Overview
Built for the job.
High-Build Primer Surfacer is an elastomeric acrylic coating for priming automotive metal, aluminum, urethane, and plastics.
SEM 42043 High-Build Primer Surfacer is a 20 oz white primer formulated for high-build applications on automotive panels. It provides a smooth, sandable base for subsequent coating layers and is suited to repair work where rapid build-up of material is required.
The formulation offers a 15-minute sandable window, a total work time of 60 minutes, and reaches full cure in 48 hours. Coverage is rated at 11 sq ft per 2 mil dry film thickness on compatible substrates including aluminum, bare metal, e-coat, fiberglass, OEM plastic, steel and other primed surfaces. Zero VOC content meets stringent environmental standards while maintaining high build capability.
Use in a well-ventilated area with appropriate personal protective equipment: safety glasses or goggles, chemical-resistant gloves, protective clothing, and a respirator as required by the listed GHS hazards (acute toxicity, eye damage, skin corrosion, etc.). Follow all H-statements on the label for safe handling.
Why Pros Choose SEM SEM
- Provides superior adhesion
- Excellent filling properties
- Works on multiple substrates, including metal and plastic
- Easy to sand
- Topcoat with most refinish material
How to Use
For use on steel, aluminum, plastic, SMC and fiberglass
- Clean the substrate thoroughly-remove oil, grease, dust, and loose material. The product is compatible with aluminum, bare metal, e-coat, fiberglass, OEM plastic, primer, SMC, and steel.
- Apply SEM 42043 High-Build Primer Surfacer to a wet film thickness that will achieve 2 mil DFT after flash (approximately 4-5 mil wet). Use a spray gun or HVLP equipment; the work time is up to 60 min.
- Allow the coat to become sandable after approximately 15 min. Lightly sand with 320-grit paper before applying additional coats if needed, staying within the 60-minute work window.
- After the final coat, let the surface dry to touch in about 1 hour. Full cure is reached after 48 hours at ambient conditions.
Compatibility
Compatible substrates: Aluminum, Plastic.
Compatible paint systems: Urethane, Acrylic.
Specifications
| Part No. | 42043 |
|---|---|
| Product Line | SEM |
| MFR Model | 42043 |
| Standard/Approvals | California PROP65 Warning: Cancer and Reproductive Harm | GHS02 | GHS04 | GHS07,GHS08 | OSHA HCS Hazard |
| Application | For use on steel, aluminum, plastic, SMC and fiberglass |
| Manufacturer | SEM |
| UPC | 646786420436 |
| Brand | SEM® |
| Color | White |
| Container Size (oz) | 20 |
| Curing Time | 1 hr Dry |
| Coverage (sq-ft) | 11 |
- Coverage
- 11 sq-ft @ 2 mil DFT (20 oz)
- Work Time
- 60 min
- Sandable Time
- 15 min
- Dry Time
- 1 hr
- Cure Time
- 48 hr
- VOC
- Zero
- Compatible Substrates
- Aluminum, bare metal, e-coat, fiberglass, OEM, plastic, primer, SMC, steel
About SEM
SEM Products specializes in paint adhesion systems, flexible coatings, and plastic repair — the go-to choice for interior and trim refinishing.
Frequently Asked Questions
What substrates is SEM 42043 High-Build Primer Surfacer compatible with?
It can be applied to aluminum, bare metal, e-coat, fiberglass, OEM plastics, primer, SMC, and steel.
How long does it take for the primer to fully cure?
The full cure time is 48 hours at ambient conditions.
When can I begin sanding or applying topcoat?
Sanding is possible after the sandable window of 15 minutes. The work (flash) time is 60 minutes, and full cure for over-coat readiness is 48 hours.
What personal protective equipment is required when handling this product?
Use eye protection, chemical-resistant gloves, protective clothing, and a respirator as indicated on the SDS.
What is the coverage rate for SEM 42043?
One 20 oz can provides approximately 11 sq-ft at a film thickness of 2 mil DFT.
Documents & Safety
- Safety Data Sheet (SDS)
- sem_42003_catalog.pdf
- dualmix_39337_service_manual.pdf
- 42043%20High%20Build%20Primer%20WhiteUSA.pdf
Signal word: Danger. Wear chemical-resistant gloves, safety goggles or face shield, protective clothing (coveralls), and a suitable respirator when handling this primer. The product is highly flammable, can cause severe skin burns and eye damage, is toxic if inhaled, and is classified as carcinogenic and harmful to aquatic life. Use only in well-ventilated areas and keep away from ignition sources. Always refer to the full SDS before use.
Why Buy from autofxmart
- Authorized distributor — authentic, factory-fresh stock.
- Fast US shipping — most orders ship within 1 business day.
- 30-day returns — buy with confidence.
- Pro-shop pricing — bulk discounts available on request.
- Expert support — questions? Email us at support@autofxmart.com.
Specifications
Full data
Frequently asked
Good to know
SEM is compatible with Aluminum, Plastic. Always ensure the surface is properly cleaned, degreased, and sanded before application to achieve the strongest adhesion and a professional finish.
The curing time for SEM is 1 hr Dry. Drying and curing times may vary with temperature, humidity, and film thickness — always consult the Technical Data Sheet (TDS) for exact cycle conditions.
This listing ships SEM in a 20 (CN) container. Check the autofxmart catalog for other sizes and bulk pricing.
Most in-stock orders for SEM ship the same or next business day from our US warehouse. Expedited options are available at checkout. Freight-class items may require an additional 1–2 days for carrier pickup.
Yes. autofxmart is an authorized distributor of SEM products. Every unit is factory-fresh, sealed, and backed by the manufacturer's standard warranty. If you have a concern, contact support@autofxmart.com and we will make it right.
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