The Process of bonded metallic powder coatings
The design features of the mixers have been specially optimised for metallic powder coatings. The entire bonding process can be controlled with surgical precision and offers absolute, certifiable processing reliability.
The critical phase of the bonding process is reached when the resin to which the aluminium flakes are to be bonded begins to soften. The range, within the resin changes from a powder to a doughy mass, is extremely short. If the temperature rises beyond this range, the mix can no longer be processed.
All the coolable modules of the mixer – the drive shaft and themixing tools, the jacket and the bowl bottom – can be cooled separately. No other mixing system comes as close to the glass transition temperature of the resin as the mixer. The result is a perfectly bonded metallic powder coating of fascinating brilliance.
can be produced to give a range of metallic finishes from silver
to gold and with all ranges of gloss and profile. By adding Aluminium, Bronze, Zinc,
Magnesium and Stainless steel pigments to the thermosetting Powder Coatings.
The most used pigment for silver metallic effect is Aluminium 1-2% in the leafing and
3-5% in the non-leafing form. With Aluminium pigments the fine Leafing grades will
produce the brightest silver and glossy effects these are the lower average particle size.
(4-12 microns) The Non- Leafing are higher average particle size (10-20 microns) and give
a sparkle effect.
Smooth Metallic effect Powder Coatings cannot be produced using the normal powder
coating process because the shear forces that occur during extrusion distort the metallic
particles causing them to loose their lustre. The extrusion process can produce some
excellent bright hammer finish effects but on the whole they tend to be silver and dark grey
Dry blending where the metal pigments are mixed with the thermosetting powder coatings
is a simple production method but can be highly dangerous process prone to explosion
with out the correct inerting methods and procedures. The finished powder will give a
brighter and glossy effect but the metallic pigment will tend to separate at the point of
application this in turn will cause pigment agglomeration and in the reclaim system cause
colour changes. Blended products cause major application problems because of the free
metal particles that exist within the mix including the clogging of guns during corona
The production of Metallic Powder Coatings is best achieved via the Bonding process that
is relatively safe and does not leave free metal particles within the powder when correctly
bonded. The Bonding process can be described as the complete attachment of metal
pigments to thermosetting Powder Coatings. The problems associated with separation and
agglomeration will disappear with reclaim equal to normal non-metallic powder coatings.
The metallic effect will be constant even with large batches.
The risks of incorporating the pigments, especially Aluminium. Can be eliminated by
determining a basis of safe operation for the process and using the best equipment for
Due to the specialist nature of this process only few Powder Coatings manufacturers have
moved into this process in house, with most choosing to use a Bonding service company
for Bonding the Metallic pigments into the base powder supplied by the Powder Coatings
The problem with any Bonding service is the time taken from sending the sample and
detailing the specification, identifying the required base Powder Coating, manufacturing
the base powder, having it Bonded and returning to the Powder Coating manufacturer and
on to the end user. A typical service would be eight weeks from receipt of colour pattern to
Bonded Powder Coatings.
Larger Bonding service companies are also the manufacturers of the metallic Pigments
that are used in the Bonding process so they can supply the raw materials for the Bonding
process. Main metallic pigment suppliers in Europe are Eckart and Benda-Lutz.