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Background...

We have aluminum rails that have been painted over a few times over the years. I believe that they were originally powder coated, but I'm not sure. They have now gotten to the point that large voids have formed between the paint and the metal and is breaking off in chunks. The metal underneath is corroded, which I believe is magnified by the salty air that comes from the salt water that is maybe 200 hundred yards away (Gulf of Mexico).

Parts of the rails can be removed, but some of them are concreted in.

Tested...

I have tested a small spot with an etching primer (spray can). I then (the next day) painted over the primer with a spray paint for color.

The primer seems to have done a great job. It seems to have bonded with the aluminum in a way.

The colored top coat looks good, but it not very durable - I could scrape it with my fingernail. I think this is the main thing that I need to change from the test, but please correct me if that is not the case. It seems that I need a top coat that does a good job sticking to the primer and is very durable.

So, my questions are...

  1. Is the spray paint a good option? Would I be better off using a brush?
  2. Is an etching primer a good long-term solution (10 years would be nice), or is there a better option?
  3. What options to I have for a top coat that is long lasting, resistant to salt air and sun, and durable enough for rails?
  4. Is this a reasonable DIY job, or would we be better served hiring professionals? (Special tools needed? Labor intensive?)
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    not with aluminum, but I've used the etching primer on galvanized materials. Based on that, don't expect 10 years on anything that will be used (ie, touched). I had to retouch annually. If you truly want a durable coating, you likely need to powder coat, which may or may not be a viable option. – DA01 Apr 1 '15 at 15:40
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I used autobody primer and autobody spray paint for metal rails. Need to allow a few hours after priming. And a good 2 hours between each top coat or you can end up with bubbles and build up.

This can be bought at big box or auto parts store (and many more colors if you buy online).

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