UNIVERSAL AQUEOUS COATING COMPOSITIONS FOR PRETREATING METAL SURFACES

摘要

A universal aqueous composition and a process for using such a composition for pretreating metal substrates is provided. The aqueous composition includes a hydroxy functional cyclic compound, such as a tannin, in an amount of at least about 500 ppm, phosphate ions, an oxidizer-accelerator, and at least one Group IVB metal compound capable of converting to a metal oxide upon application to the metal substrate, such as a fluorozirconate or fluorotitanate. The composition may further contain fluoride ions and/or iron. The composition is particularly useful for corrosion resistance with a variety of metals such as iron, steel, zinc-coated surfaces, aluminum, and alloys thereof. A disaccharide may further be provided to prolong the useful life of the composition, particularly when used in spray applications.