rust spots on exterior wall and windows

[the paddle]

Hi

What product is recommended to remove the rust stains from a masonary (rendered) wall and seal the rust? Also the nail heads, fixing the beading in the windows are rusting too, so I need to do the same thing with the windows too, before I gloss them.

Both the walls and the windows will be white. Is there one product, or two different ones? I see screwfix did one that might be OK 'Rust Converter'

but even if it was OK, I need to be able to buy it locally, and it dries black :O(

Thanks

Paddle