Waterborne coating is an effective method for reducing VOC emissions and odors.
Electrostatic coating uses electrical forces to attract coating material to the workpiece and improve transfer efficiency.

Waterborne electrostatic coating combines these two methods.

Use waterborne coating to improve environmental performance.
Use electrostatic coating to reduce coating material losses.
This combination looks attractive to factories.

However, waterborne electrostatic coating has an important point of caution.

The key point is that water readily conducts electricity.

If waterborne coatings are used for electrostatic application in the same way as solvent-based coatings, high voltage may leak into the coating material supply system, equipment may become unstable, and safety risks may increase.

Waterborne electrostatic coating requires design that encompasses not only coating selection but also coating material tanks, hoses, pumps, guns, booths, grounding, insulation, and safety procedures.

1. What is waterborne electrostatic coating?

Waterborne electrostatic coating is a method of applying waterborne coatings using electrostatic application.

Waterborne coatings use water as the main medium, making it easier to reduce VOC emissions compared with solvent-based coatings.
Electrostatic coating improves transfer efficiency by charging coating particles and attracting them to a grounded workpiece.

Combining these methods can provide the following benefits.

• Reduced VOC emissions
• Reduced odors
• Reduced coating material losses
• An improved working environment
• Improved environmental performance
• Improved transfer efficiency
• Reduced mist
• Reduced coating material consumption

However, waterborne electrostatic coating can make equipment and safety management more difficult than either ordinary waterborne coating or ordinary electrostatic coating.

This is because waterborne coating materials readily conduct electricity.

2. Water readily conducts electricity

Waterborne coatings use water as the main medium.
Water itself and substances contained in it may readily conduct electricity.

Electrostatic coating uses high voltage to charge coating particles.
However, if the waterborne coating material readily conducts electricity, high voltage may leak into the coating material supply system.

For example, the following components and areas are involved.

• Coating material tanks
• Coating material hoses
• Pumps
• Piping
• Valves
• The gun body
• The coating material circulation system
• Parts that operators touch
• Cleaning water
• Moisture inside the booth

In other words, examining only the gun tip is insufficient for waterborne electrostatic coating.
The electrical arrangement of the entire coating material supply system must be considered.

3. High-voltage leakage destabilizes the electrostatic effect

Because waterborne coating material readily conducts electricity, high voltage may leak in an unintended direction.
This can be understood as high-voltage leakage.

High-voltage leakage leads to the following problems.

• A weaker electrostatic effect
• Transfer efficiency falls
• Film thickness is unstable.
• Gun voltage is unstable.
• The equipment shuts down abnormally.
• The risk of sparking increases.
• Safety risks to operators increase.
• Coating conditions become less reproducible.

Increasing voltage in this situation does not address the underlying problem.
It may instead increase safety risks.

In waterborne electrostatic coating, insulation must be checked before increasing voltage.

4. What is insulation?

Insulation prevents electricity from flowing in unwanted directions.

In waterborne electrostatic coating, equipment must be properly insulated to prevent high voltage from leaking into the coating material supply system or toward operators.

Typical parts and areas requiring insulation include the following.

• Coating material tanks
• Coating material supply hoses
• Pumps
• Piping
• Guns
• The coating material circulation system
• The location where coating material supply equipment is installed
• Connections used during cleaning
• Parts that operators may touch

Waterborne electrostatic coating requires measures such as placing coating material supply equipment on an insulating stand, using dedicated insulating hoses, and adopting the safety structures recommended by the equipment manufacturer.

It is important not to make casual modifications based on shop-floor judgment alone.

Equipment handling high voltage must be designed appropriately after checking manufacturer specifications, safety standards, and shop-floor operation.

5. Grounding and insulation serve different purposes

Grounding is important in electrostatic coating.
Reliably grounding the workpiece attracts charged coating material to it.

Insulation is also important in waterborne electrostatic coating.

The different roles of grounding and insulation can easily cause confusion.

Grounding is a way to safely discharge electricity.
Insulation is a way to prevent electricity from leaking into unwanted locations.

Waterborne electrostatic coating requires the following approach.

• Reliably ground workpieces and jigs.
• Insulate the coating material supply system where necessary.
• Design parts that operators touch for safety.
• Prevent high voltage from flowing along unintended paths.

Confusing the parts that require grounding with those that require insulation can cause quality defects and safety risks.

6. Control of coating material tanks and supply systems is important

Control of coating material tanks and supply systems is important in waterborne electrostatic coating.

Parts that rarely caused problems in solvent-based electrostatic coating may require electrical control when waterborne coatings are used.

Check the following items.

• Coating material tank material
• Tank installation conditions
• Presence of an insulating stand
• Hose material
• Hose deterioration
• Pump specifications
• Insulation of circulation piping
• Valve and fitting materials
• Connection conditions during cleaning
• Parts that operators may touch

Safety measures are essential, particularly if the coating material supply system is configured in a way that exposes it to high voltage.

Changing the gun alone does not complete a conversion to waterborne electrostatic coating.
The entire coating material supply system must be checked.

7. Cleaning work also requires care in waterborne electrostatic coating

Waterborne coatings can sometimes be cleaned with water.
This may lead people to assume that cleaning will be simple.

However, cleaning work also requires care in waterborne electrostatic coating.

Cleaning involves high-voltage equipment, the coating material supply system, water, and operators, making unclear procedures dangerous.

Check the following items.

• Is high voltage shut off before cleaning?
• Are measures in place to deal with residual charge?
• Has pressure been released?
• Could cleaning water create an electrical path?
• Do operators understand the insulation conditions?
• Are there safe procedures for dismantling the gun?
• Are connections checked after cleaning and reconnection?
• Has a method for treating cleaning wastewater been established?

Cleaning must also be covered by SOPs in waterborne electrostatic coating.
The assumption that cleaning is simple because water can be used is dangerous.

8. Check moisture and humidity inside the booth

The booth environment is also important in waterborne electrostatic coating.

Moisture affects drying in waterborne coating.
Humidity and moisture may affect electrical stability in electrostatic coating.

The following items therefore need to be checked in waterborne electrostatic coating.

• Humidity inside the booth
• Temperature inside the booth
• Balance between supply and exhaust air
• How airflow strikes the coating surface
• Moisture accumulation
• Mist accumulation
• Booth cleanliness
• Management of booth water and wastewater
• Water on insulated parts
• Presence of condensation

Excessive humidity can cause not only drying defects but also an unstable electrostatic effect.
Temperature and humidity control is particularly important during Vietnam’s rainy season.

9. Common problems in waterborne electrostatic coating

The following problems may occur in waterborne electrostatic coating.

Quality defects and safety risks can occur simultaneously in waterborne electrostatic coating.
When a defect occurs, it is therefore necessary to check electrical conditions, water, equipment, and operating procedures alongside the coating material.

10. What to check before introduction

Check the following items before introducing waterborne electrostatic coating.

1. Is the coating material suitable for waterborne electrostatic application?

Not every waterborne coating is suitable for electrostatic application.
Confirm suitability with the coating manufacturer.

2. Is coating material resistance appropriate?

Check whether the coating material has the electrical properties required for electrostatic application.

3. Can the coating material supply system be insulated?

Check the configuration of the tank, hoses, pump, piping, and gun.

4. Are the workpiece and jigs reliably grounded?

Insufficient grounding makes both electrostatic performance and safety unstable.

5. Can the booth and drying oven accommodate the process?

Drying control is important in waterborne coating.
Check flash-off, temperature and humidity, and drying oven capacity.

6. Can cleaning and wastewater treatment be handled?

Check in advance how cleaning water and wastewater will be treated.

7. Can operators be trained?

Waterborne electrostatic coating requires operators who understand the safety procedures.

8. Does the arrangement meet equipment manufacturer specifications?

Manufacturer specifications must be checked for the electrostatic equipment, supply unit, hoses, and gun.

Waterborne electrostatic coating may require equipment installation, safety design, and changes to working standards, as well as a change of coating material.

11. What to teach operators

Operator training is particularly important in waterborne electrostatic coating.

Shop-floor personnel need to understand the following points.

• Waterborne coating materials may readily conduct electricity.
• High voltage may leak into the coating material supply system.
• Grounding and insulation serve different purposes.
• Always shut off high voltage before cleaning.
• Do not modify equipment on your own judgment.
• Deteriorated hoses and piping create safety risks.
• Booth humidity and moisture also affect quality.
• When a defect occurs, check insulation as well as voltage.

If operators do not understand the principles, they may take dangerous actions.

For example, increasing voltage because coating material is not attaching well.
Grounding a component because the equipment is unstable.
Skipping power shutdown during cleaning.
Underestimating hose deterioration.

These actions affect safety as well as quality.

Training and SOPs are essential in waterborne electrostatic coating.

12. A practical checking sequence for the shop floor

If quality defects or equipment instability occur in waterborne electrostatic coating, checking in the following order helps organize the causes.

1. Identify the type of defect.

Is film thickness insufficient?
Is deposition poor?
Is there sparking?
Has the equipment stopped?
Is drying inadequate?
First, distinguish the symptoms.

2. Examine voltage and current.

Check the settings and their actual stability.

3. Examine the possibility of high-voltage leakage.

Check the coating material supply system, hoses, tank, pump, humidity, and insulated parts.

4. Check coating material resistance.

Check whether the coating material is in a condition suitable for waterborne electrostatic application.

5. Check grounding.

Check the grounding of the workpiece, jigs, and hangers.

6. Check insulation.

Check whether water or dirt is creating electrical continuity in parts that should be insulated.

7. Check the booth environment.

Check temperature, humidity, airflow, condensation, and mist accumulation.

8. Check drying conditions.

Check flash-off, the drying oven, actual product temperature, and film thickness.

9. Check cleaning procedures.

Check power shutdown, pressure release, cleaning water, wastewater, and safety checks.

Waterborne electrostatic coating thus requires examining electricity, water, drying, and safety together.

13. Directions for improvement

The following approaches are important for stabilizing waterborne electrostatic coating.

Check coating material suitability.

Confirm with the coating manufacturer whether the waterborne coating supports electrostatic application.

Control coating material resistance.

Check resistance after thinning and establish a control range.

Design supply system insulation.

Configure the tank, hoses, pump, piping, and area around the gun to meet equipment manufacturer specifications.

Standardize grounding.

Include workpiece and jig grounding checks in daily inspections.

Create a cleaning SOP.

Document procedures through high-voltage shutdown, pressure release, wastewater treatment, and reconnection checks.

Record temperature and humidity.

Make the relationship between temperature and humidity, drying defects, and electrostatic instability visible.

Train operators.

Teach the principles and risks of waterborne electrostatic coating in language the shop floor can understand.

Schedule regular safety inspections.

Regularly inspect hose deterioration, dirt on insulated parts, moisture, leaks, and grounding.

14. How CoatureVietnam can help

CoatureVietnam examines waterborne electrostatic coating, including equipment, safety, and drying as well as coating materials.

The following support is available.

Checking the applicability of waterborne coatings

Check waterborne coating suitability for the application, substrate, coating method, and drying conditions.

Checking electrostatic suitability

Check coating material resistance, thinning conditions, voltage, and transfer efficiency.

Checking insulation and grounding

Check supply system insulation, workpiece grounding, and jig condition.

Checking booths and drying ovens

Check temperature and humidity, air velocity, flash-off, and drying oven conditions.

Creating safety SOPs

Standardize cleaning, power shutdown, pressure release, equipment inspection, and response to abnormalities.

Operator training

Teach the basics of waterborne electrostatic coating, safety risks, and daily inspection items.

Supporting equipment introduction and improvement

Support process design encompassing coating material tanks, hoses, pumps, guns, booths, and drying ovens.

15. Summary: Consider environmental performance and safety design together in waterborne electrostatic coating

Waterborne electrostatic coating can potentially combine reduced VOC emissions with improved transfer efficiency.
It is an effective option for factories seeking better environmental performance, lower odors, and reduced coating material losses.

However, waterborne electrostatic coating must be based on an understanding that water readily conducts electricity.

Handling it in the same way as solvent-based electrostatic coating may cause high-voltage leakage, unstable electrostatic performance, equipment abnormalities, and safety risks.

The basic items to check in waterborne electrostatic coating are as follows.

• Coating material resistance
• Insulation of the coating material supply system
• Workpiece and jig grounding
• High-voltage leakage
• Booth temperature and humidity
• Flash-off
• Drying oven conditions
• Cleaning SOPs
• Operator safety training
• Wastewater treatment

Waterborne electrostatic coating is an environmentally friendly method.
However, without safety design, it does not show care for operators.

Coating the Future with Science and Care

Science means controlling the electrical properties of waterborne coatings, insulation, grounding, and drying conditions through measurements and systems.
Care means establishing a process in which operators can work safely and with confidence while environmental performance improves.

CoatureVietnam examines waterborne electrostatic coating as a process encompassing equipment, safety, drying, wastewater, and working standards as well as coating changes, and supports improvements suited to the shop floor.

Related articles

• Why is drying control difficult in waterborne coating?
• Switching to waterborne coating requires attention to color matching and metamerism
• Increasing voltage is not necessarily better in electrostatic coating
• Material resistance and thinner selection determine the electrostatic coating finish
• Coating method selection checklist — Product shape, production volume and quality requirements