36 aeROsPaCemaNUFaCtURiNG | maRCh 2010
Metallics i TesTing
TesTing
times ahead
Many companies will need to replace chromium-based products in their supply
chain, but how do they go about finding alternatives?
T
he removal of chrome-based coatings, we would use surface analysis
compounds from aircraft coatings techniques like X-ray spectroscopy and
is going to cause a few headaches mass spectrometry as applied to surfaces.
for manufacturers ahead of REACH The X-ray technique will give information
(Registration, Evaluation, Authorisation on any metallic pigments, their oxidation
and registration of CHemicals) states and their abundance. Surface
regulations coming into full effect. mass spectrometry analyses sputtered
While chrome compounds provide a material and gives information on
well established and universal level of molecular composition. In terms of
performance for parts being treated the microstructure we’ll use electron
for corrosion protection, alternative microscopy to look at grain structure
formulations have yet to establish a clear and pigment particle size. Quantitative
path, although progress is being made. 3D surface topographical profiling has
Typically used in conjunction with a
Chemical species map:
also been applied to the specification and
Using mass spectrometry to
seal coat, the key advantage of chrome identify different ingredients in coating control of substrate surface roughness.
as used in metallic coatings, is to act “Quantitative surface elemental
as a galvanic cell, which when exposed, ability to understand the interfacial spectroscopy operating in high resolution
undergoes an electrochemical reaction phenomena occurring between the mode can distinguish between the two
that reduces it from a trivalent to a various ingredients, between the coating oxidation states of chromium with high
hexavalent oxidation state, essentially ingredients and the substrate layer and precision and this analysis is routinely
sacrificing itself in place of the substrate. between the coating ingredients and the used in the characterisation of such
ensuring components are protected. environment it is being exposed to. coatings. Moreover, similar capability
CERAM’s two main areas of business “The precise chemical and exists for all metallic elements to which
consist of design consultancy and microstructural makeup of the coating is it could otherwise apply.”
the testing and analysis of materials of crucial importance in optimising the The application of new products
and surface treatments. As such the galvanic mechanism. The characterisation is also highly dependent on chemical
company’s activities have frequently of metal surfaces requires a variety of composition with new systems
taken it into the area of coating approaches, including examination incorporating alternative curing and
development, working with both of chemical structures, topographical deposition methods to make the most
airframers and their suppliers. The profiles and microstructures.” of new formulations. Despite the many
effects of the restriction, set to come Part of the problem lies in the fact variables however, the importance of
into full effect in 2013 will be wide that without chrome, the large range of alternative coatings is well understood
ranging, so what methods are being used high performance applications for such by many industry leaders with the first
to develop new formulations? coatings, from critical ‘hot end’ engine products, albeit with some performance
Principal consultant for aerospace components to outer aircraft surfaces will shortfalls, beginning to filter into the
and defence Dr Chris Pickles explains: require increasingly tailored solutions so market. Much work still needs to be
“The complex chemistry involved in there will be a great deal of activity as done however, to ensure disruption can
reformulating anti-corrosion coatings new ideas are developed. be avoided before the restriction. y
depends critically on the developer’s Pickles continues: “In terms of www.ceram.com
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