METALLIC SUBSTRATE COATING COMPOSITION Russian patent published in 2007 - IPC C09D1/02 B05D3/12 B05D7/14 C09D5/10 

FIELD: protective coatings.

SUBSTANCE: invention relates to undercoat for metallic substrates designed for manufacturing articles and for applying top coating layers. Undercoat comprises silicate binder containing aqueous silica sol having SiO₂/M₂O molar ratio at least 25:1, wherein M represents sum of alkali metal ions and ammonium ion, silica particles having average size above 10 nm. Binder may further contain insignificant amount of alkali metal silicate. Content of solids in undercoat ranges between 20 and 40% (v/v) and volume ratio of pigment concentration to critic concentration thereof is below 1. Undercoat contains following proportions of components aqueous silicate sol as binder having SiO₂/M₂O molar ratio at least 25:1 and pH value between 9.5 and 11, wherein M represents sum of alkali metal ions and ammonium ion and silica particles are optionally modified with aluminum oxide and have average diameter 10-16 nm; 10-55% zinc and/or zinc alloy powder based on the weight of dry film having average particle size between 2 and 12 μm; 0-35% organic resin based on the weight of dry binder; and 0-30% organosilicon finishing material. Coating may contain zinc-free pigment(s) and filler increasing storage life time of undercoat. Method of applying undercoat onto steel substrate comprises preparing undercoat using silica sol, whose pH is adjusted to 9.5-11, and depositing undercoat onto steel substrate.

EFFECT: increased hardness and wear resistance, and enabled deposition of corrosion-resistant coating without blistering.

15 cl, 10 tbl, 14 ex