When does galvanic corrosion happen?

Q: I want to use Duplex bolts to bolt down a Monel plate. Will these materials be compatible?
A: When you mean compatible, I’m assuming you are referring to galvanic corrosion. Galvanic corrosion is when two dissimilar metals create an electrochemical reaction and corrosion occurs. Duplex and Monel can experience this but for galvanic corrosion to occur the parts involved must be wet with a solution. Galvanic corrosion cannot occur when the metals in question are completely dry however humidity might be enough to create that galvanic coupling.