Mast painting

[talbot]

I am painting a badly scratched and abraded mast. Do I need to completely sand off the anodizing before applying self-etching primer? I've done this before on a boom, and it's a huge job. I'm wondering if well-sanded anodizing will hold primer well enough.

[GreenLake]

This reference goes into details of why painting aluminum is nearly impossible.

[talbot]

Sure, I know it's difficult, but I have done it successfully on an old badly corroded boom. There are lots of posts on various forums about painting spars. However, the advice I've read is not clear about whether they are taking off old loose paint (which obviously needs to be completely stripped) or basically sound anodizing that has localized mechanical damage.

The anodized surface is very hard. It takes a while to get through it. The aluminum underneath is soft. So as soon as you break through the anodizing at any point, it becomes very difficult to sand evenly. If I could stop at just scouring the anodized surface, the job would go much faster.

The reference you provided, which indicates that the paint adhesion problem is due to surface film on raw aluminum, makes it sound as if I would be better off scratching through the anodizing but not stripping it. I'll use a self-etching primer to stick to the bare aluminum in any case. My question is, would the primer stick at all to any remaining anodized spots?

My target launch date is April 15, but that may be optimistic. A hull gel coat repair today bombed because the temperature didn't warm up to its predicted high. I should have just worked on the mast. It's inside. The boat is not.