Framebuilders - Is primer necessary on Aluminum

I was making a DIY porteur rack from aluminum. And I am using Dupicolor to paint it. Would primer be necessary for this.

I would look at the available tech data. There may be a special aluminum primer. My guess is that it is required, topcoats don't like to stick to bare metal. Maybe someone with experience will chime in and help us avoid looking it up.

I believe Zinc Chromate primer is the norm for aluminum. Used on airplanes.

Anyway, I didn't clear coat it. But here is how it turned out. Usiing aluminum stock
and electric conduit. I put 5 coats of Duplicolor on it and let it dry for about 4
weeks. But I don't think the paint will stand up to normal wear and tear. Any hints on
how to give it a bombproof coat ?
http://farm4.static.flickr.com/3256/3156319545_b00ba9ed61.jpg?v=0


http://farm4.static.flickr.com/3264/3157227765_375cd3ace2.jpg

Yes, primer is necessary. On aircraft the protective is stripped and the surface roughened up first, normally apply an epoxy based primer coat followed by 2 coats of enamel overcoat for all exposed surfaces. Works well for corrosion prevention and some impact protection. A good overview is http://exp-aircraft.com/library/alexande/painting.html

Please bear in mind that an assembly such as the rack would also have sealant between all mating parts to prevent fluid from becoming trapped in the joint.

Powder coat or one of those bedliner coatings would be pretty durable. Rattle can paint is easy but durability is going to be poor.

Another option would be to line the contact surfaces with wood or plastic that could take a beating and be replaced as necessary.