When brown rust spots (points) appear on the surface of a stainless steel electric heater, people are greatly surprised, thinking that "stainless steel does not rust; if it rusts, it is not genuine stainless steel, and the heating tube manufacturer may have replaced stainless steel with other materials." However, this is not the case. Stainless steel can also rust under certain conditions. Stainless steel has the ability to resist atmospheric oxidation, i.e., stainlessness, and also has the ability to resist corrosion in media containing acids, alkalis, and salts, i.e., corrosion resistance. However, its corrosion resistance varies with the chemical composition of the steel itself, its mutual state, service conditions, and the type of environmental medium. For example, 304 steel pipes have excellent rust resistance in dry and clean atmospheres, but if moved to a coastal area, they will quickly rust in the fog rich in salt, while 316 steel performs well. Therefore, not every type of stainless steel can resist corrosion and remain rust-free in any environment.
Stainless steel relies on a very thin, firm, stable, and dense chromium-rich oxide film (protective film) formed on its surface to prevent oxygen atoms from continuously entering and oxidizing, thereby achieving corrosion resistance. Once this film is continuously damaged for some reason, oxygen atoms in the air or liquid will continuously enter or be separated from the metal iron atoms, forming loose iron oxide, and the metal surface will be continuously rusted.
To ensure that the metal surface remains bright and rust-free for a long time, we recommend: regularly clean and wipe the decorative stainless steel surface to remove attachments and eliminate external factors that cause corrosion. In coastal areas, 316 stainless steel should be used, as 316 material can resist seawater corrosion.
