Q: I’m producing nitrobenzene to be used in dye manufacturing. The nitrobenzene is prepared by the nitration of benzene with a mixture of concentrated sulfuric acid, water, and nitric acid. I’ve tried Hastelloy C276 but its not working so well.

A: Hastelloy C276 works very well in sulfuric acid which is a reducing agent but because it has a lower chromium content, it won’t be able to handle concentrated nitric acid as well. In this case depending on the exact temperatures and concentrations you may want to up your protection to Hastelloy 2000 fastener which performs very well in both acids and oxidizers or even Tantalum fasteners which is used to the most extreme corrosive conditions

A:  Yes, this is completely normal for Hastelloy C276 to corrode in hydrofluoric acid. HF is extremely corrosive to most metals however Monel and Hastelloy C2000 fair far better than most. Though Monel bolts are very resist to HF, the highly oxidizing nature of nitric acid will corrode them. In this situation, I would suggest the Hastelloy C2000 bolts. This is a unique material  because of its ability to resistant not only Hydrofluoric acid and other strong acids, but it has a high chromium content which also makes it very resistant to oxidizers like nitric acid.