What is Fusion SEP?
KBS Fusion SEP is a self-etching primer that bonds directly to bare steel, aluminum, galvanized metal, brass, copper, chrome and most hard plastics, and the inter-coat primer for topcoating fully cured RustSeal. Fusion SEP is dry to the touch in 15 minutes and ready to topcoat in 1 hour.
55 to 82°F
Application Range
Fusion SEP is an all-purpose self-etching surfacer primer with two jobs. On bare metal, it primes steel, aluminum, galvanized metal, brass, copper, bronze and chrome directly. Between coats, it promotes adhesion so a topcoat or another primer bonds to a surface it would not grip on its own, including RustSeal that has been in place and rock hard for months or years.
Apply one thin covering coat by brush, roller, spray gun or aerosol. Fusion SEP is medium grey, so you can see exactly where you have primed, and it comes in six sizes, from a 15 oz aerosol to a 5 gallon pail. Satisfaction guaranteed.
Fusion SEP works on rigid surfaces: bare steel, aluminum, galvanized metal, brass, copper, bronze, chrome, fiberglass, GRP, SMC, polyester body filler, factory paint, fully cured RustSeal and most hard plastics. Fusion SEP is also the required first coat inside a plastic or polyethylene fuel tank before Tank Sealer. Flexible plastics need Fusion FPP instead.
- Bare Steel and Iron: clean with KBS Klean, let it dry, then apply a single covering coat.
- Aluminum: primes bare aluminum sheet and parts before the topcoat.
- Galvanized Metal: bonds directly to bare galvanized; clean with KBS Klean first, no other prep.
- Brass, Copper and Bronze: etches and primes soft metals before the topcoat.
- Chrome: primes chrome surfaces so a topcoat can grip.
- Fully Cured RustSeal: a dust coat over RustSeal cured at least 24 hours lets you topcoat without sanding.
- Factory Paint and OEM Surfaces: clean with KBS Klean, rinse, dry, then apply one thin coat.
- Fiberglass, GRP, SMC and Polyester Filler: primes rigid composites and body filler repairs.
- Hard Plastics: primes most rigid plastics. Bumper covers and other parts that flex need Fusion FPP.
- Plastic and Polyethylene Fuel Tanks: Tank Sealer alone will not bond to plastic, so Fusion SEP goes in first.
Fusion SEP does two jobs: it etches and primes bare metal, and it bonds a new topcoat to a hard, cured surface such as RustSeal or factory paint. Fusion SEP goes on in one thin coat, is ready to topcoat in 1 hour, and needs no sanding when topcoated within 24 hours.
- Direct to Metal: self-etching formula primes bare steel, aluminum, galvanized metal and soft metals.
- Inter-Coat Primer: bonds to fully cured RustSeal, so the topcoat goes on without stripping or sanding.
- Fast Topcoat: dry to the touch in 15 minutes and ready for a topcoat in 1 hour.
- Thin Film by Design: one light covering coat is generally all a surface needs.
- Any Application Method: brush, roller, spray gun or aerosol.
- Medium Grey: one color that shows exactly where you have primed.
- Heat Rated: withstands up to 250°F once cured.
- No Sanding Within 24 Hours: topcoat inside 24 hours and skip the scuff.
- Six Sizes: 15 oz aerosol, 8 oz, pint, quart, gallon and 5 gallon pail.
Not a high build primer. Fusion SEP is an adhesion primer, not a filler. To fill sanding scratches and minor surface flaws, apply KBS 2K DTM Build Primer, which can go directly on metal or over Fusion SEP.
Use Fusion SEP wherever a coating has to stick to something smooth, hard or bare: automotive restoration and body work, topcoating the KBS rust prevention system, sealing plastic fuel tanks, priming engine parts before Motor Coater, and priming metal trailers, equipment and small brass or copper parts before painting.
- Automotive Restoration
- Bare steel and aluminum panels, body filler repairs, chassis parts and factory painted surfaces before BlackTop, KBS MAXX or KBS Top Coater.
- Topcoating RustSeal
- A dust coat over RustSeal that has cured at least 24 hours lets a topcoat bond without sanding the RustSeal.
- Plastic Fuel Tanks
- Coat the inside of a dry plastic or polyethylene tank, let it cure overnight, then seal it with Gold Standard Tank Sealer.
- Engines and Engine Parts
- Motor Coater is approved over Fusion SEP after 1 hour.
- Equipment and Trailers
- Bare metal and galvanized parts on trailers, tools and equipment before a durable topcoat.
- Small Metal Parts
- Brass, copper and bronze fittings, tubing and hardware.
One gallon of Fusion SEP covers up to 400 square feet, and one quart covers up to 100 square feet. Fusion SEP goes on as a single thin covering coat, so these figures assume one coat. The 15 oz aerosol covers up to 35 square feet, sized for brackets, small parts and touch-ups.
Fusion SEP coverage per size, one thin coat
| Size | Coverage |
|---|
| 15 oz Aerosol | Up to 35 sq. ft. |
| 8 oz | Touch-ups and small parts |
| Pint | Up to 50 sq. ft. |
| Quart | Up to 100 sq. ft. |
| Gallon | Up to 400 sq. ft. |
| 5 Gallon Pail | Up to 2,000 sq. ft. |
Recoat window: topcoat within 24 hours and no sanding is needed. Between 24 hours and 7 days, skip the scuff only if the primed surface has stayed perfectly clean. After 7 days, scuff Fusion SEP with 300 grit before the topcoat.
Pro Tip: Over RustSeal that has cured at least 24 hours, a light dust coat of Fusion SEP is enough. Wait a minimum of 30 minutes, then apply BlackTop, KBS MAXX or KBS Top Coater.
Fusion SEP and Fusion FPP differ in what they bond to: Fusion SEP is for rigid surfaces that do not flex, like bare metal, hard plastic, factory paint and cured RustSeal, while Fusion FPP is for surfaces that bend, like bumper covers and dashboards. Fusion SEP comes in six sizes and is ready to topcoat in 1 hour.
Fusion SEP and Fusion FPP side by side
| | Fusion SEP | Fusion FPP |
|---|
| Made for | Rigid surfaces that do not flex | Flexible surfaces that bend |
|---|
| Sizes | 15 oz aerosol, 8 oz, pint, quart, gallon, 5 gallon pail | Aerosol only |
|---|
| Surface prep | Clean and dry | Clean, dry, then sand lightly |
|---|
| Dry to the touch | 15 minutes | 10 minutes |
|---|
| Ready to topcoat | 1 hour | 30 minutes |
|---|
| Heat rating | 250°F | 250°F |
|---|
Fusion FPP is the better choice for bumper covers, flexible trim, urethane and any part that bends, because a rigid primer on a flexing part can crack and lose adhesion. See the full Fusion SEP vs Fusion FPP comparison.
Fusion SEP is the middle step between a clean surface and the finish coat.
- Step 1: KBS Klean
- Clean and degrease the surface with KBS Klean, then let it dry.
- Step 2: Fusion SEP
- Apply one thin covering coat. Wait 1 hour before the topcoat.
- Step 3: Topcoat
- BlackTop, KBS MAXX, KBS Top Coater, KBS Top Coater Aerosol or Motor Coater. RustSeal can also go over Fusion SEP, though it is not the standard order.
Shop BlackTop Topcoat
Fusion SEP Application Directions
Temperatures, coats, dry times, spray settings and cleanup in one place.
Read Directions →
Fusion SEP vs Fusion FPP
Which Fusion primer to use on rigid surfaces and which on parts that flex.
Read Article →
Fusion SEP Over Factory Paint
How to prime over factory paint and topcoat it the same day.
Read Article →
Priming Brass, Copper and Bronze
How Fusion SEP etches and primes soft metals before paint.
Read Article →
How to Seal a Plastic Gas Tank
Why a plastic tank needs Fusion SEP before Tank Sealer, step by step.
Read Article →
KBS Spraying Guidelines
Spray gun tip sizes and pressures for every KBS coating.
Read Guide →
Have questions before you buy? Find answers to the most common Fusion SEP questions below, or
order Fusion SEP now.
Yes, Fusion SEP can go over paint. Over factory paint, clean with KBS Klean, rinse, let it dry, apply one thin coat of Fusion SEP and topcoat after 1 hour. Over RustSeal that has cured at least 24 hours, a light dust coat of Fusion SEP is enough; wait a minimum of 30 minutes, then apply BlackTop, KBS MAXX or KBS Top Coater.
For bare aluminum, use a self-etching primer. Fusion SEP primes bare aluminum directly: clean the part with KBS Klean, let it dry, apply one thin covering coat, and topcoat after 1 hour. If the aluminum part flexes, use Fusion FPP instead.
Yes. Aluminum is one of the main surfaces Fusion SEP is made for, along with steel, galvanized metal, brass, copper and chrome. One light covering coat is generally all it takes. Fusion SEP is dry to the touch in 15 minutes and ready for BlackTop, KBS MAXX or KBS Top Coater in 1 hour.
Yes. Fusion SEP bonds directly to bare galvanized metal. The only prep is KBS Klean: clean the surface, rinse, and let it dry completely, then apply a thin covering coat of Fusion SEP and topcoat after 1 hour.
Yes. Fusion SEP bonds to RustSeal that has cured at least 24 hours, even RustSeal that has been in place for months or years, so there is no need to strip it or sand it. Apply a light dust coat of Fusion SEP, wait a minimum of 30 minutes, then apply BlackTop, KBS MAXX or KBS Top Coater.
Fusion SEP is dry to the touch in 15 minutes and ready to sand, prime or topcoat in 1 hour. Topcoat within 24 hours and no sanding is needed. Between 24 hours and 7 days, you can skip the scuff only if the surface has stayed perfectly clean, which is usually hard to do. After 7 days, scuff Fusion SEP with 300 grit first.
After 1 hour, Fusion SEP can be topcoated with BlackTop, KBS MAXX, KBS Top Coater, KBS Top Coater Aerosol or Motor Coater. RustSeal can also go over Fusion SEP, though that is not the standard order. To clear over an enamel such as Motor Coater, wait at least 7 days before the clear coat.
No. Fusion SEP is a thin, self-etching adhesion primer. Its job is to bond the next coat to the surface, not to fill imperfections or build thickness. For a thick, sandable build coat, use KBS 2K DTM Build Primer, which can be applied directly to metal or over Fusion SEP.
No. Fusion SEP is a rigid primer, and a rigid primer on a part that flexes can crack and lose adhesion over time. For bumper covers, fender flares, dashboards and other flexible plastics, use Fusion FPP Flexible Plastics Primer, which is made to move with the part.
Apply Fusion SEP between 55 and 82°F by brush, roller, spray gun or aerosol, always in thin covering coats. One coat is generally enough; if you need more, apply 2 to 3 light to medium coats 3 to 5 minutes apart. Spray at 35 to 45 psi with a siphon or pot gun, or 25 to 35 psi with a gravity gun, using a 1.0 to 1.2 tip. Thinning is not generally required; if needed, reduce 5 to 10% with KBS #1 Thinner only, never lacquer thinner. Clean up with KBS #1 Thinner or lacquer thinner before Fusion SEP dries.
See all Fusion SEP questions and answers →
