Tantalum Screws for Hydrochloric Acid Resistance

Q: We currently use Titanium screws, and I would like to know pricing and lead time to replace them with Tantalum screws to improve their resistance to HCL.

A: What concentration and temp are you at with the HCl? See the HCl Iso-Corrosion curve for Hastelloy C276. Tantalum screws will definitely work in your application but may be overkill considering titanium is not very corrosion resistant against HCl. Depending on your applications temperature and concentration have you considered Hastelloy C276 screws? See the chart below. If you are below the 5mpy (mills per year 0.001″) the C276 fasteners should serve you well. If not, tantalum screws may be where you need to be.

Hastelloy C276 Bolts or Duplex Bolts for Waste Water HCl Injection

Q: We’re making some changes in our waste water treatment process and are going to using hydrochloric acid (HCl) as a means of lowering the pH levels. Will I need to upgrade my duplex bolting?

A: Assuming your waster water is at ambient temperatures the only thing you need to worry about is the concentration of the HCl. By your inlet, it may be highly concentrated requiring different bolting further upstream than down stream. Depending on the your PH, you certainly will be safe with Hastelloy C276 bolts by the injection ports. Further downstream you will probably be OK with duplex bolts as the acid injected dilutes out.

Inconel 625 vs Hastelloy C276 in Hydrochloric Acid (HCl)

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.extreme-bolt.com/hastelloy-c276-fasteners-flanges.html#Corrosion