Rust spots often appear on concrete if a metal fixture or fitting has been standing on top of the surface and faced the elements. It is often described as one of the most difficult stains to remove from a hard surface. It is important to understand what rust is as decide the best action to tackle the rust stain. Rust is the reddish-brown flaky coat on metal, caused by the corrosion and oxidisation of iron or other alloy metals. When you leave metal furniture on top of your patio, driveway or pavement the alloy get continuous exposure to water and oxygen; this then runs off onto the hard surface causing stains.
Therefore, there are several ways you can try and remove the rust with chemicals. Personal experience has told me that F9 BARC is the best cleaner for rust removal. BARC stands for battery acid restoration cleaner. Remember to use adequate PPE as always.
Applying F9 BARC to Rust
To use F9 BARC effectively to remove rust from your hard surface follow the next few steps. Power Wash (or jet wash/pressure wash) the area with a commercial grade pressure washer. This opens up the pores of the hard surface as the rust can penetrate up to 1/16 of an inch. Let the surface to completely dry. Dilute the BARC solution to 1 part water to 2 part BARC, then apply to the whole surface through a pump sprayer, not just the effected spot. Use a fine mist spray with uniform spray. The stains then should disappear as the concrete dries. If the stain remains, please reapply the solution, with a higher concentration.
To clean rust spots off your concrete driveway, patio or pavement use a jet wash and F9 BARC solution. Please seek a professional such as Surrey Jet Washing before attempting yourself.