專利摘要：
A method for treating aluminum to enhance corrosion resistance of its surface. The chemical conversion coating aluminum and aluminum alloys are exposed to an aqueous PU solution to form a PU film on the surface. The aqueous PU solution comprises: (i) 5-15% weight of water dispersable polyurethane resin, (ii) 0.1-56 weight of cross-linking agent, and (iii) 80-94.9% weight of water.