Powder coating attracts attention for its potential to reduce VOCs and recover coating material.

Because it does not use solvent, it may reduce odors and VOCs.
If recovered powder can be reused, it can also reduce coating material losses.

Factories with existing liquid coating lines therefore sometimes raise the following questions.

“Can our existing liquid coating booth also be used for powder coating?”
“Can we share the existing booth without buying a new powder booth?”
“Since this is only a trial, can we use our current booth?”

Wanting to limit equipment investment is understandable.
However, using a liquid coating booth for powder coating without modification requires care.

Although both are coating processes, liquid and powder coating place very different demands on equipment.

In liquid coating, the main control items are coating mist, solvents, VOCs, booth water, filters, and exhaust.
In powder coating, dust, static electricity, powder recovery, filters, cleanability, color changes, and baking conditions are important.

Equipment conditions must therefore always be checked before using a liquid coating booth for powder coating as well.

1. Liquid and powder coating use different forms of coating material

In liquid coating, the material is a liquid.
A spray gun atomizes it, and it attaches to the workpiece as fine mist.

In powder coating, the material is a powder.
It is charged electrostatically and deposited on the workpiece.
It is then melted and cured in a baking oven to form a coating film.

This is a particularly significant difference.

Liquid coating requires consideration of how to treat mist and solvent.
Powder coating requires consideration of how to recover dispersed powder and prevent dust from escaping.

This difference must first be understood before powder coating is performed in a liquid coating booth.

2. Dust control is important in powder coating

In powder coating, coating powder becomes airborne.

Powder that does not attach to the workpiece disperses inside the booth.
Without appropriate extraction and recovery, it causes working environment and quality problems.

Poor dust control causes the following problems.

• Operators are more likely to inhale dust.
• Powder spreads through the factory.
• Powder attaches to products in other processes.
• The previous color remains during color changes.
• The booth becomes contaminated.
• Dust escapes through the exhaust outlet.
• External complaints occur.
• Filters clog quickly.

Powder coating cannot simply be considered safe because VOC levels are low.
Stable powder coating requires proper dust control.

3. Liquid coating booth filters may not capture powder

Liquid coating booths use filters to capture coating mist.
However, those filters are not necessarily suitable for powder coating.

Powder coating particles differ from liquid mist.
They are fine, dry, and readily become airborne.

Using liquid coating filters without modification may cause the following problems.

• Powder is not captured sufficiently.
• Filters clog quickly.
• Powder passes through to the exhaust side.
• Captured material cannot be used as recovered powder.
• Dust concentration inside the booth increases.
• The cleaning burden increases.

Powder coating may require powder-specific recovery equipment or filter systems.

Even when trials are performed in an existing booth, powder capture performance, filter specifications, and dust in the exhaust must be checked.

4. Take particular care when sharing a wet booth

If a wet booth is used for liquid coating, particular care is required before sharing it with powder coating.

A wet booth captures liquid coating mist with water.
Powder coating, by contrast, is generally based on recovering powder in a dry state.

If powder coating material contacts water, recovery and reuse become difficult.
If it absorbs moisture, its flowability also deteriorates and may cause coating defects.

The following problems may occur when powder coating is performed in a wet booth.

• Powder absorbs moisture and clumps.
• It cannot be used as recovered powder.
• Powder attaches more readily inside the booth.
• Cleaning is difficult.
• Sludge-like contamination develops.
• Humidity affects powder coating quality.

It is safer not to assume that a wet booth is suitable for powder coating as it stands.

5. Recovered powder control is important in powder coating

A major feature of powder coating is that powder not deposited on the workpiece can sometimes be recovered and reused.

This is a significant benefit for reducing coating material losses.

However, using recovered powder requires control.

• Is dirt present?
• Have other colors mixed in?
• Has the powder absorbed moisture?
• Has particle size distribution changed?
• Is the mixing ratio with fresh powder appropriate?
• Is appearance quality stable when recovered powder is used?
• Has residual powder from a previous color change mixed in?

When repurposing a liquid coating booth, check whether its structure allows recovered powder to be managed with adequate quality.

Even if recovery appears possible, foreign matter or moisture contamination causes quality defects.

6. Ease of cleaning during color changes is important

Cleaning during color changes is particularly important in powder coating.

If powder from the previous color remains in the booth, it contaminates the next color.
For white, black, metallic, and vivid colors in particular, even small amounts of contamination may cause appearance defects.

A liquid coating booth may not have been designed for cleaning between powder color changes.

Powder tends to remain in the following locations.

• Booth corners
• Around filters
• Inside ducts
• The floor
• Steps and ledges on walls
• Around lighting
• Openings
• Around fans
• Jig storage areas

An easily cleaned structure is particularly important in powder coating.

Even for trials, if color changes are required, cleaning time and the risk of color contamination must be checked.

7. Electrostatic coating grounding checks are necessary

Powder coating uses static electricity to deposit powder on the workpiece.

Grounding of workpieces, jigs, and hangers is therefore important.

Poor grounding makes powder deposition difficult.
It causes uneven film thickness and reduced transfer efficiency.
Unstable static electricity also creates safety risks.

Check the following items.

• Is the workpiece grounded?
• Do jigs and hangers provide electrical continuity?
• Has existing coating film or accumulated powder impaired conductivity?
• Is contact resistance measured?
• Are powder gun voltage conditions appropriate?
• Are static electricity measures for operators and equipment sufficient?

Even when a liquid coating booth is repurposed, electrostatic control must always be checked for powder coating.

8. Check dust explosion and fire risks

Powder coating involves dust.

Depending on the coating powder type, concentration, and airborne condition, dust explosion and fire risks must be considered.

Particular care is needed when substantial airborne dust and ignition sources are present.

Check the following items.

• Powder coating safety data
• Dust concentration
• Exhaust and recovery capacity
• Static electricity control
• Explosion protection specifications
• Control of flames and ignition sources
• Electrical equipment specifications
• Cleanliness
• Presence of powder buildup

Because powder coating does not use solvent, solvent-related fire risks may decrease.
However, dust-related safety risks do not disappear.

Safety checks are essential when switching to powder coating.

9. Humidity affects powder coating quality

Coating powder can be affected by humidity.

Moisture absorption impairs powder flowability.
It may become difficult to discharge from the gun or readily form clumps.
Coating film appearance may also be affected.

Moisture or humidity may be present around liquid coating booths or wet booths.
Humidity control must therefore be checked when they are used for powder coating.

Check the following items.

• Humidity around the booth
• Dryness of the air supply
• Powder storage location
• Storage methods after opening
• Distance from wet equipment
• Presence of condensation
• Moisture in compressed air

In powder coating, it is important to keep the powder dry and in good condition.

10. Check baking oven conditions as well

In powder coating, the deposited powder is heated in a baking oven to melt and cure it.

When introducing powder coating, baking oven conditions must therefore be checked alongside the booth.

Check the following items.

• Powder coating baking temperature
• Baking time
• Temperature attained by the workpiece
• Workpiece material
• Workpiece weight
• Temperature distribution in the oven
• Conveyor speed
• Whether the existing oven can accommodate the process
• Contamination risks when sharing it with liquid coatings

Even if a liquid coating drying oven is available, it may not meet powder coating baking conditions.

In powder coating, it is important to check the booth and oven together.

11. Examine contamination risks when sharing liquid and powder coating equipment

When liquid and powder coating share the same equipment, contamination risks must be checked.

Mist or residual solvent from liquid coating may affect powder coating.
Powder dust may also enter liquid coatings.

Examples include the following problems.

• Powder attaches to liquid-coated surfaces.
• Residual liquid coating material mixes into powder.
• Color change defects occur.
• Insufficient booth cleaning creates foreign matter.
• Dirt inside filters or ducts becomes airborne again.
• Dirt inside the drying oven attaches to the film.

Shared use requires clear cleaning procedures, changeover procedures, and checking criteria.

Assuming that small quantities are harmless is risky.
Even small amounts of foreign matter or color contamination cause quality defects.

12. Common shared-use challenges in Vietnamese factories

Vietnamese factories sometimes consider repurposing existing equipment to limit investment.

This is a reasonable approach.
However, sharing a liquid coating booth with powder coating readily creates the following challenges.

Existing booth filters are unsuitable for powder.
Attempts are made to handle powder in a wet booth.
There is no powder recovery equipment.
Cleaning time for color changes has not been allowed for.
Grounding checks are insufficient.
Dust explosion and static electricity risks have not been checked.
Humidity control is insufficient.
Baking oven conditions have not been checked.
Contamination risks between powder and liquid coatings have not been examined.
The process works in trials but cannot be controlled in mass production.

Repurposing existing equipment is not necessarily a poor choice.
However, the conditions under which it can and cannot be repurposed must be identified.

13. Basic items to check before shared use

Before using a liquid coating booth for powder coating as well, check the following items.

1. Booth type

Is it dry or wet?
Is its structure suitable for powder coating?

2. Powder recovery

Are recovery equipment, filters, and recovered powder management methods available?

3. Exhaust

Does the structure prevent dust from escaping outside?

4. Cleanability

Can powder be completely removed during color changes?

5. Grounding

Is electrical continuity ensured for workpieces, jigs, and hangers?

6. Safety

Have dust explosion, static electricity, and fire risks been checked?

7. Humidity

Does the environment prevent coating powder from absorbing moisture?

8. Baking oven

Can it meet the powder coating baking conditions?

9. Contamination risks

Could liquid and powder coating materials contaminate one another?

10. Mass production suitability

Can the process operate consistently in mass production as well as in trials?

14. The value CoatureVietnam sees in assessing powder coating shared use

CoatureVietnam considers powder coating a strong option for environmental measures.

VOC reduction.
Coating material recovery.
High coating film performance.
Compatibility with automation.
An improved working environment.

It provides these benefits.

On the other hand, powder coating presents challenges in dust control, electrostatic control, baking ovens, color changes, and recovered powder management.

CoatureVietnam therefore does not simply recommend switching to powder when introducing powder coating.

Can the existing equipment accommodate it?
Is a new booth necessary?
Can the baking oven accommodate it?
Is dust control sufficient?
Can operators run it safely?
Does it meet quality requirements?
Will it actually be effective as an environmental measure?

CoatureVietnam checks these points before proposing the best approach.

This puts into practice the principle CoatureVietnam values:
“Coating the Future with Science and Care”.

Science means organizing the differences in equipment conditions between liquid and powder coating and checking dust, recovery, baking, grounding, and safety.
Care means creating a safe and stable coating process without causing shop-floor difficulties through unsuitable equipment reuse.

Conclusion

Careful checks are necessary before using a liquid coating booth for powder coating as well.

Even if the booths look similar, liquid and powder coating place very different demands on equipment.

Liquid coating requires attention to mist, solvents, VOCs, booth water, and exhaust.
Powder coating requires attention to dust, static electricity, recovered powder, filters, cleanability, baking ovens, and safety management.

Using existing equipment may be effective for limiting investment.
However, sharing it without checking conditions leads to dust dispersion, color contamination, poor recovery, inadequate baking, and safety risks.

Powder coating is attractive as an environmental measure.
That is why equipment, operation, and safety must be checked properly before introduction.

CoatureVietnam assesses powder coating introduction and use of existing equipment according to actual shop-floor conditions and proposes practical improvements without undue strain.