I think it's more that paint won't stick to a polished surface.
Also you must remove hand oils etc before painting (acetone or) with a clean rag.
Overlap the clear onto the tube so no water gets at where the lugs join the tube.
Also I use stripper rather than sand, gelled Lepage Poly Superstrippa. 3 coats, 1\2 hour between..the paint pretty much falls off and the metal is perfectly smooth.
All I can think of..G-luck.
Oh, I found Diamondcoat Varathaine to work good, hard, sticks well, no yellowing.