COATING METALS WITH OTHER MET ALS BY ELECTRICITY AND OTHER WISE To Tin Copper. — To tin copper, brass, or lead, dissolve pint of table salt and 4 ounces of cream of tartar in 5 gallons of water. Add 1 pound of tin filings. Boil the articles in this solution, stirring briskly, until the coating is satisfactory.
Tinning Copper and Brass. — Boil 3 pounds of cream of tartar in 2 gallons of water. Add 4 pounds of grain tin or tin filings. Boil vigorous ly. Put in the articles to be tinned, and continue the boiling until a suf ficient coating is deposited.
Tinning Copper.—Apply sulphuric acid with a swab to the copper arti cle, and scour with a moistened cloth dipped in dry pumice to get a per fectly smooth surface. Apply solder ing liquid over the surface and sprin kle it with powdered sal ammoniac. Heat the article until it is,hot enough to melt the solder. Then take a bar of solder and rub it over the surface.
Or melt solder inside of the dish or pan, and rub it with a swab over the inside surface. Smooth over the surface while the dish is still hot enough to keep the solder in a partly liquid condition.
Electroplating with Copper. Clean and scour the articles to free them from rust or oxide and all other impurities. Dip them in a solution of nitrate of mercury. This covers them with a thin amalgam that causes the plate to adhere firmly.
Prepare in a suitable tank a strong solution of sulphate of copper in boil ing water. When the water has dis solved all it can, strain the solution through cheese cloth. To each gallon of this solution add 2i ounces of strong sulphuric acid and dram of white arsenic. Suspend in one end of the tank a clean plate of copper connected by wire to the zinc pole of a battery. Suspend the articles to be coppered by means of a copper wire or an iron rod across the top of the tank, taking care that they do not touch each other or the plate of clean copper. Connect the rod or wire on which they are suspended with the op posite pole or battery, and turn on the current. If the battery is a single
cell, put a bag of sulphate of copper in the solution near the surface. This will keep up the strength. The con ditions most favorable to satisfactory coppering are a current of low inten sity, quite a strong solution of sul phate of copper slightly acidulated with sulphuric acid, and a tempera ture of at least 60°.
Or, for a cheaper grade of work, the dip in nitrate of mercury may be omitted.
Copper Solution for Iron.—To cop perplate cast iron, dip the articles in a mixture of 50 parts of hydrochloric acid and 1 part of nitric acid to free them from rust or other impurities. Next dip the articles in a solution of 1 part of nitric acid, and 1 part of chloride of copper dissolved in 8 parts of hydrochloric acid. Remove from the bath and polish with felt, rinse with clear water, and dip again until the desired coating is obtained, This coating may be bronzed by rubbing with a mixture of 2 ounces of sal ammoniac, ounce of oxalic acid, ounce of acetic acid, and 15 ounces of water.
Electrotyping — Coppering Solu tion for Metals. — Brine water, 3 quarts; sulphate of copper, 1 pound. Mix and immerse the articles. Use for this purpose wooden trays lined with asphalt. When a sufficient coat ing has been obtained, remove and wash in hot water and polish with felt.
Zincking. — To cover copper and brass articles with a layer of pure zinc, immerse them in a solution of chloride of zinc, and add a quantity of pure zinc shavings or filings until a considerable sediment is formed at the bottom.
To Regalvanize Zinc Work. — To renew the coating of zinc on galvan ized iron or other articles, immerse the articles in a dilute solution of 1 part of sulphuric acid to 10 parts of water until the old zinc comes off. Scour with sand and hot water until the surface is bright; dip in a solu tion of sal ammoniac and then in molten zinc. The surface of the molt en metal must be covered with a lay er of ground glass to prevent its evaporating in fumes.