What paint and color do you have now? Pics if the areas you wan to cover might help understand the pain scope. Some options come to mind:
1) Remove the boom, dissemble it, wire brush it, sand it, apply aluminum spray primer then 2 coats of your choice of paint and color like off-white rustoleum or Algrip to match.
2) Remove the boom, dissemble it, sandblast, anodize.
3) Remove the boom, dissemble it, sandblast, powder coat.
4) Replace with a used boom in good condition.
These threads might be helpful:
The spars on my 1982 Hunter 30 were originally painted white by the manufacturer. Over the years the P.O. added a couple additional coats and last summer all three, but mostly what remained of the 26 year old original coat, started peeling badly - exposing bare aluminum. At haul out last...
forums.sailboatowners.com
This winter I plan on doing a few upgrades...paint the deck, new electronics, that kinda thing. One thing I see is the slightly crusty end of my boom. I was thinking to sand it down nice and smooth then paint it...I'm partial to the dark colors or even to match my topsides which are a medium...
www.sailnet.com
My boom is a tad but scratched. Was wondering how it would look with a dark grey boom. Actually I know initially it would look good. But long term? Anyone ever do this?
www.sailnet.com
The painted mast and boom on my 1985 Ericson 35-3 were looking pretty tired when I purchased the boat in 2006. The previous owner had taken some Rustoleum gray to touch up the spots that had flaked...
tkronaboat.com