First, this is not a paid promotion. I am a local pressure washer and am sharing my experiences.

To remove rust the only product I can recommend is F9. I have used it several times and it always works.

Description
Rust can come from a variety of sources, mainly from metals or fertilizers that contain iron. Most concrete rust does not travel more than 1/16” deep into the concrete.
Orange Battery Acid is an orange flash acid “burn” that can travel down your driveway and into the street. Flash acid burn looks almost identical to rust in appearance, but it is very different. If your battery acid is white, unfortunately this can travel throughout the entire slab and there is no cleaner that can remove the white stain.
F9 BARC is GUARANTEED to remove THE MOST concrete rust, fertilizer staining and orange battery stains than ANY OTHER product on the market! F9 works on CONCRETE, BRICKS, PAVERS, TILE, STONE, STUCCO, ASPHALT, VINYL, SIDING, SHINGLES, RUBBER, SIDEWALKS AND MORE!
DO NOT USE ON GLASS

The first step in removing rust stains is to identify the stained material. If you are dealing with delicate fabrics such as Acetate, Fiberglass, Rayon, Silk, Triacetate, Wool, Leather or Suede, you should take the item to a professional cleaner. Because of the degree of difficulty involved in the removal of rust stains, it is best not to try removing the stain from these delicate fabrics yourself.

Many other types of rust-stained materials can be cleaned at home, including the following materials:

Washable fibers such as Acrylic Fabric, Modacrylic, Nylon, Olefin, or Polyester - apply lemon juice to the stain, but do not let it dry, rinse & launder

Asphalt, Linoleum or Vinyl Tile - Wipe the stain with a cloth or sponge dipped in warm sudsy water. Rinse well and wipe dry. If any stain remains, try a rust remover, such as Bar Keepers Friend Cleanser & Polish, which is safe for resilient floors when used according to package directions.

Brick, Concrete and Granite - Make a poultice from 7 parts lime-free glycerine, 1 part sodium citrate (available from drug stores), 6 parts lukewarm water, and enough powdered calcium carbonate (chalk) to create a thick paste. Apply this paste to the stain and allow to harden. Remove with a wooden scraper and repeat if necessary. Wash area thoroughly with clear water and let dry.

Carpet - Apply lemon juice and salt to the stain. Flush with water and blot well.

Ceramic or Porcelain - On the tub, sink, ceramic tile, or toilet, wet a pumice bar, and rub the iron stain. Caution: Do not use this pumice stick on the ceramic glass found on cookware or ceramic cooktops, as it will scratch the surface. A paste of borax and lemon juice also is effective on iron stains. Rub the paste into the stain and allow it to dry. Rinse with clear water, then repeat if necessary. ry with a clean cloth.

Cotton or Linen - Rub liquid dishwashing or laundry detergent into the stain. Rinse with water, then launder as soon as possible. If stain remains, test fabric for colourfastness, then use a fabric-safe rust remover, such as Bar Keepers Friend Cleanser & Polish, according to package directions.

Stainless Steel- Rub stainless steel with a damp piece of very fine grade emery paper, followed by rubbing it with a slice of onion. Rinse well with hot water and dry thoroughly with a soft cloth.