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 Our Process |
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The powder coating process
The powder coating process involves three basic steps:
1. Part preparation or the Pre treatment
2. The powder application
3. Curing
Removal of oil, soil, lubrication greases, metal oxides, welding scales etc. is essential prior to the powder coating process. It can be done by a variety of chemical and mechanical methods. The selection of the method depends on the size and the material of the part to be powder coated, the type of soil to be removed and the performance requirement of the finished product.
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Chemical pre-treatments involve the use of phosphates or chromates in submersion application. These often occur in multiple stages and consist of degreasing, etching, de-smutting, various rinses and the final phosphating or chromating of the substrate. The pre-treatment process both cleans and improves bonding of the powder to the metal.
The most common way of applying the powder coating to metal objects is to spray the powder using an electrostatic gun, The gun imparts a positive electric charge on the powder, which is then sprayed towards the grounded object by mechanical or compressed air spraying and then accelerated toward the workpiece by the powerful electrostatic charge. There are a wide variety of spay nozzles available for use in electrostatic coating. The type of nozzle used will depend on the shape of the workpeice to be painted and the consistency of the paint.
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| When a thermoset powder is exposed to elevated temperature, it begins to melt, flows out, and then chemically reacts to form a higher molecular weight polymer in a network-like structure. This cure process, called crosslinking, requires a certain degree of temperature for a certain length of time in order to reach full cure and establish the full film properties for which the material was designed. Normally the powders cure at 200°C (390°F) in 10 minutes. The curing schedule could vary according to the manufacturer's specifications |
Testing Methods
Coating Thickness
The thickness for the coating maintained is approximately from 50 to 100 microns or as per product requirement. (Digital Coating thickness measurement instrument used)
Scratch Resistance
By adding weight to the coated object, it should withstand 3000 to 4000 grams. (1 to 5 kg. Pin type testing.)
Weather Resistance
QUV lamps are used.
Chemical Resistance
Detergent test, Object immersed in chemical should withstand 3 to 4 months (depending on the chemical.)
Impact Resistance
2.25 kg weight with a diameter of 15 mm is dropped from a height of 2 feet.
Heat Resistance
The object is placed inside the oven or in an incubator for 100 hrs at 120 Celsius.
Adhesion test
Cross Cut hatch & Tape used.
Corrosion Resistance
Salt spray testing. Pre-treatment should withstand 12 hrs minimum & coating 700 hrs or as per powder specification.
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