Can a gasket made of 304 be used with anhydrous HF media?
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May I use a gasket made of 304 material for handling anhydrous HF? There is no concern regarding corrosion with anhydrous HF; the worry is rather that the gasket might absorb water. I lack experience in this area. Also, regarding volume specifications, why can’t gaskets made of silane be used?
Anhydrous hydrofluoric acid (HF) is a very strong acid that is corrosive to many materials. Stainless steel 304 contains a high proportion of iron, chromium, and nickel, and hydrofluoric acid reacts with these metals; its corrosive strength is even greater in the absence of water. Since gaskets made of 304 stainless steel can be corroded by HF, it is generally not recommended to use such gaskets in anhydrous HF media. Even if the concern is water absorption by the gasket, it is also necessary to consider that the corrosiveness of HF may lead to seal failure. As for the issue of gasket water absorption, moisture absorption by the gaskets under anhydrous conditions may lead to the dilution of HF, thereby affecting the chemical purity of the system. Furthermore, the gasket may change in volume after absorbing water, which in turn affects its sealing performance. As for silane, it is a highly reactive compound that typically reacts with any moisture or other reactive substances present in gasketing materials; therefore, to ensure safety and material compatibility, avoiding the use of gasketing materials is a preventive measure. The specific material for the gasket must be determined based on the actual operating conditions, the properties of the medium, and safety requirements. Sometimes, special materials are required (such as polytetrafluoroethylene PTFE or other special alloy materials that are more resistant to chemical corrosion) to ensure sealing performance and chemical compatibility. When handling any hazardous chemicals, relevant safety procedures and material compatibility guidelines must be followed. .
I saw someone using RPTFE; after checking, it contains glass fibers. This material isn’t very suitable for HF, but since the amount of glass fibers is low, it’s not certain whether it can still be used: lol. On the other hand, flanges designed for high-hazard applications require PN25 grade – PN16 flanges cannot be used. According to hg20606, PTFE can only be used up to PN16 level, so PTFE is also not an option: lol