Before you can electroplate an item, you need to electroclean it. There are a few ways to do this:
- Reverse-current electrocleaning (anodic)
- Direct-current electrocleaning (cathodic)
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Here’s a closer look at both processes.
With this process, you dissolve and clean the metal surface at the same time, allowing you to remove metallic residue and film. When your metal meets the cleaning solution, oxygen will be released.
Reverse-current electrocleaning is executed with an alkaline bath, but this won’t work on every type of metal. Don’t use it on aluminum, chromium, magnesium, or brass or you’ll end up with nickel-oxide residue that won’t adhere to chromium. Use direct-current electrocleaning for these metals instead.
With this method, the metal base you are electrocleaning acts as the cathode of your electrochemical process. Your base metal will be connected with metals that are more easily corroded, known as “sacrificial metals.” Whereas oxygen is liberated through reverse-current cleaning, hydrogen is liberated through direct-current cleaning. If you are working with components that have been compromised by heat treating or other sources of oxides, you may need to clean them twice and follow up with a mineral acid dip.
Combination electrocleaning (periodic-reverse)
Periodic-reverse cleaning combines both reverse and direct-current electrocleaning. You will use periodic-reverse cleaning in alkaline baths that contain chelating agents (chemical compounds that react with metal ions to form a stable, water-soluble complex). The direct-current cleaning component of this process can coax out acid that has been trapped in items with fine recesses (including hinges). Otherwise, this acid could leach out after reverse-current electrocleaning. Periodic reverse cleaning also allows oxides to be removed without the risk for etching or the accumulation of debris—problems that are common to direct-current cleaning alone.
One of the problems that you encounter with electrocleaning is the dilution of cleaner concentration. This occurs because the soil on the component and the cleaning solution react, and the reaction depletes the cleaning chemicals. If you can cut the power to the electrocleaning process intermittently, you can short-circuit the reaction and restore the cleaner to its full strength.
It’s no use sending a component for plating if you haven’t cleaned it properly. Take the time to electroclean with the method that is most appropriate for your base metal and the intended use of the component.
For questions about electrocleaning or electroplating supplies or solutions, contact Gold Plating Services.