Mast and Stainless Steel Islolation

[Storm]

What material would you recommend to isolate a large stainless steel mast band that contains the spreader arm sockets and lower tangs as well as the baby stay? The fitting is about 6 inches wide and wraps almost completely around the mast. The fitting has about 8 rivets and is thru bolted at the tangs. I removed the fitting and plan to repaint the mast and re-install. The original filling looked like it had been installed with clear silicone, however there was some pitting on the mast and the silicone had areas where I am sure it would have acted as a water trap.