OP, if you want to save the fan (the light kit), you will need to go to the AUTOMOTIVE store, and get a suitable rust preventative, then a zinc based primer, and then automotive white paint. An alternative source is Eastwood Automotive products (Pennsylvania), you can call them and discuss your problem, I have used their products on 8 cars I have rebuilt from the ground up, and have never had the areas rust out again. Their website is:
Eastwood Auto Restoration Supplies - Eastwood Auto, they have a whole line of rust preventative products.
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Pennsylvania, for 60+ years, most recently, Allentown, now TV.