| 摘要 |
Improved zinc-containing coating compositions are useful to protect ferrous-containing surfaces. They are particularly useful and highly protective against red rust. The compositions with higher zinc content can be used as very thin coatings. Those having lower zinc content are used to provide preferably a thicker coating. The compositions contain: metallic zinc in particulate form, e.g., zinc dust or zinc flake; a polyol silicate; an inhibitor pigment selected from a chromate composition (selected from strontium chromate, calcium chromate, barium chromate, a mixture of zinc chromate and zinc oxide or hydroxide, a mixture of zinc chloride and strontium chromate, a mixture of zinc chloride and strontium chromate and chromium oxide green), zinc phosphate, barium metaborate, calcium borosilicate, and a mixture of red lead oxide and calcium carbonate; and a liquid organic vehicle. When zinc dust is used as the particulate zinc, finely divided inert extenders, such as iron phosphide, may be incorporated in the composition; in such composition the zinc content of the combination can be lower without impairing the protective action provided by a coating of the composition. The polyol silicate is a solvent soluble polyol silicate ester-exchange reaction product of (1) an organic silicate consisting essentially of ortho or poly silicates or siloxanes thereof having ester-exchangeable groups of 1 to 6 carbon atoms selected from the group consisting of alkyl, hydroxyalkyl, alkoxyalkyl, and hydroxyalkoxyalkyl, siloxanes thereof, and their mixtures, and (2) a polyol which is ester-exchangeable with (1). The composition containing zinc flake, polyol silicate and strontium chromate is a preferred composition as it can provide very highly protective rust-free thin coatings of 0.05 to 0.2 mil dry thickness, that offer the advantages of a preconstruction weld-thru coating having improved flexibility for forming operation processes.
|
