Hi all. got my sump back from the welders (pinto sump shortend) and both that and my pickup pipe are back to bare metal so any recomended paints as unsure how my black hammerite would go or do i just paint the outside of the sump ?

The sump will be full of oil- that'll stop any rusting

Don't paint the inside, a single flake of paint coming off could block the oilways and kill your engine. Just paint the outside if you really want to. Hammerite chips quite easily, I prefer red oxide primer followed by Plasticoat spray paint.

Would plasticoat be stronger than hammerite. thought it was other way round but then again my chassis is done in plasticoat and is ok so far. thort oil would help protect it but wanted to be sure. thankyou for the help BenB.

Hammerite is very hard once properly cured which is great for some application but it does make it very susceptible to stone chips.

I just coated mine several times in red oxide primer since it's not on display. It's durable enough and easily touched up if you want to. TBH the sump gets pretty tatty pretty quick being so close to the road, but the Pinto will keep it pretty well oiled to prevent rust

I also paint mine with plenty of coats of red oxide. It also shows up oil leaks better than black.

give the outside of the sump a good keying with 240g, get a tin of Acid#8 etch pimer from Halfords or similar, then paint with almost anything you like, even household gloss would be OK after etching.

Hammerite is really good paint when used for what it was designed for - painting of previously rusted steel surfaces, like garden gates, hanging basket frames, it has NO automotive applications at all, it also contains silicone which will cause adhesion problems for any other type of paint.

Plasticoat as already mentioned, is what I used, great finish and has lasted well, no signs of flaking off after 5 years so far - but then as always it depends on the condition of the metal before you paint it.

I used hamerite on mine and it was fine good finish and didnt break down either

I have found hammerite made in the past decade to be absolute pants. It used to be a good product, but that has changed.

For good resistance to rust/abrasion and so on look at proper marine paints. Otherwise as stated, an etch primer to get a decent key, and then household gloss is OK. In fact as it remains a bit soft, that should help.
Have also considered truck bed paint, extremely tough paints, but it seems to only be available in 4 litres kits
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