Liquid or powder electrostatic painting

Liquid or powder electrostatic painting Electrostatic painting - process features

Electrostatic painting is a technology when paint is applied to a surface using forces of interaction between point stationary electric charges (Coulomb force). Paints and varnishes (most often they are made on the basis of water, but there are also options with an organic solvent) are applied using a special spray gun.

For the first time, an electrostatic atomizer was used in 1941 by such an American inventor as G. Ransburg. The method will imply the use of electric fields along which the movement of charged particles of the paint and varnish material is carried out.

The liquid paint begins to interact with the electrode, which is located in the gun, and as a result of this, a high-voltage negative charge (from 60 to 100 kW) will be transferred to the paint.

Charged particles, leaving the nozzle of the spray gun, will be directed along the lines of the (electrostatic) field to the product, which is grounded and on which the paint and varnish material is applied.

Process technology

The torch for painting appears due to the mutual repulsion of charged particles from the paint and varnish material. An important difference of this technology from other methods will be the absence of the need for a colorful fog, because the particles are directed along the lines that were set earlier. The transfer coefficient of paint and varnish material ranges from 70% to 95%.

The transfer rate will depend on the conductivity of the colored material, the shape of the product, and other indirect factors. The electrostatic method makes it possible to reduce the consumption of paint and varnish material, and the painting process itself is much easier.

When painting metal pipes using the standard method, it is required to turn the products over several times. In the case of an electrostatic type pistol, the part does not need to be rotated, because charged particles are directed along the lines of force, and they will easily bend around obstacles. The staining is carried out quite evenly, because at the already treated place the paint and varnish material will repel the excess of the incoming material.

Details

Types of spraying

Two types of electrostatic spraying are used - cascade and classic. By the way, the latter assumes that high voltage direct current is supplied to the electrostatic spray gun through the high-voltage cables. The classical scheme has many significant disadvantages. First of all, we will talk about voltage instability in the pistol electrode. Moreover, it is very difficult to paint, because a large cable will hamper the actions, and in order to turn off the power supply, you need to get to the transformer every time.

In the cascade method, the high voltage is not generated externally, but in the gun itself.A voltage of only 12 V is directed to it through a low-voltage cable, and already inside the device, a high degree of voltage will be generated. The transformation is carried out on a spray cascade. The used cable is flexible and thin, due to which it is extremely convenient to work with it.

The cascade method makes it possible to turn off the supply of electricity, regardless of the generator, and also to control the voltage level, and choosing the right one for one type of material or another.

The voltage itself will be distinguished by a high degree of stability, which makes it possible to significantly reduce the consumption of paint and varnish material. The main disadvantage of cascade spraying will be the high cost of equipment. But the costs are quickly able to pay off due to the economy of such technology.

Electrostatic spraying has certain limitations, which are dictated by the following circumstances:

  1. Liquid or powder electrostatic painting Properties of paint and varnish material. We are talking about liquid electrostatic painting.

    In order for the paint to properly charge at the electrode, a resistance of at least 30 kΩ is required. In the opposite case, the efficiency of staining in an electrostatic field will be radically reduced. As an example of a paint and varnish material with a low level of resistance, one can cite formulations with large additions of metallic powder (these include enamels of the "metallic" type). Until recent years, electrostatic painting was not used for the application of water-based paints, because there was a high risk of short circuits due to the electrical conductivity of liquids. The latest models from electrostatic painting equipment make it possible to work with water-based paints and varnishes.

  2. Material properties. Products that do not conduct electricity, such as wood and plastic, are difficult to paint. It will only be possible to facilitate the process with special conductive primers (in the case of plastic) or moisture (for wood).
  3. The shape of the workpieces. As mentioned earlier, the electrostatic method makes it possible to paint products of different shapes, but in a closed conductive circuit, the field voltage of the electrostatic type will be zero.

    For this reason, there is no electric floor in the deep recesses, which is why particles of paint and varnish material will not fall on such areas. Moreover, without getting into various depressions, the paint will concentrate on other areas (for example, at the edges), and this will lead to the formation of a very thick coating layer. To avoid such problems (often called the Faraday circuit), painting of hard-to-reach places is carried out using a simple spray gun - airless or even pneumatic.

Consider a staining device. Spray gun "Star 3001"

As an example, you should disassemble the Star 3001 spray gun.

This apparatus uses a high voltage cascade method. They make both mechanical and even automatic methods of improving equipment. Both models are capable of working with both airless spray and air-type mixture. There are still separate modifications for water-borne paints and varnishes and for paints made on the basis of solvent. Each model, depending on the purpose, can differ greatly in the materials used in it, and also have its own design features.

Liquid or powder electrostatic painting

It turns out that the range of equipment is incredibly wide, and therefore requires decide how exactly the electrostatic gun will be applied. The 3001 is required for working with water-based paints and varnishes. This will mean that the device is protected from short circuits, because the structure is made of a special material. But for working with organic solvents, Star 3001 is not suitable, and therefore you need to find a modification, the body of which is inert with respect to various solvents.

Problems with the Faraday circuit in an atomizer of this model are solved by turning off the power supply.

If there is no power supply, the paint material is sprayed only under the influence of pressure. The voltage control keys are located directly on the gun body, which is very convenient. Moreover, the pressure can even be controlled with your own hands - just pull the trigger. The gun is also equipped with memory, due to which up to 3 variants of the electrostatic field are supported for each type of paint and varnish material. An important parameter of any paint and varnish material used will be electrical resistance.

A probe is supplied with the device, which tests the paint and varnish material for resistance, and thus provides the best indicator for the electrostatic field.

Despite the technical equipment, this electrostatic paint gun is easy to maintain. The case can be easily disassembled, and then all mechanisms are available for visual observation. In the event of a breakdown, you can replace any elements of the gun. This circumstance makes it possible to simplify repair work, and also to reduce the cost of them.

It should be noted that the device also weighs only 0. 9 kg, and due to its lightness, it will be physically easy to work with it, and due to the ergonomic handle it will be convenient. For industrial use such a modification as "LARIUS 2 Power Systems" has been developed. This system uses a double diaphragm, due to which the paint material is injected under low pressure.

Use of technology in Russia

The electrostatic painting technology is characterized by a large number of advantages.

But in Russian conditions, the use of this type of spraying has not yet found widespread use.The main reason is the lack of a sufficient number of qualified specialists. The equipment itself is quite complicated, they need to be used, and otherwise, instead of spraying with an electrostatic type, the paint will be sprayed using a standard method, which will not give the planned effect. Another problem in Russian conditions will be the search for paints and varnishes with the required level of electrical conductivity.

If the indicator differs from the specified one, it can be used, but in any case, you cannot do without the initial information.

At the same time, it is often impossible to find out the level of electrical conductivity either from sellers or from manufacturing companies. As a result, the only way out is to buy Western-made paints and varnishes, which are much more expensive than their domestic counterparts. Another important factor will be to ensure good quality grounding. In most cases, this condition is not properly met. In the absence of grounding, the painter will paint not just the surface, but himself.

Please note that there is a popular misconception required to be told - most painters believe that the larger the torch, the sooner the surface will be processed. But in practice, this is not at all the case, and increasing the torch only makes an electrostatic apparatus into a simple spray gun.

Staining of the electrostatic type naturally holds great promise for use. The required equipment is on sale and the technology is well researched. But for greater distribution, the application of paints and varnishes by this method requires special training, and then testing knowledge in practice.

.