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 |
© 2007 H.Snelson - Aluminium
Extrusions Aluminium Fabricators
Nat Lane, Wharton Industrial Estate, Winsford, Cheshire, CW7 3BS. UK.
Tel: +44 (0) 1606 553580 Fax: +44 (0) 1606 861084
