Q: We are running a steel pickling process are considering switching from a sulfuric acid process to hydrochloric acid. Our system currently uses Inconel 625 bolting. With this be sufficient?
A: Inconel 625 is a good material for acid corrosion but for large system of hydrochloric acid, especially with the corrosion that can occur with fumes and vapors, you may want to try a Hastelloy C22 or even tantalum if the Inconel 625 does not hold up. Both perform very well in hydrochloric acid. Tantalum fasteners have the best corrosion resistance and are essentially immune to HCl but limited strength. Hastelloy especially grade C22 while not as corrosion resistant as tantalum has very good corrosion resistance to HCl and good strength as well.