Q: We are altering the chemicals we use to regulate the pH level of our manufacturing process with hydrochloric acid. I’m using some Inconel 625 bolting – will this work in the HCl too?
A: Inconel 625 bolts offer a high level of corrosion resistance for many acids, may work for your application as well but without knowing the concetration and temperatures of the HCl acid it impossible to know. However if you are replacing you bolts, you might want to consider Hastelloy C276 bolts as they would perform better in hydrochloric acid especially in higher concentrations than Inconel 625 for a similar cost. Here is a chart with more data.
https://www.specialfastenersbolt.com/h