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26 AeroSPAcemANUfAcTUrING | JANUAry 2010
The entire dynamic for
coating aircraft materials
is being rearranged as
the REACH regulations
come into force. One
such example is the
banning of chrome-based
compounds, which will
have wide implications for
the way critical structural
parts are protected.
Simon Lott reports.
Complete solution: 15-20 different Indestructible coatings are used throughout a typical turbofan
GoinG
chrome-free
A
s the European Union’s REACH and expensive process, but will also mean current formulation – which contains
(Registration, Evaluation, the publication of intellectual property. only 37ppm hexavalent chrome, is
Authorisation and restriction of Thus, with the urgent need to develop typically applied at a thickness of
Chemicals) directive continues to be alternatives, Birmingham-based coating 50µm and can be cured either at 560°C,
felt across the manufacturing industry, and paint manufacturer, Indestructible 350°C with additional bead peening or
innovations in chemical technologies is about to embark on a £160,000, 15 polishing depending on the application,
have had to come thick and fast. Of the month research project, funded in part or at 260°C with an extended dwell
sectors affected, coating producers will by Advantage West Midlands and the time. This yields a typical corrosion
be one of the hardest hit and in the area European Regional Development Fund, resistance of 3,000 hours. A smooth
of turbine coatings, the requirement to remove the substance from its range. surface alternative for improved engine
to move away from widely used, but At the heart of Indestructible’s R&D efficiency, Smoothcote, which makes
potentially carcinogenic chromium-based programme – which involves industry use of aluminium powder consisting of
coatings is an important step change that partners Rolls-Royce, Messier-Dowty smaller particles (1µm as opposed to
will need to be made in the near future. and research, testing and consultancy 5µm), is also available, offering a denser
As things stand, there is a degree of company CERAM as a sub-provider – is and more erosion resistant product
confusion over the way in which rules are its Ipcote range. Developed initially at the for improved performance. As an
to be implemented with the prospective request of Rolls-Royce during the 90s for interim measure, organic chrome free
restrictions open to a certain amount use in gas turbines and compressors for versions of these systems have become
of interpretation as well as opposition high temperature erosion and corrosion available, however these necessarily
coming from organisations such as resistance, Ipcote now consists of a host contains solvents, which bring their own
the Aerospace & Defence Industries of basecoats, sealcoats and diffusion environmental problems and are more
Association of Europe. The belief products which have since seen approval expensive to produce.
within the industry is however, that by Pratt & Whitney Canada, Snecma, The big concern overall is that viable
use of sodium dichromate – a precursor Turbomeca, ITP Spain, MTU Aero replacements will not reach the market
of many chrome-based products – will Engines, and is currently being trialled by in time to prevent the compromise
be severely limited in the near future. General Electric. of aircraft programmes. In terms of a
Registering for use is not only a complex The standard Ipcote basecoat in its practical solution, several main factors
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