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ELECTROPLATED 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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• XRF SPECTRUM PEAK: ZINC

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• XRF SPECTRUM PEAK: CADMIUM

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• XRF: SPECTRUM PEAK: ZINC + CADMIUM

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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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• METALLOGRAPHIC EXAMPLE: A

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• METALLOGRAPHIC EXAMPLE: B

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• METALLOGRAPHIC EXAMPLE: C

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• METALLOGRAPHIC EXAMPLE: D

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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 FOR Cd/Zn ANALYSIS• THICKNESS/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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