Lifted from another (boat design) board .
SS underwater sucks ,,bronze is great , if its the right bronze, and your boat has a perfect AC and DC system.
Perhaps this is the answer now that prices are falling BIG TIME!
To some extent this is true, but the primary drive for rediculously high titanium prices was really the US government. For decades it used about 95% of the worlds titanium supply, primarily for the DOD. Because of procurement rules the government could only buy from 100% US owned and located suppliers. So the few US sources had an effective monopoly on world demand, so they kept prices high, and didn't care about driving down costs.
Recently a lot of that has changed as world demand for titanium has increased, and supplies from non-US sources have increased. This has really driven down the cost to manufactur Ti.
Of course as prices have gone down, demand has risen, allowing fabrication costs to go down, allowing.... Basically a positive spiral for the cost of titanium bits. To the point that Allied Titanium can provide fasteners like bolts, nuts, screws, at around 25% more than the comparable part in 316SS for more specialized parts costs are higher, but getting better. And for truly unique parts, where both the titanium or SS would be one off productions, again we can often get pretty close to the SS price.
I am not a machinist, so I can't promise that my information is 100% correct, but as I understand it Ti is not particularly difficult to weld, though it does take some special precautions to prevent oxygen embrittlement. But basically it is just TIG welding with argon, though both sides of the weld have to be argon shielded. And the argon has to be kept in place until the temprature drops to below 800F.
As for machining, it is supposed to machine like stainless, slow, good chip removal, lots of cutting oil (at least with titanium olive oil seems to be prefered).
Salesman - Allied Titanium