Q: I’m operating a FGD (Flue Gas Desulphurization) plant and am experiencing some mild corrosion on my scrubber bolting. I’m currently using Incoloy 825 bolts. It’s mild corrosion but non-the-less I’d like to have it cleared up before I get additional issues. Any suggestions?

A: Since scrubber liquids and gases not only contain sulfuric acid but also chlorides, you have double trouble. Incoloy 825 bolts are great for some parts of flue gas desulfurization systems but sometimes not where there is scrubber slurry because its so potent. Here you may want to try Hastelloy C276 bolts which have excellent resistance to sulfuric acid as well as the ability to withstand higher chloride content than other alloys before the onset of localized corrosion in a simulated scrubber environment. Corrosive conditions are also amplified on shutdowns when acid gasses could condense on corrosion resistant bolting.  I’ve also posted a chart for you which compares steel, Incoloy, Inconel and Hastelloy in terms of flue gas scrubber corrosion.

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.