Blueish corrosion on fittings

[Cdisney]

I am geting a blueish corrosion on most of the brass fitting on my cooling system. what is the cause, is it a problem and what do I need to do??

[Kelly]

I don't believe this is a problem and is more than likely caused by the surface oxidation of brass and bronze. This is a process that typically attacks the exposed surfaces and protects somewhat the metal below. Some people put a thin coat of varnish on brass lamps and such found below decks in order to avoid this oxidation but engine brass and exterior fittings are either left to develop a patina or polished occasionally for that "Bristol" look.

[rigspelt]

Check for seawater leaks just to be certain the joints aren't weeping.