Metal Plating For Your 3D Printed Parts — A Practical Guide
06 July 2017
We’ve looked at a lot of different options for finishing your 3D printed parts on the blog, from the simple to the sophisticated. Today, we’re going to be looking in detail at adding metal plating your parts. You may ask why you’d finish parts in this way when 3D printing with metal is now feasible. While metal printing has made huge strides in recent years, it is still relatively costly compared to other techniques and often requires time-consuming post-processing steps. As a result, it will not always be practical to implement at this point in time.
Put simply, metal plating offers the best of both worlds, providing all the benefits of functional metal parts with the fast, agile production workflows offered by established 3D printing methods. For example, you might print your part in plastic, using an SLS printer, then plate it to achieve near-identical mechanical qualities to a solid metal part. This approach is being explored in industries such as automotive and aerospace for the creation of both functional prototypes and production parts, allowing one-off or limited-run designs to be created quickly, for minimal cost.
How does it work?
There are two main ways of plating 3D printed parts: electroplating and electroless plating (also called chemical/autocatalytic plating).
- Electroplating involves immersing your part in a plating solution of water and metal salts, then passing an electrical current through it, causing metal cations to form a thin coating around the part. The process is very quick and delivers a firm, long-lasting finish, although several layers may be required for thicker plating. It can also utilise a wider range of metals than electroless plating.
- Electroless plating is a similar process that — as the name implies — doesn’t require any electrical power. Instead, it utilises chemical reactions to cause the metal to bond to the part. This is typically more time-consuming than electroplating, and as the process takes place in a heated bath, may lead to part deformation. However, it does help make the finished part resistant to friction and corrosion and, in the hands of a skilled technician, allows for precise control of the plate’s thickness during its application.
Bear in mind that you can combine approaches to create your desired result. For example, your initial layer might be applied with electroless plating, then any additional ones with electroplating, to bring the finish up to the desired thickness. This will help improve the longevity of the plating bath, as the solution will only be usable for a limited number of applications, even with thorough filtration after plating.
What materials can you use to plate your parts?
You’ve got a lot of options here. Zinc, chrome and nickel are well-established plating materials for industrial applications. For electroless plating, nickel and copper are the most widely-used materials. Other materials, such as brass, gold, silver and titanium are also available, although not all of these will be suitable for functional parts and should be reserved for decorative or artistic works.
Bear in mind that the solutions used for electroless plating may only be reused a limited number of times (as mentioned above), so you may need to factor that into your ongoing material costs.
Priming your part
Before plating, you will need to prime your part, just as you would if you were painting it. With electroplating, the idea is to create a conductive surface that the metal plating can adhere to in order to achieve a smooth, even finish. Graphite works well for this purpose, and is both affordable and readily available. Just a couple of thin layers will suffice, as you don’t want the primer to obscure any fine details or affect your part’s dimensions.
For electroless plating, priming will involve oxidising your part’s surface and adding a catalytic layer for the metal to bond with.
For both techniques, ensure your part has been properly cleaned and is free of any contaminants before priming. Ideally, you should have a dedicated cleaning station as part of your workspace, as even small amounts of dirt and oil will affect the end result. Also, be sure to read your plating solution’s material specifications for any guidelines regarding priming, as certain materials may require additional preparation.
The finishing touches
Once plating is complete, you may find the finish is quite dull, particularly if you are using electroless plating. This is completely normal. Light polishing will help achieve the desired result. For stronger metals, steel wool may be required to give a smooth, bright finish. You might consider investing in a rotary tool to speed up this part of the process.