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.
Galvanic corrosion
The common technique of cleaning silverware by immersion of the silver and a piece of aluminum in an electrolytic bath (usually sodium bicarbonate) is an example of galvanic corrosion. The process involves electrochemical reduction of silver sulfide molecules (generally speaking, silver is not easily corroded by oxygen). Sulfur atoms are stripped off the silver sulfide, transferring them onto and thereby corroding a piece of aluminum foil (a much more reactive metal), leaving pure silver behind. No silver is lost in the process.