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Performance of Zinc and Zinc Alloy Platings on Grade 8 Fasteners
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Abstract
Cadmium has been identified by the United States Army's Tank and Automotive Command as a threat to worker health and the environment. Based on already completed cadmium substitute testing, an evaluation program was conducted to quantitatively analyze the resistance to vibrational loosening, torque-tension properties, environmentally assisted cracking susceptibility, and corrosion properties of zinc-based alternatives to cadmium, with and without supplemental coatings. The primary performance issues studied were fastener behavior after vibrational joint motion, mechanical performance in corrosive environments, and realistic corrosion performance. Data was generated from various laboratory evaluations and natural marine exposure of fasteners under loaded conditions. Test specimens were prepared by applying electrochemically sacrificial plating layers and supplemental coatings to 1/2-20 UNC Fine, Grade 8 fasteners and 4340 steel tensile specimens.
Program findings indicate that some zinc and zinc/cobalt plated fasteners experience a significant drop in breaking torque after cyclic joint motion that does not cause a similar change in cadmium fasteners. Zinc and zinc/cobalt alloy plating systems were also found to significantly lower the ductility of tensile test specimens when tested in a 3.5% salt solution environment at a slow, constant extension rate. Tin/zinc systems had less of an effect on the ductility of the constant extension rate samples. None of the coatings contributed to environmentally assisted corrosion cracking on test fasteners, or experienced a significant change in breaking torques during four months of marine atmospheric exposure under a nominal, dynamic load.
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Authors
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Citation
Cramer, K., Handsy, I., and Ault, J., "Performance of Zinc and Zinc Alloy Platings on Grade 8 Fasteners," SAE Technical Paper 960815, 1996, https://doi.org/10.4271/960815.Also In
References
- “Evaluation of Environmentally Acceptable Alternatives for Cadmium Plating” OCRC Final Report Army Materiel Command, Acquisition Pollution Prevention Support Office December 1991
- “Hybrid Fasteners as Potential Substitutes for Cadmium Plating” OCRC report Army Materiel Command Acquisition Pollution Prevention Support Office December 1993
- Junker, Gerhard H. “Criteria for Self Loosening of Fasteners Under Vibration” Aircraft Engineering October 1972 44 10 14 17
- Biddulph, Cliff “Zinc Plating” Metal Finishing: Guidebook and Directory Issue January 1995 93 1A 317 323
- Miller Ed Mr. Miller and Son Plating Belleville, NJ
- Bernard, M. C. Goff A. Hugot-Le Phillips N. “In situ Raman Study of the Corrosion of Zinc-Coated Steel in the Presence of Chloride: II. Mechanisms of Underpaint Corrosion and Role of the Conversion Layers” J. Electrochem. Soc. 142 7 July 1995 2167 2170
- Budman, Ed Sizelove Robert “Zinc Alloy Plating” Metal Finishing: Guidebook and Directory Issue January 1995 93 1A 324 329
- Military Specification: Studs, Bolts, Hex Cap Screws, Socket Head Cap Screws and Nuts
- Raymond, Lou “Hydrogen Embrittlement of Fasteners: Problems and Solutions; First International Technology Transfer Conference” May 17-19 1995 Denver, CO L. Raymond & Associates
- Boffardi, Bennett P. Godard Hugh P. “Practical Application of Statistics: Part 2” Materials Performance December 1989 54 55
- Parmiley, Robert O. Standard Handbook of Fastening and Joining Second McGraw-Hill Inc. 1989 1 25