PL
ENPowder coating is the standard in industrial metal finishing - and for good reason. The coating is produced without solvents, material usage reaches 95-99%, and the finished layer is harder and more durable than with wet painting.
To achieve that result, however, the process has to be carried out correctly - from preparing the substrate, through applying the powder, to curing in the oven.
Below we show how powder coating works and what determines the quality of the coating.
What does powder coating involve? The process step by step
The powder coating process consists of three stages. Each of them affects the final quality of the coating.
Stage 1 - Substrate preparation
This is the critical stage - if the surface is greasy, covered in rust or uneven, the coating will not adhere properly. Depending on the condition of the part, the following are used:
- chemical or alkaline degreasing,
- sand or shot blasting - to remove mill scale, rust and surface irregularities,
- phosphating or another conversion treatment - this improves adhesion and corrosion resistance.
A good example of a demanding part is an aluminium alloy wheel - before the coating is applied it has to be thoroughly cleaned and pre-treated, otherwise the coating will flake off at the first contact with road salt.
Read also: Surface preparation for powder coating - stages, mistakes and best practice
Stage 2 - Applying the powder
The coating, in the form of dry particles, is fed to a spray gun and given an electrical charge. Two methods are used here:
- electrostatic (corona) - the charge is applied by an electrode in the gun nozzle,
- tribo - the particles are charged by friction against the walls of the gun, without an external voltage source.
The earthed metal part attracts the charged particles, which adhere evenly to the surface. There are none of the runs and sags typical of solvent-based paints.
Stage 3 - Curing and cross-linking
The part goes into the oven. The air temperature usually sits in the 160-200°C range, but the key figure is the temperature of the metal itself - it has to reach and hold the required value for 10-20 minutes. During this time the powder melts and the molten particles bond together through cross-linking. A uniform, hard coating forms. Once cooled, the part is ready for assembly or further processing.
Read also: The role of the oven in the powder coating process
What is powder paint made of?
Powder paint is a mixture of resin, curing agent, pigments and additives that influence flow-out and mechanical resistance. The most commonly used systems are:
Polyester coatings
More stable in outdoor conditions. It is used in steel structures, fencing, balustrades and architectural elements.
Epoxy
It handles chemical and mechanical loads well. That is why it goes inside industrial halls, onto machine housings and control cabinets. Outdoors it performs less well, because UV radiation causes the colour to change.
Epoxy-polyester coatings
They combine the properties of both resins and are often chosen where both appearance and chemical resistance matter.
Read also: Types of powder coating - differences, applications and selection
The advantages of powder coating in industrial production
Powder coating stands out for several features that account for its dominance in industry:
- material usage reaching 95-99% - excess powder can be recovered and reused, which is impossible with wet painting,
- no solvents during application - no VOC (volatile organic compound) emissions,
- high mechanical resistance of the finished coating to impact, scratching and abrasion,
- an even coating thickness when applied correctly - typically 60-120 µm,
- the ability to achieve a wide range of textures and gloss levels in a single operation.
Powder coating vs wet painting - what is the difference?
Both methods protect metal against corrosion, but they differ in technology, cost and final result.
It involves applying paint thinned with solvent or water. Drying happens through evaporation. The method is flexible - it works well for very large parts, spot repairs and objects that cannot be cured in an oven. The downsides are low material usage (40-60%), solvent emissions and lower mechanical resistance of the coating.
It needs no solvents, gives a harder coating and higher material usage. It does, however, require an oven and an earthed metal part. It is not suitable for spot repairs - the whole part has to go into the booth and the oven.
For series production and metal parts working in demanding conditions, powder coating is more efficient and cheaper per m² of coating. Wet painting remains justified for oversized objects, refurbishment work and non-metallic substrates.
Read also: How does powder paint differ from liquid paint? A comparison
Corrosivity categories - what do they mean for a coating facility?
In B2B orders there is an increasingly common requirement to comply with the ISO 12944 standard, which classifies corrosive environments. The categories are labelled from C1 to C5 plus CX:
| Category | Corrosivity | Typical environment |
|---|---|---|
| C1 | Very low | Dry environments, heated interiors (e.g. offices, production halls) |
| C2 | Low | Interiors with condensation |
| C3 | Medium | Outdoors in urban and industrial climates |
| C4 | High | Industrial and coastal environments |
| C5 | Very high | Aggressive industrial or marine environments |
| CX | Extreme | Offshore, heavy industry |
The corrosivity category sets the requirements for substrate preparation and coating thickness. The technical data sheets for powder coatings state which category a given system is intended for. Before you select a coating for a project, check whether the required category is in the technical specification of the order.
The limitations of powder coating - when does this technology fall short?
Part size
Powder coating works brilliantly, but on one condition: the part has to fit in the oven for curing. If the part is too large for the chamber, then without expanding the installation the process is simply ruled out.
Process temperature
Most systems require curing in the 160-200°C range (metal temperature). With thin sheet metal or heat-sensitive materials, distortion can occur. In such cases, low-cure powders or an entirely different coating technology are considered.
Part geometry
Problems arise with very sharp edges or deep recesses and cavities. In these areas the so-called Faraday cage effect can occur, meaning weaker powder coverage. It can be reduced with the right voltage, gun settings and operator experience, but bear in mind that this is not a hands-off process.
Read also: The most common problems in powder coating and how to solve them
Where is powder coating used?
Powder coating is used across many industries where metal parts have to withstand corrosion, abrasion and heavy use. The technology works well both in series production and in architectural elements.
In metal furniture, the coating is responsible for surface durability and a uniform colour. It is applied to items such as personnel lockers, warehouse shelving and workbenches.
In white goods, powder coating protects appliance housings against moisture, detergents and scratches. The coatings are used, for example, on the housings of washing machines, refrigerators, radiators and other household equipment.
In steel structures, powder coating is used in the manufacture of:
- balustrades and fencing,
- facade elements,
- warehouse racking,
- road signs.
Powder coatings also appear in the machinery industry. They are applied to equipment housings, guards and structural frames, where they have to withstand contact with oils, impact and daily use.
Read also: What items can be powder coated?
How to choose a powder coating for your process?
Choosing a powder coating comes down first of all to answering a few questions. Where will the part operate? Outdoors, in damp and sunlight, or inside a hall? Does it come into contact with oil, detergents or chemicals? Does it heat up in use?
The choice of system depends on that. For indoor use, epoxy-polyester coatings are suitable; outdoors, polyester coatings resistant to UV radiation perform better. For elevated temperatures, high-temperature powder coatings are needed.
Before you order a larger batch, look at the technical data sheet. Check:
- the curing temperature and time,
- the recommended coating thickness,
- impact resistance and adhesion,
- the corrosivity category, if the project requires it.
Read also: How to choose the right powder coating? A few important tips
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