Muratic acid a pool product on rust. citrus based cleaner and power wash. Sometimes powdered cement will bleach out stain.
I made a mixture of detergent, bleach and water and it cleaned mine real nice.
Help answer this question...We used Olympic deck cleaner on ours. Worked great. From Lowes. Sprayed it on with a gallon pump p garden sprayer and let it sit for a couple of hrs. Then hosed it off.
For rust ? Cynthia ? I will try it !!!