Legacy Industrial's HD357 Etch is a concentrated concrete-etch and cleaning product using a Concentrated Salt as the primary ingredient. This concentrated salt ingredient acts like an acid. This product creates less dangerous fumes that Muriatic or Hydrochloric Acid does, making it safer for your application. Coverage: 500 sq ft. per gallon for DeltaDye® Concrete Stain or Sealer/Coatings Prep. This product is best applied using a pump-up deck sprayer (all plastic). Follow all safety precautions listed on the bottle/container.