Powder Coating Powder FAQs

Find answers to common questions about Thermaset powder coating powders, including product selection, colours and finishes, stock availability, curing, substrates, technical performance and troubleshooting.

Thermaset is a UK powder coating powder manufacturer with more than 40 years of experience manufacturing and supplying powder coatings for industrial, commercial and specialist applications.

Buying & Selecting Powder Coating Powder

1. What types of powder coating powder does Thermaset manufacture?

Thermaset manufactures an extensive range of powder coating powders for different applications and performance requirements.

Our ranges include polyester, epoxy, epoxy polyester and specialist powder coatings, together with primers, textured finishes, antimicrobial coatings, post-forming products and other specialist systems.

The correct powder depends on factors including the substrate, whether the product will be used indoors or outdoors, the required colour and finish, and any particular performance requirements.

If you’re unsure which powder coating powder you require, contact the Thermaset technical team for advice.

2. Do you manufacture powder coating powders in the UK?

Yes. Thermaset is a privately owned British powder coating manufacturer based in Tamworth, Staffordshire.

We formulate, manufacture, test and supply an extensive range of powder coating powders to customers throughout the UK and worldwide.

Thermaset has more than 40 years of experience in powder coating manufacture and application support.

3. Can I buy powder coating powder directly from Thermaset?

Yes. Thermaset supplies powder coating powders directly to customers, with many products also available to purchase through our online shop.

Online ordering is available to trade customers and the general public.

If you require a specialist product, larger quantity, bespoke colour or technical recommendation, contact our sales team.

4. What powder coating colours are available?

Thermaset supplies an extensive choice of powder coating colours, including popular RAL and British Standard shades.

Depending on the product, finishes can include gloss, semi-gloss, matt, fine texture, ripple, metallic, pearlescent and other special effects.

Colour appearance can be affected by gloss, texture, film thickness, substrate, application settings and lighting. Where appearance is critical, we recommend approving a coated sample before committing to a major project.

5. Can Thermaset match a powder coating colour to a sample?

Yes. Thermaset offers a bespoke colour-matching service and can match many physical samples, colour references and existing finishes.

For the best result, provide a clean, representative sample large enough to measure and assess.

We will also need to know the required gloss, texture, application, substrate and exposure environment. A coated approval panel should be signed off before production.

6. Do you keep powder coating powders in stock?

Yes. Thermaset holds more than 600 powder coatings in stock, including a broad selection of colours, finishes and specialist products.

Our stock range includes RAL, British Standard and selected approved coating systems.

Stock products can be supplied in quantities ranging from single kilos to multiple tonnes, subject to availability.

Standard box sizes are 20kg.

7. What are the minimum order quantities for Thermaset powder coating powders?

Minimum quantities depend on whether the powder coating is a stocked product, manufactured to order or specially colour-matched.

Smaller quantities of selected stock products are available through the Thermaset online shop.

For a specific requirement, contact our sales team with the product code, colour, finish and quantity required and we can confirm availability and pack size.

8. What are the typical lead times for powder coating powder?

Many stocked Thermaset products are available for prompt or next-working-day dispatch, subject to availability, order time, quantity and delivery location.

Bespoke products and colour matches require additional manufacturing and approval time.

Typical lead times for non-standard products are 12–15 working days, with approximately two additional working days for special-effect products.

Contact our sales team for an accurate lead time for your particular requirement.

9. How do I request a powder coating quotation or sample?

To help us identify the appropriate product and provide an accurate quotation, please supply as much information as possible, including:

Colour or product reference
Required finish and gloss level
Substrate
Interior or exterior use
Service environment
Required quantity
Delivery location
Any approval or performance requirements

You can contact Thermaset by telephone on 01827 55777, email sales@thermaset.co.uk, speak to your local technical sales representative or use the website enquiry form.

Choosing the Right Powder Coating Powder

10. How do I choose the right powder coating powder for my application?

Start by considering the substrate, whether the finished component will be used indoors or outdoors, its operating environment and the performance required from the coating.

Other considerations include colour, gloss level, texture, chemical exposure, weather resistance, flexibility and corrosion protection.

Different powder coating technologies provide different characteristics, so product selection should be based on the complete application rather than colour alone.

If you are unsure, Thermaset’s technical team can help you identify an appropriate powder coating system.

11. Which Thermaset powder coatings are suitable for exterior use?

Exterior suitability depends on the resin system and the specific product.

Exterior-grade polyester powder coatings are formulated to resist weathering and ultraviolet exposure.

Epoxy and many epoxy polyester products are normally intended for interior use because prolonged exposure to sunlight can result in chalking, fading and loss of gloss.

Always confirm exterior suitability using the relevant Technical Data Sheet.

More demanding architectural, coastal or high-UV environments may require an enhanced-durability system.

12. What is the difference between polyester and epoxy powder coating?

Polyester and epoxy powder coatings provide different performance characteristics.

Thermaset polyester powder coatings are designed for interior and exterior applications and provide excellent outdoor durability.

Thermaset epoxy powder coatings provide hard, durable protective finishes with excellent adhesion and chemical resistance. They are particularly suited to applications where long-term exposure to weathering and ultraviolet light is not expected.

The appropriate technology should therefore be selected according to the intended application and environment.

13. What materials can Thermaset powder coatings be applied to?

Powder coating is principally used on electrically conductive materials capable of tolerating the required curing temperature.

Common substrates include:

Mild steel
Galvanised steel
Aluminium
Stainless steel
Cast iron
Magnesium and zinc-based alloys, subject to assessment

The correct cleaning, pretreatment, primer and curing conditions depend on the substrate and its intended environment.

14. Can Thermaset powder coating be applied to aluminium?

Yes. Aluminium can be powder coated provided the appropriate preparation and coating system is used.

Suitable cleaning and conversion pretreatment are particularly important where aluminium will be used for exterior architectural applications.

The required coating system should be selected according to the substrate, environment and required performance.

15. Can Thermaset powder coating be applied to mild steel?

Yes. Mild steel is commonly powder coated but requires thorough cleaning and appropriate surface preparation.

A chemical or mechanical pretreatment will normally be required, while a primer may be recommended where increased corrosion protection is needed.

The powder topcoat alone should not be expected to compensate for inadequate substrate preparation.

16. Can Thermaset powder coating be applied over galvanised steel?

Yes, but galvanised steel requires careful preparation.

Oils, storage stains, oxidation, passivation residues and other contamination must be removed, and a suitable pretreatment will normally be required.

Galvanised substrates can release trapped gases during curing, potentially resulting in pinholes or bubbles. Preheating, degassing and an appropriate anti-gassing primer or powder may therefore be required.

Trial panels are strongly recommended.

17. What gloss levels and powder coating finishes are available?

Depending on the range and colour, Thermaset powder coatings are available in gloss, semi-gloss and matt finishes.

Fine textures, ripples and selected special effects are also available.

The final appearance can be influenced by substrate condition, film thickness, curing conditions, application settings and viewing angle.

Approved production samples are recommended where appearance is critical.

18. How much coverage should I expect from 1kg of powder coating powder?

Theoretical coverage depends primarily on the powder’s specific gravity and the applied film thickness.

Actual powder consumption can also be affected by component shape, transfer efficiency, reclaim arrangements, overspray, colour, application equipment settings and variations in film thickness.

For accurate production planning, theoretical coverage should therefore be considered alongside the efficiency of the actual coating process.

Applying & Curing Thermaset Powder Coatings

19. What curing temperature and time does Thermaset powder coating require?

Curing requirements vary by product, so always follow the product label and relevant Technical Data Sheet.

Importantly, the stated curing time normally begins when the component itself reaches the specified peak metal temperature, rather than when the component first enters the oven.

A typical polyester schedule might be 10 minutes at 180°C peak metal temperature, but this must not be assumed for every product.

Always use the curing specification supplied for the individual powder coating.

20. Does powder coating require a primer?

Not every application requires a primer.

The requirement depends on the substrate, pretreatment, coating system, service environment and required lifespan.

A suitable primer can improve properties such as corrosion protection, adhesion, edge coverage or resistance to outgassing.

Primers are commonly considered for steelwork, coastal or aggressive environments, porous substrates and projects requiring enhanced durability.

The complete coating system should be specified and tested together.

21. What pretreatment is required before using powder coating?

Pretreatment should be selected according to the substrate, contamination, service environment and required performance.

Typical systems can include:

Iron or zinc phosphate for ferrous substrates
Suitable conversion pretreatment for aluminium
Appropriate multistage treatment for galvanised steel
Cleaning, degreasing or mechanical preparation for stainless steel

Pretreatment is a specialist process. Consult the relevant chemical supplier and Thermaset’s technical team when specifying a complete system.

22. Can Thermaset powder coatings be recoated?

Many powder coatings can be recoated, but compatibility and adhesion should be established first.

The original coating should be fully cured, clean, dry and free from oils or other contamination. Light abrasion may be required to create a suitable mechanical key.

Recoatability varies between products, particularly with highly cross-linked, low-friction or special-effect finishes.

Always test the proposed system before moving to full production.

23. How should a finished powder coating be tested?

Testing should reflect the product specification and end-use requirements.

Typical checks can include:

Visual appearance
Colour and gloss
Dry-film thickness
Cure
Cross-cut adhesion
Impact or flexibility
Hardness
Chemical resistance
Corrosion or accelerated weathering where required

Test methods, conditioning time, film thickness, substrate and acceptance criteria should be agreed before production.

Laboratory test results should not automatically be treated as guarantees of performance in service.

Powder Coating Powder Technical & Troubleshooting FAQs

24. What can cause powder coating to peel or have poor adhesion?

Peeling or poor adhesion can indicate a loss of adhesion between the coating and substrate or between individual coating layers.

Possible causes include:

Oil, grease, rust or other contamination
Inadequate cleaning or pretreatment
Incorrect pretreatment chemistry
Under-curing or excessive curing
Moisture or chemical residues
An incompatible primer or previous coating
Excessive delay or contamination between coats

Check that the substrate was completely clean and dry, that the pretreatment process was correctly controlled and that the component achieved the specified peak metal temperature for the full curing time.

25. What causes pinholing or outgassing in powder coating?

Pinholes can form when air, moisture or gas escapes through the coating during melting and curing.

This can occur with porous castings, galvanised steel, flame-cut edges and substrates containing trapped contamination.

Possible remedies include preheating or degassing the component, improving cleaning and drying, controlling film thickness, using an appropriate anti-gassing product and adjusting the cure profile.

Trial processing is recommended.

26. What causes uneven colour or gloss in powder coating?

A number of factors can contribute to variations in colour or gloss, including:

Uneven film thickness
Variable peak metal temperature
Inconsistent curing time
Poor powder fluidisation
Gun-setting or application variation
Contamination or incompatible powder
Variations between batches
Substrate or pretreatment differences
Reclaim-powder imbalance
Different viewing angles with metallic finishes

Components that will be viewed together should ideally be coated using the same batch under consistent application and curing conditions.

27. What are common causes of powder coating failures?

Powder coating performance can be affected by a number of application and process issues.

Common causes include:

The metal not reaching the specified curing temperature
The required time at temperature not being achieved
Variations in oven temperature or line speed
Film thickness outside the recommended range
The wrong test method or acceptance criterion being used
Ineffective or inappropriate pretreatment

When investigating a coating failure, the complete preparation, application and curing process should be reviewed.

28. What causes poor edge coverage with powder coating?

During curing, molten powder can flow away from sharp edges, resulting in a thinner coating film and potentially reducing corrosion protection.

The problem can be made worse by:

Very sharp or poorly prepared edges
Inadequate film build
Incorrect electrostatic settings
Faraday-cage effects
Unsuitable product selection
Excessive flow during cure

Rounding or dressing edges, optimising application settings and using an edge-coverage primer such as Thermaprime EEP 140 can improve protection.

The complete system should be validated for the intended environment.

29. How can corrosion develop underneath powder coating?

Under-film corrosion normally begins where moisture and contaminants are able to reach the substrate through damage, thin areas, exposed edges, welds or preparation defects.

Contributing factors can include inadequate pretreatment, poor rinsing, contamination, insufficient corrosion-protection systems, porous welds, low film thickness and damage after coating.

Salt and other aggressive environments can accelerate corrosion.

Powder coating should therefore be specified as part of a complete preparation, pretreatment, primer and topcoat system where appropriate.

30. What preparation is required before powder coating galvanised steel?

Galvanised steel should be assessed for oils, oxidation, white rust, passivation treatments, surface defects and trapped gases before powder coating.

A typical process can include:

Cleaning and degreasing
Removing oxidation and unsuitable residues
Applying an appropriate pretreatment
Thorough rinsing and drying
Degassing or preheating where required
Applying a compatible powder or anti-gassing system such as AGP 135
Curing to the specified peak metal temperature

The precise process depends on the type, age and condition of the galvanising.

31. How should Thermaset powder coating powder be stored?

Powder coating should be stored in its original sealed packaging in a cool, dry location away from direct sunlight, heat, moisture and contamination.

Many Thermaset products specify storage below 25°C, but always check the relevant Technical Data Sheet because shelf life and storage requirements can vary by product.

Reseal opened boxes carefully.

Cold powder should also be allowed to reach application-room temperature before opening to help prevent condensation.

Use older stock first and keep different products and batches correctly identified and separated.

Need Help Choosing a Powder Coating Powder?

If you’re unsure which Thermaset powder coating powder is right for your application, our team can help you identify an appropriate product based on your substrate, environment, colour, finish and performance requirements.

Browse our powder coating powders online or contact Thermaset for product and technical advice.