Stainless steel is available in many grades, with 304 and 316 being the most commonly used. Each grade of stainless steel has a limit to the concentration of elements that it can comfortably resist: the higher the alloy content, the higher the resistance to corrosion. Exposure of a particular grade of stainless steel to a more aggressive environment than it can withstand will cause Tea Staining.
Tea Staining is a brown discolouration of the surface of stainless steel. It occurs when elements such as temperature and humidity are too harsh for that particular stainless steel in its installed condition. It is a cosmetic issue that does not affect the structural integrity or the longevity of the material. It is typically seen in coastal environments and can be controlled by selecting a suitable grade, a higher polish and with regular maintenance.