Cast-iron cookware
Because other cookware cleaning techniques like scouring or washing in a dishwasher can remove or damage the seasoning on a bare cast-iron pan, these pans should not be cleaned like most other cookware. Some chefs advocate never cleaning cast-iron pans at all; simply wiping them out after use, or washing them with hot water and a stiff brush. Others advocate washing with mild soap and water, and then re-applying a thin layer of fat or oil. A third approach is to scrub with coarse salt and a paper towel or clean rag.
Drain cleaner
Galvanized iron is actually steel covered in a protective layer of zinc, but it was soon discovered that this zinc layer naturally corroded due to exposure to the atmosphere and rainwater, as well as cement, runoff, etc. Once corrosion occurred down to the base metal, plaques and rust would form, leading to sediment build-up that would gradually clog these drains. Thus, the first motivation for drain cleaners came to be.