This biodegradable rust remover takes off heavy rust without scrubbing; all you need to do is soak your parts in it. Evapo-Rust Rust Remover contains no acids, bases, solvents or other toxic ingredients so disposal is easy and safe. One gallon of this rust remover derusts up to 300 lbs. of heavily rusted steel without harming unrusted metal, plastic or PVC.