OK all... For all of you who are doing or going to be starting a revamp of your Kat and want to use the standard bits but they have gone rusty, I was given this by my neighbour. You can reuse it, and you just put it in a container, put your bits in, leave them in for 24hrs and - way hay! - no more rust.
It says that it's an iron-oxide-specific chelating agent, not an acid or alkali (apparently that's a good thing?)
I've done a test with a old very rusty banjo bolt and here are some pics.
Before
