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Gold MIL 5541 Class 3 with gold-plated PCB

I have a gold plated PCB that is screwed down to an aluminum surface (AL 380 cast, gold Alodine, MIL-C-5541 Class 3) The gold plated PCB is contacting the aluminum and assembly will be in an area where high moisture is a possibility. Would the class 3 Alodine finish hold up against the galvanic corrosion reaction the aluminum will have against gold?

John Chou
Electronics Manufacturer - Melville, New York
2004

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It doesn't sound real good, but if the surface area of the aluminum is much greater than that of the gold it might be okay.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004

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We have an amplifier already to be in production that has a gold plated PCB mounted onto a cast A380 aluminum heatsink. The problem is that this amplifier will be in a climate where moisture might develop (due to rapid temperature change). Being far apart on the galvanic series (gold and aluminum), we are very concerned that the aluminum will rust. We need an electrical conductive path between the PCB and the aluminum heatsink for ground so clear anodizing the heatsink is out of the question. We are now going to MIL-C-5541 class 3 gold Alodine on the heatsink.

I do not know if this will be enough...should I go to class 1 where the coating is thicker at the expense of higher electrical resistance?

Is there any other alternatives? (for example, painting the area where there is no need for electrical conductivity after the Alodine process)

John Chou
Electronics MFGR - Melville, New York
2004