Mildly alkaline thin inorganic corrosion protective coating for metal substrates

摘要

Disclosed is a neutral to alkaline inorganic conversion coating composition that can be applied directly to a metal surface without a phosphatizing pre- treatment and that provides significant corrosion protection to the surface. The conversion coating composition preferably has a pH of from about 6 to 1 1 and more preferably from 8 to 10. In one embodiment, the coating composition includes at least one element from group IVB of the Periodic table, and optionally, at least one element from group VB of the Periodic Table, and an organic polymer. Preferably, the coating composition includes from 9 to 73% by weight, based on the total dry solids coating weights, of at least one element from group IVB of the Periodic Table. In another embodiment the conversion coating composition comprises at least one element from group IVB, a source of chrome, and an organic polymer. Preferably, the coating composition includes from 9 to 73% by weight, based on the total dry solids coating weight, of at least one element from group IVB of the Periodic Table. The conversion coating composition is a dry in place coating and produces a unique morphology upon drying of a continuous inorganic phase in which the organic polymer is dispersed as discrete polymer spheres. The coating composition is very versatile and can accommodate addition of a wide variety of organic polymers which can be added directly to the coating composition thus eliminating multistep coating processes.