lml@lancaironline.net Mailing List Archive

<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> In a message dated 6/14/2001 11:08:17 PM Pacific Daylight Time, lancair.list@olsusa.com writes: << Powder coating will not adhere to dirty metal. Which means if all the corrosion isn't removed from the aluminum...>> I had all of my control pushrod stock alodined professionally. When I make a pushrod I whack off a piece, and the resulting pushrod is alodined inside and out (except for the edge at the end). Presumably this is rustproof and clean, though I did have them solvent-wipe the aluminum before powder coating. The control crossover weldment did have some surface rust on it in a small area (three square inches). This part is cad-plated steel and I allowed them to lightly sandblast this before coating. So presumably my parts are clean and rust-free when powder coated. <<There is absolutely no way to tell if you have a serious crack in the metal underneath the powder coat until the part fails or the coating cracks and breaks off to reveal the problem.>> Interesting point, if true. However, I'm told that the paint on our fiberglass parts is less resilient than the underlying structure, and that if you bang the part and there's no crack in the paint, you can be sure that there's no crack in the fiberglass. While not necessarily relevant to powder coated aluminum, I wonder if it's possible to crack aluminum and not crack the coating? <<Vibration is the one operating factors that differ between bicycles and airplanes. >> Yup. It seems much worse on my bike.... (Just joking here) Seriously, though, I do appreciate Curtis' and everyone else's comments on this. I freely admit to not knowing any more about the effect of powder coating on aluminum beyond the obvious -- It looks much better when finished. I'm not saying they're wrong, not at all, but if corrosion is the big issue then I think powder coat over alodine or a cleaned surface is fine. I also think the environment in our airplanes is more benign than on the bottom of a car. The issue originally raised, however, was loss of heat treatment due to brief exposure to temperatures above 400F. Just curious here, but what are you guys going to do when you see a cylinder head temperature of 400F? Scrap the jug? I don't think so. Isn't this the same issue? - Rob Wolf LML website: http://www.olsusa.com/Users/Mkaye/maillist.html LML Builders' Bookstore: http://www.buildersbooks.com/lancair Please send your photos and drawings to marvkaye@olsusa.com.