How Does Electrostatic Spray Painting Equipment Work?

Electrostatic spraying is a coating method that uses a spray gun to positively charge electric particles while the workpiece is grounded, or negatively charged. The process delivers high transfer efficiency, reduces costs, and can improve environmental performance. The advantages of electrostatic spray painting make it a popular application choice for paint shops. Here we explore the process, its benefits and its disadvantages in more detail.

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How Does It Work?

Electrostatic spraying works on the principle that:

• Particles with a negative charge attract particles with a positive charge.
• Particles with a positive charge repel other particles with a positive charge.

The Electrostatic Process

A positively charged electron within the spray nozzle charges the paint particles. Because these particles all have a positive charge, they repel each other and break apart, resulting in a fine mist that coats evenly. There is also a magnetic effect. The negative charge of the workpiece attracts the positive charge of the paint particles across its full surface. Once coated to a certain depth, the workpiece stops attracting paint particles because the negative charge is too weak. This results in an even finish.

The "Wrap-Around" Effect

Paint particles with a positive charge 'seek out' uncoated surfaces with a negative charge. This means that the backs and sides of a workpiece draw paint toward them once the front side is coated.

What Are the Advantages of Electrostatic Spray Painting?

Electrostatic technology has three distinct advantages over conventional air spray and HVLP guns:

Superior quality coating with a faster production time

Electrostatic sprayers create a flawless and durable finish that dries quickly. Unlike brushes, rollers and other types of sprayer, they can also reach corners, crevices and the backsides of surfaces. This reduces production time, especially when spraying tubular products.

Low VOC emissions

VOCs are chemicals found in paints to:

• Preserve them
• Enhance their flow
• Create specialist properties such as resistance to corrosion

During the paint application process, VOCs evaporate and are released into the air as gases.

VOC levels and the law

High VOC exposure can have serious effects on human health and on the environment. For this reason, industrial paint shops must comply with:

• Control of Substances Hazardous to Health (COSHH) Regulations
• Volatile Organic Compounds VOC in Paints, Varnishes and Vehicle Refinishing Products Regulations :
• The Solvent Emissions (England and Wales) Regulations , SI 107
• Environmental Permitting (England and Wales) Regulations SI 675

For further details on these Regulations and how to comply, visit the HSE, British Coating Federation and UK Government websites.

Electrostatic spray painting and VOCs

The Solvent Emissions (England and Wales) Regulations , SI 107 requires that you inform your local authority and apply for a permit if you consume more than 5 tonnes of VOCs per annum. Permits cost almost œ2K p/a and failure to comply can result in hefty fines and litigation. The high transfer efficiency of electrostatic spraying can help you to comply with VOC limits by reducing:

• The number of VOC-containing products that you consume
• Your VOC emissions
• The volume of hazardous waste that you produce

Cost Savings 

Electrostatic sprayers have a high transfer efficiency of up to 90%, resulting in less:

• Paint wastage
• Clean-up and associated cleaning product and labour costs
• Spending on the disposal of hazardous waste

This is because:

1. The "wrap-around" effect makes use of spray that would ordinarily be lost as overspray.
2. Electrostatic sprayers don't need air pressure to atomise paint particles. Conventional sprayers do rely on air pressure, which creates more spatter and overspray.

Are There Any Disadvantages?

When considering adopting a new application process it's important to assess the disadvantages too. To help you do that, here's a summary of the three common disadvantages and their implications:

Link to Aohai Coating Equipment

Set-up cost

Compared to other application methods, the purchase and set-up costs of electrostatic spray painting are high. However, with reduced labour and material costs, the return on investment is greater than for other types of application.

Training the workforce

You will need to train your sprayers to use the new equipment and to maintain and clean it correctly. However, painting electrostatically will save your team time, turning training costs into savings.

The Faraday Cage Effect

An electrostatic spray gun can struggle to coat deeply recessed workpieces, such as metal lockers. This is because the paint is attracted toward the nearest negatively charged surface, which in this case, is the sides of the locker. To overcome this, spray the recess with an airless gun and then finish electrostatically.

Conclusion

The advantages of electrostatic spray painting make it an ideal application method for paint shops that want to:

• Produce a superior finish
• Reduce production costs
• Improve their environmental performance

What Is Electrostatic Painting?

Electrostatic painting is the process of charging particles in paint to more efficiently paint a work piece.

When a powerful electric charge is added to atomized paint, a significant increase in paint is added to the part. This is called improved transfer efficiency. In general this means, more paint on the part and less paint going to waste.

How Do You Measure Transfer Efficiency?

Transfer efficiency can be measured in a number of ways:

• Savings in paint cost 
  • More paint on the part, means less paint used in the process.
  • When paint consumption goes down, initial cost of purchasing paint also goes down.
    
• Less hazardous material after process is completed
  • Less paint equals less Volatile Organic Compounds (VOCs) and Hazardous Air Pollutants (HAPs) emitted into the environment, potentially decreasing permitting issues.
  • Less VOCs and HAPs lead to a greener work environment.

How Does Electrostatic Spray Painting Work?

Think grade school science. Remember protons, neutrons and electrons? All matter contains charged particles.

• Positively charged particles have more protons than electrons.
• Negatively charged particles have more electrons than protons.
• Particles with equal amount of protons and electrons are neutral.
  

Now, think about magnets. When you try to put the north or south poles of magnets together, they will naturally repel. However, if you align the north and south poles together, they will attract. The same is true for protons, electrons and neutrons.

Like charges repel, while unlike charges attract. Therefore, if we put a powerful electrical charge on atomized paint by passing the paint through a field of electrons and project it towards grounded object (or it has a neutral electrical condition), then we have created an environment that results in a natural electrical attraction between electrons and neutrons. This results in more paint being applied to the target.

Any Tips on Painting Parts with Electrostatic Spray Guns?

When using electric applicators, remember these important tips:

• Don’t be too close!
  If the gun and the part are too close together, the gun and the part become electrically connected, providing a direct ground directly to the gun. This results in no electrostatic transfer efficiency improvements
• Or too far away!
  If the gun is too far away, the charged particles will seek out other closer grounds. Generally, this is the one operating the gun. This tends to put more paint on the operator, than on the part.
• Avoid the Faraday cage effect  
  When you're trying to paint into corners, charged paint tends to go towards the closest ground, which isn’t the corner. This is known as the Faraday cage effect. In order to avoid this, it is easiest to be able lower the voltage or remove the voltage on the gun until this part of the painting process is finished.
• Always stay grounded
  Grounding is an important factor when painting with electrostatics. Keep part hooks and ground hooks clean and free of overspray. These connection points play a vital role in setting up the natural attraction of electrons  and neutrons.

Why Paint with Electrostatics?

Painting with electrostatics leads to process improvements in painting operations, ranging from automotive and aerospace to various applications that involve solvent and water-based paints.

Using electrostatics can increase productivity, reduce paint overspray, and minimize paint usage. 

Are you interested in learning more about Electrostatic Spray Painting Equipment(pt,th,tr)? Contact us today to secure an expert consultation!