Using electrostatics to spray waterborne paint

The benefits of electrostatics are well known to industrial finishing experts. Compared to conventional spraying, the electrostatic effect can bring:

• Higher transfer efficiency - more paint is attracted to and wraps around the grounded part.
• Less environmental impact – as transfer efficiency increases, paint waste decreases. This subsequently lowers volatile organic compound (VOC) and hazardous air pollutant (HAP) levels.
• Lower manufacturing costs – in addition to material savings from wasting less paint, you also have a cleaner spray booth with fewer filter changes.

More manufacturers worldwide are using waterborne coatings because of regulatory or environmental concerns, and the growing sophistication of waterborne materials.

The demand for waterborne material continues to grow. Valued at $78 billion in 2021, the global waterborne coatings market is expected to reach $105 billion by 2026.

Using electrostatics to spray waterborne material requires different equipment than what is used to spray solvent-based paint.  The equipment you choose depends on how you charge your material, giving it the proper electrostatic effect.

Waterborne coatings can be charged externally or internally.

External charging uses an external probe to charge waterborne material as it exits the spray gun. This allows material in the hose, pump and gun to remain grounded. Beyond a spray gun with an external probe, externally charging requires no additional special equipment.

External charge electrostatic spray guns are frequently used in auto-feeder, high volume, complex or large circulation systems. Although an external charge system provides good quality at its price point, it has lower transfer efficiency than a direct charge system.

Direct charging connects an electrostatic spray gun to an isolation cabinet or system. Waterborne material is charged and contained within the cabinet. A pump inside the isolation unit moves the charged paint to a spray gun that is attached directly to the system.

Direct charge isolation batch systems produce a higher transfer efficiency than external charge electrostatic spray guns. However, the capacity of some batch systems can be limited.

For example, Graco’s WB 100 and WB 3000 systems isolate charged paint in a cabinet with a pump and five-gallon pail inside. When the pail needs refilling or it is time to change colours, the entire system has to be discharged or shut down before an operator can open the cabinet to take out the container and put in a new batch of waterborne paint. 

This makes the simple systems well suited for job shops that spray a low number of large metal parts like axles, engines, escalator parts, or large garbage bins.

In contrast, Graco’s HydroShield has greater capacity. The container inside the isolating cabinet refills itself from a supply source every time the gun is de-triggered, so there is no need to shut down the entire system. This refill-upon-de-triggering capability makes HydroShield well suited for production rates greater than five gallons, for example, at Tier 1 or Tier 2 automotive suppliers.

Another advantage of the HydroShield is its advanced display module. The controller interface allows users to select spray functions, stay informed of the system status and set up a maintenance schedule.  This makes HydroShield ideal for circulation paint delivery systems, such as conveyor lines.

With the correct equipment selection, manufacturers can achieve good results when using electrostatics to spray waterborne material.

• External charge electrostatic spray guns require the least amount of special equipment.
• Direct charge isolation batch systems produce better transfer efficiency.

To determine what works best for your business, consult your local finishing equipment distributor or Graco representative. Not sure who that is? Find out.

^{References: Waterborne Coatings Market - Global Outlook and Forecast 2021–2026 https://www.arizton.com/market-reports/waterborne-coatings-market}