Q: How does 254 SMO compare with Alloy 20 and AL6XN? Can it handle sulfuric acid?
A: To answer your first question, I’ve ranked each of these specialty alloys in terms of their general corrosion resistance to sulfuric acid:
1. Alloy 20 Most
2. AL6XN Moderate
3. 254 SMO Least
Overall these alloys all perform well in saltwater and chloride environments, but for an acid application like sulfuric acid, you would likely want to choose a more robust alloy like Alloy 20 fasteners (though it always depends on the concentration and temperature of the acid environment). For strong sulfuric acid environments 254 SMO bolts are not a good fit. Alloy 20 bolts are designed to provide a moderate range corrosion resistance to sulfuric acid, specifically in the range of 20% to 40% in concentration. In hot sulfuric acid Alloy 20 bolts are known for their resistance to stress-corrosion cracking. If you are dealing with a harsher sulfuric acid environment, I’d recommend Hastelloy bolts as they can be used in much higher sulfuric acid concentrations and at elevated temperatures.