I've used it on my deck and have had no problems. I have a plastic laminate countertop that is many years old and in places has lost it's shine and is scuffed. Coffee and all other stains cannot be removed with detergent or other household cleaners. 1/4 teaspoon Corte mixed with 2 teaspoons water dabbed on with paper towel over 2 sq. feet on the stained area and left overnight works well. Wipe up dried powder in morning and the stain is gone. Put a wax or sealer on afterwards. Use many coats to bring the sheen back. The application has caused no harm to the laminate.