Selvam, M. and John, S. and Balasubramanian, V. and Shanmugam, N.V. and Srinivasan, K.N.
(1986)
Immersion blackening of galvalume coatings for photothermal conversion of solar energy.
Bulletin of Electrochemistry , 2 (1).
pp. 17-19.
ISSN 0256-1654
Abstract
A method for producing black coatings on 'tiahralume' by immersion technique has been
studied for solarthermal energy utilization. An electrolytecontaining 100gll nickel sulphate,25
gll ammonium molybdate, 30 gll ammonium sulphate operating at 70°C at a pH of 3.5-4.5 for
an immersion time of 20 seconds produces black coatings with optical properties of K= 0.90
and L = 0.30. The coating is post treated in 5 gll sodium dichromate at 60°C for 30 seconds to
enhance the corrosion resistance, as otherwise the black coating gets discoloured to brownish
shade upon exposure to atmosphere. The influence of bath composition, pH, temperature and
immersion time on the optical.properties (<f) is studied. Influence of post treatment is also
considered-Thermal cycling test showed that the coating is fairly stable.
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