. Journal . more marked if water is allowedtc act for a longer period than was done in these experi-ments. The variations in the results are probably dueto the amount of zino iron alloy formed, dependent onthe temperature employed. Sample No. 5. vapourisedcopper, although the zinc coating was the heaviest, yetthe corrosion was in this case the least, due no doubt tothe amount of brass coating formed beneath the compara-tively thin zinc coating. On testing this sample, asin the other cases, with copper sulphate solution, insteadof a brown precipitate of copper, a bright metallic depositwas obta
. Journal . more marked if water is allowedtc act for a longer period than was done in these experi-ments. The variations in the results are probably dueto the amount of zino iron alloy formed, dependent onthe temperature employed. Sample No. 5. vapourisedcopper, although the zinc coating was the heaviest, yetthe corrosion was in this case the least, due no doubt tothe amount of brass coating formed beneath the compara-tively thin zinc coating. On testing this sample, asin the other cases, with copper sulphate solution, insteadof a brown precipitate of copper, a bright metallic depositwas obtained and no further action seemed to the results of these experiments and other tests,it may be concluded that vapourising offers equal andprobably greater resistance to ordinary corrosive influencethan hot-galvanised iron coated with an equal weightof zinc, and the resistance is considerably increasedby repeated moistening and drying, so as to form an oxidewhich renders the surface less Fio. 5.—Apparatus for vapour-galvanUlng with metallic zinc The second process referred to at the Ix-ginning of thepaper, namely, tho molten zinc vapour process, doesnot nc-cssitnte the use of zinc dust, nor are thematerials to be coated brought into contact with themolten metal or anv of its compounds; they an-placed in a separate chamlx-r filled with zinc vanonror placed above the molten zinc. A convenient formof apparatus is 8ho«-n in Fig. 5. It consists of «ninner drum, C, composed of wire netting or g*! which the articles to be galvanised arc placed. Ihi^cage or hollow drum is slowly rotated inside »«>»?cylinder, H, composed of wrought iron, in which themetallic zinc is heated by means of gas or an electncfurnace or any other suitable means, to a temi>eralurr Vol. XXVIII, No. 8.] COLES—VAPOUR- GALVANISING. 401 sufficiently high to volatilise the zinc. Hydrogen or othersuitable gas is forced into the apparatus througli the tube,A, and a pilot of hydrogen i
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectchemist, bookyear1882
