Powder coating or liquid coating: which is better?

Painting is essential when making a mechanical case for electronic devices, but what should you choose between powder coating or liquid coating? These are two of the most viable alternatives for your projects, but there is no single answer as to which is the best of the two. Rather, some specific characteristics of the two processes can help you understand which option is more functional for your specific case.

It is during the design phase of the mechanical device that the most suitable finishes are identified to make it functional and aesthetically pleasing. In fact, the role of the coating chosen for your devices is not only to improve their visual appearance, but also to offer specific characteristics in terms of resistance, durability and solidity within the context of the use for which they are intended.

elmec can help you find the optimal solution for you, acting as a multifunctional hub, combining the skills of its in-house team with cooperation with valuable external partners. It is they who enable us to expand our operations and adapt to your project needs, providing a wide range of specialised machining.

Liquid painting

Industrial liquid coating is a process carried out manually and involves spraying liquid paint onto the surface of the product. During this process, special compressed air guns are generally used, which deposit miniaturised liquid on the material to be treated. However, there are various application techniques available for this type of coating, such as high-pressure spraying, mixed spraying or electrostatic spraying. After painting, the treated mechanical devices enter special ovens with moderate baking temperatures of between 60 and 80 degrees.

The process can therefore be used on both metals and non-conductive materials such as plastics. By liquid varnishing your electronics cases, you can also provide metal areas free of varnish (achieved by selective masking or simply directing the jet) that are functional for the conductivity of electrical contacts.

In addition, the manual execution and the type of raw material used allow even particularly complex geometries to be homogeneously covered, resulting in an even distribution of thicknesses.

The workpieces to be treated should always pass through a SURTEC pre-wash and chrome-plating step, which ensures uniform adhesion of the paint to the product: these are additional steps that entail a little extra investment, but do not nullify the convenience and practicality of this type of processing.

Powder coating

Powder coating is a generally automated finishing process in which special thermosetting powder paints are applied to metal. To produce such coatings, binders are created, into which pigments are then integrated, before the compound is pulverised and given a particle size distribution curve suitable for the purpose.

Thermosetting resins are generally used, such as epoxy, acrylic, polyester, hybrid and many others. Powder coating is essentially an electrostatic process, but how does it work? Dedicated equipment charges the metal part to be treated with a positive charge and the paint with a negative charge.

The material to be processed is covered with paint through the use of manual or automatic electrostatic guns to achieve a uniform film on the surface. After that, the articles enter a baking oven: unlike liquid coating, for powder coating high temperature is essential and the parts are heated up to 180 – 200 degrees.

Here, too, it is necessary to go through a washing phase and a treatment aimed at increasing the adhesion of the paint to the surfaces. The paint thicknesses obtained tend to be greater than with liquid paint (approx. 60-100 microns) and offer more effective protection against external influences. On the other hand, powder coating does not distribute evenly on more difficult geometries, such as corners or edges: electrostatic charges attract more product here.

Leaving conductive metal areas in this case is slightly more complex, as it requires the use of special adhesive tapes that can withstand the high temperatures of the final stage of the process (up to 200°C).

Aluminium powder coating

Aluminium is the material that most often enters our core work and it is a material that is particularly difficult to paint properly. It is therefore essential to carefully select the type of paint, as well as the processing to be carried out, and powder coating is among the treatments of choice for this material.

Thanks to this process, the metal surface is protected for a long time against corrosion, its resistance to chemicals that could impair its functionality is increased, it has more adhesion and a longer service life. To achieve excellent results, however, it is essential that the device to be treated is previously optimised for this type of painting, clean and free of burrs.

Difference between powder coating and liquid coating

There are many differences between the two types of coating, although they are both valid processes for electronics metalwork.

The first difference is related to the materials on which the two processes can be performed: while liquid coating can be used on numerous surfaces, powder coating is reserved for metals, due to the high baking temperatures required by the treatment.

Liquid painting is perfect for small and medium series, has low set-up costs and does not require a minimum quantity of paint to be started. In addition, it allows original colours to be produced, which can be easily matched to any type of project. In fact, a wide range of colours and effects (chrome, pearlescent, soft touch and so on) can be obtained with the liquid technique.

Liquid paint is quick to execute and also allows finishes with exceptional strength and durability. On the other hand, in the case of poorly executed processes, it is easy to have bubbles or drippings on the painted device, and it must be emphasised that liquid paints often contain environmentally unfriendly solvents.

The costs and setup times for powder coating are higher than for liquid coating, making it more suitable for large series. In addition, there is a minimum quantity of powder coating to be purchased of around 25-50 kg. However, the parts that can be produced are numerous and run into the hundreds, making larger projects easily scalable. Among the pluses of the process is the fact that it does not involve the use of harmful solvents and is therefore environmentally friendly: making the process even more efficient is the easy recovery of the paint particles that do not adhere to the material, which can be recovered, recycled and fed back into the process.

Powder coating also makes the formation of runs substantially impossible, although, as mentioned, it is more suitable for large series also because a change of colour is not exactly immediate and practical.

So, in conclusion, is powder coating or traditional liquid coating better? It depends on your project, the material to be processed, your needs.

Do you have doubts or questions about the two processes, or are you unclear which one is the most suitable for your electronic device case? Contact our technicians to analyse the project with them and find the most effective solution to your needs!