Pickles are preserved in a solution of salt and acid (usually vinegar). This will corrode common metals which will result in a leaky container and possibly a toxic dose of the metal to the pickles. If your pickle container was made out of gold, platinum or some other very unreactive metal, this wouldn't be a problem, however, this is not usually economically feasible. Hence pickles are commonly stored in plastic containers. Which property of the plastics makes the storage of pickles possible?