The present invention discloses a
chromium-free treatment liquid for preparing
corrosion resistant oxidation film at
aluminium alloy surface as well as the
processing and use method thereof, characterized in that said treatment fluid utilizes a
cobalt (III) salt as a main salt and a hypermanganate and a
nitrate as a composite oxidizing compound to prepare a composite Co-Mn oxidation film having favorable
corrosion resistance performances at
aluminium alloy surface. The formula for said treatment liquid is that each litre solution contains
cobalt salt of 5 g / L(-1)-20 g / L(-1), kalii permangana of 1 g / L(-1)-4 g / L(-1),
sodium nitrate of 1 g / L(-1)-4 g / L(-1), promotor (chlorides and fluorides) of 1 g / L(-1)-4 g / L(-1),
sodium acetate of 20 g / L(-1)-50 g / L(-1) and
wetting agents (
sodium dodecylbenzene sulfonate, OP-10) of 0.5 g / L(-1)-1 g / L(-1). Saic
processing and use method comprises (1)sanding the
aluminium alloy until its surface is smooth and even; (2) pretreating the
aluminium alloy surface; (3) performing a conversion
processing by using the treatment fluid; (4) cleaning-up using water and atmospheric-
drying naturally. Said treatment fluid in accordance with the present invention possesses the advantages of
environmental protection due to its
hexavalent chromium-free, fast film-forming speed, simple process, uniform rete, strong
corrosion resistance, few environment
pollution, and the like.