Thanks for the explanation. I would have thought the opposite though for another reason. In other words, one would want the formed, blind side of the rivet to be the same as the material being riveted. I'm attaching a stainless block hanger to an aluminum boom. The galvanic action would be nil at the attachment or grip point if both the aluminum rivet and boom are the same material. Wouldn't the grip point of the fastener be the most critical area rather than the head of the rivet?