Dissimilar Metal Issues-Galvanic Corrosion Table.
Tip: Wherever possible, especially in a corrosive environment, do not mix metals.
When two different metals are in contact and subjected to a corrosive environment, there is a current flow between them. This flow causes corrosion of the least corrosion resistant metal (active) to increase, and corrosion of the more corrosion resistant (inactive) metal to decrease. The corrosion rate is related to the distance between the two metals in the ranking on the Galvanic Corrosion Table (see next page)
Keep metals which are in contact the same wherever possible. If not, ensure that are well suited in the Galvanic Corrosion Table (i.e proximate to each other in the table)
As you can see from the table, the marriage of Aluminium with Stainless Steel is not recommended and will generally lead to corrosion of the Aluminium (Anode) with the Stainless Steel (Cathode) remaining sound.