14th Oct 2026
Coating defects can affect the appearance, durability and protective performance of an industrial finish. They can also increase material waste, delay production and lead to costly rework.
Many defects are caused by problems with surface preparation, spray equipment, application technique or environmental conditions. Here, we look at four common coating defects and the steps operators can take to prevent them.
What causes industrial coating defects?
Producing a consistent coating requires the equipment, material, operator and spraying environment to work together.
Common causes of coating problems include:
- Incorrect spray pressure
- A blocked, worn or unsuitable spray tip
- Incorrect coating viscosity
- Poor spraying distance, angle or speed
- Uneven overlap between passes
- Excessive airflow
- Unsuitable temperature or humidity
- Incorrect film thickness
- Surface contamination
- Inadequate preparation
- Incorrect drying or overcoating times
Always check the coating manufacturer’s product data sheet before spraying. This should provide the recommended pressure, tip size, viscosity, film thickness and application conditions.
Four common coating defects
|
Defect |
What does it look like? |
Common causes |
Prevention and repair |
|
Poor gloss |
A dull, hazy or uneven finish |
Poor atomisation, incorrect viscosity, unsuitable thinner, thin coating, excessive airflow or unsuitable conditions |
Check the coating and equipment settings. Maintain an even film thickness and consistent spraying technique. Abrade, clean and recoat more serious defects. |
|
Dry spray |
A rough, dusty or granular surface |
Excessive pressure, gun held too far away, fast-evaporating thinner, high temperature or strong airflow |
Use the lowest pressure that achieves proper atomisation. Maintain the correct spraying distance. Abrade the rough surface, remove dust and recoat. |
|
Overspray |
Coating particles deposited beyond the target or on adjacent surfaces |
Excessive pressure, worn spray tip, wide fan pattern, poor gun angle or uncontrolled airflow |
Select the correct tip and fan width. Keep the gun perpendicular to the surface and replace worn tips. Remove settled material before recoating if necessary. |
|
Cracking |
Fine lines or deeper fractures in the coating |
Excessive film thickness, premature recoating, incompatible materials, incorrect curing or substrate movement |
Apply the specified film thickness and observe curing times. Remove cracked material back to a sound layer before preparing and recoating the surface. |
Poor gloss
Poor gloss can occur when coating droplets do not flow together to create a smooth, reflective film. This may be caused by poor atomisation, incorrect viscosity or coating that begins to dry before reaching the surface.
To reduce the risk, use the correct spray tip and pressure and maintain a consistent distance, speed and overlap. Check that the coating is mixed and thinned according to the manufacturer’s instructions.
Minor defects may sometimes be polished where the coating allows. More serious problems will usually require abrasion, cleaning and recoating.
Dry spray
Dry spray develops when coating droplets partially dry before reaching the component. The result is a rough or powdery finish.
Holding the gun too far away, using excessive atomising pressure or spraying in high temperatures can increase the risk. Strong airflow and an unsuitable thinner may also cause the coating to dry too quickly.
Use the lowest pressure that still produces a consistent spray pattern and maintain the recommended spraying distance. Affected areas should normally be abraded and cleaned before recoating.
Overspray
Overspray occurs when coating particles travel beyond the intended target or settle on nearby surfaces. Excessive overspray wastes material and can leave a rough deposit on finished areas.
Common causes include excessive pressure, a worn spray tip, an unsuitable fan width and poor triggering technique.
Operators should keep the gun perpendicular to the surface, use even passes and avoid spraying beyond the component’s edges. Worn tips should be replaced before the spray pattern deteriorates.
Coating cracking
Cracking can expose the substrate and reduce the coating system’s protective performance.
It is often caused by excessive film thickness, applying the next coat too soon or using incompatible materials. Incorrect mixing, rapid drying and movement of the substrate can also contribute.
Monitor wet film thickness during spraying and check dry film thickness after curing where required. Follow the coating manufacturer’s instructions for mixing, pot life, drying and overcoating intervals.
Cracked coating should be removed back to a sound layer or the substrate before the surface is prepared and recoated.
A simple coating-quality checklist
Before spraying
- Check that the surface is clean, dry and correctly prepared.
- Confirm the coating’s mixing and thinning requirements.
- Check temperature and humidity.
- Select the correct spray tip and pressure.
- Test the spray pattern.
During spraying
- Maintain a consistent distance, angle and speed.
- Use even overlap between passes.
- Monitor wet film thickness.
- Look for changes in the spray pattern.
After spraying
- Follow the correct drying and overcoating times.
- Inspect the finish between coats.
- Check dry film thickness where required.
- Record the settings and conditions used.
Improve coating consistency with the right equipment
Preventing common coating defects requires suitable equipment, correct setup, good surface preparation and consistent operator technique.
Airblast Eurospray Direct supplies industrial spraying equipment, spray tips, accessories and replacement components to help businesses achieve more reliable application and consistent coating quality.
Explore our industrial spraying range online or contact the Airblast team for help choosing the right equipment for your application.
