High quality surface finishing is vital for the long life of any reactive metal. Besides the aesthetic appeal and colour finish, a surface finish is essential to protect reactive metals like iron and carbon steel from rust and corrosion.
There are two main finishes for metal surfaces: powder coating or wet paint. Both have their advantages and disadvantages depending on the type of surface finish you are after.
While both finishes contain resins, additives and pigments, only paints contain solvents. The solvent in paints acts to keep all components suspended in liquid form. Powder coating, as the name suggests, is applied as a dry powder.
This difference in chemical composition between the two finishes affects a range of factors including application method, equipment required, colour matching, texture and more.
Before either coating is applied, the surface requires a thorough cleaning to remove any oils, dirt, moisture or contaminants to ensure the finish adheres to the treatment surface.
For powder coating, the powder is applied using an electrostatic gun. The gun creates a negative charge, which means the negatively charged powder is attracted to the grounded surface. Once the finish has been applied, it is cured in an oven, which creates thermal bonds between the powder particles.
Like powder coating, paints are also applied with an electrostatically charged spray gun. While paints easily create even colour coats, they are prone to dripping and sagging and often require significant expertise to achieve the desired finish.
While the application methods are similar, the resulting finishes will have very different properties.
Powder coating – Advantages
Powder coating offers a number of benefits over wet paints.
If your primary concern is creating a tough, durable protective surface, then powder coating is the way to go. Compared to painting, powder coating is more resistant to chipping, scratching and other damage. This makes the process ideal for heavy-duty applications like building and infrastructure materials.
Health and safety
The solvents in paint emit volatile organic compounds (VOCs). These are a major source of industrial pollution and are particularly dangerous when inhaled. Since powder coating doesn’t contain solvents, it is better for the environment and safer to work with. Fewer health and safety precautions are required when working with powder coating compared to working with paints.
Liquid paint is also highly flammable, which makes it dangerous to store. Powder coating, on the other hand, isn’t flammable and is completely safe to store.
While powder coating has higher up-front costs (because of the set-up costs and equipment required for application), it tends to be cheaper in the long run.
Powder coating has a better utilisation rate than paint. About 70% of paint is lost to overspray. Powder coating lost to overspray, however, can be collected and reused, meaning material loss can be kept under 5%.
Powder coating application also doesn’t require the level of training and expertise that painting requires. This means that labour costs can be kept down as you don’t require trained experts for application.
Finally, powder coating isn’t subject to the same environmental and health and safety regulations as spray painting. That means that less investment is needed for environmental and safety compliance and disposal costs are lower.
Powder coating – Disadvantages
While powder coating has some clear benefits, it does have its drawbacks.
Powder coating can be particularly difficult to colour match. Paints can be quickly and easily mixed to create the desired custom colours. Powder coats, however, cannot. Because of its dry powder composition, different colours don’t actually mix but instead will create a speckled pattern of the two colours.
Custom powder coating colours can be created, but it requires a special production run, which is time consuming and expensive compared to simply mixing paints.
Creating a thin, smooth or high-gloss finish with powder coating can be extremely difficult. Painting provides a much higher degree of control over the layering and gloss of the surface. This is why paints are used for car bodies and other applications that require high-gloss finishes.
While powder coating application doesn’t require the level of expertise that spray painting does, it does require significant specialist equipment. This includes electrostatic guns and a curing oven. The cost of this equipment generally makes powder coating impractical for most home DIY enthusiasts.
Despite the downsides, powder coating is still a superior method of finishing metal surfaces. It’s durability, ease of application and health and safety benefits make it ideal for a range of heavy duty applications.