Working Around Common Adhesion Problems While Plating Onto Plastics
There are many practical reasons a manufacturer may want to electroplate a metal material onto a plastic product. For example, a metal coating can strengthen the plastic substrate and protect it against wear. Metal can also act as a sacrificial barrier that protects against corrosion, and a metal finish can add luster to an otherwise “dull” plastic item, significantly enhancing the substrate’s aesthetic appeal
However, there is one obvious challenge that can negatively impact the results in metal-on-plastic plating applications: insufficient adhesion. Because metal and plastic are such dissimilar materials, they do not always maintain contact with each other during the electroplating process. There can also be issues such as flaking or peeling after the end-user receives the finished product — and that can make your customer think twice about keeping your company as a supplier.
How to Improve Adhesion
The most common reaction when a metal coating does not adhere to a plastic substrate is to blame the metal — or the plating methodology. In truth, there are several factors that can negatively impact the overall result, such as:
- Not applying a base coat: Because metal does not adhere well to plastic, it’s often necessary to metalize the substrate by applying a base coat. Electroless plating can fulfill this requirement. Electroless plating relies on an autocatalytic reaction (instead of an electric current), which tends to promote better adhesion when working with plastics. It will also create a “metal-on-metal” finishing solution that will improve the long-term results. The plater can then add a top coat of gold, silver or whatever else the customer desires.
- Not activating the surface: It’s often necessary to make the surface of the substrate “active” to ensure sufficient adhesion. In other words, the plastic must be ready to receive the metal coating. Activation entails the application of a multi-step pretreatment process that includes presoaking the workpiece in an alkaline solution, followed by electro-cleaning, pickling, descaling and ultrasonic cleaning.
- Not using a chemical treatment: In situations where there is little or no compatibility between the plastic substrate and the metal coating, using a chemical adhesive promoter can overcome the bonding challenge. Water or alcohol-based promoters typically work best when plating onto plastic materials such as polyolefins, engineering plastics and epoxy thermoset products.
Contact SPC to Learn More About Plating Onto Plastics
SPC has been a metal finishing pioneer for more than 90 years. We’re one of the few companies in our industry that have mastered the process of plating onto plastic. We know how to address and overcome the obstacles that could prevent you from achieving the results you expect. Contact us for more information and to schedule a convenient consultation today.