Treating rust on your 73–87 C10 frame is essential for preservation. The right rust converter can stop active rust and give you a paintable surface. Here’s what works best.
What Is a Rust Converter?
Rust converters chemically react with iron oxide (rust) to create a more stable compound (usually iron phosphate or iron tannate). This stops further rust progression and creates a primer-like surface for paint or undercoating.
Top Pick:
Rust-Oleum Automotive 2-in-1 Rust Reform & Seal Spray – One of the best consumer-grade rust converters available. Converts rust and seals the surface in one application. Great for frame rails, crossmembers, and under-cab areas.
How to Use It on Frame Rails:
- Wire brush or media blast loose scale and flaking rust
- Do NOT strip all the way to shiny metal – rust converter needs some rust to react with
- Apply converter to all rusty surfaces
- Allow to dry fully (usually 24 hours before topcoating)
- Apply undercoating or chassis paint over the converted area
Best Application Method for Frame Rails:
- Use a brush for heavy buildup areas (better penetration)
- Use spray can for accessible surfaces
- Use an undercoating spray gun for full frames
After Rust Conversion:
Apply a quality undercoating or chassis paint to seal and protect. Popular choices:
- Rust-Oleum Professional Undercoating spray
- POR-15 chassis paint
- Eastwood Internal Frame Coating (for inside the frame box)
Don’t Forget the Inside:
The inside of the square-section frame rails traps moisture and rusts from the inside out. Drill access holes and use cavity wax or internal frame coating.
Prevention Going Forward:
After treating and painting, annual undercoating inspections are key. Touch up any bare spots before winter/salt season.
What rust treatment are you using on your Square Body? Share your results!