Development of Cad Plating Replacement with Alkaline Zinc Nickel Electroplating for Threaded Fasteners / Components

Aircraft structure and propeller systems utilize both high and low strength steel, cadmium plated threaded components and fasteners throughout its structure.   Threaded joints and fasteners manufactured from these alloys require sacrificial protective coatings due to the corrosive environment.  Cadmium (Cd) has been the baseline coating for such threaded joints and fasteners for many years due to its many desirable functional qualities.  In addition to corrosion protection, cadmium also provides excellent lubricity characteristics; however, cadmium is a toxic metal and known carcinogen that poses environmental and occupational safety and health risks throughout the life cycle of the plated parts.  Under United States Air Force (USAF) SBIR AF081-101,  ES3 is currently investigating a cadmium plating alternative; alkaline zinc-nickel (Zn-Ni) coating, which ES3 refers to as IZ-C17+.  ES3 has conducted a feasibility study and related testing necessary for USAF aircraft and engine/propeller system usage by studying torque tension relationships and other plating characteristics, such as corrosion characteristics as compared to typical Cd plating.  This paper will present test results to date and anticipated benefits for the Department of Defense (DoD) and commercial industry.