Classic Mini sill rust prevention

[Moopig]

Hi there, hoping you can help me with this. I have a Classic Mini which has been restored in the past but I am having some issues with the paintwork on the sills. Initially I noticed that the paint as cracking and coming off, seeming to not be well adhered.



So, concerned of what may be lurking underneath I set about it with a scraper and in almost no time and with little effort I have the paint completely removed revealing a lovely sold sill underneath





Some thinners removed the remainder of the underseal



So looking at it, it seems that the car has been painted, then undersealed, then painted over the top of the underseal.
So what is my best solution going forward? I would like to once again underseal, then paint over the underseal again, but I am nervous of this issue occurring again.
What is the best prep to do to the current paintwork to make sure the underseal sticks, then are there any recommendations for underseal that is stable for painting over the top of?

Any advise, assistance or recommendations would be gratefully received

[Belle427]

If it's fairly rust free I would have it painted body colour and leave the underseal alone.
Is this a car used all year round or just summer?

[Doesitdrive]

If you want to paint over something use stonechip, after a good coat of rust converter has gone off properly, and probably strip and do both sills from bare metal.

[Moopig]

Belle427 said:

If it's fairly rust free I would have it painted body colour and leave the underseal alone.
Is this a car used all year round or just summer?

The car isn't used a lot, but it is used all year round so I'd much rather keep it protected

[Moopig]

Doesitdrive said:

If you want to paint over something use stonechip, after a good coat of rust converter has gone off properly, and probably strip and do both sills from bare metal.

Do you have any recommendations for a stone chip paint?
I'd really rather not take the sills back to metal as they are rust free with a good coating of paint on them.
Is it not advisable to stone chip over paint?

[Doesitdrive]

Moopig said:

Doesitdrive said:

If you want to paint over something use stonechip, after a good coat of rust converter has gone off properly, and probably strip and do both sills from bare metal.

Do you have any recommendations for a stone chip paint?
I'd really rather not take the sills back to metal as they are rust free with a good coating of paint on them.
Is it not advisable to stone chip over paint?

Stone chip is readily available and far better than underseal, it adheres like paint.

My thinking is, if the paint has failed in places the rest is likely to.

Water get under underseal , it lifts, water stays there rusting the car. Seen a lot of sills where this happens.

Not starting again you could be repeating the process regularly.

Do it once and do it properly lol.

[dontlookdown]

Is it just the sills?

If the rest of the underbody has also been treated this way, the same thing will be happening,.or about to happen, in other places. Worth getting the car in the air and having a good poke around to check.

[Moopig]

The only issue has been the outer paint coming off, there does not seem to be any issues with anything getting underneath the underseal and corrosion.
The outer sills and valances (all having this issue) are the only place where the underseal has been painted over.
Does stone chip give a heavily textured finish?

[Belle427]

I wouldn't say heavily textured, probably won't notice it anyway.
I personally just like to see it painted, which if done properly is perfectly durable.
You can see what's happening too before it gets too late, a clear coating from the bilt Hamber range can be applied over it, you need UC for this. (Underbody clear)
If existing paint is sound clean it up and just apply the UC.

Edited by Belle427 on Friday 17th July 08:15