3650. To Zinc or Galvanize Grey-Iron Castings

3650.      To Zinc or Galvanize Grey-Iron Castings. Cleanse the articles in an ordinary chafing mill, which consists of a barrel revolving on its axis containing sand; when the sand is all removed, take them out and heat one by one, plunging, while hot, in a liquid composed as follows: 10 pounds hydrochloric acid, and sufficient sheet zinc to make a saturated solution. (See No. 3473 (To Make Soldering Fluid for Soft Solder).) In making this solution, when the evolution of gas has ceased, add muriate, or preferably sulphate of ammonia, 1 pound, and let it stand until dissolved. The castings should be so hot that when dipped into this solution, and instantly removed, they will immediately dry, leaving the surface crystallized like frost-work on a window pane. Next plunge them while hot, hut perfectly dry, into a bath of melted zinc, previously skimming the oxide on the surface away, and throwing thereon a small amount of powdered sal-ammoniac. If the articles are very small, inclose them in a wrought-iron basket on a pole, and lower them into the metal. "When this is done, shake off the superfluous metal, and cast them into a vessel of water to prevent them from adhering when the zinc solidifies.

3651. To Zinc Copper or Brass Vessels

3651.    To Zinc Copper or Brass Vessels. Boil the vessel in a solution of chloride of zinc, adding a quantity of zinc turnings to the solution.

3652. Boettger's Process for Coating Copper and Brass with Zinc by a Wet Process

3652.    Boettger's Process for Coating Copper and Brass with Zinc by a Wet Process. Place zinc in grains or powder in a non-metallic vessel, and cover the zinc with a concentrated solution of sal-ammoniac; warm to ebullition, and introduce into the mixture the objects of copper or of brass which it is desired to coat, after having properly cleansed them. After a few minutes, the object will bo covered with a brilliant firmly adhering deposit of zinc. (See No. 3312 (To Granulate Zinc).)

3653. To Coat Copper with Zinc

3653.     To Coat Copper with Zinc. To granulate the zinc, a clean surface of copper may bo coated with zinc by placing the two metals in contact in a solution of caustic soda or potash. (See Fig. I., No. 3665.) In the cold the deposit of zinc takes place slowly, but at 100° it is effected rapidly.

3654. Purcher's Method of Coating Zinc with Iron

3654.    Purcher's Method of Coating Zinc with Iron. Dissolve 5 ounces pure sulphate of iron, and 3 ounces sal-ammoniac, in 5 pounds of boiling water, and immediately immerse the objects to bo treated. After from 1 or 2 minutes the loose black deposit is removed by brushing it off with water. The principal effect of this operation is a perfect cleaning of the surface. The immersion in the hot iron solution is then repeated, with the difference that the objects, when taken out, are heated, without rinsing, over a pan of live coals as long as the ammoniacal vapors arc evolved. When, after several immersions, the coating is considered thick enough, it is polished by brushing, and will ever afterward be a perfect protection against oxidation. It imparts a fine black lustre to the coated surfaces.