lol i thought those were yours in the picture, i was going to say holy crap those are like brand new. I recently rebuilt my engine, the bypass pipes are just plain steel, but they might be zinc coated stock, not sure on the coating.
Anyway, mine were really rough from corrosion on the outisdes. I sanded the outside down using steel wool in a parts washer, and sandpaper on the rougher parts, and then painted it with engine paint. I thought about buying a new one and sending it to get powdercoated or something but I think they are 70+ new and it just wasn't worth it for a bypass pipe. As long as it doesnt leak or rust though I'm happy.