Ultra-black coatings for space instruments: A comparison of traditional Ebonol C processes and a method for future repeatability

Ultra-black coatings have served various roles in space instrumentation and hardware. The Ebonol C coating has been used for various missions requiring low reflectivity on aluminum substrates that are electrically conducting. This coating is produced through the formation of a cupric oxide structure on an intermediate layer of copper applied to the aluminum. For many years, this commercial formulation has been used ubiquitously for space instruments. The coating relies upon details of the copper base layer that have been trade secret at various finishing companies, and the availability of the Ebonol C formulated chemistry from the chemical supplier. In recent years, this product has been discontinued at various times, leaving vendors to either rely on expired stock or to formulate their own equivalents. Here, we detail the processing methods, chemistries, and resultant coating structures that produce reflectance performance equivalent to baseline historical reflectance data. This process detail will ensure equivalent performance for such coatings for future missions and link the performance to past and currently deployed instruments.