Cartridge heaters come in many shapes and sizes, and the outer tube can be made from a variety of materials. The most common of these materials are 304 Stainless Steel or 304 SS, 316 SS, Inconel or other metals such as brass. However, as you are probably aware, most of these metals though offering good corrosion resistance on their own, when combined with the right mixture of dissimilar metals, liquid catalyst, and elevated temperatures results in a rapid corrosion and premature failure of the electric heating element. When it comes to really nasty stuff like hydrochloric acid or sulfuric acid forget about it.
For example if you use a 316 stainless steel cartridge heater in deionized water or water with chlorine, the heat generated by the cartridge heating element, actually accelerates the corrosion process resulting in premature failure of the cartridge heater. This process can be slowed down by passivating or electro-polishing the stainless steel sheath of the heating element or adding a protective coating like Teflon. However, the down side to these corrosion prevention methods is they add time and costs to manufacturing your cartridge or tubular heating elements.
A better solution to cartridge heater corrosion might be to use an alumina cartridge heater from DT Heaters and Controls. These cartridge heaters offer superior thermal properties and chemical compatibility over traditional cartridge heater designs.
Features and benefits:
- High Watt Density
- Rapid Thermal Response
- Direct Contact with Water and Metal
- Long Heater Life
- Oxidation Free Design
- Low Leakage Current
- Inert to most Chemicals
- Flow Through Design