Steel hardline for air line

I'm looking to run steel hardline for my airline and not stainless because I'm going to have it powdercoated. I've seen discussions on using brake line for air line (since I'm only using 3/ but I wasn't too sure about this idea although it apparently has worked for others. I was wondering about your opinion on this and if you disagree with using it, then what size line would you recommend and what fittings to use? It has been mentioned that one could run regular compression fittings or PTC fittings but once again, I'm not so sure about this just because none of this has been confirmed by truly reliable sources...thoughts?

i did mine with steel 3/8 line and flare fittings, worked good for me

like steel 3/8 brake line and brake line fittings?

I've never used steel line for air, but I use it for brake line all of the time If it will hold up to the pressures of the brake system and be as reliable as a brake system needs to be, why couldn't you use it for air?

i used .032 1/2 4130 it worked good or maybe it was .028 meh.

One thing we foumd with any kind of steel lines in the industry I'm in. Air = moisture (even a little bit) and you're gonna get rust. Even a tiny bit can wreak havoc on your valves. You can powdercoat stainless no problem. The thing is, you will never have an issue with stainless ever!

stainless is just so expensive lol...plus, since I plan on powdercoating it, I wouldn't even use the shiny prettiness of stainless so it would seem like a waste...perhaps I could just double up on the water traps to help..

you can put 80 water traps on it and still have moisture, it will rust from the inside out and leave you stuck on the wide of teh road eventually

run aluminum fuel line from summit you can probably powdercoat it and never have it rust

Would aluminum fuel line withstand 200 psi? If so, I might switch to this also.