Surface Preparation: The metal surface must first be thoroughly cleaned to ensure that no dirt, grease, oils, or contaminants are present, which could affect the etching process. This is typically done using a degreasing agent or an acid-based cleaner. After cleaning, the metal is rinsed to remove any residues from the cleaning agents. The part is then dried, often in a controlled environment, to avoid any contamination.

Masking (if needed): Masking is applied when only specific areas of the metal should be etched, such as in printed circuit board production. A protective layer, typically made from photoresist or vinyl, is applied to the areas that should remain unetched. This is particularly useful when precise patterns need to be etched onto the metal. In some processes, such as photochemical etching, the mask is exposed to light through a patterned stencil to transfer the design.

Etching Solution Preparation: The etching solution is composed of acids or other chemicals designed to dissolve the metal in a controlled way. For steel, solutions such as ferric chloride or nitric acid may be used. For copper, ammonium persulphate or ferric chloride solutions are common. For aluminium, an alkaline etching solution is often used. The concentration, temperature, and pH of the solution are critical and are controlled depending on the material and requirements.

Immersion or Spray Etching: Immersion etching involves fully submerging the metal part in the etching bath. This is ideal for larger parts up to 2.4 metres, ensuring an even etch across the surface. The metal part stays in the tank for a specific time depending on the desired effect, with temperature and chemical concentration controlled to manage the reaction speed. Spray etching involves applying the etching solution onto the surface using spray nozzles. This is useful for large parts or when more localised, precise application is required. Spray etching is also used for intricate designs or when controlled distribution is needed.

Etching Reaction: As the metal interacts with the solution, a chemical reaction dissolves the exposed areas, creating the patterns or marks. The etching time, concentration, and temperature determine the depth and intensity. Special care is taken to ensure uniform etching across large surfaces up to 2.4 metres.

Rinsing and Neutralisation: Once etching is complete, the part is removed from the solution. The metal is immediately rinsed with water to stop the chemical reaction. A neutralising solution, such as a mild alkaline bath, may be used to ensure the chemicals are fully neutralised.

Drying and Final Inspection: The metal part is thoroughly dried to prevent water spots or corrosion. A final inspection checks that the etching meets design specifications. Post-etching treatments such as passivation or coating may be applied to improve durability and corrosion resistance.