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Chromium-free conversion layers
Trivalent and hexavalent chromium is used in various
surface treatment techniques: e.g. as chromium plating
of aluminium or to passivate surfaces after various
pre-treatment processes, such as zinc phosphating or
galvanisation.
The chemical and other properties of trivalent and
hexavalent chromium are known well enough and
recognised.
In the light of 2007 (ELV 2000/53)* and of June
(RoHS 2002/95/EC, electrical spare parts exclusively
for the automotive sector) users find difficulties in
processing chromium-containing products.
More and more companies are banning chromium from
their chemical processes.
The R&D Department of the Kluthe Group has developed
a chromium-free programme with the name Decorrodal.
The Decorrodal AL 200 range is based on the properties
of titanium, zirconium, polymers and/or silanes.
Two chromium-free systems from this series were tested
on varnished aluminium building pieces and approved in
accordance with the requirements of Qualicoat.
The inspection report is available on request.
Decorrodal AL 230 A in combination with Decorrodal
AL 270 OR is used in conventional pre-treatment
installations where post-rinsing is performed.
This chromium-free system is used on e.g. aluminium
pieces and cast aluminium.
The results obtained in practice exceed the quality of
a traditional chromium plate.
Decorrodal AL 240 A was developed for “No Rinse”
applications for aluminium, magnesium and galvanised
parts.
This one component compound can be used on many
alloys and gives an appreciable improvement of the
varnish adhesion.
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