Technology spoTlighT i EnginEs
will need to be addressed. The aircraft
industry has become accustomed to
the performance levels delivered by
chrome containing products as they offer
the key properties of good adhesion,
corrosion resistance and the ability for
molecules to crosslink and promote a
stable oxide film. As such, chrome is a
key part of the overall formulation and
has typically been used in all aspects of
turbine coatings, be it in pre-treatments,
primers, basecoats or sealcoats.
Within a typical turbofan, 15-20
different coating products are specified
High performance: The Eurofighter Typhoon is one of Time for change: Ipcote encompasses a whole range
to protect against heat and corrosion. many programmes supplied by Indestructible of basecoats, sealcoats and diffusion products
For example, Ipcote is relied upon to
protect the central shaft, a component
that carries the load of the engine and conditions. A further consideration the amount of materials that would
also provides the interface with the major is that as weight drives development need to be investigated and tested for
rotating parts. The normal procedure and materials improve, the decreasing certification.
is to apply a conductive, sacrificial thickness of shaft walls has placed With every challenge however,
basecoat with a non-conductive sealcoat additional pressure on coating products. lies opportunity and Indestructible’s
on top to seal any porosity and to give Of course, integrity is everything, position in the market as an SME and
a smoother finish. Typically made from and there are a variety of cases where the progress it has made, has drawn
highly corrodible steel, engine shafts rely current alternatives cannot match the the attention of several important
entirely on the coatings to protect from requirements of certain applications, manufacturers. Technical sales manager,
condensation and oil contamination, the compromising service lives and the safety Graham Armstrong explains: “For one
effects of which are exaggerated by the of components. One particular test using project with Eurocopter, we are looking
perpetual heating and cooling. Engine a former Ipcote product containing 5% at magnesium and aluminium treatments
oil for example can typically pick up chromic acid ensures that the product for components like gearboxes.
between 400-800ppm moisture, a figure will last for between 4,000 and 5,000 Eurocopter approached us 18 months
that increases substantially under adverse hours in a salt spray environment. ago because it wasn’t getting much help
Current products with already vastly from the larger companies. We were
reduced chrome contents due to previous able to change its systems to totally
environmental legislation are typically chrome-free with the exception of the
tasked with achieving only 1,000 hours. primer we supply, which we’re working
While this can be achieved, chrome-free on. Indestructible has formulated
products still fall short of this necessary some samples and there’s now a whole
time span. matrix of trials to be done on various
There is also the fact that those panels and multi-substrates, looking at
products that do meet or come close to steels, various grades of aluminium and
the necessary performance requirements magnesium. Altogether this will probably
are not stable enough to be stored for be three to four years in gestation but we
extended periods of time (typically were chosen because we will be able to
offering a usable life of four to six produce a custom product.”
weeks), meaning that it is impractical Amid its own research and similar
to apply such products in the field. developments with other major
Additionally, while chrome compounds manufacturers, it is hoped that the
offer largely universal characteristics reformulation of all coatings within the
across a variety of materials, this is not Ipcote range will be completed within
Finding the right formula: The chrome content of
the case for many proposed alternatives, the next few years. ❙
current products has already been greatly reduced
complicating and greatly extending www.indestructible.co.uk
AEROSPACEMANUFACTURING | JANUARy 2010 27
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