Varnished, powder-coated or galvanised? UV-resistant, waterproof or beautifully shiny? A huge variety of surface coatings is available – constituting an integral part of everyday industrial life. But how can you find the perfect coating for your production process or very latest development? We can help you with the decision-making process.

Surface coatings: True all-rounders

Some materials already meet all the demands made on them in their pure form. Others need a little help – for example, by way of a surface coating. Coating in the narrower sense is a supplementary manufacturing process according to DIN 8580. Coatings may fulfil numerous tasks, consist of different materials and be found in different thicknesses. Some are used purely for their visual benefits – ensuring that a component looks particularly good. Much more important, however, are functional surface coatings which add additional properties to the parts in question.

The multitude of coating types used means that there are virtually no boundaries to the wishes and ideas of producers and users alike. However, not all surface coatings are equally suitable for all conceivable purposes.

What are the characteristics of a suitable surface coating?

The perfect surface coating is the one that best meets your individual requirements. In order to make the right choice, you should give thought to at least three different aspects beforehand.

1. They can be easily integrated into the production process

The coating of any kind of component is always an additional work step – one which is either integrated into the process right from day one or one which has to be included retroactively. This gives rise to the question as to which surface coating method best suits both the process and the component. One of the ways of categorising the different coating methods is to distinguish between the aggregate states of the respective coating materials

Gaseous coating materialLiquid coating materialDissolved coating materialSolid coating material
Physical or chemical vapour depositionVarnishing, painting, plasticising, enamelling, dip coatingChromating, galvanising, tin plating, nickel plating, electroplating, phosphating, sol-gel processing, anodisingPowder coating, brazing, deposition welding, fluidised bed coating, sputtering, thermal spraying

2. They meet all the requirements

Alongside the method actually used to apply the surface coating, the selection process will primarily focus on the final properties, whereby a distinction is made between two different categories: The quality of the coating itself and its specific properties.

Surface coating quality

You can use three different parameters to assess the quality of a surface coating because you will be looking for different results depending on the area of application involved. The primary factors on which to base your decision are:

  •  Adhesive strength: How well does the coating stick to the substrate?
  •  Coating thickness: How thick is the coating applied?
  • Durability, resp. corrosion resistance: How well and how long does the coating last?

Surface coating properties

Surface coatings are true all-rounders. With the right coating, the properties of the substrate can be enhanced, or desirable features added. These include, for example:

  •  Visual design
  •  Scratch resistance
  •  Lubricating properties/frictional resistance
  •  Corrosion protection
  •  Oxidation protection
  •  Radiation protection
  •  Temperature resistance
  •  Thermal conductivity
  •  Electrical conductivity/resistance

Refining materials such as metals and plastics using a surface coating opens up a range of opportunities as many coatings are capable of simultaneously fulfilling a number of different requirements. A tin coating, for example, is an impressive choice because it has a classy, silvery-white appearance, is a good conductor and is highly temperature-resistant – all properties which are currently in demand in the automotive industry, the household appliance sector and many more.

3. They are perfect for the field of application concerned

As already described above, surface coatings are used in numerous different areas. This leads to another important criterion on which to base your decision: Even if coatings are intended to basically serve the same purpose, completely different materials might be used. For example, it is absolutely vital that the coating of an artificial joint which is intended to let this joint move more smoothly is biocompatible and generally causes no harm to the body. On the other hand, a certain lubricating effect is also desirable when using a ball joint in a propulsion technology application. In the latter example, however, it is not necessary to use biocompatible surface coatings, which are often more expensive, to fulfil this task.

Getting the most out of using the right coatings

Whether we are talking about a simple varnishing application using a spray gun or powder coating where metal powder is applied in several steps: Surface coatings are now a part of everyday life across all industries – from the wood-processing sector to the medical technology and aerospace industries – designed to get the most out of the components and products used. As is often the case, there is no such thing as a universal solution. In order to find the perfect surface coating, you should clarify the requirements resulting from your production process, budget, substrate material and respective area of application, as well as which properties you would like to have, as precisely as possible. You will then be in a position to make an informed decision on the right coating to use to benefit in the long term.

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