| abstract |
Compositions and processes are disclosed for producing improved environmental protection, corrosion resistance and improved paint adhesion for metals e.g., ferrous, aluminum, or magnesium alloys, as well as other substrates upon contact. The compositions and processes comprise use of one or more Group IV-A metals, such as zirconium, in combination with one or more Group III-A metals, such as cerium, in an acidic solution with one or more oxyanions or other non-fluoanions to stabilize and solubilize the metals while fluorides are specifically excluded from the processes and compositions above certain levels. The processes can contain pretreatment stages that serve to activate a substrate surface and/or promote formation of mixed-metal oxide matrices through use of an oxygen donor. The compositions are at a pH below about 7.0 and are preferably in a range between about 1.0 and about 4.0. The coatings may contain surfactants, sequestering agents, or organic additives for improved corrosion protection and paint adhesion. The substrate may be treated by immersion, spray, fogging or rollcoat. |