ELECTROPLATED FASTENERS A CAUTIONARY … fasteners a cautionary tale clive arnold and emily gower ....
Transcript of ELECTROPLATED FASTENERS A CAUTIONARY … fasteners a cautionary tale clive arnold and emily gower ....
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• ELECTROPLATED FASTENERS
• BAE SYSTEMS INTEGRATED SYSTEMS TECHNOLOGY POLICY:NO CADMIUM PLATING
• RoHS: 0.01% (100 PARTS PER MILLION) BY WEIGHT
CHROMATE
Zn
STEEL SUBSTRATE
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HEADLINES
• CADMIUM ELECTROPLATED FASTENERS HAVE BEEN SUPPLIED AS “ZINC” ELECTROPLATED PARTS
• CADMIUM HAS BEEN DETECTED IN ZINC ELECTROPLATED FASTENERS
• BS/EN/ISO SPECIFICATIONS FOR ZINC ELECTROPLATED FASTNERS DO NOT PROVIDE FOR RoHS COMPLIANCE
• XRF METHODS HAVE BEEN DEVELOPED FOR CHEMICAL ANALYSIS OF ELECTROPLATED FASTENERS
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• SUPPLY OF “Zn” (Cd) PLATED FASTENERS
• Cd PLATED FASTENERS SUPPLIED AS “Zn” PLATED FASTENERS. COATING ALSO BELOW THICKNESS SPEC
• PRODUCT, STOCK, SUPPLY CHAIN & COST ISSUE
• ONE ELECTROPLATING CO. SUPPLIED THREE DISTRIBUTORS
• SUPPLIER COMMENT: “WE DID NOT EXPECT ANYBODY TO NOTICE”
• RESULT: • SCREEN ALL FASTENERS FOR CHEMISTRY & THICKNESS
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• DETECTING CADMIUM IN FASTENERS
• SWAB TESTS – UNRELIABLE X
• AAS – (ATOMIC ABSORPTION)DESTRUCTIVE/TIME CONSUMMING X
• X-RAY FLUORESCENCE (XRF) –PNON-DESTRUCTIVE/RAPID
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• X-RAY FLUORESCENCE
• INCIDENT X-RAY BEAM STRIKES SAMPLE• EXCITATION OF CHARACTERISTIC XRF RADIATION
(PHOTOELECTRIC EFFECT)• ELEMENT SPECIFIC CHARACTERISTIC RADIATION IS DETECTED• ENERGY OR WAVELENGTH DISPERSIVE• SOFTWARE EVALUATES SPECTRUM
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• EXAMPLE: Zn/Cd COATING CONFIGURATION
• TOTAL LAYER THICKNESS 3-5 MICRONS (E.G BS 3382 1961)
CHROMATE
Zn
Cd
STEEL SUBSTRATE
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• DEVELOPMENT OF XRF DETECTION METHODS
• METHOD 1: Zn/Cd CHEMICAL ANALYSIS & Zn + Cd THICKNESS
• METHOD 2: THICKNESS MEASUREMENT OF Zn AND Cd LAYERS
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• XRF CALIBRATION – BULK MATERIAL
• SOLID Zn DISCS WITH TRACE Cd ABOVE & BELOW RoSHVALUES
• VERY USEFUL IN DETERMINING LOWER DETECTION LIMITS
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• SOURCES OF Cd IN Zn PLATED FASTENERS
• LOW GRADE ANODES
• INSUFFICIENT STRIPPING OF Cd PRIOR TO Zn PLATING.
• CADMIUM FLASH ON S/STEELS PRIOR TO Zn PLATING.
• CONTAMINATION OF Ni STRIKE BATH WITH Cd.
• CONTAMINATION OF CHROMATE PASSIVATE SOLUTION.
• OPERATOR ERROR/MALPRACTICE?
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• FASTENER COATING SPECIFICATIONS
• SPECIFICATIONS FOR COATING OF FASTENERS ARE PROBLEMATIC IN TERMS OF Cd CONTAMINATION.
• EXAMPLES:
• BS 3382:1961. PERMITS 2.5% IMPURITY IN COATING INCLUDING CADMIUM IN ZINC.
• BS EN ISO 4042: 2000. NO PROVISION FOR PURITY OF COATING.
• BRITISH STANDARDS POSITION: NO PLAN TO MODIFY OR PRODUCE NEW STANDARD TO ACCOMIDATE REQ. OF RoHS IN ELECTROPLATED COATINGS.
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• OBSERVATIONS
• SMALL PLATING CO. MAY NOT HAVE XRF QUALIFICATION.
• FASTENER DISTRIBUTORS MAY NOT HAVE XRF CAPABILITY.
• Zn COATING THICKNESS ALSO FOUND TO BE AN ISSUE.
• SUPPLY CHAIN RELYING ON C OF C FROM PLATING CO. WHO USE “TRADITIONAL” METHODS FOR THICKNESS.
• NO CHEMICAL ANALYSIS CERTIFICATION IS CURRENTLY PROVIDED ON CERTIFICATE OF OF CONFORMITY.
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• SUMMARY
• CADMIUM HAS BEEN DETECTED IN ZINC ELECTROPLATED FASTENERS.
• BS/EN/ISO SPECIFICATIONS FOR ZINC ELECTROPLATED FASTNERS DO NOT PROVIDE FOR RoHS COMPLIANCE.
• XRF METHODS HAVE BEEN DEVELOPED FOR CHEMICAL ANALYSIS OF ELECTROPLATED FASTENERS.
• WATCH OUT THERE IS Cd ABOUT.
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•ACKNOWLEDGEMENTS
• BAE Systems Integrated System Technologies: Nick Papanicolaou, Sandy Thomson, Ian Ross, Harry White
• BAE Systems Shared Services PAG: Roger Hoodless, Allen Vale, Patrick Gemmell,
• Fischer Instrumentation (GB) Ltd, Paul Cave, Ray Scruby
• Bruker AXS ltd
• MBH Analytical Ltd
• Institute of Metal Finishing. Southern Branch
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• ABREVIATIONS
• Zn – ZINC
• Cd – CADMIUM
• XRF – X RAY FLUORESCENCE (CHEMICAL ANALYSIS METHOD)
• AAS – ATOMIC ABSORPTION (CHEMICAL ANALYSIS METHOD)
• SEM/EDAX – SCANNING ELECTRON MICROSCOPE + XRF
• BS/ISO/EN – INTERNATIONAL/EUROPEAN/BRITISH STANDARD
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BAE Systems Integrated System Technologies (Insyte) Limited Victory PointLyon Way, Frimley, CamberleySurrey, GU16 7EXUnited KingdomTelephone +44 (0) 1276 603000Fax +44 (0) 1276 603001
email [email protected]/insyte