Monel bolts have high strength, toughness, and good corrosion resistance over a wide temperature range because they are made of a nickel-copper alloy. Monel bolts stand out for their exceptional resistance to hydrofluoric acid, a particularly difficult acid to handle, in all concentrations up to the boiling point. Monel bolts may be the most resistant of all frequently used specialty alloys for applications involving hydrofluoric acid.