john,
The gasket material selection is related to the service is operating on;- the large variety of available materials makes it difficult to create a comprehensive standard for the selection materials. However, most of the major gasket suppliers can give you details of how one particular material suggested by them will minimise the corrosion problems you have, how and why will it work. They will also provide the relevant and guaranteed m and Y figures for the flange calculations (if required). Perhaps, at a small cost, they might provide you with their internal materials selection guide, if you prove yourself a reliable customer...
In the view of your post, I suspect that there is due a lot more engineering on those joints than a cookbook to select a gasket material. The most important is to admit there is a problem and ask for suggestions on how to solve it. Try also read the NACE MR0175 and NACE MR0103 for corrosion in sour service, it just might be applicable to your case....
cheers,
gr2vessels
