Would Araldite Super Strength 2-Part Epoxy Work
Would Araldite Super Strength 2-part epoxy repair a cracked cast aluminium petrol tank?
For this repair Selleys recommends a different product: Selleys Knead It Multipurpose or Selleys Knead It Steel epoxy putty. These repair compounds are resistant to petrol and diesel and suitable for repairs to metal and aluminium tanks. You might need to "V" out the crack so you can force the Knead It well into the repair.
The reason to reach for a putty rather than a liquid epoxy on a cracked casting comes down to two things: fuel resistance, and the ability to fill a prepared groove rather than just wet a joint.
Why fuel resistance is the deciding property
An adhesive on a fuel tank is in permanent contact with petrol or diesel. Plenty of strong adhesives are not rated for that, and the failure is gradual — the bond softens and lets go weeks later rather than immediately.
Both Knead It Multipurpose and Knead It Steel are documented as resistant to a broad range of chemicals: hydrocarbons (including petroleum-based products such as petrol and diesel), esters, ketones, alcohols, halocarbons, aqueous salt solutions, and dilute acids and bases. That is the property that qualifies them for this job.
By contrast, Selleys' published data for Araldite Super Strong 5 Minute Epoxy makes no fuel-resistance claim. Its stated limitations are that it will not bond PTFE, polyethylene or polypropylene, that the bond softens above 60 °C (strength restored on cooling), that leather and rubber should be pre-tested, and that the product may discolour under UV. Nothing there addresses continuous immersion in petrol, which is why Selleys directs this question to Knead It instead.
The same reasoning rules out a high-temperature silicone: Selleys Silicone 401, for example, is explicitly not recommended for use with petrol, distillate and some other hydrocarbon solvents.
Knead It Multipurpose and Knead It Steel — published figures
| Property | Knead It Multipurpose | Knead It Steel |
|---|---|---|
| Working time @ 25 °C | 3–5 minutes | 3–5 minutes |
| Hardening begins | 5–10 minutes | 5–10 minutes |
| Initial cure | 60 minutes | 60 minutes |
| Full cure @ 25 °C | 24 hours | 24 hours |
| Shore D hardness at full cure (ASTM D2240) | 80 ± 5 | 80 ± 2 |
Indicative data only, not intended for the preparation of specifications.
Three to five minutes of working time is not long, and the clock starts once the material is kneaded to a uniform colour. On an awkward casting, that means all the preparation — degreasing, grooving out the crack, drying — has to be finished before you open the pack. Mix only as much as you can place in that window; if you need more, do the repair in stages.
At 60 minutes the material reaches initial cure and can be drilled, sanded, machined, filed, sawed or painted. That is genuinely useful on a casting, where you may want to dress the repair back flush to the original profile. Full cure at 25 °C takes 24 hours, and set time increases at temperatures below 20 °C — a cold shed will slow the whole process down. If the material is stiff and hard to knead, allowing it to warm to room temperature makes it workable again.
Shore D 80 puts the cured putty in rigid-solid territory, which is what you want holding a crack in a casting closed.
Preparing the crack
- Make the tank safe before any work begins. This is a fuel tank; treat the residual fuel and vapour with the seriousness they deserve, and read the safety data sheets for any product you use.
- Find the full extent of the crack. Cracks in castings almost always run further than the visible line.
- "V" out the crack — grind or file a groove along it so there is a channel with real depth for the putty to key into. A putty smeared over the surface of a crack has almost no thickness and no mechanical lock; one forced into a V-groove has both.
- Clean and degrease the groove and the surrounding metal, and let it dry completely. Cast aluminium in a fuel tank is a contaminated surface by definition.
- Knead the putty to a uniform colour, then work quickly — you have 3–5 minutes.
- Force the putty well into the groove rather than laying it on top, and work it out onto the surrounding surface to spread the load.
- Leave it at least 60 minutes before dressing it back, and 24 hours at 25 °C for full cure. Allow longer below 20 °C.
Limitations and honest expectations
- A cracked casting on a pressurised or load-bearing component is a structural failure. An epoxy putty repair is a repair to the crack, not a restoration of the casting's original strength.
- If the crack is in a location that flexes or carries mounting loads, expect it to propagate beyond the repair over time.
- Set time increases below 20 °C for both products.
- Follow the safety directions on the pack and the product safety data sheet, available through the Selleys website.
Safety: the products, and the thing that is more dangerous than all of them
The page already says to make the tank safe before any work begins. That instruction outranks everything below it: the residual petrol and vapour in a fuel tank are a far greater hazard than any adhesive classification on this page, and grinding a crack open is an ignition source held against a container that has held fuel. Purge and ventilate the tank properly, or have someone do it who does this for a living.
With that said, here is what the repair products themselves carry.
| Product | Classification |
|---|---|
| Knead It Multipurpose | Warning — skin sensitisation Category 1A (allergic skin reaction), H315 skin irritation, H319 serious eye irritation, chronic aquatic hazard |
| Knead It Steel | Warning — H317 skin sensitisation Category 1A, H315, H319 |
| Selleys Silicone 401 RTV, ruled out above for fuel | Danger — H318 causes serious eye damage, H315 skin irritation |
What follows for this repair
Category 1A sensitisation collides directly with the technique. 1A is the sub-category used where there is strong evidence a substance sensitises humans — a step more definite than a plain Category 1. And the whole method for an epoxy putty is to knead it in your fingers until the colour is uniform, then force it into a groove by hand. That is maximum skin contact by design. Sensitisation is not irritation: it is permanent once acquired, and afterwards a smear that previously meant nothing provokes a reaction. Knead it inside disposable nitrile gloves — you can still see the colour change and feel the warmth the directions describe.
H319 belongs to the grinding step, not the putty. V-ing out a crack in cast aluminium throws metal particles at your face, and you will have the putty's own eye classification on your hands at the same time. Safety glasses or goggles from the moment the grinder comes out until the repair is dressed back.
The aquatic classification on Knead It Multipurpose has a practical consequence here. Uncured material must not reach drains or stormwater. This job usually happens on a driveway or in a shed with a floor drain, alongside degreaser and drained fuel. Wipe excess onto paper and bin it; do not rinse uncured putty down anything.
There is no lower-hazard substitute for this job. Fuel resistance is what narrows the choice to these two products, and their classifications are effectively identical. The control is gloves and eye protection, not a different product.
Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand.
Common questions
Would Araldite Super Strong work instead?
Selleys' recommendation for this job is Knead It, because the Knead It compounds are documented as resistant to petrol and diesel. Araldite Super Strong's published data makes no fuel-resistance claim, and its bond softens above 60 °C.
Which Knead It should I use?
Either is suitable for repairs to metal and aluminium tanks. Their working times, cure schedules and chemical resistance are the same; Knead It Steel is quoted at Shore D 80 ± 2 and Knead It Multipurpose at 80 ± 5.
How long before the tank can hold fuel?
Full cure at 25 °C is 24 hours, and longer in cooler conditions. Initial cure at 60 minutes allows machining and painting, not service.
Can I sand and paint the repair?
Yes. After the 60-minute initial cure the material can be drilled, sanded, machined, filed, sawed or painted.
Do I really have to grind out the crack?
Selleys' advice is that you might need to V out the crack so the Knead It can be forced well into the repair. On a casting, that groove is what gives the putty depth and a mechanical key.
Why is the material hard to knead?
Cold. Allow the polymer to warm to room temperature and it becomes workable, which also gives you the full 3–5 minutes of working time.
What about a leaking fuel line or joint rather than a casting?
See sealant to stop fuel leaks.
Is there a Knead It for underwater or automotive use?
Yes — the specialist putty range includes Knead It Aqua and Knead It Auto Fix.
Would Araldite Super Strong work instead?
Selleys' recommendation for this job is Knead It, because the Knead It compounds are documented as resistant to petrol and diesel. Araldite Super Strong's published data makes no fuel-resistance claim, and its bond softens above 60 °C.
Which Knead It should I use?
Either is suitable for repairs to metal and aluminium tanks. Their working times, cure schedules and chemical resistance are the same; Knead It Steel is quoted at Shore D 80 ± 2 and Knead It Multipurpose at 80 ± 5.
How long before the tank can hold fuel?
Full cure at 25 °C is 24 hours, and longer in cooler conditions. Initial cure at 60 minutes allows machining and painting, not service.
Can I sand and paint the repair?
Yes. After the 60-minute initial cure the material can be drilled, sanded, machined, filed, sawed or painted.
Do I really have to grind out the crack?
Selleys' advice is that you might need to V out the crack so the Knead It can be forced well into the repair. On a casting, that groove is what gives the putty depth and a mechanical key.
Why is the material hard to knead?
Cold. Allow the polymer to warm to room temperature and it becomes workable, which also gives you the full 3–5 minutes of working time.
What about a leaking fuel line or joint rather than a casting?
See sealant to stop fuel leaks .
Is there a Knead It for underwater or automotive use?
Yes — the specialist putty range includes Knead It Aqua and Knead It Auto Fix .