Corrosion questions - confused with opinions...!

[theguitardoctor]

Hi all....

 

Sorry if this subject is a bit flogged to death, but I am confused after all the searching through threads and the like...

 

What I think I understand from various posts:

 

1. A Galvanic Isolator is good for helping protect against Galvanic Corrosion, but an Isolation Transformer such as the Airlink version is way better.

 

2. The anodes, if kept in good order should also help in the fight against corrosion.

 

3. Anodes only protect an area within a few feet of the spot they're welded to, but any more and they get knocked off in locks.

 

4. Comastic (Epoxy coating?) or Coflex (Single coat Vinyl?) is way better than 3 coats of Intertuf Bitumen type coatings at protecting against galvanic corrosion.

 

What I am confused by:

 

1. If I have a GI or Isolation Transformer (IT), what happens if my shoreline connected neighbours do not have either...will they attract corrosion to my boat...??

 

2. Can anodes be fitted on the baseplate near to the edges..? Would this add extra protection at the chance of a bottom scrape if unlucky...?

 

3. Some owners paint their hull with red oxide under the blacking...does this help against corrosion Galvanic or otherwise..?

 

 

I am confused and I don't know what is true, what is urban myth and what is possible/impossible....

 

[Guest]

I really am losing the will to live.........

[blackrose]

 

 

1. A Galvanic Isolator is good for helping protect against Galvanic Corrosion, but an Isolation Transformer such as the Airlink version is way better. Yes.

 

2. The anodes, if kept in good order should also help in the fight against corrosion. Yes.

 

3. Anodes only protect an area within a few feet of the spot they're welded to, but any more and they get knocked off in locks. Yes - about a 6ft radius, but more don't necessarily get knocked off, it depends what sort of boat, how thick the anodes are and where you put them. I've got some 1" thick anodes welded on the sides of my boat. They have tapered edges and they're protected by the protruding baseplate.

 

4. Comastic (Epoxy coating?) or Coflex (Single coat Vinyl?) is way better than 3 coats of Intertuf Bitumen type coatings at protecting against galvanic corrosion. Comastic isn't epoxy - these are two different systems, but I think they are all better then bitumen. Two-part epoxy is just about the best you can get if it's properly applied.

 

What I am confused by:

 

1. If I have a GI or Isolation Transformer (IT), what happens if my shoreline connected neighbours do not have either...will they attract corrosion to my boat...?? No, you would be isolated.

 

2. Can anodes be fitted on the baseplate near to the edges..? Would this add extra protection at the chance of a bottom scrape if unlucky...? You can try, but anodes are only supposed to work on "line of sight" not around corners, so you won't add protection to the sides.

 

3. Some owners paint their hull with red oxide under the blacking...does this help against corrosion Galvanic or otherwise..?

NO! Definitely not! If you want an underwater primer try International Primocon. I have 2 coats of Primocon under 3 coats of Rylards bitumen blacking (Rytex)

Edited November 1, 2011 by blackrose

[bottle]

Hi all....

 

Sorry if this subject is a bit flogged to death, but I am confused after all the searching through threads and the like...

 

What I think I understand from various posts:

 

1. A Galvanic Isolator is good for helping protect against Galvanic Corrosion, but an Isolation Transformer such as the Airlink version is way better. Yes

 

2. The anodes, if kept in good order should also help in the fight against corrosion. Yes

 

3. Anodes only protect an area within a few feet of the spot they're welded to, but any more and they get knocked off in locks. Yes

 

4. Comastic (Epoxy coating?) or Coflex (Single coat Vinyl?) is way better than 3 coats of Intertuf Bitumen type coatings at protecting against galvanic corrosion. Debatable, it will get scraped off no matter what it is

 

What I am confused by:

 

1. If I have a GI or Isolation Transformer (IT), what happens if my shoreline connected neighbours do not have either...will they attract corrosion to my boat...?? No

 

2. Can anodes be fitted on the baseplate near to the edges..? Would this add extra protection at the chance of a bottom scrape if unlucky...? They can be fitted wherever you want, protection should increase, you will be lucky not to scrape the boottom

 

3. Some owners paint their hull with red oxide under the blacking...does this help against corrosion Galvanic or otherwise..? No, blacking should be sraight onto the clean hull

 

 

I am confused and I don't know what is true, what is urban myth and what is possible/impossible....

 

[blackrose]

I really am losing the will to live.........

 

Why? The man repairs guitars, I don't think he ever professed to be an expert on steel boats. We all had to start somewhere...

 

But perhaps he could have searched the forum archives.

 

Edit: Sorry, he did search the archives!

Edited November 1, 2011 by blackrose

[steelaway]

I really am losing the will to live.........

 

 

 

And it's very likely the hull will out live you! - and him!

 

Worry about something else for the next 20 years?

 

Alex

[Guest]

And it's very likely the hull will out live you! - and him!

 

Worry about something else for the next 20 years?

 

Alex

 

[theguitardoctor]

Thanks for the replies, I understand a little more now.

 

I apologise if it's bugging one or two people, but if you asked me what effect scale length has on the feel of a guitar or what the advantages of a compound radius are or even why guitar necks are radiused, why it's feasible to make a Faraday Cage on a Stratocaster but not a Les Paul, then I could tell you....and I do, often many, many times to many different people. New hobbyists are always moving towards guitars...I see it as good for business despite going over old ground....

 

As Blackrose said...we all started somewhere, and what you take for granted as common knowledge is new ground for me. Current travelling through guitars (it actually doesn't, even in an electric guitar, unless of course it's Active circuitry) I understand, current through water and its consequences on metal...I'm getting there.....

 

[Guest wanted]

I really am losing the will to live.........

How long have we got?

[Guest]

Thanks for the replies, I understand a little more now.

 

I apologise if it's bugging one or two people, but if you asked me what effect scale length has on the feel of a guitar or what the advantages of a compound radius are or even why guitar necks are radiused, why it's feasible to make a Faraday Cage on a Stratocaster but not a Les Paul, then I could tell you....and I do, often many, many times to many different people. New hobbyists are always moving towards guitars...I see it as good for business despite going over old ground....

 

As Blackrose said...we all started somewhere, and what you take for granted as common knowledge is new ground for me. Current travelling through guitars (it actually doesn't, even in an electric guitar, unless of course it's Active circuitry) I understand, current through water and its consequences on metal...I'm getting there.....

 

GD iits not the fact you asked it was my anticipation of the inevitible re run of conflicting advive that will follow, unfortunately the definiative guru on electrical matters no lomger plays with us I suggest you pore over his (gibbo) excellent smartgauge web site most of what you need is there.

 

ed to add linky

Edited November 2, 2011 by MJG

[Chris Pink]

why it's feasible to make a Faraday Cage on a Stratocaster but not a Les Paul, then I could tell you....and I do, often many, many times to many different people.

 

I know a little about guitars from the other end, so to speak, but this is a new one on me, pray amplify?

 

 

The other thing to note about galvanic corrosion is that you do need a culprit, ie another steel boat within a reasonable distance with a hookup that shares your earth and has some kind of minor fault condition that sends a current through the earth (well to be exact through the water, through your boat and to earth - all electrolysis requires an electrical potential), though a pontoon will do in the absence of another boat. This implies that the people most at risk are those in marinas with hook-up and metal pontoons. The most sure way to protect against this kind of galvanic action is to unplug when not on the boat. It is also worth pointing out that you can create your own electrolysis with your rudder or propellor (especially brass and bronze).

[alan_fincher]

The most sure way to protect against this kind of galvanic action is to unplug when not on the boat..

Although, as you have made specific reference to pontoon moorings, it does seem to be generally, (if not universally!), accepted that just by being on a pontoon where your boat is not connected to mains, but berthed between two that are, it can be affected.

 

Would you accept that, as I have certainly been shown boats that spend most of there life like that, where there is evidence they have suffered ?

 

EDITED: For grammar - (which probably is still wrong!).

Edited November 2, 2011 by alan_fincher

[Chris Pink]

 

Would you accept that, as I have certainly been shown boats that spend most of there life like that, where there is evidence they have suffered ?

 

 

 

What????!!! Je n'y comprends pas Monsieur.

 

If there is no electrical connection between your boat and the other (or pontoon) then it will not suffer.

Edited November 2, 2011 by Chris Pink

[theguitardoctor]

I know a little about guitars from the other end, so to speak, but this is a new one on me, pray amplify?

 

 

The other thing to note about galvanic corrosion is that you do need a culprit, ie another steel boat within a reasonable distance with a hookup that shares your earth and has some kind of minor fault condition that sends a current through the earth (well to be exact through the water, through your boat and to earth - all electrolysis requires an electrical potential), though a pontoon will do in the absence of another boat. This implies that the people most at risk are those in marinas with hook-up and metal pontoons. The most sure way to protect against this kind of galvanic action is to unplug when not on the boat. It is also worth pointing out that you can create your own electrolysis with your rudder or propellor (especially brass and bronze).

 

Thanks for the info....to answer your query also...

 

A faraday cage is usually created (aftermarket mod...Fender deem it character when Strat's buzz and rattle..!!) within a Stratocaster as it has single coil pickups (basically a microphone for all intents and purposes, that "pick up" the string vibrations). Single coils are wound in a singular direction and thus have no hum cancelling ability therefore are affected by signals within a resistance or oscillation/cycling circuit...i.e TV's & Computer Screens (less so since we left the old CRT types), dimmer switches, fluorescent tubes, track lights etc. Boat electrics may well do it, I have yet to try this theory....

 

This plays havoc with recordings etc.

 

One answer is to run humbuckers, so named as they are hum cancelling having 2 coils side by side run in opposite magnetic polarity directions. The other option is a Faraday cage...basically shield all cavities with copper tape, soldering across each join to basically enclose the controls of the pickups within said cage. This contains the magnetic field and shields it from 60 cycle hum and interference.

 

I've seen Faraday cages within humbucker loaded guitars but generally they do very little or nothing....it really is the perception of the user there as I think it's an unnecessary mod on double humbucker guitars....

 

Some pickups are just plain noisy at the end of the day though, so in extreme cases, they need changing.....

 

GD iits not the fact you asked it was my anticipation of the inevitible re run of conflicting advive that will follow, unfortunately the definiative guru on electrical matters no lomger plays with us I suggest you pore over his (gibbo) excellent smartgauge web site most of what you need is there.

 

ed to add linky

 

Fair enough, I misinterpreted it from its shortness of reply....my apologies.

[Guest]

Fair enough, I misinterpreted it from its shortness of reply....my apologies.

 

Not required

 

- have you sussed out the site I linked to yet though?

[theguitardoctor]

Not required

 

- have you sussed out the site I linked to yet though?

 

Yes I have had a look at it thanks, although with guitar electrics as a side of my own work, I start over-thinking things, hence why I wondered if you can pick up stray current from unguarded/unprotected neighbouring boats.

 

I understand how the Isolation Transformer works over the GI and for the extra £200 I think its a worthwhile investment, especially when the GI's need testing at intervals to ensure they're still working....

[davey b]

Thanks for the info....to answer your query also.... This contains the magnetic field and shields it from 60 cycle hum and interference.

 

 

I'm not convinced it will affect the magnetic flux... may be the stray currents induced by the fluxes will be carried around by the cage and therefore not interfere with the pick-ups...

 

And do your clocks run fast or are you French? We run 50Hz in UK mains electricity (though it will vary +/-, it's true)

 

 

 

 

A level physics was a lot more than 20 years ago Not sure how all this GI and anodic mularchy works at all. The definitive answer will sell quite well, I reckon

[theguitardoctor]

I'm not convinced it will affect the magnetic flux... may be the stray currents induced by the fluxes will be carried around by the cage and therefore not interfere with the pick-ups...

 

And do your clocks run fast or are you French? We run 50Hz in UK mains electricity (though it will vary +/-, it's true)

 

 

 

 

A level physics was a lot more than 20 years ago Not sure how all this GI and anodic mularchy works at all. The definitive answer will sell quite well, I reckon

 

Yes, 60 cyclic hum is USA...as are most of the guitars and pickups (aftermarket) in them although the UK is making a good show now. I get so used to reading about 60 cyclic hum that it's second nature...although UK is classed as 50-60Hz on all musical products anyway and 230-240V so I don't even think about it as it's always referred to as 60 cyclic hum in my industry..!!

 

My reply was simplistic (on purpose) and I've re-read my answer and you're right, it was not explained in the best way as it can be interpreted in several ways... So here goes.....

 

A Faraday cage is an enclosure designed to exclude electromagnetic fields. It is an application of Gauss's law, one of Maxwell's equations. Gauss's law describes the distribution of electrical charge on a conducting form, such as a sphere, a plane, a torus, etc. Intuitively, since like charges repel each other, charge will "migrate" to the surface of the conducting form. The application is named after physicist Michael Faraday, who built the first Faraday cage in 1836, to demonstrate his finding.

 

It's very likely you woke up this morning in a Faraday cage, made your breakfast in another Faraday cage, and drove a Faraday cage to work. Depending on your particular job, you may have spent much of your day in front of yet another Faraday cage.

 

The concept of a Faraday cage is logically attributed to Michael Faraday, an 18th Century pioneer in the field of electromagnetic energy. Faraday studied the work of earlier scientists such as Benjamin Franklin and theorized that electromagnetic waves naturally flowed around the surface of conductive materials, not through them. For example, if a metal box containing a mouse were placed directly in the path of an electrical current, the electricity would flow over the box but not into the compartment with the mouse. The mouse would not be electrocuted. Such a box would be considered a Faraday cage.

 

The important concept to remember is that a Faraday cage acts as a shield against the effects of electromagnetic energy. When a car is struck by lightning, the metal frame becomes a Faraday cage and draws the electricity away from the passengers inside. A microwave oven's door has a screen which prevents electromagnetic energy from escaping into the room. Electronic parts which generate radio frequencies are often protected by Faraday cages called RF shields. Even a concrete building reinforced with lead or rebar can be considered a Faraday cage.

 

Few consumers of electronic products would ever ask the for a Faraday cage, but designers and engineers understand the importance of electromagnetic shielding very well. Whenever sensitive electronic parts are used in machinery, some form of shielding is generally in place, whether it be the machine's metal shell, a capsule or a grounding wire. If the electronic parts generate electromagnetic energy of their own, a Faraday cage must be used to shield users from excessive exposure. This is why mobile phone use is often discouraged in hospitals or other public places with electronic equipment. Unshielded equipment may be exposed to the microwave energy created by cell phones or other radio transmitters.

 

I'll be a lot more specific in future, I avoided it as it's a boating forum..!!

[bigcol]

So you like, and are interested in guitars then?

 

:D

 

I found your post interesting though re faraday cages

 

Col

[mayalld]

The other thing to note about galvanic corrosion is that you do need a culprit, ie another steel boat within a reasonable distance with a hookup that shares your earth and has some kind of minor fault condition that sends a current through the earth (well to be exact through the water, through your boat and to earth - all electrolysis requires an electrical potential), though a pontoon will do in the absence of another boat. This implies that the people most at risk are those in marinas with hook-up and metal pontoons. The most sure way to protect against this kind of galvanic action is to unplug when not on the boat. It is also worth pointing out that you can create your own electrolysis with your rudder or propellor (especially brass and bronze).

 

 

It is often stated that if you have no earth, you are in no danger.

 

I would disagree with that assertion.

 

Assume that your neighbours boat has an earth fault, and that it has effectively created an electrolysis cell between its hull and the metal pontoons.

 

Clearly, the majority of the activity will be focussed across the few inches of water to its own pontoon.

 

However, some activity will also be going on across the 8 feet of water to the next pontoon. Or rather it will be across 8 feet of water when you aren't there!

 

When you are there, your boat sits in the electrolyte in the path of the electrons that are passing between your neighbours hull and YOUR pontoon. Your boat is a far better conductor than the water, and the path of least resistance between the faulty boat and your pontoon involves your boat.

 

The result will be metal deposition on one side of your boat and loss on the other side, whether you have a shoreline or not.

[Chris Pink]

My suggestion is to create am electronic device that turns your boat into a giant cathode and thus deposits metal from other boats on your hull. Preferably the copper.

 

Research is in progress.

[WotEver]

My suggestion is to create am electronic device that turns your boat into a giant cathode and thus deposits metal from other boats on your hull. Preferably the copper.

 

Research is in progress.

• 
   
  
• Create a large battery bank.
  
• Connect the -ve to your hull.
  
• In the depth of night run cables from the +ve to every other boat in the marina.
  
• Eventually all the other boats will sink and yours will sit far lower in the water.
  

 

Tony (who's learning off Bizzard)

[Chris Pink]

• 
   
  
• Create a large battery bank.
  
• Connect the -ve to your hull.
  
• In the depth of night run cables from the +ve to every other boat in the marina.
  
• Eventually all the other boats will sink and yours will sit far lower in the water.
  

 

Tony (who's learning off Bizzard)

 

We need to use the marina earth as the anode cable, more cost effective and already installed, except of course for those with GIs or isolation transformers wired correctly.

 

Though it shouldn't be too difficult to remove the zinc from the pontoons.

Edited November 3, 2011 by Chris Pink

[Doorman]

Why? The man repairs guitars, I don't think he ever professed to be an expert on steel boats. We all had to start somewhere...

 

But perhaps he could have searched the forum archives.

 

Edit: Sorry, he did search the archives!

 

I can somewhat understand Martin's frustration at seeing another topic on hull corrosion appear on the the forum. But, as you correctly state, we all did have to start somewhere and moreover, there are new forum members who may not be aware of the archive facility.

 

Back on topic.

 

This subject is close to my heart as I've witnessed some pretty badly corroded hulls in my short time on the water. Indeed, having spent the last couple of weeks at a very busy Marina/Boatyard to have some paintwork carried out on our own boat, I have recently seen some very dire examples of unprotected hulls.

 

When you consider the spiralling cost of steel, together with that of labour charges (to effectively re-plate your boat), surely it is prudent to invest in some method of avoiding the effect of galvanic corrosion, whether it be a Galvainic Isolator, or an Isolator Transformer (my preference), it makes sense.

 

Also, in an effort to further stall the effects of this phenomena, we had our hull grit blasted then covered with a two-pack epoxy coating last year. Having just examined the hull whilst in a boat shed, our outlay was well rewarded. The hull was virtually unmarked below water and that's after traversing the notoriously difficult Audlem flight, to and from our moorings.

 

I had previously used three coats of Intertuf 16 on our first boat and left it out of the water for a week. On slipping that boat out a year later, all of the Intertuf had disappeared. What a waste of time and effort!

 

One other deterrent that I've added during the last fortnight, is four 4kg anodes to replace the 2.5kg originals that were due for renewal anyway. The theory is, that as I will not have to black the boat for another five, maybe six years, the larger anodes shall last that much longer than the standard provision for a 60' boat.

 

I certainly hope they do anyway!

 

Mike

Edited November 3, 2011 by Doorman

[Chris Pink]

I can somewhat understand Martin's frustration at seeing another topic on hull corrosion appear on the the forum. But, as you correctly state, we all did have to start somewhere and moreover, there are new forum members who may not be aware of the archive facility.

 

Back on topic.

 

This subject is close to my heart as I've witnessed some pretty badly corroded hulls in my short time on the water. Indeed, having spent the last couple of weeks at a very busy Marina/boatyard to have some paintwork carried out on our own boat, I have seen some very dire examples of unprotected hulls.

 

I've been talking to people on the Canal du Midi where it is becoming a real problem, especially in brackish water as more and more people expect to be hooked up to mains power while moored.

 

To the extent than steel boats are fast losing value compared to GRP (apparently).