Metal etching is the process of selectively burning images, such as brand names onto metal parts by using chemicals. The process is used to treat various parts such as: advertising premiums, knives, printing presses, printed circuit boards, digital read-out symbols, contacts, contact arms, cathodes, chopper wheels, die cavities, discs, drive bands, electrical connectors, electric shaver heads, electronic chassis, elements, EMI shielding, and encoder discs, etc. The technique is also used to produce an assortment of parts such as: heat sinks, heater elements, I.D. plates, plated jewelry, magnetic recording head laminations, motor laminations, name plates, wiper contacts, rotor switches, microwave components, electron gun grids, electron tube grids, bus bars, cams, carrier plates, flat springs, flexures, fluid logic components, and front panels, etc.
There are various types of metals that can be etched such as molybdenum, nickel and its alloys, steel, phosphorous bronze, titanium, zirconium, zinc, and tin, etc. Strong acids such as ferric chloride, hydrochloric acid, and nitric acid are used in the etching process.
When you want to etch an image into metal, the image should be placed on the metal with a stencil. In printmaking, a material called a waxy ground is placed over the metal and the artist scratches away at the wax to form the image. For a printed circuit board, copper is attached to an insulating material. An acid is then put onto it and the unwanted copper is eaten away by the acid, which leaves only the circuit board.
In general the acid is applied and it eats away at the metal everywhere except the stencil. This process can create a raised surface for the image or lettering. In printmaking, you would then apply an ink to the raised surface and put it on paper. The etched plates have a limited life when they are used in printmaking as the raised metal image starts will eventually wear down.
The thickness of the etched area is determined by how long the metal is placed in the acid as well as the type of metal and acid that are used. Each type of metal may react differently with each type of chemical. You can create new etchings by covering the original etching with an acid resistant material and placing the metal in acid again.
This process involves very toxic chemicals and trained personnel with adequate protective clothing should carry out the etching in well-ventilated rooms. Utmost care and caution should also be taken in disposing of the residual chemicals.