rx7locost wrote:
ajmacdon wrote:
So getting paint to stick to new steel can go badly sometimes. A trick my farmer FIL taught me was to hit new, bare steel with a rosebud or big tip oxy torch before painting, same with freshly sandblasted steel. You can see it sweat out moisture which makes sense but I think that moisture carries some oils with it (this is one my engineer brain struggles to make sense of but it just works, every time). I have had incredible luck by cleaning with soap and water, acetone, torch until it stops oosing moisture (you can move at 1ft/2sec or so, it's not a slow process, you can watch the moisture front evaporate fast), acetone one more time, then primer. I've skipped the second acetone a few times with no issues either. Plus, then you're painting warm steel which I also think helps.
Alex
Alex, I believe that this is not true, At least not enough to ne noticeable by the naked eye. The byproduct of the torch's flame is CO2 and H20. The H2O condenses on the cold steel when torch is first applied. Then as the steel warms up, the water no longer condenses and instead, the water that had just condensed on the steel evaporates. Steel does not absorb water nor is it porous. Your farmer FIL was misled. All is not lost though. The heated steel may have helped dry the paint slightly quicker.
Oh, trust me, I'm fully aware of the combustion chemistry and all the reasons this should be total BS. However, even with full cooling before painting I've had the paint stick significantly better than fresh metal I've painted without the torch step.
Maybe it's just burning off any oil left after the acetone wipe? I've searched my science based soul for a reason this should work and, like you, that part of my brain calls BS. More than one engineer has been burned by not listening to the farmer, though.
Alex