Hello , I need to clean a very stained and dirty concrete floor before some workmen paint it.
Any suggestions on what cleaning materials to use.
Thanks.
Charlie.

You don't tell us much at all about the stains so all I can say is what you need is on this page. Concrete cleaning products to be used before painting or staining a concrete surface by Seal-Krete.

There are some very good degressers, and then coming back with some form of acid to help etch into the concrete, But with that said many oil stains will not come out after it is soaked into the concrete only lighten

Thanks guys , the floor had already been painted and the stanls look like rust and what I can only call 'grime'.
Thanks for your help.

For rust use Whink. Find Whink Rust Stain Remover, 6 oz and other Chemicals & Cleaners at Aubuchon Hardware

I think its an acid that eats the rust but you still need to etch the surface so keep my first link for future reference.