Nothing so sophisticated. Just Krylon satin clear. I had it, I tried it and I liked it. It may discolor over time but if it takes on some patina... then that's OK too. For me anyway.
Just adding that when I did my Stromberg WWs with Alodine, the first dunk they copped was for 10 secs on freshly beaded carbs. Color was too light. Secind dunk was for another 10 secs; colour was darker but was looking better. After another 10 seecs in the soup I had the colour I wanted. Scoot, the longer you leave em in the darker they become. I wanted to try it a bit at a time till I got the colour I want. The other thing is that different carbs may have a different ratios of zinc, tin, antimony and other metals in their castings, so they may all react differently to the Alodine solution. This is why I tried it 10 secs at a time till I got the shade I wanted. Rat