Got a normal concrete patio...a couple of places where some metal objects were placed now have some rust stains (grill, my charcoal starter chimney, etc). Is there a chemical I should use? Rent a power washer maybe?
if they are not too bad , sweep up any loose debris or dust , tyhen try some CSR or similar product. If it dissolves the rust stain , hose off , or flood with lots of water .
Try a cleaner containing oxalic acid such as Zud, Bar Keeper's Friend, or naval jelly. CLR is another (liquid) product that dissolves rust and recommended for concrete--see if CLR at half-strength removes the rust. Expect the rust to disappear but some very-clean looking spots for some months. A power washer will help even out the clean spots.
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