The invention provides a method for preparing a micro-arc oxidized
coating with high
solar absorptivity and high
emissivity. The invention solves such a problem associated with prior Al-
alloy coating that the solar-absorptivity,
emissivity and bond, etc. can't meet the requirements from such fields as
aerospace and decoration. The procedures are: placing a cleaned Al
alloy in a stainless steel electrolytic tank as an
anode, taking the stainless steel electrolytic tank as a
cathode, supplying power by a pulse micro-arc oxidizing power supply, controlling the
current density to be 0.5- 30A / dm<2>, positive
voltage 240-1000 V, power supply frequency 50-3000 Hz, duty rate 10-50%, and controlling the
electrolyte by a cooling circulating water to be no more than 30 DEG C, pH value of the
electrolyte 8-12, carrying out micro-arc oxidization for 5-180 min., and then obtaining a
ceramic coating. The invention reduces the cost and improves the product performance. The invention obtains a
ceramic coating that has a
solar absorptivity on Al
alloy surface more than 0.90 and
emissivity more than 0.80, in addition, the coating is of high
hardness (more than 1000 Hv) and good bond with the substrate.