Missouri University of Science and Technology Rolla United States
Missouri University of Science and Technology Missouri S and T collaborated with Dipsol of America Dipsol and Boeing Research and Technology BR and T to develop and evaluate low contact resistance passivation layers for Department of Defense electrical system components. Specifically, the team examined five different types of passivation layers that were free of hexavalent chromium for low hydrogen embrittlement LHE ZnNi coatings. Passivations included a trivalent chromium passivation TCP or CrIII, a Co-Free TCP, and a Modified Co-Free TCP developed at Dipsol as well as two cerium based conversion coatings CeCCs developed at Missouri S and T using cerium chloride and cerium nitrate sources. Hexavalent chromium passivation on electroplated ZnNi was used as a reference. Characterization of the electrical, electrochemical, corrosion, and materials performance of the passivation layers was done to evaluate the corrosion performance and electrical resistance after neutral salt spray exposure. The major outcome of this project was to identify the most promising passivation layers that are free of hexavalent chromium and can be used on LHE ZnNi plated electrical connectors for military electrical system components.