Chemical etching, a process also known as chemical milling or acid etching, is a popular subtractive manufacturing process, used to etch, engrave or cut very intricate or very delicate lines into metal surfaces. Using corrosive bases and acids, industrial metal parts manufacturers with proper knowledge of chemicals and their reactions with specific metals can achieve highly specialized etching with limited mechanical labor. Chemical etching can be used to achieve decorative or artistic finishes, such as engraving in a photo, or it can be used to create finishes for industrial purposes. It can be used to finish all sorts of products, including but not limited to: circuit boards, dies, plaques, printing plates and stencils. The process can be performed on nearly all metals, particularly copper, nickel, brass and steel, as well as most types of glass and silica.
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Benefits of Chemical Etching
Chemical etching is cost-effective, efficient and requires few tools. It is faster, more accurate and less expensive than comparable operations, such as hand etching and mechanical etching. Note that chemical etching performed on metals is most effective when it is performed on thin materials, like foil or sheet. It can, however, be used with thicker methods. To find out what chemicals go best with your material(s) and application(s), get in contact with a trusted etching leader today.
Process of Chemical Etching
Chemical etching is performed in a number of steps, five to be precise. These steps are: cleaning, masking, scribing, etching and demasking. The first step, cleaning, is a preparatory step by which contaminants like oil, residue, primer coatings and grease are removed so that the surface material will not have any issues with accuracy or depth during etching. To clean surfaces, manufacturers usually either apply a solvent to them, or they immerse whole parts in deoxidizing solutions or alkaline cleaners. Next, during masking, manufacturers apply a maskant material to the whole of the surface. This way, when it comes time to etch, any surface area covered in this maskant will not be able to be etched, as they are essentially hidden, or "masked." In order for them to work properly, it is important that they adequately adhere to the surface on which they are placed. After masking comes the third step, scribing. During scribing, those areas that will be etched are rid of the maskant. The fourth step is etching. Manufacturers achieve etching not by laser drilling or stamping patterns on, but by immersing the piece in a chemical bath. While immersed, the metal of the part and the chemicals of the bath react with one another, causing erosion along the exposed pattern lines. The longer the time a piece spends in a chemical bath, the deeper its etching will be. After etching, a chemically machined part is damasked. This is the process by which both the remaining maskant and the etchant in which the part was just bathed are removed. Typically, this is conducted either simply using cold water or cold water with additives. Sometimes, the part is also put in a deoxidizing bath. Rarely, the chemicals are scraped off by hand.
Forms of Maskants
Maskants are available in a variety of different forms and compositions, and they may also be applied in a variety of different ways. Non-conductive liquid chemical maskants, for example, may either be applied via dip masking, during which the part is dipped into an open tank of maskant and then allowed to dry, or flow coating, during which maskant is cascaded over the part. To apply conductive liquid maskants, manufacturers sometimes use electrostatic deposition, which is a process during which the maskant is sprayed onto the surface of the material. To ensure that the maskant sticks, electrical charges are applied to it as it is sprayed. Sometimes, the maskant is not a liquid chemical, but rather paint or tape that is coated on in a single layer or multiple layers. Also, in the case of photo engraving, the maskant used is a photoresist. Likewise, the by which maskants are removed, scribing, can be performed in a number of different ways. For decorative purposes, for example, manufacturers may remove the maskant by hand with a scribing knife or etching needle. If the project is being undertaken for an industrial purpose, on the other hand, manufacturers will remove the maskant using the help of a template or CNC automation. Manufacturers may also engage in a third method called scribe and peel. During scribe and peel, the desired design or pattern is cut into the masking layer, thus revealing areas of the metal part that should be etched. To remove a photoresist, manufacturers must expose the part to a targeted light.