Material selection for fluorsulfonic acid environments

What device? Pipes? Pump? Heat exchanger? Reactor? Or something else? If it’s not explained clearly, others cannot engage in discussion.

This post was last edited by cfleon on 2020-5-29 08:38. A few days ago, I responded to a query from a user in Shanghai; the corrosion conditions there are similar, involving high-temperature sulfuric acid. For your application conditions, titanium, nickel-based alloys, and super stainless steels are all unsuitable; consider using zirconium instead, specifically ZR702. (Of course, the ZR702 still faces risks in the combination of 70% sulfuric acid at high temperatures and 160 degrees: the data shows it can withstand 150 degrees with 70%, or 160 degrees with 60%). As for hydrofluoric acid, zirconium is available at this temperature and concentration. If money isn’t a concern, then Ta tantalum. It is recommended to prepare a set of hanging slabs. After all, if Zr can be used, it can save some silver. The chart was in the previous post; I can’t find it for now. Asmi alloy, hope it’s useful to you.

Thank you very much... I plan to conduct hanging slab experiments

Heat exchangers: In the past, graphite heat exchangers were prone to corrosion

Under conditions of a mixture of 70% sulfuric acid and 2% hydrofluoric acid at around 160 degrees Celsius, if metal materials must be used, gold, platinum, and tantalum are the only options available. However, these materials are extremely expensive, beyond the reach of ordinary companies. What model of graphite heat exchanger were you using before? What resin is used for impregnation? What is the lifespan? If all aspects are well managed, it should have a long service life.

It can be easily handled with our ZS1032

This environment can be described as quite harsh. It should be noted that, after reading the replies above, many of the statements are incorrect; for example, titanium, zirconium, and tantalum cannot be used because HF is present in it； For the precious metal silver, this concentration and temperature range of sulfuric acid are too high and not suitable. Regardless of the type of equipment, considering only corrosion resistance, some reliable metal options include: 1. Iridium, ruthenium, gold, and platinum. These four materials exhibit excellent corrosion resistance under such operating conditions. However, the reality is that they are all extremely expensive; moreover, iridium and ruthenium are very brittle and difficult to work with. Unless it’s for laboratory use or some other specific purpose, your boss will be furious if you use these materials. 2. Materials that can simultaneously tolerate medium-concentration, high-temperature sulfuric acid + HF, and are of good quality at reasonable prices, can probably only be found among nickel-based corrosion-resistant alloys. In the production process of HF, for example, the reaction that produces Ca(HSO4.F)HF using fluorite powder and concentrated sulfuric acid at 150°C involves the most severe corrosion; therefore, this reaction takes place in a pre-reactor made of Hastelloy C-276. HF can to some extent suppress the corrosion of Hastelloy C-276 by concentrated sulfuric acid, but the concentration of sulfuric acid in your case is clearly not that high, so the inhibitory effect of HF is limited. Moreover, for sulfuric acid at a concentration of 70% and a temperature of 170°C, which is already at its boiling point, these conditions have reached the upper limit for nickel-based alloys that can withstand corrosion by medium-concentration sulfuric acid: Hastelloy B3 ； Additionally, the concentration of HF may also need to be considered. The local concentration may exceed 2%. However, regarding the corrosion mechanism of HF, a higher concentration and temperature do not necessarily lead to an increase in the corrosion rate; therefore, under strict control of oxygen/oxidants, it is recommended to use Hastelloy B3 for testing first. 3. I would also like to talk about high-purity silicon carbide materials. This material is widely used abroad, and in China there have been precedents of using it in heat exchangers in recent years (although its workability and brittleness need to be overcome). One of the advantages of this material is its excellent corrosion resistance to sulfuric acid at all concentrations; it is also one of the few ceramic materials that can resist HF corrosion. (According to data from a domestic silicate research institute, exposure to pressurized hydrofluoric acid at 140°C for 7 days showed no visible corrosion.) Therefore, considering both corrosion resistance and availability, this material may also be suitable. Of course, the fascinating aspect of corrosion in the world is the \"butterfly effect\" – in real-world conditions, even small changes can lead to significantly different levels of material corrosion. Therefore, the information mentioned above is for reference only; it is recommended that the original poster conduct further experiments based on their own actual circumstances and taking the above suggestions into account.

What material is this? Could you provide more details? handshake

Thank you, it’s quite professional. We also plan to try using silicon carbide as a material, but sealing is an issue at such high temperatures