The copper powder painting process - what are the steps and why is it done?

As a result, copper needs to be painted, not only to protect it from the elements but also to provide effective electrical insulation. Find out what is used to paint copper and why.

Can copper be painted?

Yes, it is not only possible but also advisable to paint copper - especially when it comes to components used in the electrical and electronic sectors. By applying a suitable paint to, for example, bus ducts made of this metal, an insulating coating with suitable physical, chemical, aesthetic, and functional properties can be created. The result is effective electrical insulation that can be used for applications such as batteries, charging stations, and power banks in the automotive and e-mobility industries.

Coating copper is also an excellent way of improving its corrosion resistance and increasing its resistance to weathering, moisture, dust, and other hazards. With the right method and paint, it is possible to maintain the appearance and properties of the component over time.

Copper oxidation - why does copper darken?

Painting copper can also protect it from darkening as a result of progressive oxidation. How does this happen?

Copper reacts with oxygen in the air and the resulting copper oxides give the metal surface its characteristic reddish or reddish-brown colour. In some environments, copper can even take on a blue or green colour (e.g. when nitrogen or sulphur oxides, or carbonates are present in the air).

The oxidation of copper, although aesthetically undesirable, can be counterintuitively very beneficial, as the copper oxides form a protective layer on the surface of the metal, preventing the development of corrosion.

Ways of painting copper

Copper can be painted in a number of ways. Apart from the traditional application of paint by brush, roller or spray, powder painting is also used, which is ideal for copper components such as flat bars, bus bars, bus ducts, connectors or other electrical components. It provides a hard and damage-resistant insulating coating with excellent physical, functional, and aesthetic properties.

Powder-coated copper components can also be combined with electroplated coatings, such as silver, nickel, tin, or other metals. This allows the component to be used in a wide variety of conditions, including the most difficult.       

Electris offers our customers the latest powder coating technology for copper and aluminium components, together with the appropriate masking techniques and the combination of these coatings with galvanic coatings: tin, silver or nickel plating. We powder coat components of many sizes, shapes and types and provide them with appropriate insulation. We use epoxy and polyester paints with high insulation parameters (45 kV/mm). We also offer many colours, for example: black, white, grey, dark grey, orange and others - according to individual customer requirements.

Before painting copper, regardless of the method chosen, the surface must be properly prepared. Firstly, it should be degreased and any dirt or old paint removed. This will ensure proper adhesion and the expected parameters of the new coating.

The oxidation of copper, although aesthetically undesirable, can be counterintuitively very beneficial, as the copper oxides form a protective layer on the surface of the metal, preventing the development of corrosion.

How should copper parts be stripped of paint?

The process of removing old paint from copper can be tedious and depends on the type of preparation used, but there are ways to be successful.

In an industrial environment, the following techniques can be used to clean copper.

• Sandblasting. This involves cleaning the surface with a jet of sand or other abrasive under high pressure. It is effective in removing rust, paint or organic contaminants, but it does not work well on delicate components.
• Chemical cleaning using special chemicals that react with contaminants and old paint to dissolve them.
• Electrochemical cleaning. This technique uses an electrolyte and an electric current to remove contaminants from the copper surface.
• Mechanical rubbing or grinding. For smaller components or delicate surfaces, mechanical cleaning methods such as scrubbing with a steel brush or sanding with sandpaper can be used. However, this method must be used very carefully to avoid damaging the surface of the copper component.
• Ultrasonic cleaning. This method involves immersing the copper component in a special chemical solution and subjecting it to ultrasonic treatment. It is effective in removing very fine contaminants but requires specialised equipment.

How to degrease copper components?

We have already mentioned the darkening of copper, which is caused not only by the oxidation process but also by the grease deposited on it, i.e. the patina. Its removal is necessary to restore the surface to its original appearance and to prepare it for the application of copper paint. How is this done?

Again, the techniques described above work well. In industrial environments, chemical, electrochemical, mechanical and ultrasonic degreasing are the most effective. The choice of method depends on, among other things, the size of the parts to be degreased and the nature of the surface.

How to polish copper?

The best solution is to use ready-made polishes and liquids for polishing copper and brass. To avoid damaging the surface, it is advisable to apply them with special polishing cloths.

Which paint to use to paint copper?

To paint copper and maintain the functionality of the component, it is necessary to choose paints designed for this type of surface. It is necessary to use products with very good adhesion, long-term durability, resistance to damage or corrosion, as well as fast drying times. It is also very important to select the right layer thickness and insulation parameters.

The most commonly used paints for painting copper include

• epoxy paints, which contain epoxy resins as the main component. They have high mechanical strength, which means they are resistant to abrasion, scratching and mechanical damage. Epoxy paints adhere very well to a variety of substrates, including copper, and provide a durable and effective coating. They are resistant to fading and discolouration, which means they retain their attractive appearance for a long time. Epoxy paints are resistant to UV radiation and changing weather conditions, making them ideal for outdoor applications;
• polyester paints are durable, weather and corrosion-resistant. Widely used in the automotive, construction, furniture and other industries, polyester paints allow beautiful effects to be achieved on copper surfaces while providing protection from the elements;
• polyurethane paints, which are recommended for creating anti-corrosion coatings;
• acrylic paints, which are easy to apply and dry quickly, making them a popular choice for painting copper when work needs to be completed quickly. They are ideal for protecting and refurbishing copper pipes, for example.
• alkyd paints, which are good for painting radiators and copper central heating systems. Polyvinyl acetate paints, which are used for painting copper components outdoors.

Does plating thickness matter?

The thickness of the plating layer is critical for copper components, especially when used in the electrical industry. When designing a component and its functionality, the appropriate plating colour and layer are selected. What is it and how does it affect a copper component?

• It provides electrical insulation. For copper components used in electrical power systems, the correct thickness of epoxy coating ensures proper electrical insulation. This is important to prevent short circuits and maintain the uninterrupted flow of energy through copper components.
• It also provides adequate corrosion protection. A well-chosen layer of epoxy will effectively protect copper from corrosion to which it can be susceptible in adverse environmental conditions such as moisture (e.g., wind turbines or railway tracks), salt (e.g., offshore wind farms) or atmospheric pollution. A thicker layer of epoxy creates a protective barrier that shields the copper from external influences.
• It influences the mechanical strength. The right coating can also increase the mechanical strength of copper components. It protects copper from scratches, impacts or other mechanical damage, which can be significant for components in industrial environments or those exposed to heavy mechanical stress. It provides durability and resistance. A thicker epoxy coating can also contribute to the durability of copper components and their resistance to weathering, UV radiation or chemicals. As a result, these components can retain their functional and aesthetic properties for longer.