Aerospace Use Of Hexavalent Chromium And Soluble Nickel In Relation To REACh 7 th October 2009 From...

Aerospace Use Of Hexavalent Chromium And Soluble Nickel In Relation To REACh

7th October 2009From 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

2 © 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.


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


Aerospace Equipment Sector Cr6+ Use and Status

Substance Process used in Why important in Design Status of Alternatives

Hard chrome plating

Provides sealing surface for hydraulic seals, wear resistance to moving parts and corrosion protection

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.

Chromic acid anodising

Provides best corrosion protection of the various anodising methods and has least detrimental effect on fatigue properties of the base material.

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.

Sealing of anodising on aluminium alloys

Provides the best corrosion protection, particularly in applications which will not be painted for environmental and weight benefit.

Alternatives are still being evaluated. Best candidate requires nickel salts so no environmental advantage.

Passivation baths for stainless steel

Used to ensure best resistance to corrosion from stainless steels and necessary to comply with aircraft industry standards

Alternatives do exist but are not compliant with international aircraft industry standards.

Passivation of cadmium plating

Used to ensure that cadmium plated parts meet international standard for corrosion protection

Alternatives exist for about 70% of new designs. Not possible to apply without equipment re-design to producst already qualified.

Chromic Acid

Sodium Dichromate

Note: The original substances are not present in the final product


Aerospace Equipment Sector Cr6+ Use and Status


Corrosion protection

Provides surfaces with corrosion protection to guarantee component life.

Trivalent chrome alternatives under development, but not equivalent life nor validated in an engine environment.

Oxidation protection

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

Corrosion protection of complex geometries.

Some alternatives available but not validated in an engine environment.

Two-part epoxy paint systems

Protection against wet corrosion on complex geometries.

Some alternatives available but not validated in an engine environment.

Various chromate salts

Paints, both primer and topcoats

Used to give required corrosion protection from paint in the aircraft operating environment.

Alternatives available for use on some new designs but not all. Change of paint to existing designs not yet accepted without extensive testing.

Chrome phosphate


Aerospace Equipment Sector Nickel Use and Status


Abrasive coating

Provides a means to guarantee engine performance and is essential in achieving component lifetime through improvements in fatigue resistance.

No known alternatives.

Wear resistant coatings

Provides improved wear resistance to surfaces and guarantees component lifetime through mitigation of fatigue failures.

Alternatives exist for some applications and can be used on existing designs. No alternatives are proven for fatigue and wear resistance for critical parts.

Nickel platingProvides the best corrosion protection, particularly in applications of complex geometry.

Alternatives are still being evaluated. Currently none provide an environmental advantage.

Nickel platingProvides the best corrosion protection, particularly in applications of complex geometry.

Alternatives are still being evaluated. Currently none provide an environmental advantage.

Electrochemical machining (ECM)

Used to provide means of machining complex shapes.

Alternatives exist for some geometries but manufacturing is more complex and would require re-validation.

Nickel sulphamate /

nickel chloride

Nickel sulphate / nickel nitrate



Aerospace Equipment Sector Ni 2+(aq) Use and Status


Nickel SulphateNickel Hypophosphite

Nickel PhosphiteNickel Chloride

Nickel Sulphamate

Electroless Nickel plating

Unique as being the one hard coating process which is electroless and so will plate on complex and internal geometries as there are no electrode, electric field intensity or line of site issues

Some potential from electroless nickel boron but as yet not proven for endurance, and not available in supply chain.

Nickel AcetateSealing of anodising on aluminium alloys

Provides good corrosion protection on 7000 series alloys in a sealing solution which does not contain chrome 6+ ions

Alternatives are still being evaluated in same task as that to replace dichromate sealing. So far, alternaitves have inferior corrosion performance.



Example Data – Rolls-Royce Testing Status For Hexavalent Chrome Replacements

0

5

10

15

20

25

30

35

40

Today's "chrome"applications

Validated chrome-freereplacement exists

Potential chrome-freereplacements not yet

validated

No known chrome-freereplacement exists

Other aerospace companies have programmes in place with similar results


Typical Uses Of Hexavalent Chrome And Soluble Nickel

Aircraft paints Engines

Landing gear

Primary and secondary flight control actuation


Materials In A Current Civil EngineRolls-Royce Example

Nickel40%

All Others5%

Steel25%

Titanium30%

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.


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


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.


Supporting Information

Additional slides with further supporting information to the earlier tables follow this slide for use if required.


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.


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


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.

Aerospace Use Of Hexavalent Chromium And Soluble Nickel In Relation To REACh 7 th October 2009 From...

Documents

Transcript of Aerospace Use Of Hexavalent Chromium And Soluble Nickel In Relation To REACh 7 th October 2009 From...