Alloy 20 vs Duplex Zeron 100 Bolts

Q: I was thinking of ordering some Duplex Zeron 100 bolts for some mild sulfuric acid. How does that compare to Alloy 20? My alloy 20 bolts are suffering some mild corrosion.

A: Zeron bolts do offer a higher level of general resistance to corrosive environments compared to grades 2205 and 2507. Yet a Duplex bolt in grade Zeron 100 will not really offer more corrosion resistance compared to Alloy 20 in a sulfuric acid environment (of course this depends on your exact corrosive environment). Since you are having issues with the Alloy 20 fasteners moving to Duplex Zeron would not be recommended. We would suggest considering a higher level of protection from sulfuric acid, and to try a Hastelloy C276 bolt which offers excellent resistance to sulfuric acid even in hot conditions.

Alloy 20 vs. Hastelloy C27 Bolt for H2SO4

Q: I have a hot sulfuric acid application that utilizes approximately 25-32% sulfuric acid. I really need a corrosion resistant bolt but due to the vastness of the operation, I’m wondering if there is a lower cost option than Hastelloy.

A: For hot sulfuric acid in your concentration range, we would need to know the operating temperature to make a recommendation. However generally the most economic option would be Alloy 20 bolts, but for Alloy 20 bolts to be successful in your application the temperature would need to be below 150F. Beyond 150F, you are better off with Hastelloy C276 bolts otherwise you will suffer a significant corrosion rate in Alloy 20 and likely premature failures.

Titanium or Hastelloy Bolts for Sulfuric Acid?

Q: I read that titanium regenerates a protective layer quickly in presence of water. Does that mean its okay to use it with sulfuric acid with steam present?

A: Titanium fasteners are probably not the best solution for sulfuric acid but may work depending on your concentration and temperature. Titanium is best used for corrosion resistance to chlorides and salt water. For sulfuric acid, Hastelloy C276 bolts would be a much more robust solution and will be your best option for corrosion resistance to sulfuric acid for most conditions. However to be certain we would need to know the temperature and concentration of your application.