In response to the increasing herdth end disposal costs related to the use of cadmium end requests from international customers, it is imperative that alternative coating systems be developed to replace cadmium. With this in mind, the effectiveness of Ion Vapor Deposited Aluminum (IVD/Al), Zinc Nickel (Zn/Ni) and Tin Zinc (Sn/Zn) as
environmentally compliant replacements for cadmium was evaluated. Variations of each coating were tested for corrosion resistance, thickness, uniformity, adhesion and torque-tension behavior when applied to steel (DIN) threaded fasteners and flat sheet specimens.
Test results indicated that non-chromated IVD/Al coated with a commercially available, lubricious-PTFE formulation exhibited corrosion and torque-tension behavior directly comparable to that of the chromated (conversion coated) cadmium. In addition, it was shown that this combination provided an effective base coat to which organic topcoats would readily adhere.
KEY WORDS: DIN Bolts, Ion Vapor Deposition, PTFE, Cadmium Plating, Salt Spray, Adhesion, Lubricity, Torque-Tension, Al, Zinc Nickel, Tin Zinc