Black permanganate conversion coatings on aluminium alloys for thermal control of spacecraft

Authors:
  • RRR. Uma Rani
    R. Uma Rani
  • SMS. M. Mayanna
    S. M. Mayanna
  • HBH. Bhojraj
    H. Bhojraj
  • DBD. R. Bhandari
    D. R. Bhandari
Publisher website
Google Scholar
Abstract
A black conversion coating on aluminium alloys in an electrolyte system consisting of potassium permanganate, copper nitrate, arsenic trioxide and nitric acid was investigated. To optimise the process, the effects of various operating parameters, i.e. electrolyte concentration, operating temperature, treatment time and coating thickness, on the physico-optical properties of the coating were investigated. The chemical nature of the coating was evaluated with EDX and infrared spectral studies. The microstructure of the coating was investigated with SEM. The thermal nature of the coatings was evaluated by thermal studies. The space worthiness of the coating was evaluated by humidity, thermal cycling, thermovacuum performance tests and measurement of optical properties. The black coating provides higher emissivity as well as higher solar absorptance in the order ∼0·80.