Boat is a 2001 and has several original Perko drains, one of which had corroded so badly in the center screen area it had cracked. After replacing, not an easy task, the new one started to tarnish. Just a few cleanings later the chrome plating on the brass screen only started to deteriorate and show the brass. The body is chrome plated cast bronze and not affected. It’s a 2-7/8” OD flange and a 1-1/4” pipe. These drains are expensive and hard to find. The extensive maintenance and eyesore is driving me crazy. All the others are fine in the boat. Anyone experience this? Ideas? Also I have tried several different coatings and the discoloration continues to come back.