Will this need painting over?

[maxp]

When jacking the car up today, I managed to flake some of the paint off from the skirting seal.

Is this worth repainting / sealing? Im worried about it rusting.

[RCBRG]

whats the car? something known to be bad for rust?

i personally wouldn't care, my sills are in a FAR worse state than that!

[maxp]

Its a Mk1 (2002) ford focus.

I know its nothing special at all, but its actually been very well looked after and I intend to have it for a good few years

[mudster]

It looks like there is already surface rust behind the underseal. I would take off the underseal with a wire brush in an angle grinder back to sound metal, treat the rust and then reapply some underseal type protection.

[maxp]

Something like

http://www.halfords.com/webapp/wcs/stores/servlet/...

Followed with:

http://www.ebay.co.uk/itm/290905358850?ssPageName=...

Perhaps?

[Viperz888]

I wouldn't bother with the rust dissolver stuff - I could never get it to do a decent job. Better (but messier) to use a grinder or wire wheel in my opinion.
As for underseal, there a re lots of good ones but they all work in slightly different ways so worth reading up a bit. Some good ones to look out for are Dinitrol, Gravitex, Waxoyl, but there are many more.