chrome as an insulator between bronze and aluminum?

      I'm no chemical expert, but afaik every material may act in this way, as long as it is enclosing one of the parts (or at least the area close to the contact area, if the parts aren't constantly submerged). However, I don't know, how aluminium and chrome behave in Saltwater. Most certainly, it will depend on the aluminium-alloy being used, so you should ask the manufacturer of the aluminium parts first. (due to the context I suppose that we are taking about an application in marine technology, were pure aluminium is virtually never used, as it would corrode in saltwater even with no other metaks close by)
      An electric isolation between the parts (e.g. a plastic or rubber coating or a flat seal in places with constand contact) should certainly improve conditions. (especially as "anchor winch" sounds like an area were abrasion of the chrome plating is likely)