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Frequently Asked Questions about coating

Powder coating is an electrostatic process in which a spray gun is used to apply powder to metal. In the furnace, the powder melts to form an even layer and a stylish, protective and durable coating. Rotocoat also has years of experience with the application of special powders such as textured, metallic and anti-graffiti powders.

To guarantee the long-term bonding of the powder coating, proper pre-treatment is essential. Black steel often undergoes mechanical pre-treatment, but Rotocoat also provides chemical pre-treatment using iron phosphating. Iron phosphating is highly suitable for products used inside the home, but also for agricultural machinery, machine parts and parts for the automotive industry

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Rotocoat specialises in the powder coating of galvanised steel, steel, aluminium and stainless steel. Rotocoat also provides liquid paint systems in combination with hot-dip galvanising. Depending on the setting in which the product is used, one, two or sometimes three coats of paint may be applied. However, powder coating guarantees better protection for profiles and edges than liquid paints and the price-quality ratio is better, particularly in the long term.

For a good result and a long service life of the coating it is important for the substrate of all materials to be free of sharp edges and burrs. A substrate that is as smooth and flat as possible always leads to a better result than a rough surface, for example because less dirt attaches to the surface and the layers of the coating get formed properly. A porous surface makes blisters or craters more likely during powder coating, for example with cast aluminium, steel castings, thermal-sprayed material and hot-dip galvanised material with thick layers.

Do you want advice about the best approach to protecting your product? Don't hesitate to get in touch with Rotocoat, see map at the left side of this page.

Rotocoat has various production lines for both small and very large assignments. To decide whether Rotocoat can coat a product, we need to know the length, width, height and the weight.

Click here for the line sizes at the various locations.

Galvanised steel or aluminium with a powder coating has a long useful life. To preserve the appearance, any dirt should be removed regularly. The location of the product will determine how often and how the surface should be cleaned. After cleaning products have been used, it is important to rinse the surface with clean water.

Generally, coarser dirt can be removed by spraying with mains water. Products that cause scratches such as sandpaper, steel wool and steel brushes should not be used. Cleaning products should be chemically neutral, with a pH between 5 and 8. So alkaline products like ammonia or soda and acid products such as sulphuric acid or cleaning products containing phosphoric acid should not be used. Very dirty products may be cleaned using a polishing cleaner. These scouring products may be used extremely cautiously to remove local and extreme concentrations of dirt that ordinary products fail to remove.

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Depending on where the product is used, Rotocoat will advise a coating with one, two or three layers. With aluminium or hot-dip galvanised steel used outside, a single-layer system will often be adequate (chromate conversion coating will be needed). For outside use in which condensation, dirt and mist accumulate and the product is not rinsed naturally, for example under a canopy or a roof, Rotocoat advises a twin coating. For products exposed to extreme outside conditions, for example at sea or on coastlines, we advise a triple-coat system.

The first layer of a twin coating consists of epoxy powder coating, the second of a polyester powder coating. A triple-coat system consists of two layers of epoxy powder coating and one layer of polyester powder coating. It is also important for the coating to be cleaned regularly to prevent dirt sticking to the coating and reducing its useful life.

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Sometimes, after a number of years, a coating may change colour, start to look dull and seem to become powdery. This is known as 'chalking'. It is usually caused by using poorer quality paints or powder coating.

With powder coating, it affects the colour black (RAL 9005), all reds and also green (RAL 6009). This happens when powder has been mixed with epoxy instead of polyester. Epoxy is not a very colour-fast medium, particularly when exposed to UV radiation (sunlight). Polyester is known to be very colour-fast indeed. Rotocoat uses only powders with pure polyesters.

During the powder coating process, the powder is applied electrostatically. No solvents are needed and so there is less of a burden on the environment. Powder coating does not produce any hazardous fumes and there is no fire risk. Nor are there any harmful residues. Powder that does not adhere to the material is used again.

Liquid paint systems need solvents and so those systems are more of a burden on the environment than powder coating. Liquid paints can release dangerous vapours and there is a fire risk. There is also harmful waste and excess paint has to be disposed of as chemical waste. Liquid paints may be cheaper in the short term, but in the longer term powder coating, certainly in combination with hot-dip galvanising, is the sensible choice in terms of the environment and costs. If you want more information, please get in touch, see map at the left side of this page.