Common Mistakes in Electrochemical Etching and How to Avoid Them
Comments Off on Common Mistakes in Electrochemical Etching and How to Avoid ThemElectrochemical metal etching is used to add letters, numbers, patterns, or other designs on objects without damaging or altering the metal or its structural integrity. Also known as electro-etching or electrolytic etching, electrochemical etching is a process for marking metal using an electrolyte-soaked electrode pressed against a stencil on a metal part. An electric current from the electrode dissolves the metal beneath the stencil, creating a mark. The longer the electrode is held against the metal, the deeper the mark will be.
Electrochemical etching is compatible with a range of applications, from tracking production information, adding manufacturers’ markings, or even incorporating branding or artistic details. At its core, electrochemical etching is a relatively simple process; however, there are some common mistakes to avoid in order to achieve the best appearance and durability. Here, we’ll look at some best practices and tips for success.
Surface and Structural Defects
There are several common defects and damage that can happen in electrochemical etching processes. Some primarily affect how the finished piece looks or the clarity and crispness of markings. Others are more structural, or can leave pieces weak and vulnerable to future damage or breakage.
- Undercutting. This happens when the etchant solution removes metal under the resist and surface of the piece. As a result, the top surface is not fully supported, and it overhangs the area that was removed. In some applications, it can push etched features like grooves or channels out of tolerance, which impacts part performance.
- Over-etching. If the piece is left in contact with etching chemicals for too long, an excessive amount of metal is removed, which can damage the piece’s structure or cause lines, text, and other markings to fade.
- Under-etching. In this case, not enough metal material is removed during etching, causing incompletely-formed markings or even flaps or flakes of metal that trap the chemicals or debris.
- Uneven etching. This can happen if the etchant is not mixed consistently, if electrical current flows unevenly, or if resistance is uneven. The result is areas where more or less material is removed than intended and is often due to improper cleaning and prep or a poorly-adhered resist.
- Pits and voids. These are tiny divots, dents, or depressions in the surface where excess material was removed.
Halos
Halos are blurry spots, light rings, or imprecise transitions between etched and unetched areas on a workpiece. The material often looks hazy, partially etched, or discolored in these areas. Some examples include:
- Irregular lines and undefined edges.
- A hazy or blurry area surrounding the etched area or feature.
- Oxidized rings.
- Light or discolored areas between closely-spaced, tiny features.
Halos can happen for a number of reasons, including uneven or excess contact with the etchant chemicals, a resist that lifts or does not adhere properly at edges, improper cleaning of the metal surface that leaves residue, oil, or particles behind, or rapid evaporation of the etchant.
Rust
Rust can form immediately after etching or over time as a result of the etching process. Not only is it unsightly, rust makes markings less clear and can impact the performance of the piece over time. Rust can be caused by:
- Acid residue that is not fully neutralized after etching.
- Contamination with Ferric Chloride that can corrode metal over time.
- Flash rusting due to exposure to high-humidity after washing and degreasing post-etching.
- Moisture that gets trapped in deep etchings or intricate designs.
It’s important to neutralize etching chemicals immediately to stop the reaction, as well as to ensure pieces are fully dry by applying heat or a water-displacing oil. In some steel applications, passivating the material both removes surface free iron and contaminants and restores its protective oxide layer.
For steel, especially, using distilled water for rinsing and ensuring the part is thoroughly dried is recommended to avoid introducing more contaminants.
Understanding Etching Defect Causes and Solutions
Despite its relative simplicity, achieving clear, crisp, even markings with electrochemical etching and avoiding common defects requires attention to detail and careful preparation. Each of the following factors have a big impact on the appearance and overall quality of the finished etching.
- Pre-treatment: Surface degreasing, cleaning, and drying to remove oils, grease, residues, and particles prior to masking and etching.
- Electricity and power supply: Proper voltage and current density; Condition of electrodes, power units including rheostat and amperage meter, and connections.
- Etchant chemistry: A variety of electrolytes can be used, and they can be acidic or basic.
- Sodium chloride (NaCl).
- Hydrochloric acid (HCl).
- Sulfuric acid (H2SO4).
- Sodium hydroxide (NaOH).
- Copper sulfate (CuSO4).
- Ferric Chloride (FeCl3).
- Cupric Chloride (CuCl2).
- Nitric Acid (HNO3).
- Potassium hydroxide (KOH).
- Neutralizing: Critical to stopping the etching process and removing chemical residue; Helps to prevent halos rust, undercutting, and over-etching.
Resist Problems
A resist is a layer of material used to control which parts of a workpiece are etched and which are not. The resist creates a physical boundary on the piece and prevents contact between etchant chemicals and the metal surface. It can be a vinyl sticker, tape, paint, marker, or another material that will not dissolve or peel away when the chemical and electricity are applied.
It’s critical that the resist is prepared correctly for the material and the chemicals being used so that it will stay in place throughout the process. Common problems include:
- Poor adhesion. This is often due to parts not cleaned and dried properly, oils and residue, or particles, especially at the edges. It can cause the resist to lift, dislodge, or loosen enough to allow some etchant to seep under, resulting in blurred lines, imprecise etchings, roughness or overetching.
- Thickness. If the resist layer is too thin it may not adhere well, or it may break down when exposed to chemicals, resulting in excess or unwanted etchings and markings.
- Material mismatches. If the resist material is too porous or hydrophilic it could absorb chemicals or not form a reliable barrier. The resist must be made with adhesives, paints, inks, and vinyls that are compatible with specific etchant being used.
Contact the Experts at Universal Metal Marking
Universal Metal Marking prioritizes quality workmanship in our comprehensive electrochemical etching, laser marking, and engraving services to create clear, permanent, legible markings on materials and finished products for customers in a variety of industries.
We use trusted, non-immersive etching equipment, power supplies, and solutions from Marking Methods that produce reliable, high-quality results efficiently. Parts are cleaned and conditioned with APC all-purpose cleaner, and we use electrolyte solutions MSC-1(an acidic solution compatible with a wide range of metals) and 59NC (a non-chloride solution for stainless steel and titanium).
With over 50 years of experience, our team understands the details of how to prevent defects and part damage in the etching process. Contact us today to learn more about our services or request a quote to start your order.




