I used silicone on my new rear window seal,now i read it causes rust,it was not easy for me doing it,you guys have any advice,car is a keeper and in mint condition.
1980 w116 chassis

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W123 1985 300TD naturally aspirated

It depends on the type of cure. Some silicones contain acetic acid that can cause problems with aluminum, dunno about steel. But unprimed steel will rust no matter what is used. If you primed the body before you put down the silicone, you should be good.