Copper Sheath: For water heating & for heating water solutions which are non-corrosive to copper.
Steel Sheath: Immersion in oils, molten salt baths, alkaline cleaning solutions, tars and asphalt. Suitable for casting into aluminum.
Stainless Steel Sheath: Corrosive liquids, food processing equipment.
Incoloy Sheath: Air heating, radiant heating, cleaning and degreasing solutions, plating and pickling solutions, corrosive liquids.
Other sheath materials are also available for application considerations. Commonly specified are SS 304, SS 316, SS 321 & Incoloy tubes along with titanium for severely corrosive solution heating.