Q: Are there any materials I can use with the strength of 17-4PH in the H1150 heat treat, but with better corrosion resistant properties. I have low levels of sulfuric acid and chlorides that seem to be attacking the 17-4 steel.
A: The best choice for both extreme strength and corrosion would be Inconel 718 bolts. Inconel 718 may be overkill as it can provide excellent corrosion resistance to concentrated acids and chlorides at high temperatures while boasting min yield of 175KSI. However if you are looking for a big improvement in both corrosion and strength this will do it. Another material worth considering would be Inconel 625. This is basically the un-aged sister material of Inconel 718 having good corrosion resistance and a strength similar to that of 17-4 H1150. Inconel 625 would a significant improvement in corrosion resistance to sulfuric acid over 17-4 PH while maintaining a similar strength.