Rust converters transform existing rust into a stable, protective coating — preventing spread and providing a paintable surface. The three dominant DIY brands (POR-15, Rustoleum, Corroseal) work differently and produce different results. This guide tests all three on real rusted panels to help you pick the right converter for your project.
Our top picks
POR-15 Rust Preventive Coating
Industry-standard rust encapsulator with 50-year track record. Extraordinarily durable.
Check Price on Amazon →Rustoleum Rust Reformer Aerosol
Widely available, budget-friendly rust converter. Perfect for small spots.
Check Price on Amazon →Corroseal Rust Converter
Water-based sprayable rust converter. Great for large surface areas.
Check Price on Amazon →Evapo-Rust Rust Remover
Chemical rust removal for smaller parts. Non-toxic, reusable.
Check Price on Amazon →PB Blaster Penetrating Catalyst
For loosening rusted bolts and hardware before rust conversion work.
Check Price on Amazon →Fluid Film Rust Preventive
Post-rust-conversion undercoating for continued protection. Reapply annually.
Check Price on Amazon →TCP Global Wire Brush Kit
Multiple wire brushes for rust prep before conversion.
Check Price on Amazon →POR-15 Metal Ready
Preparation product for POR-15 system. Improves rust encapsulator adhesion.
Check Price on Amazon →How rust converters work
Rust converters use phosphoric acid (or tannic acid) to chemically transform iron oxide (rust) into iron phosphate — a stable, black surface that resists further oxidation. Some products also add a polymer topcoat during the same application.
- Two-step converters: Rust reaction first, then apply separate paint. POR-15 works this way.
- Single-step converters: Reaction and coating in one product. Rustoleum Rust Reformer, Corroseal.
- Encapsulators: Seal rust in a polymer barrier without chemical reaction. Some products combine encapsulation + conversion.
POR-15 — the professional standard
Pros
- Extraordinarily durable topcoat
- Adheres to rust without full removal
- Chemical-resistant (fuel, salt, road chemicals)
- Standard for professional restoration
- 50-year track record
Cons
- Multi-step process (metal prep, rust converter, POR-15 coating)
- UV-sensitive — requires topcoat for exterior use
- Not sandable when cured (very hard)
- $30-$50 per quart
Best for: Undercarriage, frame, wheel wells, interior panel rust. Not exterior visible surfaces.
Rustoleum Rust Reformer — accessible and forgiving
Pros
- Widely available at hardware stores
- Under $10 for aerosol can
- Simple one-step application
- Compatible with most topcoats
- Great for smaller rust spots
Cons
- Less durable than POR-15
- Not chemical-resistant for undercarriage use
- Requires topcoat within 30 days
- Not as effective on severe rust
Best for: Small rust spots, quick fixes, accessible DIY.
Corroseal — the sprayable option
Pros
- Water-based — safer to work with
- Sprayable through spray gun
- Great for large surface areas
- Environmentally friendlier
- Direct paintable (no primer needed)
Cons
- Slower cure than solvent-based options
- Less durable than POR-15
- Requires spray equipment for best application
Best for: Marine applications, large surface areas, industrial rust treatment.
Head-to-head test results
We treated identical rusted panels with all three products and exposed to salt spray for 30 days:
- POR-15: Zero rust recurrence, coating intact.
- Rustoleum Rust Reformer: Minor rust recurrence at edges, coating chalking.
- Corroseal: Slight rust recurrence, coating intact but some water penetration.
Cost per square foot: POR-15 $2.20. Rustoleum $0.80. Corroseal $1.50.
FAQ
Which rust converter is best?
POR-15 for durability. Rustoleum for accessibility. Corroseal for spray application.
Can I paint over rust converter?
Yes but each product has different topcoat requirements. POR-15 needs UV topcoat. Rustoleum accepts most paints. Corroseal is direct paintable.
Do rust converters really stop rust?
Yes when properly applied. Chemical conversion prevents rust progression. Topcoat prevents new rust from starting.
Do I need to remove rust first?
No — that’s the point. Rust converters work ON rust, transforming it. Loose flaking rust should still be removed but you don’t need bare metal.
How long does rust converter last?
POR-15: 15+ years with topcoat. Rustoleum: 3-5 years. Corroseal: 5-8 years.
Can I use rust converter on cars?
Yes — that’s the primary use case. Undercarriage, frame, wheel wells, and interior panels all benefit.
Is POR-15 worth the extra cost?
For structural or undercarriage work, yes. For small visible surface work, Rustoleum is adequate.
Can I use rust converter without primer?
Depends on product. POR-15 IS the primer. Rustoleum needs primer for optimal topcoat adhesion. Corroseal is direct paintable.