Hi,
Paxair "90% He - 7.5% Ar - 2.5% CO2". The helium is much lighter than air, thus requiring a higher gas flow rate in order to keep the weld pool from being contaminated. This mixture theoretically could be used on other metals, although most common used with stainless steel.
Stargon "96.25% Ar - 2.75% CO2 - 1% Hyd" may be used only for authentic stainless steels, since the hydrogen will cause imbrittlement and cracking in ferritic and martensitic materials. The hydrogen is a reducing agent, taking away the oxides, leaving a cleaner weld.
Hope this helped you out!
Vicki
The 90/7.5/2.5 gas is for short-arc,unless you have a machine that can force a spray out of it.(powermig 300 comes to mind)It is one of the things that gets lost about the powermig,everybody thinks aluminum.