The best type of aluminum

​I don’t have a definitive answer, but here are two references that may help: 
A chart with comparative ratings for various applications, including surface treatment:  https://www.normalien.de/pdf/en/Content_Alu14_E.pdf

An overview of technique for preparing aircraft aluminum to receive paint:  http://www.zenithair.com/kit-data/ra/paint2.html

Hope this helps!

​Sorry for the delay. Dr. Rosie Grayburn at the Scientific Research Laboratory located at Winterthur Museum has suggested the following:

“I wouldn’t recommend anything anodized as a support as this potentially can give rise to cracks in the paint/ground later on. AlSi alloys are used for casting, so probably not a good candidate. Apart from that I would suggest any of the following that fit these categories:

–  Alloyed with magnesium will have good corrosion resistance
–  Alloyed with zinc will be very hard, copper less so but still very tough.”

If it were me I would opt to go with Mg over Zinc in this case. It probably will not be an issue, but if there is the SLIGHTEST chance of Zn ions somehow leaching into your ground/paint why risk that as we now know there are so many problems associated with zinc.

I would be curious to know if oil paint applied to panels composed of AlMgMn0 dried quicker than paint applied to AlMg, since Mn can be such an effective siccative. It has long been stated that linseed oil on lead sheets or in lead trays oxidizes at a far faster rate. This is a separate issue from which is more appropriate as a substrate for oil painting. However, I would avoid using a metal panel containing Zn for the caution stated above and for any possible anti-oxidative effects.