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Old 02-03-2013, 07:28   #1
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Painting Aluminium?

I've managed to get a 20ft x 3" aluminium pole to make a spinnaker/ heads'l pole. I got it from a metal liquidator place and it's a manky looking thing, so before putting fittings on I want to paint it.

What is the best prep. to make sure the paint will last?
Obviously degreaser, then what?
The paint will probably be white spray can stuff.

Who knows how to make this work without it all peeling in 6 months?

Vic
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Old 02-03-2013, 07:43   #2
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Re: Painting Aluminium?

normaly if un-anodised give a light sand,degrease.

then a coat of etch primer
2 coats epoxy primer
then 2 coats 2 pack polyeurathane.

though 3'inch diam seems a bit small,what is the wall thichness?
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Old 02-03-2013, 08:04   #3
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Re: Painting Aluminium?

The gold standard is a light abrasive blasting.

Next best is Alumiprep (phosphoric acid)/ Alodine treatment.

Next best is coarse grit sanding.

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Old 02-03-2013, 08:16   #4
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Re: Painting Aluminium?

Quote:
Originally Posted by VirtualVagabond View Post
What is the best prep. to make sure the paint will last?
The paint will probably be white spray can stuff.

Who knows how to make this work without it all peeling in 6 months?
Vic
IMHO "long-lasting, quality paint job that won't peel in 6 months" and "white spray can stuff" constitute an oxymoron.

1. light blasting or sanding
2. Alumiprep / etching
3. epoxy prime
4. high quality final coats with 2-part polyurethane, Awlgrip etc.
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Old 02-03-2013, 08:27   #5
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Re: Painting Aluminium?

Aluminum hates paint in a salt water environment. The first thing it will do at any air/paint/aluminum interface is to start blistering up the paint, like a cancer spreading throughout the body. I just wanted to let you know that this is what you are up against.

Long term, what is going to look best is to let it create its own very tough oxide, which looks far better than blistering paint. If all you want is for it to look good short term, then you might as well use a three dollar can of Krylon, because even the most expensive coatings will not stay on long term. Been there....done that. I have used all the expensive aluminum primers and recommended procedures for application from AwlGrip, Sterling, Interlux etc and nothing works long term.

Use a burgundy colored 3M pad for metal to remove any excess oxidation. It will temporarily give it a nice brushed effect.

Aluminum oxide is what sticks best to aluminum.
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Old 02-03-2013, 09:35   #6
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Re: Painting Aluminium?

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Originally Posted by David M View Post
Aluminum hates paint in a salt water environment. The first thing it will do at any air/paint/aluminum interface is to start blistering up the paint, like a cancer spreading throughout the body. I just wanted to let you know that this is what you are up against.

Long term, what is going to look best is to let it create its own very tough oxide, which looks far better than blistering paint. If all you want is for it to look good short term, then you might as well use a three dollar can of Krylon, because even the most expensive coatings will not stay on long term. Been there....done that. I have used all the expensive aluminum primers and recommended procedures for application from AwlGrip, Sterling, Interlux etc and nothing works long term.

Use a burgundy colored 3M pad for metal to remove any excess oxidation. It will temporarily give it a nice brushed effect.

Aluminum oxide is what sticks best to aluminum.
I agree that unpainted aluminum is the best choice.

I also agree that blistering can be a big problem. My experience however has been almost paint problem free.

Panope was first sandblasted and painted in 1976 and since then has only received overcoating and spot paint work. Blistering has been virtually non existent. Even painted spars that had stainless fasteners tapped into the metal had very few/small blistering problems.

Davids experience has been very different and I am sure that he as done equal or better paint prep/work. One theory that I have that explains this large paint performance variation is where and how the boat is used.

Panope has been in Washington state inland waters (and my backyard) most of its life. It does rain here with great frequency and my guess is that the rain helps wash the salt away. Also, the cooler temperatures might make a difference. We have always rinsed the decks with a bucket of sea water and the boat did spend a year in the sea of Cortez (1989).

Any other ideas about location and corrosion?

Steve
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Old 02-03-2013, 09:48   #7
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Re: Painting Aluminium?

probaly best not to invest too much apart from giving it a sand 3' diam is very small for a 20 ft extrusion on a 60ft loa boat like yours,ours is 4' and about 2.5mm wall and 22 ft and even that is a bit light.
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Old 02-03-2013, 14:14   #8
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Re: Painting Aluminium?

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probaly best not to invest too much apart from giving it a sand 3' diam is very small for a 20 ft extrusion on a 60ft loa boat like yours,ours is 4' and about 2.5mm wall and 22 ft and even that is a bit light.
Hi Alex,
The wall is 3.175 mm, so quite beefy, and I only fly a yankee, not a full genoa.
I'm tempted to just clean it up and leave it natural because I've had no success with painting aluminium in the past.

Vic
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Old 02-03-2013, 14:36   #9
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Re: Painting Aluminium?

I was just looking up this same thing -- painting aluminum. This is guy said he painted his outdrives and that the paint job lasted for four years.
BoaterEd - Painting Aluminum (Especially Outdrives)
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Old 02-03-2013, 14:58   #10
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Re: Painting Aluminium?

G'Day Vic,

HEre's another method that looks pretty good and lasts well -- used it on the new mast on Insatiable I and it still looks ok 16 years later:

Sand off all corrosion and mill scale, use ~120 grit and sand the tube in long, continuous passes for the whole length. When you have a fairly uniform pattern of long "grooves", wash with soap and water, dry and wipe with Alumiprep or other phosphoric acid metal prep solution. The latter will give it a fairly non-shiny surface. When that is dry, paint with Tectyl, a clear one pot polyurethane coating made by Valvoline IIRC. Put on two or three coats. Can be sprayed, brushed or simply wiped on with a clean rag.

In the case of our mast, the vertical grooves somehow picked up sunlight, especially in low sun angles, and it sort of glowed... very different from the other non-painted masts. When the inevitable dings happen, you can scrub with a scotchbrite pad and simply wipe on some more Tectyl.

And we had a similar pole on that boat -- relatively thick walled 3 inch diameter tube, 17.5 feet long, so essentially the same. Used it with a big symmetrical kite and no problems with strength. The smaller diam and thicker wall seems to be common practice here in Oz, different in the US where most folks go larger diam, thinner wall for some reason.

Glad to see that you are getting down to some smaller details... escape must be nearing!

Cheers,

Jim
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Old 02-03-2013, 15:20   #11
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Re: Painting Aluminium?

Quote:
Originally Posted by Charlie View Post
I was just looking up this same thing -- painting aluminum. This is guy said he painted his outdrives and that the paint job lasted for four years.
BoaterEd - Painting Aluminum (Especially Outdrives)
That's a good article and if I had the time and dedication I might tackle it, but getting this pole built and in service is just one of a million jobs we're ploughing through before we head down to the Caribbean in a couple of weeks.
From the advice here so far, it's either make a big project of it, or let it oxidize, and let it oxidize will probably be my choice after cleaning it up and getting it stain free and shiny.

When does the fun part start again???

Vic
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Old 02-03-2013, 15:35   #12
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Re: Painting Aluminium?

Quote:
Originally Posted by Jim Cate View Post
G'Day Vic,

HEre's another method that looks pretty good and lasts well -- used it on the new mast on Insatiable I and it still looks ok 16 years later:

Sand off all corrosion and mill scale, use ~120 grit and sand the tube in long, continuous passes for the whole length. When you have a fairly uniform pattern of long "grooves", wash with soap and water, dry and wipe with Alumiprep or other phosphoric acid metal prep solution. The latter will give it a fairly non-shiny surface. When that is dry, paint with Tectyl, a clear one pot polyurethane coating made by Valvoline IIRC. Put on two or three coats. Can be sprayed, brushed or simply wiped on with a clean rag.

In the case of our mast, the vertical grooves somehow picked up sunlight, especially in low sun angles, and it sort of glowed... very different from the other non-painted masts. When the inevitable dings happen, you can scrub with a scotchbrite pad and simply wipe on some more Tectyl.

And we had a similar pole on that boat -- relatively thick walled 3 inch diameter tube, 17.5 feet long, so essentially the same. Used it with a big symmetrical kite and no problems with strength. The smaller diam and thicker wall seems to be common practice here in Oz, different in the US where most folks go larger diam, thinner wall for some reason.

Glad to see that you are getting down to some smaller details... escape must be nearing!

Cheers,

Jim
Hi Jim,

That sounds like an excellent 'middle of the road' option.
I'll have a look for Tectyl and if I can get half a dozen good years out of it I'll be more than happy.

Vic
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Old 02-03-2013, 15:38   #13
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Re: Painting Aluminium?

Quote:
Originally Posted by VirtualVagabond View Post
That's a good article and if I had the time and dedication I might tackle it, but getting this pole built and in service is just one of a million jobs we're ploughing through before we head down to the Caribbean in a couple of weeks.
From the advice here so far, it's either make a big project of it, or let it oxidize, and let it oxidize will probably be my choice after cleaning it up and getting it stain free and shiny.

When does the fun part start again???

Vic
There is a way in between. Prep with the burgundy 3M pad and then polish it using 3M alloy wheel polish from the car parts section. This stuff goes beyond what I understand from metals and it's quick and cheap and lasts.
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Old 02-03-2013, 18:51   #14
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Re: Painting Aluminium?

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Originally Posted by s/v Jedi View Post
There is a way in between. Prep with the burgundy 3M pad and then polish it using 3M alloy wheel polish from the car parts section. This stuff goes beyond what I understand from metals and it's quick and cheap and lasts.
Thanks Nick,
If I run out of time with Jim's Tectyl idea this will be plan B.

Vic
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Old 02-03-2013, 19:16   #15
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Re: Painting Aluminium?

Theres always the Old way! sand litely,and wash down and wipe with vinegar,(a mild acid) and paint! worked for years and no blistering ! just a thought!
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