Specify 316 or 444 for inner with stainless jacket.
USA is just about the only country where 304 stainless is acceptable for the inner liner of generator stacks.
316 and 444 steels liners are the most common elsewhere around the world. To maintain extended warranties, all other stack manufacturers state to paint the aluminized steel outer jackets - how often do you see that happen? The correct spec up front is to use stainless steel outer jackets.
Jeremias standard is 444 stainless inner and 430 stainless outer. Specify better steels and let’s compete with others' premium cost products!