by hot dipping process also on pure iron or cast iron as well as on steel.
(2) The thickness of lead coating depends on the surface roughness of specimens. The smoother the specimen is, the less is the thickness of coating, e. g., the amount of lead coating on the specimens polished with sandpaper or buff is 0.0091-0.0121mm thick, and 1.10-1.34gr/dm2.
(3) Hydrochloric acid works more effectively for lead coating than nitric or sulphuric acid, and when zinc or tin is added, the amount of lead coating is much increased.
(4) Tin chloride or ammonium chloride powder sprayed onto the specimen after hydrochloric acid etching works better for coating than it is used in molten or aqueous solution.
(5) It becomes clear that ammonium chloride contributes as flux only to “primary coating” and tin chloride to both primary and especially secondary coating (cf. 4th report).
(6) When lead powder is mixed to ammonium chloride by up to 30% or to tin chloride by up to 150%, it not only makes the coated film thicker, but also gives bright and smooth film on the specimen.
