I am in the process of sealing my heating ducts with mastic. The aluminum (I assume) ducts are suspended in my crawl space with copper hangers. Before I removed the old fiberglass insulation, those copper hangers were separated from the metal ducts by the insulation. Now the copper hangers are in contact with the ducts and some of them are loose.

Do I need to worry about a corrosion issue with these 2 metals or would it be fine leave the hangers in contact with the ducts and wrap the replacement insulation around the outside of both of them?