Electrostatic Coatings – How to Measure the Resistance

An electrostatic coating machine is a device used for the coating of non-conductive metallic surfaces with a charge inducing electrostatic field. It includes a variety of electrical steps and is operated by means of a controller. It can be used for various applications including the coating of metal surfaces. The following discussion provides an overview of electrostatic coating machines and their application.

electrostatic coating machine

In the figure, indicated in the lower left in the figure, is an electrostatic coating machine of the rotating atomizer head sort, that is mostly comprised of a cylinder shaped of an electrical insulating material (e.g. polytetrafluoro-ethylene) and an electric motor (not shown) that is contained in the cylinder. When the electrostatic charge induced by the magnetic field to the electrically charged particles in the electrically conductive material that is the Electrostatic Induction Coil (EIC).

One may observe that the EIC has a metal sleeve surrounding it. The other end of this metal sleeve is connected to the motor that is located inside the electrostatic coating machine body. This motor is then connected to the other end of the sleeve that is connected to the external paint supplied through the inlet pipe. When the electrostatic charge induced flows into the paint supplied, the electrostatic charge causing the paint to adhere to the metal surface that is being coated. Then the flow of the water and the electrostatic charge separate the oil and the paint.

An example of this kind of coating is the indirect charging type coating machines. This consists of two tanks, one having the liquid oil and the other the electrostatic charged paint. As the oil is pumped into the tank containing the paint, it passes through the metal casing. As the paint passes through the casing, it attracts the metal atoms and bonds with them, forming a protective coating on the tank walls.

Another example is the direct current electrostatic coating machines. Here, as the fluid passes through the induction electrode unit, it is induced to have a direct current. This current is then applied to the object that needs protection. When the current passes through the internal paint path by electrostatic induction, the charged particles are bonded to the paint on the object and the coating is formed.

You may be wondering how the electrostatic coating machine works. How does the electrostatic charge to get into the paint passing through the internal paint path by electrostatic induction? The answer to this is quite simple. The induction electrode portion of the machine consists of a coil and the belt is connected to a DC motor. The coil is placed in a way that it gets all the DC energy when the belt is rotating and this energy is then used to charge the liquid paint.

To ensure accuracy in your electrostatic spraying machine measurements for electrostatic coatings, you will need to measure the resistance of the paint against the current passing through the coil and the fluid. There are various types of resistors that can be used for this purpose. The resistance should be measured using Ohm’s law, which states that the resistance increases as the current increases. The current measured should always be less than the maximum value of resistance that the coating equipment can tolerate. It is important to note that the resistance will change depending on the type of material to be coating and also due to the humidity and temperature of the working environment.

The resistance that is measured is called Capacitance. This is also called resistivity. Another term that you will come across is the voltage drop and it is simply the amount of voltage that is lost when the charged paint passes through the electrostatic coating machine’s nozzle. The other term that you will come across is the fluid flow rate and it is the speed at which the heated fluid flows through the nozzle. In order to have an accurate measurement, you should place the measuring device in a position that will give you an indication of what the value of capacitance is. Electrostatic coatings require a constant input from the Electrostatic Charger and the measurement of this Capacitance is very important when selecting a suitable embodiment suitable for the implementation of the electrostatic coating machine of the desired type.