Q: I’m currently using Monel 400 hex head bolts in salt water. Should I be using K500? What’s the difference?
A: Basically, Monel K500 is a precipitation hardened version of Monel 400. This means the material goes through a heat treating process that changes the alloy’s structural matrix to increase its tensile and yield strength. Monel K500 bolts will give you similar corrosion resistance as Monel 400 bolts, but with added strength. Alloy K500 bolts will provide about 3 times the yield strength (110ksi vs 45ksi) and double the tensile strength (160ksi vs 83ksi) when compared Monel 400 bolts. Overall, if the Monel 400 is failing from a strength perspective, then Monel K500 bolts will be a good choice. However if the Monel 400 bolts are failing due to corrosion, a more corrosion resistant alloy may be needed like titanium bolts or a high performance nickel alloy fastener like Inconel.