Stain from RA4 blix!

This is tough!

Once the brown rusty colored stain from the blix of RA4 dries, it seems permenant. Is there anyway to chemically remove it from:
1. painted wood furniture
2. counter top made of marble/Corian kind of thing...
3. fabric

Thanks for all kinds of help I find here. I am having both fun and mess with color enlargement.

The stain is iron - RUST, in other words. Oxalic acid can be used to remove rust. See (for example) http://www.doityourself.com/stry/4-uses-for-oxalic-acid