Directed Vapor Deposition of a Cadmium Replacement Coating for High Strength Fasteners
Abstract
Corrosion protection of high strength fasteners is of utmost importance due to the critical nature of structural loads transferred through them and their potential for galvanic corrosion. Therefore, adequate corrosion protection is a necessity to sustain both the structural integrity of fastener connections and to prevent preferential corrosion of connected members at the expense of galvanically-coupled fasteners. Traditionally, electroplated cadmium layers and hexavalent chromium rinses have been employed for these applications due to their excellent corrosion performance and lubricity for threaded applications; however, cadmium and chromate are hazardous substances, known human carcinogens and subsequently have high handling and disposal costs. These environmental, health and safety issues have resulted in more stringent OSHA and EPA regulations. These factors have increased the need to develop new coating technologies and corrosion protection systems for cadmium plating and chromate conversion coating replacement. Luna Innovations Incorporated, in partnership with Directed Vapor Technologies International, Inc. (DVTI, Inc.), performed work on a reduced-scope solution to SERDP WPSON-08-01 by using a directed vapor deposition (DVD) process to deposit Zn-Ni-Co ternary alloy coatings onto high strength steel substrates as a cadmium plating replacement option. The main objective of the program was to demonstrate the feasibility of producing a vapor deposited Zn-Ni-Co ternary alloy that exhibits improved corrosion resistance over that of typical cadmium coating processes while at the same time reducing the propensity for hydrogen embrittlement on coated fasteners in service. The reduced-scope research program consisted of a year of funding to demonstrate coating feasibility and culminated in corrosion performance characterization of several coated high strength steel substrates.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 2009
- Accession Number
- ADA520633
Entities
People
- Adam Goff