Electroplated hard chromium (EHC) is a proven coating process, but many environmental, health, and safety (EHS) issues and regulations are associated with its use. As a result, the Department of Defense (DoD) has investigated and implemented thermal spray coatings to replace EHC in its maintenance facilities.
Tthe United States Air Force Research Laboratory – Advanced Power Technology Office (AFRL – APTO), in conjunction with Concurrent Technologies Corporation (CTC), sought both electroless and electrochemically deposited chromium- (Cr-) free coatings that could treat NLOS parts. Most suitable candidates contained nickel (Ni), which has other health concerns. It also is listed on the Environmental Protection Agency’s list of hazardous substances and is on the watch list as an emerging contaminant by the Office of the Deputy Under Secretary of Defense for Installations and Environment Chemical and Material Risk Management Directorate (CMRMD). As a result, Ni-based products are expected to become more heavily regulated and, thus, not suitable for mid- to long-term solutions.
To address this problem, the team investigated non-Cr and non-Ni technologies (i.e., largely cobalt-based coatings), with fewer health concerns and potentially reduced restrictions as compared to EHC.