A die casting surface finish can provide durability, protection, and a decorative appearance. Over the next few months we will explore different types of finishes and how they are beneficial for different types of die cast parts.
Due to the fact that a die cast part needs to be heated during decorative finishing processes (such as plating and painting), it is vital for the die cast part to have both a good internal structure and good surface finish. These are achieved through good design for both the tool and the component. Planning ahead for the finish you need can help to potentially minimize surface finish problems as well as any potential porosity issues.
Types of decorative finish:
• Smooth and Shiny: In cases where a smooth and shiny surface is required, the density of the casting itself must be higher so that the part can be plated and buffed repeatedly. This type of finish requires the most preparation of the casting to achieve a smooth surface under the coating. Smooth and glossy finishes have the least ability to hide any surface imperfections.
• Satin and Textured: For satin finishes, brushing or media blasting can be used to achieve the desired surface finish before coating.
The 5 Most Common Decorative Finishes:
1. Painting
2. Powder Coating
3. Antiquing
4. Ceramic Coating
5. Plating
1.) Painting
Lacquers, paints, and enamels can easily be applied to die cast parts and work for both decorative and protective purposes. As with any finish, special considerations must be taken at the design stages of the part to plan for the type of painting finish you need. Precautions are taken in order to remove any oils from the cast surfaces. For best results, a conversion coating is applied after cleaning to ensure good adhesion of the coating to the die cast surface.
2.) Powder Coating
Powder coating is commonly used as a decorative finish because it is able to hide minor flaws in the surface, the thickness is better controlled and more uniform, it is quite durable, very glossy, and has great color consistency and vibrancy. Powder coating yields a very hard, high anti-corrosion finish which makes it better at resisting dings and scratches. Unlike paints, powder coating reaches its final cured hardness during the baking cycle. Paints continue to cure for a period of time after baking, which may cause a delay in subsequent assembly operations. Powder coating is also quite environmentally friendly because the process produces no hazardous air pollutants or waste byproducts.
3.) Antiquing
In order to create an antique look, zinc castings electroplated with copper (or any other of its alloying agents), can be covered in a layer of colored components, such as copper sulfide. This casting is then ‘relieved’ – a process which entails the removal of some of the colored layers on highpoints in order to present the underlying layer of the yellowish brass or the reddish copper. The parts are then treated with lacquer in order to prevent tarnishing.
4.) Ceramic Coating
Ceramic coatings provide a very thin and decorative coating for die castings. Similar in thickness to anodizing, ceramic coatings can be applied to the entire part surface and in some cases even internal threads can be coated. Since the coating is very thin, any surface imperfections in the die casting will show through. Care must be taken with surface prep operations to ensure the desired final finish is achieved.
5.) Plating
Plating can be applied to die castings using either the electroless or electro-plating processes. Electroless plating is used primarily as a protective and/or used to enhance electrical conductivity. In some cases, it can be used as a decorative coating. Electro-plating is capable of achieving the best cosmetic plating finish on die castings, since multiple layers of plating are applied and buffing/polishing can be performed after each layer. In general, plating processes are the poorest at hiding underlying surface conditions and require the most surface prep operations to achieve the desired final finish.
With over 75 years of die casting surface finishing expertise, our engineers will evaluate your requirements to recommend the best design and finishing options. Contact A&B Die Casting today!