Barnacles on Aluminum/painting bottom right!

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cape15
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Barnacles on Aluminum/painting bottom right!

#1

Post by cape15 »

Anyone have any suggestions on how to best remove the calcified "disc" left over from barnacles? I have an unpainted Pacific. Also...any suggestions on painting? I have a mooring and these barnacles seem unavoidable.
Chaps
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Re: Barnacles on Aluminum/painting bottom right!

#2

Post by Chaps »

If you are planing to paint the bottom and are going to prep the metal by blasting or aggressive disc sanding then the barnacle rings will be removed in the process. Blasting is best, then apply an epoxy bottom primer like Interlux 2000e then apply an aluminum compatible anti-fouling paint like Pettit Vivid or Ultima Eco.
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Challenge
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Re: Barnacles on Aluminum/painting bottom right!

#3

Post by Challenge »

Cape15,

welcome to the board lots of great people & info here! :beer:

There is a paint company on the cape in Falmouth called e-paint that I have had good luck with. Primer then non copper antifoul.

http://www.epaint.com/

They are pricey! I am not sure how much the others cost, (I have a small boat!)

Good luck

Rick
steve-r
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Re: Barnacles on Aluminum/painting bottom right!

#4

Post by steve-r »

I recently looked at a potential purchase that had some hull corrosion, and the surveyor recommendation was:
-soda blast (messy -needs an enclosed area ) or chemical strip to remove everything to bare metal ( sandblast removes too much material and may leave a wave pattern in the hull )
-light sanding
-then acid etch
-then Alodine treatment
-"Alodine" is a non-anodic protective coating. Alodine {aka Iridite, aka Chromate Conversion} is a microscopic thin film commonly prescribed on aluminum to Provide an Excellent surface prep for paint, Aid in Corrosion Resistance, and Impose desired Electrical 'Resistance' characteristics"

-then E-Paint Epoxy primer
-lastly E-Paint - designed for aluminum boats
I'm not sure why but 2 sources said E-paint ( newer technology) was more effective than Trilux II ....and yes, more expensive.
Steve Ronson
18' Kellahan CC
Chaps
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Re: Barnacles on Aluminum/painting bottom right!

#5

Post by Chaps »

You need a different surveyor IMO
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steve-r
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Re: Barnacles on Aluminum/painting bottom right!

#6

Post by steve-r »

Chaps, please enlighten me.
The boat was suffering from more than normal electrolysis.
Based on everything else he advised me about wrt that boat, including its value and inherent electrical issues, it seemed like a credible recommendation.
His view was do it right to correct the problem up front , or expect that the corrosion will continue to bubble under the new bottompaint.
Appreciate some clarification . Thanks
Steve Ronson
18' Kellahan CC
Chaps
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Re: Barnacles on Aluminum/painting bottom right!

#7

Post by Chaps »

steve-r wrote:I recently looked at a potential purchase that had some hull corrosion, and the surveyor recommendation was:
-soda blast (messy -needs an enclosed area ) or chemical strip to remove everything to bare metal ( sandblast removes too much material and may leave a wave pattern in the hull )
-light sanding
-then acid etch
-then Alodine treatment
-"Alodine" is a non-anodic protective coating. Alodine {aka Iridite, aka Chromate Conversion} is a microscopic thin film commonly prescribed on aluminum to Provide an Excellent surface prep for paint, Aid in Corrosion Resistance, and Impose desired Electrical 'Resistance' characteristics"

-then E-Paint Epoxy primer
-lastly E-Paint - designed for aluminum boats
I'm not sure why but 2 sources said E-paint ( newer technology) was more effective than Trilux II ....and yes, more expensive.
I'm at a disadvantage because I can't see this specific boat but generally speaking his recommendations are ill advised in my opinion as to how an alloy boat bottom can/should be prepped and painted in the real world.

First, soda blasting an aluminum boat bottom in preparation for painting is a waste of time because the media isn't aggressive enough to profile (clean and roughen) the metal properly. It might remove the bulk of the old paint but that doesn't get you where you want to be.

Secondly, a light sanding still doesn't get you there sufficiently and you will likely still have plenty of paint and embedded corrosion left on the hull after all that work and expense.

An acid etch might be appropriate on a new, bare hull for some purpose, perhaps as a precursor to a no blast/no sand paint process but that is not an option on this boat and another unneeded step.

Alodine treatment is a nasty, somewhat dangerous compound in inexperienced hands and is difficult to properly incorporate into a boat paint prep process. Additionally, to be done correctly requires a spotless, bare and unoxidized surface which is terrifically difficult to achieve on anything other than a new, bare hull. Not saying someone can't apply alodine to an aluminum boat and think they are accomplishing something but in order to achieve the desired results that alodine can provide requires painstaking prep work.

E-Paint, have not tried the epoxy primer, might be as good as anyone else's, have applied the paint, lousy results in my experience, I will not put it on.

As far as his opinion of sandblasting is concerned he might consult the marine paint manufacturers and find that every one of them recommends grit blasting of alloy boat bottoms to bright metal and some even to specific mil standards before applying their paint systems, either that or heavy abrading with 60-80 grit sanding discs. His conclusion that sand blasting may remove too much material and produce uneven patterns in the hull could definitely apply to performing conventional dry blasting on glass reinforced plastic hulls but somehow extending that warning to an aluminum hull only confirms that he doesn't know what he is talking about.

Hope this helps
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goatram
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Re: Barnacles on Aluminum/painting bottom right!

#8

Post by goatram »

Steve bring the boat to Chaps. He has the means, equipment, and the knowledge
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