What is Selleys Knead It Autofix, and where should you use it?

Selleys Knead It Autofix is a fast setting, co-extruded epoxy repair system made for repairing and rebuilding parts around the car, caravan or boat. It is supplied as a stick of putty with the resin and hardener extruded together. You cut off the amount you need, knead it until the colour is uniform, then press or mould it into place, where it sets hard without sagging, running or dripping.

The thing to understand before you start is the pace. At 25°C you have 3–5 minutes to get the mixed putty onto the job and shaped. Cut and knead only what you can place inside that window, and do the preparation before you open the pack.

What the key numbers mean in practice

• 3–5 minutes at 25°C — the time you have to apply it after kneading. Because this is a chemical reaction rather than a drying process, a hot day shortens it and a cold one stretches it out.
• Allow 60 minutes before handling — the point at which the repair can be touched and moved without deforming it.
• Full cure in 24 hours at 25°C — the point at which the repair has reached its final state. Drilling, sawing, sanding and painting belong after this, not before.
• Application temperature 5–40°C — the ambient range Selleys nominates for applying it. Working outside that range is applying the product outside its stated conditions.
• Service temperature −40°C to +120°C continuous, and intermittent to +140°C — where the cured repair can live. Continuous means sustained exposure; intermittent means short excursions, not a normal operating temperature.

Those are two different milestones. A patch handled at an hour is stable enough to move; it is not yet ready to be drilled, tapped or put under load.

Selleys gives a practical way to judge the set without prodding the repair: keep a small piece of the kneaded putty aside. When that offcut is hard, the repair has reached the same state.

Where to use it

Knead It Autofix is aimed at automotive and vehicle repairs — reshaping, rebuilding and repairing auto parts. The page lists these specific applications:

• Petrol tanks, radiators and oil tanks
• Rust holes, dents, scratches and panel repairs
• Anchoring bolts and screws, where its anchoring properties are the point rather than the filling
• General repair and rebuilding work around the car, caravan or boat

Because it will not sag, run or drip, it holds its shape on a vertical panel or the underside of a component while it sets — you can build up a lip or a fillet on a surface that is not horizontal and it stays where you put it.

If your repair is not vehicle-related, look at the rest of the Knead It range on the specialist fillers and putty page — Knead It Multipurpose and Knead It Steel cover general repairs and metal respectively, and Knead It Aqua is designed for wet and underwater repairs.

How to apply it

1. Clean the surface thoroughly. On a vehicle this usually means removing oil, grease, road film and any loose rust or flaking material before you cut the putty.
2. Cut off the amount you need and knead it until the colour is uniform. The uniform colour is the indicator that the resin and hardener are properly combined. Streaks mean the mix is incomplete, and an incompletely mixed epoxy does not reach its intended strength.
3. Apply within the working time. Press it firmly into the repair and mould it to the shape you want — it can be moulded to shape once kneaded together.
4. Allow 60 minutes before handling.
5. Allow the full 24 hours to cure before drilling, sawing, sanding or painting.

Shaping the putty while it is soft is worth the effort: every minute spent getting the profile close by hand is several minutes of sanding avoided later.

Working conditions and temperature limits

Two temperature ranges apply and they are not the same thing. The application temperature is 5–40°C — the condition you mix and apply in. The service temperature is −40°C to +120°C continuous, with intermittent exposure to +140°C — what the finished, cured repair tolerates. The continuous rating is the one to design around; if a repair sits somewhere that runs above 120°C in normal operation, it is outside that rating regardless of the intermittent figure.

Hazard classification

Classified as hazardous under Safe Work Australia GHS 7, with the signal word Warning.

• Sensitisation — Skin — Category 1. H317: may cause an allergic skin reaction.
• Skin corrosion/irritation — Category 2. H315: causes skin irritation.
• Eye damage/irritation — Category 2A. H319: causes serious eye irritation.

It is not classified as Dangerous Goods under the Australian Code for the Transport of Dangerous Goods by Road & Rail or New Zealand NZS5433.

What is in it

Chemical entity	CAS number	Proportion (w/w)
Pentaerythritol–propylene oxide–mercaptoglycerol polymer	72244-98-5	10–30%
2,2-Bis(4’-glycidyloxyphenyl)propane	1675-54-3	1–10%
Bisphenol-A epoxy resin	25068-38-6	1–10%
2,4,6-Tri(dimethylaminomethyl)phenol	90-72-2	1–10%
Non-hazardous ingredients	—	Balance

The classification that matters here is H317, not H315. Skin irritation is a local, reversible effect — it stops when you stop. Sensitisation is different: it is the immune system learning to react to the material. Once that has happened it is generally permanent, it can be set off by far smaller exposures than the one that caused it, and it is acquired through repeated casual contact rather than through one bad incident.

That matters because of how this putty is used. The directions above tell you to knead it until the colour is uniform, and streaky putty is weak putty — so the temptation is to work it bare-fingered until it looks right, and to do the same on the next repair. Knead it inside disposable nitrile gloves. The epoxy resin and the glycidyl ether listed above belong to the chemical class that carries skin-sensitisation classifications across epoxy products generally, and the amine hardener is the kind of component behind irritation classifications; the SDS does not attribute the classification to any one ingredient, so neither does this page.

The product is effectively 100% non-volatile, so there is very little vapour to breathe while you work. The route that matters is skin, and eyes if you rub them with contaminated fingers. Dust is a separate question: once cured, the repair is drilled, sawn, sanded and painted, and that produces dust. Wear a dust mask for that part and keep the area ventilated.

Protection

• Gloves — nitrile rubber; the SDS suggests these as suitable for intermittent contact, with the user making the final assessment. Essential wherever a sensitisation classification applies.
• Eye protection — safety glasses, or eye/face protection.
• Ventilation — natural ventilation is adequate under normal use conditions; add a dust mask when sanding the cured repair.
• Wash hands, face and exposed skin thoroughly after handling, and before eating, drinking or smoking. Take off contaminated clothing and wash it before reuse.

First aid

Exposure	What to do
Eyes	Hold the eyelids apart and flush continuously with running water. Remove contact lenses if present and easy to do, and keep rinsing — for at least 15 minutes, or until advised to stop by a doctor or the Poisons Information Centre. If irritation persists, get medical attention.
Skin	Remove contaminated clothing and wash with plenty of water and soap. Effects may be delayed — if a rash or itching develops, including hours later, get medical advice, because that may indicate sensitisation rather than irritation.
Inhalation	Move the person to fresh air and keep them at rest until recovered. Seek medical advice if effects persist.
Swallowed	Rinse the mouth with water. Do not induce vomiting. Give a glass of water to drink and seek medical advice. Never give anything by mouth to an unconscious person.

If poisoning occurs, contact a doctor or the Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand — with the container to hand. Selleys emergency line: 1800 220 770 in Australia, 0800 220 770 in New Zealand.

Common questions about Selleys Knead It Autofix

How long do I have to work with it once it is mixed?

3–5 minutes at 25°C. Cut and knead only as much as you can place and shape in that time.

When can I handle the repair?

Allow 60 minutes before handling. That is not the same as fully cured.

How long until it is fully cured?

24 hours at 25°C. Leave drilling, sawing, sanding and painting until then.

How do I know it has actually set?

Keep a small piece of the kneaded putty aside when you apply the repair. When that offcut is hard, the job is done — and you have not disturbed the repair itself to find out.

Can I use it on a petrol tank?

Yes. Selleys lists petrol tanks, radiators and oil tanks among its applications.

Can I paint over it?

Yes, once cured. It can be drilled, sawed, sanded and painted.

Will it run or sag on a vertical panel?

No. It will not sag, run or drip, which is why it works on vertical and overhead repairs where a liquid product would not stay put.

How hot can the repair get?

−40°C to +120°C continuous, and intermittent exposure to +140°C. Treat 120°C as the working ceiling for anything running at temperature all the time.

Can I apply it on a cold morning or in the middle of summer?

The stated application temperature range is 5–40°C. Outside that, you are applying it outside its specified conditions, and the working time will shift in any case.

Can I use it to anchor a bolt or screw?

Yes. Anchoring bolts and screws is one of its listed uses, and Selleys lists excellent anchoring properties as a feature.

Can I use it for rust holes?

Rust holes, dents, scratches and panel repairs are all listed applications. Clean the surface thoroughly first — that step matters more on a corroded panel than anywhere else.

What if the colour is still streaky when I apply it?

Keep kneading. Uniform colour is the signal that the two components are mixed, and mixing is what starts the cure.