Cleaning corroded Dali element

I picked up a pair of cheap Dali Evidence 370, and they have some corrosion on the woofer elements. I can clean them with IPA, but I think they need some sort of treatment to avoid it happening again. Any tips on what to use? I can use some etching primer and possibly a second coat of spray paint, but I'm not sure if it's the ideal way to prevent it.

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