Aerospace Use Of Hexavalent Chromium
And Soluble Nickel In Relation To REACh
7th October 2009
From a combined Goodrich and Rolls-Royce review of the
implications of REACh for the aircraft industry
Goodrich: J Henshaw; G Armstrong
Rolls-Royce: A Page; J Watson; C Phillips; A Phillips
© Goodrich Actuation Systems Limited 2009
CONFIDENTIAL
Chromium And Nickel Compounds In Current
Products
 The Aerospace industry
 Currently uses hexavalent chrome and nickel compounds in a number
of flight critical applications for various reasons
 Has been researching viable alternatives for many years
 Has found that very few alternatives are successful in the aircraft
environment
 Compared to other industries, requires a significantly longer time to
introduce changes into existing products due to the extensive testing
obligations to comply with airworthiness requirements.
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CONFIDENTIAL
Chromium and Nickel Compounds In Current
Products
As an example
 Components supplied for an Airbus A 320 aircraft (typically engines, flight
control actuators, landing gear etc)
 Original equipment deliveries planned until at least 2018
 Fleet support required until approximately 2040
 Supplied products include extensive use of:
–
hard chrome plating; Chromic anodising; Sealing of anodising on aluminium alloys;
passivation baths for stainless steel and cadmium plating; sacrificial paints using
chrome phosphate; conversion coatings on magnesium and aluminium; nickel
plating; tribomet coatings for wear and sealing; electrochemical machining.
Problem
 The above products have been fully tested and certified for flight
 Changes require extensive retesting to prove that they represent a comparable
safe alternative
 Introduction onto the aircraft / engine typically takes between 5 and 10 years
–
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Assuming that the alternative has already proved to be technically capable
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CONFIDENTIAL
Aerospace Equipment Sector Cr6+ Use and Status
Substance
Process used in
Hard chrome
plating
Chromic Acid
Chromic acid
anodising
Sealing of
anodising on
aluminium alloys
Sodium
Dichromate
Passivation baths
for stainless steel
Passivation of
cadmium plating
Why important in Design
Provides sealing surface for
hydraulic seals, wear resistance to
moving parts and corrosion
protection
Provides best corrosion protection
of the various anodising methods
and has least detrimental effect on
fatigue properties of the base
material.
Provides the best corrosion
protection, particularly in
applications which will not be
painted for environmental and
weight benefit.
Used to ensure best resistance to
corrosion from stainless steels and
necessary to comply with aircraft
industry standards
Used to ensure that cadmium plated
parts meet international standard for
corrosion protection
Status of Alternatives
Alternatives, e.g. HVOF, available for about 50% of
applications but they have to be designed in from new.
Substitution in mid life not an option.
Alternatives exist for some applications and can be used
on existing designs. No alternatives are proven for
fatigue critical parts or parts made from castings.
Alternatives are still being evaluated. Best candidate
requires nickel salts so no environmental advantage.
Alternatives do exist but are not compliant with
international aircraft industry standards.
Alternatives exist for about 70% of new designs. Not
possible to apply without equipment re-design to
producst already qualified.
Note: The original substances are not present in the final product
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Aerospace Equipment Sector Cr6+ Use and Status
Substance
Process used in
Corrosion
protection
Chrome
phosphate
Oxidation
protection
Why important in Design
Provides surfaces with corrosion
protection to guarantee component
life.
Status of Alternatives
Trivalent chrome alternatives under development, but
not equivalent life nor validated in an engine
environment.
Provides oxidation protection to
surfaces used at high temperature.
Alternatives exist for some applications based on
trivalent chrome. These can be used in existing designs
no alternatives are proven for fatigue critical parts.
Organic barrier
coatings
Two-part epoxy
paint systems
Corrosion protection of complex
geometries.
Protection against wet corrosion on
complex geometries.
Used to give required corrosion
Various
Paints, both primer
protection from paint in the aircraft
chromate salts and topcoats
operating environment.
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Some alternatives available but not validated in an engine
environment.
Some alternatives available but not validated in an engine
environment.
Alternatives available for use on some new designs but
not all. Change of paint to existing designs not yet
accepted without extensive testing.
CONFIDENTIAL
Aerospace Equipment Sector Nickel Use and
Status
Substance
Process used in
Why important in Design
Abrasive coating
Provides a means to guarantee
engine performance and is essential
in achieving component lifetime
No known alternatives.
through improvements in fatigue
resistance.
Nickel
sulphamate /
nickel chloride Wear resistant
coatings
Nickel plating
Nickel plating
Nickel sulphate
/ nickel nitrate
Status of Alternatives
Provides improved wear resistance
Alternatives exist for some applications and can be used
to surfaces and guarantees
on existing designs. No alternatives are proven for
component lifetime through
fatigue and wear resistance for critical parts.
mitigation of fatigue failures.
Provides the best corrosion
protection, particularly in
applications of complex geometry.
Provides the best corrosion
protection, particularly in
applications of complex geometry.
Alternatives are still being evaluated. Currently none
provide an environmental advantage.
Alternatives are still being evaluated. Currently none
provide an environmental advantage.
Electrochemical
Used to provide means of machining Alternatives exist for some geometries but manufacturing
machining (ECM) complex shapes.
is more complex and would require re-validation.
Note: The original substances are not present in the final product
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CONFIDENTIAL
Aerospace Equipment Sector Ni 2+(aq) Use and
Status
Substance
Process used in
Nickel Sulphate
Nickel Hypophosphite
Nickel Phosphite Electroless Nickel
plating
Nickel Chloride
Nickel Sulphamate
Nickel Acetate
Sealing of
anodising on
aluminium alloys
Why important in Design
Status of Alternatives
Unique as being the one hard
coating process which is electroless
Some potential from electroless nickel boron but as yet
and so will plate on complex and
not proven for endurance, and not available in supply
internal geometries as there are no
chain.
electrode, electric field intensity or
line of site issues
Provides good corrosion protection
Alternatives are still being evaluated in same task as
on 7000 series alloys in a sealing
that to replace dichromate sealing. So far, alternaitves
solution which does not contain
have inferior corrosion performance.
chrome 6+ ions
Note: The original substances are not present in the final product
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CONFIDENTIAL
Example Data – Rolls-Royce Testing Status
For Hexavalent Chrome Replacements
40
35
30
25
20
15
10
5
0
Today's "chrome"
applications
Validated chrome-free
replacement exists
Potential chrome-free
replacements not yet
validated
No known chrome-free
replacement exists
Other aerospace companies have programmes in place with similar results
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Typical Uses Of Hexavalent Chrome And
Soluble Nickel
Aircraft paints
Engines
Primary and
secondary
flight control
actuation
Landing gear
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Materials In A Current Civil Engine
Rolls-Royce Example
All Others
5%
Steel
25%
Nickel
40%
Titanium
30%
Current Technology:
•
All steel and all aluminium parts of an
engine (the outer casing) are coated in
mixtures containing hex chrome in at
least one layer of the coating system:
Usually in all 8 – 10 layers.
•
Even if alternatives are available during
manufacture, hex chrome is needed for
product repair.
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Summary
 Changes to products are governed by legal airworthiness
requirements which also define the requirements for retesting
when changes are made
 Testing must be to the same standard and vigour as occurred for
the original aircraft / engine airworthiness approval
 Safe replacements are at various stages of technical approval
 Many examples exist where safe alternatives have not yet been
developed or proven
 Substance elimination under REACh must take account of the
special needs of the aircraft industry due to the safety implications
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Conclusion
 With very few exceptions, hexavalent chrome and soluble nickel are not in the final
product on aircraft. There is no exposure of them to the public. Exposures to
downstream workers and during manufacture is restricted via a highly restricted
and controlled environment. e.g. Component maintenance manuals and Nadcap
 Credible alternatives have not yet reached a stage of maturity to give confidence
that they could be implemented within current estimates of the REACh time table.
 With enough research work, hexavalent chrome and soluble nickel compounds
could be significantly reduced in future aircraft models provided that the
alternatives can be proven to satisfy the demanding technical standards for
airworthiness.
 Existing aircraft will need to be maintained for several decades with a safe and
stable supply of spares. Validation of retrospective design changes is significantly
more challenging than new product introduction
 If any of these substances are listed on REACh Annex XIV, then
the aircraft industry will require exemption for existing aircraft
programmes.
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CONFIDENTIAL
Supporting Information
 Additional slides with further supporting information to the earlier
tables follow this slide for use if required.
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CONFIDENTIAL
Alternatives tested for hard chrome plating
 WC-Co-Cr applied by HVOF spray coating




Limited application opportunities due to adverse impact on base material
Successful in some applications
Geometry constraints so not a universal substitute
Very limited availability in supply base
 W-Co electroplated nano coating
 Potential option to produce hard surfaces for seals to run on
 Still in R&D phase – no commercial availability
 Not proven for seal running
 Diamond like carbon
 Not a viable option following testing due to poor adhesion and poor endurance
– required coating thickness cannot be achieved
 PVD Coatings
 As for Diamond like carbon – not a viable option following testing due to poor
adhesion and poor endurance – required coating thicknesses cannot be
achieved.
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© Goodrich Actuation Systems Limited 2009
CONFIDENTIAL
Alternatives tested for chromic anodising
 Sulphuric anodising
 Coating has to be 5 times thicker than chromic for equivalent
corrosion resistance
 Fatigue properties of base alloy are damaged by this process
 Cannot be used on aluminium parts made from castings
 Can only be used on non fatigue sensitive parts made from bar or
forging
 Boric Sulphuric Anodising
 Works well but still needs dichromate sealing for acceptable
corrosion resistance
 Minimal reduction in fatigue properties
 Boeing IPR so cannot be used on Airbus products
 Keronite PEO Coating
 Thicker coating than chromic anodising
 Claims that it does not reduce fatigue properties - not proven
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CONFIDENTIAL
Alternatives for Electroless Nickel Plating
 None yet evaluated
 The key attribute of the electroless nickel process is that it is
electroless and so does not have the geometric constraints of
electroplating or spraying processes (edge effects and line of site
issues)
 Possibility for electroless Nickel-Boron plating but not readily
available and not yet tested by GAS.
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CONFIDENTIAL