Chemical etching, otherwise known as acid etching or chemical milling, is a chemical process used by many industrial metal parts manufacturers to etch, cut or engrave very delicate or precise lines into metal through the use of corrosive acids and bases. Requiring knowledge of chemicals and their reactions with certain metals, chemical etching is a specialized procedure that includes almost no mechanical work.
Almost all metals can be processed using chemical etching, such as steel, brass, nickel, copper and more, as well as most types of glass with similar effects. The different types of metals require different etchants in order to achieve the desired results in terms of depth of etching. Instead of mechanical etching or hand etching which require specialized tools, there are very low tooling costs for chemical milling, and complete parts can be finished in a matter of hours. There are a number of industrial uses for the process of etching, as well as decorative or artistic purposes for the procedure. Objects manufactured using chemical etching include stencils, plaques, printing plates, circuit boards, dies and more. The metals on which etching is most effective are usually thin, such as metal sheets or foils, although thicker parts such as coins and plaques are commonly etched too.
There are numerous steps to the etching, or milling, process. First, the material or part to be etched is thoroughly cleansed of all oils and chemicals which it may have been exposed to during the forging or fabricating. Next, the masking or protective layer is applied in order to prepare the part for the etching design. The types of masking used can be tape, paint, elastomer or plastic. This masking is coated onto the part or metal sheet, sometimes in a number of layers if for a complicated pattern. Using a scribe and peel method, the desired pattern or design can be cut into the masking layer to reveal areas of the metal part which the acid or reagent will come into contact with. If using a photoresist as the masking layer for photo engraving, the part needs to be exposed to targeted light in order to develop the masking layer in the pattern desired. Once the reagent is applied to the metal part, it reacts with the metal and corrodes the surface along the lines of the pattern or design. Once the desired depth of etch is achieved, the chemical and the masking layer can be removed from the part to reveal the completed etching. Chemical etching is a often a more cost-effective and time-effective manufacturing solution than mechanical or hand milling.
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