Fluoropolymer primer having improved scratch resistance

A coating composition comprising

• a. about 10%-90%, by weight of the total of (a) and (b) solids, of a particulate polymer of monoethylenically unsaturated hydrocarbon monomers completely substituted with fluorine atoms or a combination of fluorine atoms and chlorine atoms, the polymer having a number average molecular weight of at least 20,000;
• b. about 10%-90%, by weight of the total of (a) and (b) solids, of a binder which comprises
• 1. about 5%-95%, by weight of the total of (1) and (2), of a colloidal silica which air-dries to form a continuous film when laid down by itself,
• and
• 2. about 5%-95%, by weight of the total of (1) and (2), of a salt of a polyamide acid represented by the structure ##STR3## where G is a hydrogen or a carboxyl group;
• .fwdarw. denotes isomerism;
• R is a tetravalent organic radical containing at least two carbon atoms, no more than two carbonyl groups of each polyamide acid unit being attached to any carbon atom of said tetravalent radical;
• R.sub.1 is a divalent radical containing at least two carbon atoms, the amide groups of adjacent polyamide acid units each being attached to separate atoms of said divalent radical;
• and
• n is a number large enough to give the polyamide acid an inherent viscosity of at least 0.1, measured as a 0.5% solution in N,N-dimethylacetamide at 30.degree. C.,
• neutralized with a stoichiometric amount of a tertiary amine;
• c. about 10-90%, by weight of (b) (2), of N-methyl pyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, cresylic acid, sulfolane or formamide;
• d. about 0.2-20%, by weight of the total of (a), (b) (1), (b) (2), (c), and (d), of mica particles, mica particles coated with pigment, or metal flake;
• and
• e. a liquid carrier.