Had a puncture today, when I changed the wheel I noticed the jacking points are coroding.

What is the best way to stop or slow down corosion on the jacking points and along the sills.

1997 Marea HLX

treat them with a decent rust converter...

something like this is getting good reviews

http://www.bilthamber.com/hydrate80.html

And then hammerite them

It is sometimes a good idea to paint them other than black to highlight them as the jacking points.

This is dependant on how low the sills are as you wouldn't want them seen unless underneath.