While metal finishing processes such as electroplating and electroless plating provide numerous benefits, the presence of post-plate tarnishing can diminish the value of the plating process over time. Tarnish is essentially a thin layer of corrosion that frequently develops on the surface of a part in the form of a dull blackish or grayish film. While silver is the metal that is generally associated with tarnishing, it can occur on just about any type of metal such as aluminum, copper and brass. They only metals that are normally immune from post-plate tarnishing are precious metals like gold, palladium and platinum.
What Causes Metal to Tarnish?
Tarnishing occurs when a metal surface reacts with a nonmetallic compound that is present in the surrounding environment. While oxidation (from the oxygen in the atmosphere) is generally the most common cause of tarnishing, it can also result from a reaction with other materials such as hydrogen sulfide or sulfur dioxide. Excessive moisture and humidity, extreme temperatures and even certain types of packaging materials can accelerate the tarnishing process.
How to Remove Tarnish from Industrial Metal Surfaces & Parts
While it is possible to remove tarnish from a metal product, it is often a difficult, time-consuming process.
- Hand-sanding or polishing can eliminate small amounts of tarnish.
- Heavy-duty industrial processes such as abrasive blasting, which involves the high-pressure projection of water and a blasting media such as glass beads, steel shot or aluminum oxide onto the part. Abrasive blasting must be executed with extreme caution to avoid damaging the substrate surface.
Post-Plate Tarnishing Procedures
A better alternative to having to remove tarnish is to prevent it from occurring in the first place. Several effective anti-tarnishing techniques can be applied upon completion of the plating process:
- Application of coatings: Various coatings have demonstrated the ability to slow the tarnishing process after plating, specifically triazoles, chromates and lacquers.
- Creating a mechanical barrier: It is possible to use materials such as desiccants and protective wraps to establish a barrier that minimizes exposure to atmospheric oxygen and moisture.
- Nitrogen bagging: This process entails placing the part inside a bag filled with pure nitrogen, which removes the oxygen that leads to the formation of tarnish-causing metal oxides.
Sharretts Plating Company Takes Appropriate Steps to Prevent Tarnishing
Choosing an experienced metal finishing company is a critical step for ensuring that your plated parts are less vulnerable to the damaging effects of tarnishing. As a leading metal finishing industry innovator for more than 90 years, you can trust the experts at SPC to implement the most effective anti-tarnishing post-plating techniques for your project. Contact us for more information and a no-obligation project quote today. Or Contact us for Consulting Services Today!
