METHOD OF MAKING SELECTIVE COATING Russian patent published in 2010 - IPC C25D11/10 F24J2/48 

FIELD: chemistry.

SUBSTANCE: method involves preliminary fat removal, surface etching and electrochemical coating. The surface loosening steps comes after the etching step, which involves chemical zinc plating from an alkaline solution with subsequent removal of zinc in an orthophosphoric acid solution. The coating process is carried out on alternating asymmetrical current with ratio of average cathode and anode current equal to 1.5:1 and voltage of 8-15 V using an electrolyte at 25±5°C having the following composition in g/l: Al₂(SO₄)₃●18H₂O 35.0; NiSO₄●7H₂O 35.0; formalin 1.5; citric acid 1.0.

EFFECT: more efficient conversion of collector solar energy to heat energy and lower cost of the coating.

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