Minimum 1500MPa tubular for use in seawater application

This kind of question scares people because of the obvious problem associated with using high strength materials around corrosive environments. If you use a precipitation hardening stainless you can get the strength, but your life under tensile stress and seawater exposure is limited. If that's within your allowable parameters, there are options to pursue. But, if that is acceptable, maybe just a martensitic steel will do the job, stainless if necessary to delay SCC failure under accidental seawater exposure.

Would a titanium alloy meet your requirements?

Many Thanks, I was not looking to scare anyone, under the accidental sewater flooding the compressive and buckling stress the item in subjected to is diminished, due to load sharing. A titanium alloy would work, costing is the issue as ever unfortunately. Looks like a PH grade will the best overall solution, thanks for the sanity check.

MM