FEBRUARY 2018 | 33
Window Technology
CURRENT THINKING ON
ALUMINIUM PRETREATMENT
by Wojciech Brozyna – MD of Aluprof UK
There has been a lot of
speculation of late on the choice
of pretreatment used on powder
coated aluminium profile. With
‘chrome’ based systems likely to
be banned under EU’s REACH
(Registration, Evaluation, Authori-
sation & restriction of Chemicals),
where are we now and what
should you specify?
There are two National and
European standards that cover
the aspect of architectural pow-
der coating, BS 6496:1984, which,
despite it being withdrawn earlier
in 2017, is still referred to. BS EN
12206-1:2004 is the current har-
monised standard. The Qualicoat
Standard, now in its 15th edition,
encompasses BS EN 12206-1:2004,
this BS EN standard was compiled
along the lines of the European
Qualicoat standard at the time of
writing.
The BS EN standard does refer
to pretreatment systems, but
is vague of what to specify, if
anything. What is well known is
that chrome based pretreatment
systems perform very well and
have the benefit of being around
for many years with an extensive
track record. Qualicoat recognis-
es both chrome and chrome free
pretreatment systems and are en-
couraging members to adopt the
newer chrome free technology.
Pretreatment of aluminium
includes the cleaning and etching
of the surface of the aluminium
with the addition of a very thin
‘conversion layer’ which bonds to
the aluminium and seals it from
air and moisture. It is the ‘conver-
sion layer’ that also offers a ‘key’
for the subsequent powder coating
to adhere to the profile. So, the
most important part of the powder
coating process is the very process
that is invisible once coated!
Chrome based pretreatment sys-
tems have been proven to be car-
cinogenic in application, i.e. when
the pretreatment is being applied
to the aluminium. The finished
powder coated extrusion carries
no chrome residue so is entirely
safe in use and recycling.
Aluprof, based in Poland, have
been members of Qualicoat since
2003, they have been awarded
with licence number ‘1508’ and
carry the prestigious ‘Seaside’
option on powder coating for
more exposed conditions where
required. Aluprof offer the option
to specify chrome or chrome-
free pretreatment systems to suit
the specifier, should they have a
strong preference, as they utilise
both pretreatment systems in their
production facility.
Whilst the National and Europe-
an standards are frequently seen
in specifications, it is encouraging
to see the growth of the ‘Qualicoat
Standard’ being referred to in a
growing number of specifications.
What is unusual though, is the oc-
casional specification of the AAMA
standard, which has been seen
from time to time. AAMA, the
American Architectural Manufac-
turers Association, is not currently
recognised in the UK.
Aluprof’s vertical powder coating line, Poland
Whilst over half of the members
of Qualicoat UK & Ireland have
made the switch to ‘Chrome Free’
pre-treatment systems within their
plants, a number are staying with
chrome pretreatment, for now.
The Qualicoat organisation, based
in Zurich, have made it clear to
members that they fully support
the use of chrome free pretreat-
ment systems and that this would
be a pre-requisite for continued
licence holders if a ban on the use
of chrome in pretreatment systems
was initiated again by REACH. It
is understood that the ban is for
the sale of such chrome pretreat-
ment systems and not the use,
so conceivably companies could
carry stock of the chrome pretreat-
ment system for continued use for
a limited time.
So, the reason for some appli-
cators not changing ea