Q: I’m running a hydro-treating process that is running at 350-390°C where we’re producing H2S and NH3. Any ideas on a bolt that can handle the temperature and chemicals?
A: In this type of process you having to deal with high temperatures and the formation of sulfuric acid (H2SO4) from the H2S especially when things cool or on re-starts. An ideal fastener material for this situation would be Hastelloy C276 bolts. The Hastelloy family of nickel alloys, all usable at temperatures greater that 1500F/800C, so well within your temperature range. In terms of corrosion potential from sulfur, ammonia, sour gas and other contaminants, the main contributor to corrosion will be the sulfuric acid, and for that acid, Hastelloy C276 will be an excellent material to consider.