Protecting exposed 6061 aluminum from corrosion?

[Arthurc]

I’ll start by acknowledging that the best solution is anodizing, painting or powder coat, that said due to the size and limited effort I’d like to put into this I’ve ruled those out for now.

I’m building a flagpole for a property on the water and am doing it out of 2.5” 6061 tube welded into 2 12ft sections with a base of .25 6061 plate. I’m aware the salt water air will corrode this pretty quick if not treated so hoping someone has found a clear etching or other solution to keeping aluminum better protected. In time I’ll get it anodized or painted but want to use it for a year before making that call.

Unfortunately Stainless was crazy expensive so aluminum it is…

Any advice or past experience would be appreciated.
AC

 

[Bkay]

You are correct that the effects of corrosion are fast with aluminum. It will very quickly develop an aluminum oxide coating, but after that, the aluminum oxide will prevent further corrosion. So you can simply buff/sand to the finish you want an leave it. That's what I did with my aluminum flag staff.

An alternative if you don't like the "patina" of aluminum oxide are products like Sheila Shine or Sharkhide which are easy to use (spray or wipe on and wipe off). They are clear and go a long way to keeping things shiny until you decide to go another route. I have that on the skin of my boat.

 

[Comodave]

Maybe look at Sharkhide as said above.

 

[Arthurc]

Oh good to know, those products sound perfect. I’ve got limited experience with aluminum so this is super helpful!

 

[Gotwex]

This stuff is awesome. I used it on a polished steel stairway, 3 stories, 9 years ago and it looks like the day I applied it. I have also used it on bare metal exposed to high heat and it really stand up.

https://permalac.com/

 

[Arthurc]

I’ll get all three and try them. Permalac looks cool and more protective, I like that it cleans up with acetone if you ever want to change it.

 

[Rebel112r]

6061 aluminum is pretty corrosion resistant without any coating.. for a flagpole I would guess that it is T6..Built an airplane using it, and only outer surfaces were painted. Inner skins were left bare and never had a corrosion problem.. Painting is not a big deal either. I used 4 step, alumiprep, alodine, simply brush on hose off. then epoxy primer and polyurethane topcoat. They also make self etching primer which saves a little work. For a flagpole, either bare or painted. Hope this helps.

 

[Arthurc]

Yep it’s T6 extruded pipe. I use to think that aluminum 6061 was corrosion resistant but have learned after installing several L angle pieces on my dock that it is structurally but 6061 with no protective coating looks very weathered after a short period.
I’m going to test all three solutions one on each piece and see how they do. The point gets some serious winter weather so will likely see some direct spray.

 

[twistedtree]

A lot depends on the finish you want. I built an aluminum walkway over a granite pier to a gangway down to a dock. It's exposed to salt spray 24x7x365. As Bkay said, it develops an oxide layer then stabilizes and doesn't progress beyond that. It's the same thing that happens with AL boat hulls that are left bare.


If you want a shiny, polished surface, or a painted surface, be prepared for a lifelong project to prep, finish, blister, repeat. Or if a more patina finish is acceptable, just do nothing and walk away.

 

[Arthurc]

Brushed would be my preference with a polished emblem on top, I’ll get this anodized and clear the top at some point but really not sure how tall, do I want two flag halyards or one and got curious about products folks have used since I might make changes.
The other thing I’m thinking about is it’s going to be two tight fitting 12’ tubes with an insert between, i suspect I’ll need to grease that to keep them from really sticking as they oxidize.

Slight side note, 6063 seems to hold its finish much better than 6061 (they do claim that’s true) but the 6063 parts I put on the dock look brand new.