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.

Q: I need bolts for a well pump exposed to sour gas? I’ve currently use Incoloy 825 bolts which works reasonably well, but I’m wondering if there is a better choice that is more economical and could offer equal or better corrosion resistance – any ideas?

A: A great nickel alloy bolt to combat sour gas and oil well corrosion is Hastelloy C276. Hastelloy fasteners offer excellent resistance to sulfuric acid, sour gas, brine, sea water and chlorides which makes them a perfect solution for oil well corrosion. Hastelloy C276 has very similar working range to Incoloy 825 bolts with a typical yield of 49 KSI and a working temperature limit of 1500F. While Hastelloy C276 is generally a more expensive material than Incoloy 825, because of the high volume of Hastelloy C276 fasteners used, it actually will be a less expensive with higher performance.

Q: I have down hole application containing sour gas and high chloride levels. The temperature the bolts are exposed to is around 150F and I’m having trouble with cracking. I tried Super Duplex 2507 but am still having issues. Any ideas?

A: Super Duplex 2507 does provide good resistance to stress corrosion cracking, pitting and crevice corrosion in warm chloride environments to around 570 F, but I think in combination with the sour gas, and perhaps stress of your operation, it may need something more robust. A great material for a combination of sour gas, chloride, high strength and temperatures to consider is Incoloy 925. Down-hole oil & gas rely on this material for its excellent resistance to sulfide stress cracking and stress-corrosion cracking in H2S environments. It has a high operating temperature of 1200°F which is well beyond what you need. It is also has a much higher yield strength (120 ksi) compared to Super Duplex 2507 bolts of 82ksi.