1. 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
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2. 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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3. 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
Assuming that the alternative has already proved to be technically capable
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4. Aerospace Equipment Sector Cr6+ Use and Status
Note: The original substances are not present in the final product
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5. Aerospace Equipment Sector Cr6+ Use and Status
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6. Aerospace Equipment Sector Nickel Use and Status
Note: The original substances are not present in the final product
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7. Aerospace Equipment Sector Ni 2+(aq) Use and Status
Note: The original substances are not present in the final product
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8. Example Data – Rolls-Royce Testing Status For Hexavalent Chrome Replacements
Other aerospace companies have programmes in place with similar results
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9. Typical Uses Of Hexavalent Chrome And Soluble Nickel
Primary and secondary flight control actuation
Aircraft paints
Engines
Landing gear
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10. Materials In A Current Civil Engine Rolls-Royce Example
Nickel
40%
All Others 5%
Steel
25%
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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11. Safe replacements are at various stages of technical approval
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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12. 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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13. Supporting Information
Additional slides with further supporting information to the earlier tables follow this slide for use if required.
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14. 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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15. 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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16. 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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