Aluminum hulls and quicker electrolysis??

Guys,

Im slipped next to a 40 foot Chris Craft Roamer which is fully aluminum. He's doing a full refit. Probably about 50% done. The remainder of the work will be performed in the water.

Others on my dock arent happy about it because they said that a fully aluminum boat will contritbute to the faster breakdown of all our zincs. Yay or nay?? Hes my neighbor! I'm freaking out!

I think that if anything his boat would be the one having a problem not the glass boats.

Absolute baloney. If any of the dock talkers even mention the word "electrolysis" they clearly don't know what they are talking about. Electrolysis has nothing to do with corrosion on boats. It's simply a catchy term that the uniformed have latched on to just like the hair salon people using "electrolysis" to remove body hair.

If an aluminum boat does leak DC current, he will sink long before it has any effect on your boat. ABYC Certified Marine Corrosion Analyst.

Boatpoker:


Could you explain for the forum how the terms, electrolysis, galvanic corrosion, etc. are used relative to boats. I am ChE and those terms are confusing to me as applied to boats.


David

djmarchand said:

Boatpoker:


Could you explain for the forum how the terms, electrolysis, galvanic corrosion, etc. are used relative to boats. I am ChE and those terms are confusing to me as applied to boats.


David

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Forget "electrolysis" it is a different process used for a specific (irrelevant) purpose. AC/DC Galvanic & Stray Current & Electrolysis Mythology.

Common fallacy in human thinking. Like the guy that tries to time the lights or splits tens at the blackjack table.

"Can't be a man 'cause he doesn't smoke the same cigarettes as me".


Thanks for posting this. It is good to be aware of biased thinking.

Crap, excuse my start. Al is a creat building material. To day Al is almost as resident to salt/fresh water issue as steel. Take a look around you. Many ALCAN house cruisers, some almost 30 yrs old are still on the water. New construction Al boats serve the recreational as well as commercial industrial market. The navies of the world as well.

We all want boats to last forever, get a grip. Who has owned a boat for over 15 years and who cares when you sell how long it’s life will be. We of the “Tupperware ware” society cannot comment and for the most part have no knowledge of metal boats. I owned “steel” for 37 years and mixed Al with it.

The makers, modern, CC and Marenett made great boats and per dollar value are still a great buy.

One last rant, electrolytes an issue we all face especially in salt and brackish water. Proper wiring on your boat coupled with proper dock wiring is necessary. Ever wonder why swimming is not allowed in marinas?
.

Isn’t aluminum LOWER on the galvanic scale than zinc? If so, the aluminum goes first.

No. Simply not true.

Here's my neighbor. She's gonna be beautiful when done. Solid rig. 15 foot beam.

Ask yourself if electricity from an aluminum boat is different than from any other source?

/sarcasm
Don't try to chew gum and walk while you ponder this question. Oh, no. It's those aluminized electrons, watch out. Boat cooties, watch out. If lightning strikes an aluminum boat in a marina it can transport all of the other boats into a black hole, or a time-warp, watch out.
/end sarcasm /for the moment

Greetings,


From a paper on such things written by Michael H. Mallon, research assistant, Department of Agricultural Engineering, Oregon State University, and by Edward Kolbe, commercial fisheries engineer, OSU Marine Science Center, and assistant professor of agricultural engineering, Oregon State University:



Electrolysis—Traditionally, this term has described all forms of electrochemical corrosion, including both galvanic action and stray-current corrosion. Strictly speaking, it is the producing of chemical changes by passing an electric current through an electrolyte.


Electrolyte—A solution that contains charged particles ("ions") and, therefore, conducts electricity.


Galvanic action—When two different metals are immersed in an electrolyte and connected together electrically, either directly or by a conductor, a current will flow from one to the other. The metal more prone to corrosion will corrode; the other will be protected. This effect is called galvanic action.

Stray-current corrosion—If a voltage difference is accidentally impressed on two underwater metal components, one of them (the more positive one) will corrode. This effect is called stray-current corrosion.


Further: ...passing a current through an electrolyte creates an electrolytic process. Seawater is an electrolyte, dissimilar metals created a current and one of them corrodes away in the process. The whole world calls that electrolysis, even if it is not a voluntary practice intended to break down the electrolyte. No one in the marine industry cares about what happens to the electrolyte seawater, we only care about the electrodes and which one corrodes away. Boaters know it is a process that involves an electrolyte and dissimilar metals, that is good enough for all but the likes of...

Thanks for the info. Sheesh, tough crowd.

The previous poster is correct. You have no need to understand the difference betwen electrolysis, electrolytic action, stray current corrosion or galvanic corrosion. You may simply cut & paste from wikipedia as he does and thats fine. However if you own an aluminum boat I'd think you'd want to hire someone that has been trained in these matters and understands that the differences are more than mere sematics.

Greetings,
Mr. BP. Golly. Thanks. I never knowed it was so complimicated....

RT Firefly said:

Greetings,
Mr. BP. Golly. Thanks. I never knowed it was so complimicated....

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Only to the uninformed and uneducated.

I have spent a significant amount of time and money on my educations on these matters taking courses including courses from Ed Sherman, Paul Fleury, Dave Rifkin and Kevin Ritz. My investment pales in comparison to the 40yrs my good friend and dock neighbor invested. He retired a year ago as President of IEEE and now consults with the US Navy on corrosion mitigation of their newer electric warships. He also consults with the new Panama canal.

Please don’t tell the US Navy or the Panama Canal that they could have saved a fortune in research consultancy fees if they had just slipped you a few bucks to show them how to use Wikipedia.

Boatpoker: You're a marine surveyor, correct? Do you talk to your clients who are inexperienced and fresh to the boating life the same way you have done here? I remember over the winter you gave me some rude response on another one of my liveaboard threads. I have a good memory....


I wouldn't pay you one cent for a survey. Experience and accolades are very important but being a teacher and imparting information are just as important in my book.

Nobody ever appreciates my rudeness. What's he got that I haven't got?

I used to be halfway smart on electrowinning. I won't bore anyone with the details except to say it is how zinc, copper and a few other metals in their final forms are produced. Plus this generalist statement won't get BP's knickers in a twist identifying sources just as RT did.

I went in circles with a previous boat chasing galvanic corrosion about 5 years ago. There are very few people out there who truly understand the subject so overall BP makes some good points. I used the term electrolysis with one Tech, and he asked me if we were talking about woman’s hair removal. I didn’t use the term again after that.

Fletcher500 said:

I went in circles with a previous boat chasing galvanic corrosion about 5 years ago. There are very few people out there who truly understand the subject so overall BP makes some good points. I used the term electrolysis with one Tech, and he asked me if we were talking about woman’s hair removal. I didn’t use the term again after that.

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It sure would be nice if people who dump on incorrect understanding and terminology, as your tech did, could then help enlighten the rest of us rather than holding that special knowledge to themselves.

twistedtree said:

It sure would be nice if people who dump on incorrect understanding and terminology, as your tech did, could then help enlighten the rest of us rather than holding that special knowledge to themselves.

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I didn’t think it was a big deal at the time, and more funny than anything else. Bigger fish to fry.

Greetings,
Mr. (saint) tt. Re: Post #21: But then they wouldn't be special people with special knowledge anymore would they?

RT Firefly said:

Greetings,
Mr. (saint) tt. Re: Post #21: But then they wouldn't be special people with special knowledge anymore would they?

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Yup.

South of Heaven said:

Boatpoker: You're a marine surveyor, correct? Do you talk to your clients who are inexperienced and fresh to the boating life the same way you have done here? I remember over the winter you gave me some rude response on another one of my liveaboard threads. I have a good memory....

I wouldn't pay you one cent for a survey. Experience and accolades are very important but being a teacher and imparting information are just as important in my book.

Click to expand...

Amen and Amen. Some, that make their living from science, like to make it sound like only a Wizard can help. I am a wizard and, earned a living as EE, CE, and ME, and I do everything I can to help others to help themselves. But then, maybe its different if you are a "Marine Injineer" maybe you do have to be a wizard. Maybe he has a big family to support.



He puts his pants on one leg at a time, just like you do. Relax, read. and repair. RRR

Original question was will it erode my zincs.
Answer, significant corrosion of zincs only if there is a hard wired electrical connection between your boats.
A possible one would be if neither vessel had an isolating transformer between boat earth and a common shore supply earth ie they were wired together by the shore supply earth wire.
Solution make sure your boat is electrically isolated including the earth / common.

If the owner of the Roamer is wise he'll install an isolation transformer, which will offer him protection from other vessels around him, and vice versa, as others have said, he probably has more to worry about than anyone else. Seriously, all metal vessels should be equipped with isolation transformers.

And, all the other FRP vessels should be equipped with either a transformer or a galvanic isolator, the latter at the very least. With that they are protected from any galvanic current corrosion effects generated by the Roamer, or anything else in the vicinity.

In corrosion training instructors go to great lengths to warn students against using the "electrolysis" word, strictly speaking they are right, it's incorrect (and the ABYC Standards echo this), and I don't use it when discussing, lecturing or writing about these matters, but the truth is it's not a matter if significant importance when a non-corrosion expert uses it, everyone knows what is intended. It is, however, a bit of a clue when the word is used by someone who claims to be knowledgeable or schooled in the subject.

This article covers aluminum corrosion specifically: https://stevedmarineconsulting.com/understanding-and-preventing-aluminum-corrosion/

This covers corrosion in general: https://stevedmarineconsulting.com/unraveling-the-corrosion-mystery/

I was captain/engineer (yeah I was a 'deal' for the owners back then) of a large aluminum motorsailer some years ago. She wasn't a new boat, so I'm surprised I found the problem, but any oil leaking out of the 4 Jimmy diesels (2, 471 gensets and 2, 671 mains) was corroding wherever it dripped on the hull. I immediately had drip pans made and installed.
So, check the engine room carefully.

"Electrolysis" was actually the original terminology used when streetcar lines leaked DC current to underground piping creating corrosion leading to water and gas leaks.

The National Association of Corrosion Engineers was formed to solve the problem and used the term for years. NACE essentially invented cathodic protection.

It is only recently that they have tried to correct the naming mistake from nearly 100 years ago.

So it may be a little harsh to say that anyone using the term electrolysis doesn't know what they are talking about.

I know a few highly educated people with their CIP 2, 3 or 4 certifications that slip up and use the term on occasion, as they've been experts for so long.

But I do agree it is not the technically correct term.

NS:

Point taken, and interesting history on NACE. I should have limited this to marine industry-trained folks, I suppose this is more of an issue in my universe, we, as an industry, only began to delve deeply into corrosion more recently when compared to NACE.

Having said all that, my professional colleagues in Australia routinely use the term electrolysis when discussing galvanic corrosion.