| 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 to provide preferably a thinner coating. The compositions contain preferably; metallic zinc in particulate form, e.g., zinc dust or zinc flake; a polyol silicate a residual polyol or polyol polymer, and an inhibitor pigment selected from an alkaline earth chromate, a comixture of zinc chromate and one or more of the finely divided silicates, carbonates, oxides, hydroxides, and sparingly soluble compounds of magnesium and calcium, a comixture selected from a metal chromate-3 compound which metal is not lower than iron in the electrochemical series-plus a sparingly soluble metal compound filler which metal is also not lower than iron in the electrochemical series. In substitution for or in conjunction with the chromate inhibitor a phosphate and or borate inhibitive pigment composition which metals are higher than iron in the electrochemical series can be used as a synergistic coinhibitive composition. These compositions can be incorporated in or reacted with the polymeric portion to reduce leachability. The coatings may even be used advantageously without zinc if use is next to or in contact with a zinc coating, either under or over the zinc coating as a composite coating, with cosynergistic protection. Finely divided inert extenders such as iron phosphide, may be incorporated in the composition; in such compositions comprising the inhibitor or coinhibitor pigment 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-exchanged reaction product of (1) an organic silicate consisting essentially of ortho silicate or siloxanes thereof having ester-exchangeable groups of 1 to 6 carbon atoms selected from the group consisting of alkyl, hydroxyalkyl, alkoxyalkyl, and hydroxyalkoxy alkyl, siloxanes thereof, and their mixtures, and (2) an aliphatic polyol which is ester exchangeable with (1). The residual polyol or polymeric polyol may be loosely or preferably unreacted with the silicate. The composition containing either zinc dust or zinc flake, or their blend, polyol silicate, polyvinyl butyral, and strontium chromate is a preferred composition as it can provide very highly protective rust-free thin coatings of 0.05 to 0.2 or 0.3 or 0.5 mil dry thickness, that offer the advantage of a preconstruction weld-thru coating having improved flexibility for forming operation processes.
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