Often when design requires that dissimilar metals come in contact, the galvanic compatibility is managed by finishes and plating. The finishing and plating selected facilitate the dissimilar materials being in contact and protect the base materials from corrosion.
For harsh environments, such as outdoors, high humidity, and salt environments fall into this category. Typically there should be not more than 0.15 V difference in the "Anodic Index". For example; gold - silver would have a difference of 0.15V being acceptable.
For normal environments, such as storage in warehouses or non-temperature and humidity controlled environments. Typically there should not be more than 0.25 V difference in the "Anodic Index".
For controlled environments, such that are temperature and humidity controlled, 0.50 V can be tolerated. Caution should be maintained when deciding for this application as humidity and temperature do vary from regions.
Metallurgy Index (Volt)
Nickel, solid or plated, titanium and alloys & Monel (0.30)
Aluminum, wrought alloys of the 2000 Series (0.75)
Aluminum, wrought alloys other than 2000 Series aluminum, cast alloys of the silicon type (0.90)
Aluminum, cast alloys other than silicon type, cadmium, plated and chromate (0.95)