Eli Campbell Jr., age 13, of Patterson, N.J., for his question:
HOW DOES ELECTROPLATING WORK?
Electroplating is the process of putting a metallic coating on a metal or other conducting surface by using an electric current.
The article you want plated must first be thoroughly cleaned of grease and dirt by dipping it in acid and alkaline cleaning solutions. It is then put in a solution of the metal with which it is to be coated, and connected to the negative end of a source of electricity.
The positive electric terminal is then connected to another conductor which is also dipped into the solution. The electric current separates the metal in the solution and the coating is deposited on the article’s metal surface.
If the metal in the solution and the metal of the positive terminal are the same, the electricity may remove metal from the terminal to replace metal taken from the solution.
The thickness of the layer deposited on the article depends on the strength of the electric current and on the duration of the bath. The terms triple plated and quadruple plated indicate various thickness of plating, not separate layers deposited on the surface.
Electroplating is used to improve the appearance of materials, for protection against corrosion and to make plates for printing and cther reproduction work.
Ornamental and protective platings are very thin, usually between one and two one thousands of an inch thick.
For plating gold, silver, copper, zinc and cadmium, cyanide solutions of the same metals are often used. Copper and zinc may also be plated by acid sulfate solutions.
Chromium is plated with a chromic acid solution and nickel is plated with nickel sulfate. Other metals plated for commercial use include platinum, lead and tin. Alloys of two or more metals may be deposited by using a solution of salts of the metals that make up the alloy. Alloys used for plating include brass, black nickel, lead tin and bronze.
Electroplating is also used to reproduce medals or other objects. This is called electroforming. The old name for this process was galvanoplasty.
One kind of electroforming is the reproduction of type forms and engravings for the printing industry. This is called electrotyping.
In electrotyping, a mold or cast is made in some soft material, such as wax or guttapercha. The wax is made conductive to electricity by applying a film of graphite or metallic powder.
The mold is then set in the electroplating solution and put through the same process as in other forms of electroplating.
Electrolysis is the process in which an electric current is passed through a liquid, ‘causing a chemical reaction to take place. If the liquid is water, electrolysis “breaks up” the water into two gases: hydrogen and oxygen. If the liquid is a solution that contains a metal, electrolysis breaks up the solution so that the metal is removed.