Aluminum Conversion Coating Temperatures

[Louis]

Hello folks. In a bit of a bind here. I've been working on my wings outdoors (Aluminum, Aeronca Sedan) Finished stripping them of the old paint. Next step is to acid etch, conversion coat and prime. Running out of warm temps, mostly down in the 50's F here or less. The Poly-fiber primer is advertised to work down to near freezing temps, but I can't find any minimum temps listed for conversion coating. Someone on another group said I shouldn't try it below 70F. Any thoughts? Also, how immediate should conversion coating be applied after the acid etch? I'm wondering about doing the acid etch one day and the conversion coating the next day. Thanks!

[Bill Berson]

I had a paint shop in Alaska. It likely never got above 60 in the hangar. We scrubbed the etch with scotchbright till water lays flat. Then Alodine about an hour later.

[Louis]

Thanks! Got one wing alodined. Seemed like it went well.. I guess I won't find out for sure until the paint sticks. What paint did you usually use for a topcoat in your shop?

[Bill Berson]

We used DuPont Imron over DuPont Corlar epoxy primer thinned for flowout. But that was 40 years ago….

[Bill Berson]

Imron will blush (go dull) if painted outside and left overnight in the open sky and gets dew on it.

[Louis]

Thanks, Bill. That's very useful to know. I have one side of one wing left to prime then I'll probably be done until spring. I talked to the paint store here in Fairbanks and they said that Imron is still the most popular paint for metal planes, followed by Poly-Fiber Aerothane.