primer...
The link you posted is pretty good.primer technology,and paint in general,has advanced a lot in the last few years.the metal conversion coatings and treatments mentioned are really used to deal with the thin layer of aluminum oxide that rapidly forms when aluminum is exposed to air.They "convert" the oxide to a paintable substrate.
depending on the alloy involved,the oxide layer can vary in hardness and thickness...from white powder on pure aluminum to the invisisble layer a few molecules thick on marine grades.all you likely need is an acid etch.vinigar will work (and it's real cheap)but for more severe oxidation,i had good luck with a scoth-brite pad and the stuff you find at the grocery store used to clean rust and lime deposits (CLR...LIME AWAY,etc).
these products are far more potent than vinigar,often containing muriatic and or phosphoric acids.use this liberally (wear rubber gloves and goggles please) scrub with scotch brite,and rinse liberally with water.let dry and prime asap.the oxide layer forms rapidly.
for primer,go to a commercial paint store and get a 2-part etching primer.any brand that is labeled for use on aluminum is fine.as long as it's self etching during the cure stage.
most of these primers are safe to be top coated with everything from hard enamel to 2 part urethane.check for compatibility and let your wallet choose.use a chemically "neutral" agent for sanding paper,use only stainless for a brush.no steel or iron oxide in the sanding paper.thats why i use scotch-brite.Be prepared to spend money on good primer.don't go cheap.
alodine treatment and zinc chromate were used extensively in aviation to paint aluminum,both are now harder to find and very pricey.zinc chromate especially,is being banned in canada for public use.it has long term toxic effects due to the metals it contains.getting to expensive for commercial use due to enviromental controlls required.
everybody's switching to 2 part primers,some of which are water based and much safer.
when i painted the bumper on the ford i owned,it was a heavy aluminum bull guard,etched and primed as above,top coated with the bed liner kits you buy at the hardware store.it stood up extremely well to 2 years of road-salt sand,gravel,water...you name it.no flaking or peeling.the top coat took hits from rocks and didn't even chip.
