Missouri University of Science and Technology (Missouri S&T) will collaborate with Dipsol of America (Dipsol) and Boeing Research & Technology (BR&T) to develop and evaluate low contact resistance passivation layers for Department of Defense (DoD) electrical system components. The team will investigate the two most promising non-chromate passivation layers, trivalent chromium passivation (TCP) and a modified cobalt free (Co-Free) version of TCP, developed by Dipsol. Electrical, electrochemical, corrosion, and materials performance of the passivation layers on test substrates and fully functional electrical connectors will be studied to identify conversion coatings that meet military specifications for electrical resistance. The major outcomes of this project will be the identification of environmentally benign passivation layer(s) that can be used on low hydrogen embrittlement (LHE) ZnNi plated electrical connectors for military electrical system components along with knowledge of the mechanisms of degradation and failure.

Dipsol’s IZ-C17+ LHE ZnNi plating process, which has been approved by the U.S. Air Force and Boeing for aerospace and military applications, will be used as the LHE ZnNi coating. Missouri S&T and Dipsol will work together to evaluate and optimize the TCP and Co-free TCP passivations on LHE ZnNi test substrates that were previously developed, including darker color passivations, if the user community deems it necessary. Missouri S&T and Dipsol will then coat and assemble DoD approved connectors that will be tested and evaluated by Boeing per military MIL-DTL-38999 specifications. Shell to shell contact resistance before and after corrosion testing will be done, as will materials analysis of the connectors. Electrochemical and analytical techniques will be employed to understand the performance of the coating systems based on scientific principles and fundamental mechanisms. Missouri S&T will also study a novel electrical contact measurement system that is more robust and reproducible than the current MIL-DTL-81706B method.

This research will identify materials, processes, methods, and procedures needed to replace cadmium and hexavalent chromate coatings on LHE ZnNi coatings used for DoD electrical components. Test protocols for rapid and effective performance evaluation of environmentally friendly passivation layers on LHE ZnNi will be investigated and optimized. The team of Missouri S&T, Dipsol, and Boeing will provide the fundamental knowledge, industrial expertise and supplier base, and end user performance evaluation that will result in coatings able to meet the DoD requirements for electrical connectors.