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PostPosted: Thu Apr 02, 2009 2:34 pm 
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Location: Ettalong Beach, Central Coast, Australia
It would seem to me that if the older parts were anodised, and still look great, the corrosion we are seeing is not electrolytic, its caused by the coating not being as good as anodized.

Geoff.


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PostPosted: Thu Apr 02, 2009 4:44 pm 
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Corrosion around stainless fittings in anodized masts is a problem, but I have never seen it spread like it does underneath the coating on the akas.


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PostPosted: Thu Apr 02, 2009 7:27 pm 
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Tom Ray wrote:
Corrosion around stainless fittings in anodized masts is a problem, but I have never seen it spread like it does underneath the coating on the akas.


+1 Agreed.

Keith has a good closeup off the cancer-corrosion of the e-coated aka. My 2 year old e coated metal looks about like Keith's while the 3+ year old annodized (early production) metal looks entirely corrosion free. The annodized metal's finish is very thin, flat black, and does not look like paint so much as it looks like a carbon black powder - if that makes any sense.

Guess I need to snap a few pics to better explain.

If you want to really see some truely disturbing corrosion, remove the rear x-brace. The brass inserts, the Stainless Steel Soc Cap Screw & washer together with the aluminum have really made a nice battery. :shock:
This "underneath" part is hard to detect until you remove the brace.

There is a small gap between the boat hull and the bottom of the x-brace caused by the brass inserts just slightly above the hull. I can almost guarantee you will find 1/8" cake of oxidized aluminum. The corrosion on the akas is mostly cosmetic; the corrosion under the x-braces is a potential part failure IMO. We are talking major aluminum disintegration/pitting here.

$225 total for a front & rear x-brace ($125 + $100) won't make for a cheap replacement either. And to think, all this time I was worried about the aka hinge pin wear. :lol:

PS If you do remove the braces - pick up some new Stainless Steel Soc Caps (bolts) for replacements at ACE hardware (60 cents each)


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PostPosted: Thu Apr 02, 2009 7:51 pm 
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Yakaholic, your experience is very helpful. The galvanic cell involving the xbar SS Soc Caps/aluminum brace/water (saltwater when sailing on the ocean) is really serious because it is difficult to wash clean and probably does not dry rapidly. It is a particularly serious type of corrosion--actually has a name, crevice corrosion.

Kasten Marine Design http://www.kastenmarine.com/aluminum.htm has a comment about this type of corrosion:
Quote:
Aluminum alloys are subject to crevice corrosion, since they depend on the presence of oxygen to repair themselves. What this means is that wherever aluminum is in contact with anything, even another piece of aluminum or zinc, it must be painted with an adhesive waterproof paint such as epoxy, or it must be protected with a waterproof adhesive bedding, or both. A plastic wafer alone as an isolator is not enough. Salt water must be prevented from entering the crevice; otherwise corrosion will result.


Do both your anodized parts and e-painted parts show the same degree of corrosion at this point?

Frankly, I can't (but I must) wait for a year to pass to see if my little anode experiment worked, and, if there is a difference between the front and back xbars/akas.

Keith

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PostPosted: Thu Apr 02, 2009 8:18 pm 
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Chekika wrote:
Yakaholic, your experience is very helpful. The galvanic cell involving the xbar SS Soc Caps/aluminum brace/water (saltwater when sailing on the ocean) is really serious because it is difficult to wash clean and probably does not dry rapidly. It is a particularly serious type of corrosion--actually has a name, crevice corrosion.


Well, its worse than you think :shock:
Beneath the rear aka brace on either side is not 2 but 3 threaded brass insert "holes" in the hull! You only use the outer 2 - I don't know what the center brass hole is for - unless for a sidekick mount (Adventure kayak mode?) Anyway, what this means is that there is a brass hole or "cup" to hold salt water under the rear aka x-brace creating a permanent battery hidden away under it. :shock: Once salt water gets into this hole there is no way to wash it out. Washing it with a hose is just not likely to reach this hidden cavity.

This salt water "cell" of brass+steel+aluminum = an amazing mess under the xbrace.

I will have to pull the annodized xbraces to see for sure - but they have none of the telltale "crevice corrosion". Based on my experience and observation the annodized metal should have been kept.

PS - I'm not sure is there are 3 holes per side on the forward x-bar until I pull it.
PPS - It may be that my 2007 Island hull is unique with 3 brass holes per side on the rear x-bar mount, but that seems unlikely.


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PostPosted: Thu Apr 02, 2009 8:55 pm 
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Yakaholic, I've had my rear xbar off a couple times recently and don't remember 3 brass recepticles. I'm fairly certain my late '07 has only 2 per side per brace.

Keith

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PostPosted: Thu Apr 02, 2009 10:28 pm 
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Chekika wrote:
Frankly, I can't (but I must) wait for a year to pass to see if my little anode experiment worked, and, if there is a difference between the front and back xbars/akas.
Keith


A year! I've got noticeable bubbling on one of my akas after 3 months. (Yes, I hose them down religiously after each outing)

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PostPosted: Fri Apr 03, 2009 3:10 am 
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Chekika wrote:
Yakaholic, I've had my rear xbar off a couple times recently and don't remember 3 brass recepticles. I'm fairly certain my late '07 has only 2 per side per brace.

Keith


I figured my hull might be a factory mistake. Had my rear xbrace off yesterday and there are absolutely 3 brass inserts per side. Mine is one of the first boats made Oct. '06 delivery and maybe Hobie was unsure of how the xbars would attach or what the final size or spacing would be. Who knows how many early boats have them? All I know is that extra hole is a nice saltwater trap.

I filled extra holes with grease, figuring a grease barrier might slow down electrolysis - like putting grease on a battery terminal.

Us earlier adoptors get all the surprises :wink: Still, I wouldn't trade all the sailing time I got for anything.


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PostPosted: Tue Aug 24, 2010 12:24 am 
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I wanted to revive this, as its some time later, my corrosion is now far worse, and now I am wondering if anyone has had their aluminum blasted and anodised.

Geoff


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PostPosted: Tue Aug 24, 2010 1:09 pm 
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I'm interested in this too. Particularly the crossbar corrosion in the hidden mounting points.

How are we all doing, one year later?

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PostPosted: Tue Aug 24, 2010 2:31 pm 
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NOHUHU wrote:
I'm interested in this too. Particularly the crossbar corrosion in the hidden mounting points.

How are we all doing, one year later?

At 20 months old, mine are an absolute mess. I'm hoping it's mainly cosmetic rather than structural.
Welcome back Geoff.

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PostPosted: Tue Aug 24, 2010 10:18 pm 
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Thanks Chris,

I spoke to Sailing Scene, the main Sydney dealer, and they said they had no experience of anyone blasting the coating off the metal. I was frankly very surprised. We talked about spot repairs earlier, but I don't want to do that unless someone has had GREAT results.

Geoff


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PostPosted: Thu Aug 26, 2010 4:53 pm 
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I've had an offer to get mine powder coated for a slab of beer. Trouble is, I'll be without the boat (in AI mode) for a couple of weeks. Still, I'll prolly do it and will report back on the results.

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