Rust is the enemy of every campervan conversion. UK conditions — road salt, coastal moisture, and predictable rain — mean that even well-maintained vans develop corrosion. Treating it properly before insulating is essential.
This guide covers Kurust (the UK's most popular DIY rust converter) and how to use it effectively on a van build.
What Is Kurust?
Kurust is a phosphoric acid-based rust converter manufactured by Hammerite. It reacts with iron oxide (rust) to form a stable, water-insoluble compound called iron phosphate. This creates a black protective layer that prevents further rusting and provides a primer-ready surface.
Key properties:
- Converts rust to a stable black coating
- Water-based (low VOC)
- Dries in 30-60 minutes
- Can be painted over with most paints
- Costs about £8-10 for 250ml (enough for most van panel jobs)
How Rust Converters Work
Rust converters use chemical reactions rather than mechanical removal. The active ingredient (phosphoric or tannic acid) reacts with rust (Fe₂O₃) to form iron phosphate or iron tannate — chemically stable compounds that are not affected by oxygen or water.
Important: Rust converters only work on rust that still has some metallic iron underneath. If the metal has completely rusted through (holes), you need welding — no chemical treatment will fix it.
How to Use Kurust on a Campervan
Step 1: Assess the Rust
Surface rust (orange powder): Kurust works perfectly. Wire brush off loose flakes first. Scale rust (flaking layers): Remove as much loose scale as possible with a wire brush or angle grinder with a wire wheel. Deep pitting (visible depressions): Kurust will treat the surface, but the pits will remain. Fill with metal filler after treatment. Holes: Kurust cannot fix holes. Weld new metal or use a repair panel.
Step 2: Prepare the Area
- Wire brush or grind away all loose rust and paint
- Clean with white spirit or panel wipe to remove grease
- Mask off surrounding areas
- Wear gloves and eye protection
Step 3: Apply Kurust
- Shake the bottle thoroughly
- Apply with a brush (included in the bottle cap) or an old paintbrush
- Spread in a thin, even coat
- Do not apply too thickly — it runs and takes hours to dry
The solution turns from milky white to deep blue-black as it reacts. This colour change shows the reaction is working.
Step 4: Leave to React
Kurust needs 30-60 minutes to fully react at 15-20°C. In colder weather (typical UK garage conditions at 5-10°C), leave it for 2-3 hours or overnight.
Step 5: Rinse or Wipe
Once dry (black surface), you can either:
- Rinse with water and dry (recommended for painted areas)
- Wipe with a damp cloth (for areas that will be covered by insulation)
Step 6: Prime and Paint
The treated surface is now inert. Apply a rust-inhibiting primer (Hammerite or zinc phosphate primer) followed by your top coat.
For areas that will be hidden behind insulation: still apply primer — it provides an extra barrier against future moisture.
Best Rust Treatment Products Compared
| Product | Type | Coverage | Best For | UK Price |
|---|---|---|---|---|
| Kurust | Phosphoric acid converter | ~5m² per 250ml | Surface rust, small areas | £8-10 |
| Fertan | Tannic acid converter | ~3m² per 500ml | Heavy rust, scale | £12-15 |
| Bilt Hamter Hydrate 80 | Tannic acid converter | ~2m² per 500ml | Professional builds | £18-22 |
| Rustoleum Rust Reformer | Paint + converter | ~4m² per 400ml | One-step treatment | £15-18 |
| Dinitrol RC 800 | Cavity wax + converter | ~1m² per 1L | Box sections | £16-20 |
Kurust: Best value for most van jobs. Available at Halfords, Screwfix, B&Q.
Fertan: Stronger formula for heavy rust. Available online and at specialist auto stores.
Bilt Hamter Hydrate 80: The professional's choice. More expensive but better long-term results, especially on van chassis and subframes.
Where to Treat Rust in Your Van Before Building
Priority 1: The Metal Floor
Before laying any insulation, treat the entire floor pan. This is the area most exposed to road salt and moisture.
Process:
- Remove the plywood cargo floor (if fitted)
- Wire brush or angle grind the entire floor
- Vacuum all dust
- Apply Kurust to any rusty areas
- Once dry, apply a coat of Hammerite Direct to Rust
- Allow 24 hours to cure before insulating
Priority 2: Wheel Arches (Inner)
The inner wheel arches get blasted with road salt and grit. They are also typically under-coated from the factory, but this coating degrades.
Process:
- Pressure wash the arches
- Scrape off loose undercoating
- Wire brush any visible rust
- Apply Kurust
- Once dry, apply Dinitrol or Bilt Hamber UB cavity wax
Priority 3: Door Bottoms
Water drains through the door bottoms. The drain holes regularly get blocked, leaving water sitting inside the door.
Process:
- Remove the interior door card
- Check the bottom of the door cavity for rust
- Treat with Kurust where needed
- Spray cavity wax inside the door
- Clear the drain holes with a zip tie
Priority 4: Scuttle Panel / Windscreen Area
Moisture and debris collect under the plastic scuttle trim at the base of the windscreen.
Process:
- Remove the plastic scuttle panel
- Clean out all leaves, moss, and debris
- Wire brush any rust
- Apply Kurust
- Paint with stone-chip resistant paint
- Refit with foam strip to prevent future water trapping
Tools You Will Need
| Tool | Purpose | Price |
|---|---|---|
| Wire brush set | Loose rust removal | £5 |
| Angle grinder + wire wheel | Heavy rust | £30 |
| Respirator mask | Dust protection | £15 |
| Panel wipe | Surface cleaning | £5 |
| Kurust | Rust conversion | £9 |
| Hammerite primer | Sealing | £12 |
Common Mistakes
Mistake #1: Applying Kurust over painted areas. It only works on bare rust.
Mistake #2: Not wire brushing first. Kurust cannot penetrate through loose scale.
Mistake #3: Expecting it to work on holes. If you can see daylight through the rust, it needs welding.
Mistake #4: Not priming afterward. The black iron phosphate layer is stable but not UV-resistant or abrasion-resistant. It needs paint or primer for long-term protection.
Conclusion
Kurust is the first line of defence in van rust treatment. It is cheap (under a tenner), easy to apply, and effective on surface to moderate rust. For any UK van conversion, treating the bare metal with Kurust before insulating is an essential step that prevents future structural problems.
Our process: Wire brush → Kurust → rinse → zinc primer → Hammerite top coat. Total cost per van: £30-50. Time: one afternoon. Longevity added: 5-10 years of rust-free service.
