While some stains can be rinsed away with a pressure washer tougher stains such as rust require an acid based cleaner like muriatic acid.
Cleaning oil from concrete with muriatic acid.
Scrub the gray stain with a solution of 1 cup liquid chlorine bleach 1 cup powdered laundry detergent and 1 gallon of very hot water.
The surface becomes etched and clean which allows for the proper adhesion of a new coating.
Before washing your driveway with muriatic acid try a degreaser on oil stains and a solution of one part bleach to three parts water on mold and mildew.
Muriatic acid is diluted hydrochloric acid and is a very potent chemical.
It cleans concrete by removing the topmost layer of your driveway.
Use it only as a last resort to clean stains.
The acid works well on concrete and on many masonry projects because it neutralizes alkalinity.
Mold rust and other stains can mar the clean beauty of your concrete lessening the visual impact and even the curb appeal of your property.