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PostPosted: Mon Nov 28, 2011 10:37 am 
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Location: Seattle, WA and more times than not, Camano Is, WA USA
Since Winter weather is here and the AI has been put to rest, there are a few touch ups I need to do on my AI and what a better time than now.

After reading 'Have you popped your akas lately', I realized I needed to do something about mine. When Hobie so generously replaced my cracked hull this summer, and my akas where moved from my old hull to my new, they looked very similar to yours, Nohuhu, with the bolt holes larger and softer than they should be. Since then I have seen the white markings of the aluminum decomposing white powder on my hull. I know I need to do something about it. I read the posts below, and have a lot of really good ideas to work from. I would like to do this project correctly and so I listed the steps I think I should take and have a few questions too. Any input any of you might have on helping me with my project would be greatly appreciated. :)

#1. Unscrew and remove the front and back aka brace bars.
#2. Unscrew and remove the paddle bungee from the aka bar.
#3. Sand down all 4 of the aka bars. ? What size sand paper would be best?
#4. Paint a base coat on all the aka bars. ?Is Alodine still considered the best base coat? If not, what type and brand of base coat would be best?
#5. Paint a black coat of paint on top. ?Is a good marine grade aluminum paint still considered the best type of top coat? Any brand name better than another?
#6. Attach an anode to the aka brace bars. ? In the posts, this was done after the base and top coat was painted on. Possibly a silly question, ?How does this work if there are two coats of paint between the anode and the aluminum? :oops: Have any of you wrapped a piece of zinc strip you would use to keep moss off your roof, around the aka brace, or even just stuff a crumpled up piece of this zinc strip into the small space where you screw the aka brace on the hull of your AI?
#7. Screw the aka brace bars back on, using loc tight.

viewtopic.php?f=71&t=11660&start=45&hilit=aka+bar+corrosion
viewtopic.php?f=71&t=28740&start=0&hilit=painting+akas
viewtopic.php?f=75&t=39233&start=0&hilit=aka+bar+corrosion
viewtopic.php?f=75&t=11534&start=0
viewtopic.php?f=75&t=12073&start=0&hilit=aka+bar+corrosion

Thank you for any help you can give me. :)

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PostPosted: Mon Nov 28, 2011 3:21 pm 
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Location: Kailua 96734
Replacing the crossbars is a good move if the holes are enlarged. You could try JBWeld and redrilling the holes, and larger top washers for awhile. One edge of the washers must be removed to fit then in there.

As far as paint goes, I would use this rustproof acrylic latex primer:
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http://www.kilz.com/masterchem/v/index.jsp?vgnextoid=fe2a9172e4d53210VgnVCM1000006b0910acRCRD

And topcoat:
Image
http://www.kilz.com/masterchem/v/index.jsp?vgnextoid=b2fd5f86a6331210VgnVCM1000008a05d103RCRD

This paint is pretty cool and useful for stopping rust, although aluminum oxide may require a different approach than iron oxide. You can choose a smooth or "hammered" surface. (They use tiny glass flakes to promote bonding and texture).

I am not familiar with acid baths/etching for aluminum so I would skip that myself. Others can advise you on this.

Smooth sand to the bare metal, - you don't want deep scratches. Aluminum starts to react with air the instant it's exposed, so I would not wait long before applying the primer.

The Xylene-based finish coat is a little unusual. You need to apply a second coat within the first hour (touch dry) or it's best to wait 2 weeks for any followup coats.

Avoid smoking around this stuff. I hear that could be bad for your health. :wink:

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PostPosted: Mon Nov 28, 2011 6:34 pm 
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Location: Lake Macquarie NSW AUSTRALIA
Don't forget just before any painting to wipe down with a wax and grease remover. Even fingerprints can cause the paint to lift. I use a 'Prepsol' which is a trade name down this way. It leaves no residue, evarorates quickly and removes dust and everything else that shouldn't be there.
Best of luck with it Fly'n C Lion.

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Last edited by Slaughter on Tue Nov 29, 2011 2:40 am, edited 3 times in total.

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PostPosted: Tue Nov 29, 2011 12:58 am 
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Location: Sydney - Parramatta
Got to be chrome-

[youtube]http://www.youtube.com/watch?v=y9mh6t0ILvE&feature=player_embedded[/youtube]

Go on, be the first! :lol:

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PostPosted: Tue Nov 29, 2011 2:52 am 
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He's using LA rainwater there, I see. :lol:

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Last edited by NOHUHU on Tue Nov 29, 2011 12:01 pm, edited 1 time in total.

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PostPosted: Tue Nov 29, 2011 5:10 am 
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Location: Cape Coral, FL
The best way to permanently stop the corrosion would be to not paint. Leaving the aluminum exposed will allow the aluminum to from a self limiting patina that will prevent further corrosion. Painting or coating aluminum is actually the worst thing you can do. The slightest scratch will cause accelerated corrosion under the paint and will bubble the paint. Looks kind of like pox. Only way to stop that is grind it off and paint again.

Unfortunately, it's ugly, but I've seen full size yatchs left this way to no ill effect.

If you use zinc, it needs to be in constant contact with the water. You must remove the paint in the contact point between the aluminum and zinc. You will need to bond (create an electrical pathway) from all the individual components of akas and crossbars with copper wire. The joints themselves will create to much resistance. You may want to use zinc that was design for marine applications, they already have bolt holes and make the zinc in better shapes and sizes for your application.

Good luck,

J

Ps. When it's my turn to deal with that I will be stripping the paint and leaving it.

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PostPosted: Fri Dec 09, 2011 1:43 pm 
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Location: Seattle, WA and more times than not, Camano Is, WA USA
My revised list to refinish my aka bars:
#1. Unscrew and remove the front and back aka brace bars.
#2. Unscrew and remove the paddle bungee from the aka bar.
#3. Sand down with gentle sand paper, all 4 of the aka bars.
#4. Clean sanded aka bars with Prepol.
#5. Paint a base coat on all the aka bars. I was thinking of using Alodine, but after reading the MSDS sheet on this stuff, I'm thinking I see if there is something else out there. :shock: Naasssty stuff!!
#6. Attach a sacrificial anode to the aka brace bars.
#7. Paint a good marine black coat of paint on top.
#8. Screw the aka brace bars back on, using blue loc tight.

Nohuhu, thank you for the heads up on the second coat of xylene based finish coat. I'll be quick, and leave the smoking to beach fires.

Slaughter, looks like Prepsol is over on this side of the water too. I can pick it up at an autobody store here. Thanks.

CGMoo, Chrome? Hummm..... Now that would be interesting.... a new fad.....Hey!!!! YOUR COW JUST STUCK IT'S TONGUE OUT AT ME!!!!!! :o :o :o :shock:

Kayakman7, I for sure am the last person to talk to about chemical reactions, but from what I am experiencing, I saw the area where the screw goes through the aka bar into the boat, and at that area there is no paint, but it is where the majority of the aluminum decay is happening. The paint on the aka bars is blistering and falling off, but its not reacting as strongly as where there is no paint and the screw goes through the aka bar into the boat.

Thank you everyone for your advice. I'll have my AI looking brand new when I go out on the water again. :D

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PostPosted: Fri Dec 09, 2011 2:30 pm 
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FCL, the area where the screw passes through the aka is where you would expect to get the maximum galvanic corrosion - at the interface between the two dissimilar metals. I haven't tried Kayakman7's suggestion, but I can attest that when I repainted my akas, the bubbling recurred fairly quickly and worse than ever. Also, you might like to include using paint stripper in your list. It's a long tedious job removing the paint with fine sandpaper and the paint continually clogs the sandpaper.

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PostPosted: Fri Dec 09, 2011 3:42 pm 
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#8 In my experience that's were it builds up first. It spreads to the underside of the bars from there. So in a rebuild I would add plastic washers under the Akas and maybe a silicon sealant.

#6 Don't paint the anode though, it needs to react with oxygen. And it needs to contact bare aluminum.

BTW, can you chrome aluminum?

Ya know, I've come to love that cow. Glad it doesn't shoot methane at us.

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PostPosted: Mon Dec 12, 2011 3:23 am 
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Fly'n C Lion wrote:
Hey!!!! YOUR COW JUST STUCK IT'S TONGUE OUT AT ME!!!!!! :o :o :o :shock:


He can a cheeky cow at times :D

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PostPosted: Mon Dec 12, 2011 12:32 pm 
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chrisj wrote:
FCL, the area where the screw passes through the aka is where you would expect to get the maximum galvanic corrosion - at the interface between the two dissimilar metals. I haven't tried Kayakman7's suggestion, but I can attest that when I repainted my akas, the bubbling recurred fairly quickly and worse than ever. Also, you might like to include using paint stripper in your list. It's a long tedious job removing the paint with fine sandpaper and the paint continually clogs the sandpaper.


If You were to leave the akas bare, you would need the entire surface uncoated. What happens when only a small section is exposed, is that area becomes the focus of all the galvanic corrosion, and you see a severe reaction. When the whole surface is exposed, then the reaction is muted and self limiting.

Electroplating and painting are both weak in that the tiniest scratch will allow the galvanic reaction to start and it will continue UNDER THE PAINT OR PLATING and spread until you sand it clean.

Anodizing is different because it is an actual change in the metal composition on the surface. Scratches will still corrode but won't continue under the surface.

Cheers,

J

Ps, there are places online that wil anodize fairly inexpensively.

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