What size? What temperature? What pressure? What fluid on the inside? What's on the outside (i.e, is this submerged in seawater?) What gases? What application? You have not provided enough information for anyone to even start to provide an answer.
Also did you do a search on this forum? This sort of question has come up before. By looking at what has been suggested for other posters, you might arrive at an answer for your application.
Patricia Lougheed
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.