CFS RustOff
Gel
Thixotropic phosphoric acid gel for rust passivation, iron oxide removal and surface conversion on ferrous metals. Clings to vertical surfaces — no runoff, maximum dwell time.
What It Does
CFS RustOff Gel is a thixotropic phosphoric acid gel designed for in-situ rust treatment on ferrous metal surfaces. Unlike liquid acid products, the gel formulation clings to vertical and overhead surfaces without running — maximising acid contact time and chemical conversion efficiency.
Phosphoric acid reacts with iron oxide (rust) to form iron phosphate, a stable, adherent conversion layer that passivates the surface and inhibits further corrosion. This is true rust conversion, not just removal — the treated surface is chemically stabilised and paint-ready.
The formulation is safe on fibreglass gelcoat, painted surfaces and most marine hardware at working concentrations, making it suitable for use aboard vessels without system disassembly.
- Thixotropic Gel Format Clings to vertical and overhead surfaces. No runoff, maximum dwell time, no waste.
- Rust Conversion — Not Just Removal Converts iron oxide to stable iron phosphate. Treated surface is passivated and primed for coating.
- Ready to Use No dilution required. Apply directly from container with brush, cloth or plastic spreader.
- Favourable Transport Profile Formulated to minimise transport classification complexity. Confirm current SDS classification before shipping.
- Wide Substrate Compatibility Safe on gelcoat, fibreglass, painted metal and most marine alloys at standard application rates.
Product Data
| Parameter | Value | Notes |
|---|---|---|
| Active Acid | Phosphoric acid (H₃PO₄) | — |
| Format | Thixotropic gel | Flows on agitation, sets at rest |
| Dilution | Ready to Use | No dilution required |
| Appearance | Translucent amber gel | — |
| Viscosity | Gel — self-levelling when spread | Non-drip on vertical surfaces |
| pH | ~1.5–2.5 (product) | — |
| Transport Classification | See current SDS | Depends on product version and dilution |
| Signal Word (SDS) | WARNING | GHS07 |
| Application Temp. | 5–45°C | Best results above 15°C |
| Recommended Dwell | 15–60 minutes | Depends on rust severity |
| Shelf Life | 24 months | Sealed, out of direct sunlight |
| Country of Origin | Australia | Made in Queensland |
Where CFS RustOff Gel Works
Marine Hardware & Deck Fittings
Stanchions, cleats, chain plates, winches and deck hardware. Treat in-situ without disassembly.
Structural Steel
Jetty structures, bridge members, fabricated steelwork. Surface passivation prior to priming or coating.
Vessel Hull & Topsides
Rust weeping from fittings, rust staining on gelcoat, ferrous contamination on fibreglass surfaces.
Engine Bays & Machinery
Engine brackets, raw water fittings, exhaust components, machinery mounts and bilge hardware.
Workshop & Fabrication
Pre-treatment of steel components before welding, priming or powder coating. Flash rust removal.
Superyacht & Prestige Vessels
Delicate surface treatment where surface integrity is critical. Safe on gelcoat and premium painted surfaces.
Before & After
Real-world results from CFS RustOff Gel applications on marine hardware, structural steel and fabricated components.
Marine fitting / flange 
Welded steel structure 
Structural steel bracket 
Steel panel — half treated How to Use
Remove loose rust, flaking paint and heavy contamination mechanically (wire brush, scraper). The gel is most effective when it has direct contact with the rusted metal surface.
Apply CFS RustOff Gel directly to the surface using a brush, plastic spreader or cloth. Apply a liberal coat — 1–3mm thickness is ideal for vertical surfaces.
Allow the gel to work for 15–60 minutes. Light surface rust: 15–20 min. Heavy oxidation: 45–60 min. Gel will darken and may form a light grey/black iron phosphate layer.
For heavy rust, agitate the gel into the surface with a stiff brush part-way through dwell time to improve conversion efficiency.
Rinse thoroughly with fresh water. The surface should show a grey/blue iron phosphate conversion layer. Repeat treatment if rust remains. Prime or coat promptly after drying.
Pack Sizes Available
Spot treatment and small areas. Ideal for deck hardware and fittings.
Vessel maintenance kit and general use. Most popular format.
For contractors, shipyards and trade users. Commercial treatment projects.
Product Documents
CFS RustOff Gel FAQ
How does CFS RustOff Gel differ from liquid rust converters?
CFS RustOff Gel uses a thixotropic (gel) formulation that clings to vertical and overhead surfaces without running. This maximises acid contact time and chemical conversion efficiency — liquid products run off before they can fully react with the rust.
Does CFS RustOff Gel remove rust or convert it?
CFS RustOff Gel converts rust (iron oxide) to iron phosphate — a stable, adherent conversion layer that passivates the surface and inhibits further corrosion. The treated surface is chemically stabilised and paint-ready. This is true rust conversion, not just cosmetic removal.
Is CFS RustOff Gel safe on gelcoat and painted surfaces?
Yes. CFS RustOff Gel is safe on fibreglass gelcoat, painted surfaces and most marine hardware at standard application rates. It should not be used on zinc, galvanised or aluminium surfaces. Always rinse adjacent surfaces thoroughly.
How long should the gel dwell on the surface?
Allow 15–60 minutes depending on rust severity. Light surface rust: 15–20 minutes. Heavy oxidation: 45–60 minutes. The gel will darken as it converts the iron oxide to iron phosphate.
Can I paint directly over the treated surface?
Yes. After rinsing and drying, the iron phosphate conversion layer provides an excellent primer base. Apply your chosen primer or coating promptly after the surface is dry to maintain the passivation benefit.
What surfaces can CFS RustOff Gel be used on?
CFS RustOff Gel works on ferrous metals including mild steel, structural steel, cast iron, and marine-grade steel. It is commonly used on deck hardware, stanchions, engine bays, structural steelwork, and vessel hull rust staining.