Funky Underside of Radar Arch

[denpooch]

Hey Guys. I could use your advise on this issue with cracking around the lighting fixtures on the underside of the radar arch.
There are four exterior lights on the arch which are utilized to light the cockpit. The surface is cracking around one of them and the others are developing blisters almost as if there is rust under the coat which in turn is contaminating the surface. I don't know if the arch is painted over metal or a fiberglassed surface.
Has anyone ever seen this? Would you have any recommendations for attacking this problem?

Image.1.jpg

Thanks.

[bud37]

Your arch is aluminium with a painted surface......that looks like corrosion on the aluminium under the paint maybe from the holes for the lights or the grounding / dissimilar metals there...

[tomschauer]

If its an aluminum arch, and I believe it is. You have water getting from above, trying to get out at the lights and creating some corrosion on the aluminum.
Find and stop the leak, pull the lights, sand and paint the affected areas and good for several more years.

[denpooch]

Great. Thanks. Now... how to match the paint !

[Midnightsun]

I agree, looks like electrolysis happening there. 12v power metal light case, aluminum arch and then throw in some water, not good.

Suggest fixing the damage, painting and then using a decorative trim ring in order to avoid the impossible task of matching the paint. Not sure how large the diameter of the bad surface but maybe change the light for something much bigger to hide the damaged area.

[denpooch]

Good thinking Han. Thanks.

[km1125]

If you can't match it, then mask off a larger area and paint in a complimentary color, like you MEANT for it to be there.