Im supposing your refering to the inner part since the outer is only cosmetic.
I would think the inner would be left cold rolled maybe called rolled 2B. the welded areas should be acid cleaned of any weld coloring. and perhaps smooth polished with a polish wheel. if the welder is clean, then a simple acid wash will work, not so important as the fermenters. But I have seen some pretty bad welds on ferementer extremities which made fine beer.
as for the outside, I prefer "checked" for the look and its ability to look good even when its not just cleaned.