STAINLESS STEEL CAN TARNISH AND RUST......
Cleanliness is essential for maximum resistance to corrosion. Surface contamination by dirt or other materials hinders the ability of stainless steel to reform the passive layer and traps corrosive agents, reducing corrosion protection. In many cases, standard household cleaners can be used to clean and maintain stainless steel hardware items. Soap, ammonia, and detergent and water are used to clean normal dirt. Cleaning should always be followed by rinsing with clean water. It is advisable to wipe the surface completely with dry towels.
In selecting cleaning practices, consider the possibility of scratching and the potential for post cleaning corrosion caused by incompletely removed cleaners. Select only cleaners that are not abrasive, not acidic, and low in chloride. Many antibacterial cleaners used to clean and sanitize door hardware contain high levels of chlorides, which will cause corrosion if not properly removed from the surface by rinsing. Routine cleaning is essential, especially in environments that have elevated levels of atmospheric corrosion. Proper care for your stainless steel door hardware will result in many years of durable use.
Acknowledgements: Stainless Steel Industry of North America