Painting an ally mast

the skin metal on aircraft is typically etched, anodised and primed. The surface of aluminium if you take a cut (or sanded piece) and expose it to air is rubbish for painting (and bonding)- the oxide/hydroxide layer, whilst reasonably protective to corrosion from the air, is quite weakly bound.


So, the parts are degreased (half an hour in a warm, alkaline bath) to remove oils etc.
Then etched (half an hour in a hot bath of chromic sulphuric acid) which creates a honeycomb-like structure of more tightly bound oxide. this is unfortunately unstable in air; it must be used within eight hours
Then anodised in a bath of chromic acid or phosphoric acid- this creates an even stronger oxide that has about four hours surface stability in air
the etched and anodised surfaces have decent corosion resistance as is- as you see with boat masts, they don't require any further treatment to stnad up to a lifetime of use in salty environments. But, as mentioned, the surface becomes rubbish quickly as far as bonding and painting go, so they are sprayed- with aircraft, the market leading primer by a long way is Cytec's BR127 (this is the yellow). It's nasty stuff to work with- horrible solvents and chromate are a fantastic combination...

Take home message: if you want a good painted surface on anodised metal, you need to paint it fresh out of the anodiser. Otherwise: forget it. It's not the paint that will fail; it's the surface of the metal isn't strong enough.

You'd need to use an etch primer such as that used when painting aircraft, I believe the name is 'yaffle yellow' from Azko Nobel. You need to be quick though as generally it works best if the base layer is sprayed while the primer is still wet ie within 3hrs.

Back when I was a nipper, Fireflies had Ali masts with wooden tops. I have a feeling the Anodizing was either no good or non existant, and the masts were frequently painted, often white. It always flaked, and always looked crap. Even a pitted old ali mast looks better than a flaky painted one.

And one big flake of paint would make the mast look pants!

Also what would the effect of salt water have to the paint?

How hard/easy is it for a complete painting novice like myself to paint an
ally mast and have it turn out well? Let's say for instance I want my mast
blue, what do I do? The likely hood of me doing it is extremely low but I'm
interested to know if I could do it well and what I would have to buy and do
to make a good job of it.
Surely any paint would crack and flake away as the mast flex and bends?

Doug H