Question
…I am looking for a used aluminum yacht…I have read all your articles on how to care for an aluminum yacht. However, how to look for serious problems on a used (25 years old) aluminum yacht?
I know that I can check the electrical installation with a meter, but can I find any alarming signs of electrolysis in a yacht that is in the water? Are there any other areas on a used aluminum yacht that I should pay attention to?
My question concerns hull corrosion and the resulting lower strength of the hull.
Thank you John for so detailed answer. I just ordered silver chloride reference cell.
And make sure the engine screws are A4 stainless and that an insulating agent like Ted gel is used so you won’t get corrosion between the screws and the access panel
Thanks. But that’s for later if I buy this boat. Corroded screws are not a deal breaker for me 😉
I would also recommend you also to check visually inside the water tanks.
Quite often they are corroded, specially with older boats
Hi Kors,
Good idea, I should have mentioned that.
I have a naive question: what does aluminium corrosion in the bilge look like? I have Googled but still don’t know. How does one distinguish it from harmlessl scurf one might find in a bilge?
Hi Ron,
If it’s true corrosion there will be white powder or paste if it’s wet. Wipe that away and then look carefully with a magnifying glass for pitting.
Agreed with John and all the comments.
One detail, use Tef-Gel (made by USS) on all SS screws on the boat. “Ted-gel” os mentioned. Perhaps a typo, but beware of the several knock-offs with names very similar to TefGel.
Emphasize looking inside the water tanks. If they are unpainted, and have never had chlorinated city water in them, probably OK. They may have hundreds of white pustules a few mm diameter.
If there is not a decent visual access to the tanks, I would insist on one being cut for survey, if that is at all possible.
Look carefully at any beautiful recent paint. Some years ago I was in Garcia’s yard and saw them cutting off and replacing most of the bottom plates. The boat had sailed from Australia to Europe with a wind generator using the hull as the negative “wire”, been seriously pitted, then filled and painted for selling. Not surprisingly, Garcia’s customer and the previous owner were in court.
Above based on 20 years sailing an aluminium boat, with (so far) no corrosion issues, following John’s advice, and meeting a goodly number of other owners. Don’t let the age alone of the boat put you off.
Kors and Neil,
thank you for your suggestion about checking inside the water tanks.
It looks from the pictures that the access is good so I should be able to look inside through the inspection hole.
As well as the shaft tunnel, I’d suggest also looking closely anywhere steel, stainless, or any other metal, is in contact or even within cooee of the aluminium. I’ve inspected many offshore structures where the Al has completely disappeared from galvanic (dissimilar metal) corrosion. Check behind base plates even if they have rubber insulators, remove some bolts and check bolt holes for enlargement. In my experience you don’t need contact for dissimilar metal corrosion – if the components are close enough, and wet and salty enough, the electrons find a way.
Hi Dan,
Absolutely, but that’s more deck stuff that can be fixed relatively easily, and Michael was interested in deal-breaker issues with the hull.
Hi Guys,
I’m doing inspection on that 24 years old Aluminium yacht now.
Today I’ve found some underwater corrosion under the paint.
At this picture you can see the worst area:
https://drive.google.com/file/d/1nBz1ZDXBK1w3LkEcYvZfHVkCI4ojTven/view?usp=sharing
I’m aware that on such a old boat there will be some corrosion. However, I’m wondering could this level of corrosion is something to go away?
Electrical check tomorrow.
Thank you for any advice.
Michal
Hi Michal,
Yes, that does not look good. Definitely an electrical check both in and out of the water is required, plus removal of all the paint etc covering the damage so it can be properly assessed. I would also look for dissimilar metals under the water. That lower rudder bearing carrier looks suspicious to me. Also, the rudder may not be properly connected to the rest of the hull.
Hi John,
thank you for reply. We just went back from inspection. Electrical check with silver chloride reference cell showed problem with stray current (decrease of potential from -1,026V to -0,886V when connecting shore power). Then we took the boat from the water and have found corrosion (pitting) around the hull. Also deep galvanic corrosion around two thru hulls.
But I’m still not 100% sure if this is enough to give up this boat (I can probably get very good price and I like other aspects). The aluminium in the bilges looks like new (except around those 2 thru hulls).
I think I need a consultation with good marine surveyor that knows aluminium problems. Can you recommend anyone?
Hi Michal,
Sounds like you have found the problem.
The only person I know is Tony Knowles, who surveyed my boat when I bought her, but I’m not sure if he is still in business: https://www.yachtinsidersguide.com/listing/newport-marine-surveyors
Hi Michal,
Steve D’Antonio is an occasional contributor to AAC on technical matters and an ABYC Certified Corrosion technician, and consultant. More about his work can be found at steve d’antonio marine consulting (https://search.yahoo.com/search?fr2=p%3ads%2cv%3aomn%2cm%3asa%2cbrws%3achrome%2cpos%3a1&fr=mcafee&type=E210US714G0&p=steve+d%27antonio+marine+consulting) where numerous articles on corrosion may be found.
He has read your initial question and, although quite busy right now, may be helpful remotely.
Good luck with this.
My best, Dick Stevenson, s/v Alchemy
Hi Dick,
thanks a lot! I saw his wise comments but I didn’t know that he also provides consultations
I wrote to Steve.
All the best.
Michal
Hi Michal,
I don’t know if you’re still looking, but perhaps this may come in useful for other prospective buyers as well.
My partner and I have been searching for an aluminium boat to buy for the last 6+ months (set on that the path by reading AAC!) and, like you, went through the process of asking: “how bad does the corrosion have to get before it’s a deal-breaker?…”
We’ve been working with Colin as a consultant, so he has patiently instructed us through that process, which has been great learning.
Because we have considered options in both Europe and the Americas, I posted on alloy boat groups for surveyor recommendations and then reached out to ten (ok, maybe it was a few more than that…) or so surveyors and went through the process of reading sample surveys. I can recommend the ones below based on interactions with them and sample surveys only, since we haven’t gotten to the stage of surveying yet!
(All of these surveyors are open to traveling.)
If you’re based in the U.S., I received many recommendations for Dylan Bailey (he will do ultrasound as well). He has been very responsive and helpful by email but could not currently travel beyond the U.S. and Caribbean. Jon Howe, in Florida, is semi-retired, but he may be open to surveying within the state (otherwise he will recommend Dylan!).
If you work with a surveyor who can’t do ultrasound, but would like ultrasound testing, Certified NDT in Washington do ultrasounds only (no surveys). They are very available by phone and email.
In Europe you might consider Davide Zerbinati (Italy), who is extremely responsive and very detail-oriented. He also supervises builds and repairs.
In France, Loic Blanken has a very good reputation and is also prompt and available.
The same is true of CEEMIN (which was founded by Yvon Quernec).
Lamarque & Guyon also have a good reputation, but I have not been in touch with them.
Theo Van Rijwijk, in the Netherlands, was very helpful via phone, very willing to travel, and is a metallurgist. His sample survey was very detailed.
I have to say that, so far, the surveyors I’ve reached out to have been the most forthcoming people in the marine industry, willing to share information on what to watch out for even when they weren’t available to survey and so didn’t stand to profit from it. I was deeply appreciative.
Anyway, if you’d like any further info, I’m happy to share. And, good luck with your boat search!
Cheers,
Alessandra
Hi Alessandre.
Great information, thank you!
Hi Alessandra,
thank you for your awesome comment!
You saved me (and probably others) plenty of time.
I gave up the last boat that I visited, but I’m still looking. Next week I’m going for a trip to Germany and Netherlands.I’m in Poland right now. If I’ll find promising boat I’ll probably make a contact to mr Theo Van Rijwijk from the Netherlands.
Thanks again and good luck with your research.
Michal
Hello John and Phyllis, I’m a long-time subscriber who is under contract to purchase a late model aluminum hull Allures that is located in Martinique.
I spent the morning reading your material about aluminum hulled vessels. Thank you for all of that great information. (It is a bit intimidating.)
The survey is scheduled for next week in Martinique. The problem is that my surveyor cancelled due to a health emergency.
I’m seeking another surveyor who has experience with aluminum hulled vessels, and wonder if you or your e
Readers have any recommendations?
Hi Thomas,
I don’t have any recommendations given that both guys I used are retired, but have a read through the comments above, there are several suggestions there. Particularly Alessandra’s comment.
Thank you John – I missed those recommendations in my reading. I’ll pay more attention to the comments in the future!