Tin-free steel (TFS) is also called electrolytic chromium/chromium oxide coated steel. The material consists of mild steel base with a coating of chromium-chromium oxide, to protect the steel base from corrosion prior to fabrication. TFS containers need to be coated on the inside and outside with additional protective coatings like enamels and lacquers to make them corrosion resistant. Their main use in aerosol containers is to make aerosol bottoms and tops.