One of the reasons usually given for not recommending stainless steel for tank material is its susceptibility to chloride pitting. Excess chlorides over time may start a micro-pitting process and ultimately stress corrosion cracking. Chlorides are probably the single biggest enemy of stainless steel. Next to water, chloride is the most common chemical found in nature. In most environments, however, the PPM is so small the effects on stainless steel are relatively miniscule. In extreme environments, such as an indoor swimming pool, the effects over time can cause stress corrosion cracking. Gold and platinum in their natural state, are the only elements to be completely corrosion proof. But stainless steel has proven over time, in thousands of applications to be the best material to combat the elements that cause corrosion.
Other than the extreme exposure of chlorides, low acid levels with elevated temperatures, stainless steel such as 304 and 316 have been used for years in the metal finishing industry and are very good tank materials for CHEMEON TCP-HF; to a limited degree 317 & 347 SS materials have been used as well. SS is mostly resistant to chlorides, fluorides, oxidants and acids, extremes in these elements over time can cause problems. Mild steel on the other hand is not recommended as a tank material as it is a low carbon steel, is much softer, is malleable and ductile and bends fairly easily. Mild steel tanks can be lined, however, with polyvinyl chloride (PVC) or PVDC among others.
Note: Many CHEMEON TCP-HF customers have been using SS tanks for many years without incident.