Acid etching metal is the process of using a specific type of acid to create designs on metals. The chemical process uses a strong acid, also called an etchant, to remove material from the surface of a metal. In an acid etching metal process pattern is created on metal materials without altering the fundamental properties of the metal. What does acid etching do to metal? The acid lowers the pH of the base material in specific areas while the rest of the metal is left alone. The controlled removal of the metal allows patterns to be made on the surface of many types of metal. Acid etching metal has been used for many years in both commercial environments and artistic expressions.
Understanding Acid Etching Metal
In traditional acid etching on metal, we use strong acid or mordant acids to cut into metal parts that are unprotected to create a design. The process is simple. After covering the metal with an acid-resistant substance called resist, the artist would leave areas blank or scratch through the resist to develop images. Acid is then applied to the image or design, and the exposed metal would dissolve away in the acid solution. This means the areas on top of the resist would have no effect from the acid etching metal process, as those areas were protected by the resist coating.
Acid Used In Acid Etching
Different acids are more effective for specific metals and applications. The choice of acid affects the speed of the etching, surface finish, and safety requirements before, during, and after the acid etching metal process.
- Ferric Chloride
Ferric chloride is one of the most common chemical etchants that is used in metal etching. Ferric chloride solution yielded great results on copper, brass, and stainless steel. Its solution is more stable and less likely to release toxic fumes than any of the other acids in acid etching.
- Nitric Acid
Nitric acid is too, commonly used for etching various metals, including stainless steel. Nitric acid is useful for cleaning and producing precise etched patterns. While nitric acid is a much faster option over ferric chloride, it requires careful handling.
- Hydrochloric Acid
Hydrochloric acid is another type of etching chemical. Hydrochloric acid produces strong reactions with most metals and reacts fairly quickly, producing Hydrogen gas. Therefore, proper ventilation is necessary. Hydrochloric acid does an excellent job of removing oxide layers as well as leaving the substrate with a clean, etched surface.
- Sulfuric Acid
Sulfuric acid is slower than nitric acid and hydrochloric acid, and produces smooth surface finishes. Sulfuric acid works especially well with aluminum and zinc applications.
Metals Used In Acid Etching
Different metals respond to an acid etching process differently. Here are commonly used metals:
Stainless Steel
Any of the acids we described: hydrochloric acid, nitric acid, or sulfuric acid, will etch stainless steel nicely. The chromium content in stainless steel creates a protective layer that requires heavier acids. To etch stainless steel evenly, thoroughly prepare the surface, removing the protective layer.
Carbon Steel
The timing of the etching process is very important with carbon steel, and it is imperative to prepare the metal beforehand. The steel, once prepared and acid etched, will provide consistent results throughout the entire surface area. Carbon steel can be used for decorative panels, name plates, components for industrial purposes, etc.
Copper/Brass
Copper is a great metal to use in an acid etching process because copper responds super well to multiple iterations of acid in the process. Simply stating, copper needs to dissolve, and it will usually turn into cupric chloride later in the process. Brass, though a copper alloy, will etch quite similarly to copper as well.
Aluminum
Aluminum requires certain acids and careful control over the process to etch properly. Aluminum has an oxide layer that inhibits acid attack. Proper surface preparation must remove this layer to allow the acid to penetrate evenly.
Acid Etching Process: Step by Step
The acid etching metal process requires careful preparation and precise method execution to get the best result. Each step in the process contributes to the quality and the final look of the etched surface.
- Surface Preparation
The most important step in the whole acid etching process is the preparation. Prep the metal surface until it is completely free of all oils, dirt, fingerprints, and oxidation. If prep is poor, the etching will be uneven and disappointing.
- Applying the Resist Coating
Etch resist materials can include nail polish, stickers, vinyl, electrical tape, and even permanent markers such as Sharpies. Apply the resist coating to the metal surface, making sure to cover the entire surface evenly.
- Setting Up the Pattern
Remove the resist covering from the areas needing to be etched. You can use stencils, masking, and direct drawing to create your arrangements. Be sure to check the pattern carefully before you proceed to the next stage of etching.
- The Chemical Process
Once you have prepared the metal, you either submerge it in the acid solution or apply the acid for the controlled brushing methods. The temperature of the etching solution directly influences the speed of the etch, with hotter acids than cooler acids being imposed.
- Finishing and Disposal
Once this process is complete, you need to remove all coatings of the resist using the necessary solvents. Check the final piece for quality and check to ensure the depth of the whole piece is consistent. You should clean the finished part and be sure it is dry before any handling or future processes.
TMNetch Etching Services
TMNEtch provides competitively priced precision acid etching metal services for copper, stainless steel, and aluminum applications. TMN was established in 2011 and has been offering high-quality etching solutions to customers in a broad range of industries across the country.
- Copper etching with tolerances as tight as ±10% of material thickness
- Stainless steel etching that includes half-etching and full-etching services
- Aluminum etching for lightweight and high-strength applications
- Part sizes that could make up to 1500mm x 600mm.
- Double-depth etching capabilities on one side
The company manages complete acid etching metal projects from design consultation to finished parts and has international shipping capabilities. Visit TMNetch to look through their complete metal etching services and to discuss your specific needs.
FAQs About Acid Etching Metal
Is acid etching permanent?
Yes, acid etching metal will create permanent changes to the surface, meaning the acid itself is physically removing material. It creates markings that will not wear through or fade over time.
How much does acid etching cost?
The costs of acid etching metal depend on the size, complexity, quantity, and type of metal. Simple name plates and signs will be less expensive than the more complex decorative panel. If you are in production mode, the per-part costs drop significantly at volume.
Is laser etching better than acid etching?
There is no single best method of etching metal. Laser etching is quicker and works with more materials, but has higher equipment costs. Acid etch metal processes are less costly for initial setup and are on a cost per square inch basis, more economical for larger areas. Ultimately, the decision will depend on unique application considerations.
Wrapping Up
The acid etching metal process is an effective means of creating permanent patterns, markings, and decorative features on metals. So what does acid etching do to metal? Permanent changes to the metal that also improved its function and appearance. The process itself uses controlled chemical reactions to selectively remove specialized quantities of material, leaving protected areas unchanged.