Powder coating

Powder coating is a relatively new metal coating technique and was first introduced in the early 1970's. In this process, powdered resins along with coloured pigments are applied to metal products using an Electro-static charge. The product is then "baked" in a high temperature oven causing the powder to melt, flow, and then cure, forming a molecular fusion bond. The result is a surface - to- coating bonding unlike any other.

Over recent years the application of thermosetting powder coatings on Aluminium has increased dramatically. The wide variety of powder types now available allow the engineer or architect to specify powder coating with confidence.

As with solvent based paints thermosetting powders can be formulated to produce high and low gloss decorative coatings , Metallics as well as textured & hammered finishes. The standard colour range gives customers ample choice and if need be, special colour matches and finishes can be made.

 

The Process.

Aluminium components are cleaned and to improve adhesion they can be primed. It is very important that during the priming stage the component is kept clean, for this reason Anodising although expensive is an ideal pre-treatment for painting .

Zinc chromate can also used, but over the last few years a number of problems have arisen with this form of pre-treatment.

The components are then suspended on a jig or wire and passed through the spray booth where the powder is applied by Spray Guns . Powder spray guns can be adjusted for powder and air volume, after spraying the paint is cured in an oven. Time and temperature vary in accordance with paint types but 200°C for 20minutes is an average.

	Type of Powder
Property	Standard Polyester	Enhanced   Polyester	Epoxy	Hybrid	Polyurethane	Acrylic	PVDF
Exterior Durability	Good	Excellent	Very Poor	Poor	Good	Excellent	Excellent
Corrosion Resistance	Good	Good	Excellent	Good	Good	Good	Good
Impact	Excellent	Poor	Excellent	Excellent	Good	Poor	Excellent
Flexibility	Excellent	Good	Excellent	Excellent	Good	Good	Excellent
Adhesion	Excellent	Excellent	Excellent	Excellent	Excellent	Excellent	Poor
Cost	Medium	Medium / High	Medium	Low	Medium	High	High
Film Appearance @ 50µ	Good	Very Good	Good	Good	Excellent	Good	Poor
Volatile Emissions	Very Low	Very Low	Very Low	Very Low	Low	Very Low	Very Low
Low Bake	Yes	No	Yes	Yes	No	Yes	No
Chemical Resistance	Good	Good	Excellent	Very Good	Good	Very Good	Good
Gloss Range	10-95%	20-95%	5-90%	5-90%	5-95%	30-90%	30-60%
Heat Resistance	Very Good	Good	Poor	Good	Very Good	Good	Good
Abrasion	Good	Good	Very Good	Good	Good	Good	Poor
Compatibility	Good	Good	Good	Good	Good	Very Poor	Very Poor