KBS Cavity Coater — Cavity Wax for Long-Term Rust Protection on Enclosed Metal

Cavity Coater delivers over 4,000 hours of salt spray protection per ASTM B-117 testing on steel — more than 4 times the protection of conventional cavity waxes. It also passes low-temperature flake testing (to −60°F), water displacement testing, and compatibility testing with cadmium, magnesium, and aluminum.

Cavity Coater is designed for any enclosed or hard-to-reach metal surface. Automotive applications include rocker panels, boxed frames, inside doors, inside fenders, windshield cowls, trunk lids, hoods, A-posts, B-posts, tailgates, and the back sides of bumpers. It also works as an anti-seize coating on nuts, bolts, screws, shafts, pipe fittings, gaskets, chain drives, and general machinery.

For enclosed cavities, use the Cavity Coater Aerosol with a KBS Cavity Wand. Attach the Cavity Wand to the aerosol can, insert the wand into the cavity, depress the spray tip, and withdraw at about one foot per second. Repeat for complete coverage. After use, invert the can and spray for 10 seconds to flush the wand.

For bulk quart or gallon sizes, apply through a KBS Schutz Underseal Spray Gun with a 48-inch 360-degree spray wand, thinned 30–50% with KBS #1 Thinner or mineral spirits, at 90–150 PSI.

Cavity Coater requires minimal surface preparation. Remove any readily accessible loose, scaly rust. If grease or oil is present, clean the surface with KBS Klean first. The surface must be dry before application. Cavity Coater is specifically designed to penetrate and protect even imperfect surfaces — bare metal is not required.

Do not caulk or paint over Cavity Coater. Cavity Coater is a final-step product applied to interior cavities after all exterior paints and coatings have completely cured. Topcoats will not properly adhere to Cavity Coater.

If you are using both RustSeal and Cavity Coater, apply and fully cure RustSeal first on the exterior, then apply Cavity Coater to the interior cavity. See the FAQ below for the full RustSeal + Cavity Coater workflow.

Yes — combining RustSeal and Cavity Coater gives you the ultimate inside + outside rust protection: RustSeal protects the exterior of the surface, Cavity Coater protects the interior cavity. Order of application matters: apply and fully cure RustSeal first, then apply Cavity Coater. RustSeal will not adhere to Cavity Coater, but Cavity Coater applied over fully cured RustSeal is not a problem.

Coverage rates at 1 mil thickness:

Aerosol: 125 sq. ft.
Quart (32 oz.): 200 sq. ft.
Gallon (128 oz.): 800 sq. ft.

Cavity Coater is also available in 5-gallon pails and 55-gallon drums for shop and fleet applications.

The Cavity Coater Aerosol with Cavity Wand works best when the temperature is between 70–80°F. Once cured, Cavity Coater is rated to resist cracking and flaking down to −60°F, making it suitable for cold-climate vehicles and equipment.

Standard cavity waxes sit on the surface and can crack, drip, or lose adhesion over time. KBS Cavity Coater is a corrosion inhibiting coating (CIC) that super-penetrates into welds and seams through capillary action, displaces water, and forms a self-healing film that stays put — even in extreme cold. It provides over 4,000 hours of ASTM B-117 salt spray protection, which is more than 4 times the protection of conventional cavity wax products.

Yes. Cavity Coater has lubricating properties that protect against carbon fusion and make future disassembly easier. It can be applied to nuts, bolts, screws, shafts, pipe fittings, gaskets, press-fit assemblies, valve assemblies, chain drives, and other metal fittings to minimize corrosion and reduce parts replacement costs over time.