My understanding on Evaporust is that it keeps eating on any rust particles in the solution even when put back into a sealed container, even when sealed from air. Also heard that straining or filtering the big and little chunks out of the liquid helps it last longer when not in use. Can't prove any of this by me as it's only hearsay on my part. I am still using that cheep old grocery store vinegar on things I need to de-rust.