I'll take a stab at a couple of the general questions. Galvanic attack and all corrosive repsonses are extremely service and material specific. You cannot use a standardized ASTM test to calculate definitively what your gal/cor repsonse will be. Especially considering that the standard ASTM tests are performed ina short time frame that may or may not extrapolate properly to a long term service. You can however use them as a 'rule of thumb' or 'ranking' reference to estimate. Services such as these are miscalculated everyday, and alloys often upgraded. The only way you can know for sure is to perform tests on the exact medium, materials, cycling, temperature, etc. for your service in question.