RE: [SabreSailboat] Re: stray current and electrolysis
I think I may have some of the same issue (1997 S402). From inspection of the keel foot, it looks it goes into the mud about 1ft or so; see attached pictures of the paint blistering. Does this look like what you had?
We go through zincs pretty quickly too.
We have galvanic isolator and bonding is all good, according to the experts. Not sure if the isolator is still any good – that will be the next thing to check, but I guess I may have to epoxy?
Well that certainly puts some doubt in the hot marina theory. In thinking some more, I can add another piece of data. The reason for moving to a new slip was that we discovered at unusually low tide the keel was in the mud at the old slip. When hauled most of the barrier coat was off the bottom of the keel. There were also large areas of the keel with failed barrier coat. So along with new bottom paint, the keel was stripped to bare metal and recoated with 5 coats of epoxy.before reapplication of Micron 66. Possibly it was the large keel area with exposed lead that was contributing to zinc consumption. However, it doesn’t explain why there was high zinc consumption 2 years ago when the keel was still in good shape. So, I’m happy with my current status, but still somewhat mystified. I do have the standard W27 engine, although I find it hard to believe one engine would cause higher zinc consumption than another brand.
From: Sabresailboat@yahoogroups.com [mailto:Sabresailboat@yahoogroups.com] On Behalf Of Dave Evans
Sent: Sunday, November 11, 2012 5:39 PM
Subject: Re: [SabreSailboat] Re: stray current and electrolysis
We're on a mooring; never been on or near shore power (except on the hard). This summer put three zincs
on the shaft: all gone. But a good bit of the Maxprop zinc remains!
On 11/11/2012 6:49 PM, scruz_loose2 wrote:
Couple of other thoughts. First, if the hot marina theory is correct, I would expect boats on a mooring to show much lower zinc consumption. Second, I wish I knew a test for the "hot marina" condition. Nobody seems to mention that.
- I have been curious about this subject so I put forth the question to a respected surveyor up this way, Mark Corke. Following is his reply, I hope ya'll find it helpful & the dang thing doesn't word wrap.....Basically there are two schools of thought on bonding, you either bond everything or you bond nothing. Problems arise when the bonding system is bad and there is any corrosion in the system and thus poor electrical contact between skin fittings. For everything to stay at electrical equilibrium the connection must be of the highest order but most boats this is not the case. For one thing most of the connections are in the bilge and if covered with sea water part of the time corrosion leads to a break down of the circuit and an inevitable increase in electrical resistance.
Thus if you have say 10 underwater metals such as a strut, seacocks and other through hulls connected and the circuit is in perfect order everything will be held at a similar electrical potential and the only thing that should degrade is the zinc anode. If the electrical system is bad and the anode connection is poor or missing then the seawater which is a weak electrolyte starts to eat away at the next metal up the chain which is usually a skin fitting or the prop.
The system that is more common in Europe is not to bond anything at all, e reason for is a a bronze sea cock or skin fitting which is attached to a rubber hose is electrically isolated from the other fittings and therefore there can be no electrical circuit so it is protected.
However things start to get complicated when you have a bit of salt water in the bilge as this has the effect of connecting at least some of the fittings together thus creating albeit a poor circuit and this in turn could lead to degrading of some of the fittings especially the bronze bits.
Things get even more interesting when you add electricity into the mix. Say you have a faulty connection on a bilge pump this can leak current into any bilge water where it finds it's way to ground through any means possible which often means a skin fitting. This is bad enough with 12 volts but things get really hairy id you have a 110 volt leak into the bilge, this is one reason why Sabre now install all there boats with galvanic isolators which prevents 110 volts from getting to ground through a skin fitting which could kill someone swimming in the water next to the boat.
So in a nutshell. I think bonding is a good idea but it has to be in perfect order to work correctly and all metal fittings that come into contact with seawater on the outside of the boat have to be connected. Make sure that all wiring is in perfect condition aboard especially the bonding circuit.
As for the lightning protection, a direct strike will fry everything on board. Bonding helps in cases of minor static or side strikes but a direct hit will go down the mast and may blow a large hole in the bottom of the boat irrespective of the size of the cable. It is also worth noting that it is less about the side of cable and more about the surface area if struck as the charge runs on the surface and it is for this reason why lightning conductors on buildings are copper straps rather than cables.
Hope this helps. Please call if I can help further or you want to chat about this.
MarkFrom: Bob Jenning <b.jenning@...>
To: "Sabresailboat@yahoogroups.com" <Sabresailboat@yahoogroups.com>
Sent: Tuesday, December 18, 2012 7:13 PM
Subject: Re: [SabreSailboat] Re: stray current and electrolysisThis is really good stuff. On the sailnet site there's a group that believes the thru hulls should not be bonded to the same connection point as the lightening protection system which on Sabres is one in the same. Actually their take was the thru hulls shouldn't be bonded at all for fear of a lightening strike following the path of least resistence & blowing a hole in the hull.So if bonding the thru hulls to the same place as the lightening system is considered bad by some, where does one bond the thru hulls? Does it make sense to bond them to the engine block? Providing you don't have a drive shaft saver, it is a direct path to the water by way of the shaft & is that considered isolated from the lightening system?Is the problem on Sabres exasperated because all the thru hulls are bronze & require aditional protection when compared to a boat w/ marlon (sp) thru hulls?What's your take on this RC?From: mainecruising <mainecruising@...>
Sent: Saturday, December 15, 2012 10:23 AM
Subject: [SabreSailboat] Re: stray current and electrolysisDave, It is a good book but may take a few reads if you are not up on the molecular, chemical and electrical theory portions of it. Some of it deals with wood or metal boats do but don't gloss over those sections as there is a lot that can be taken from them that translates to your glass boat.... This is not so much a "how to" book as a science of corrosion book. Without the science the "how to" is useless, thus I really like this book... What I find most are often when it comes to corrosion are the simple things: *** The leading offender of aggressive/fast corrosion is almost always your boat, not a neighbors boat***** *DC corrosion (your own boat usually) is FAR MORE AGGRESSIVE than any AC corrosion. AC caused corrosion issues are quite rare.. AC can cause death, so must be done correctly, but is not a huge offender in corrosion issues. *Energized bonding circuits where a DIY or yard used the bonding circuit as a return path for the batteries. Green is BONDING/EARTH potential, not a neg return wire. In the summer I see this perhaps every other week. very, very common... *Hot water tank element failure and leakage *Bilge pumps either mis-wired (switch in neg lead) or poor open connections in the bilge. *Improper routing of wires in bilges with cracked or voided jackets of improper jackets for marine use like the welding cable used by Sabre. *Dissimilar metals used in seacock systems like a 60-40 Home Depot brass ball valve slapped on an 85-5-5-5 bronze thru hull. Also brass male adapters are FAMOUS for causing advanced corrosion when connected to bronze seacocks. *Leaking AC devices such as cheap automotive battery chargers. NEVER use anything but a Marine UL battery charger. *Failed galvanic isolators. New GI's must be "Fail Safe" so when or if they fail you retain safety ground. *No galvanic isolator or isolation transformer.. *Chafed wires *Improper grounding eg: multiple separate ground points on the boat -RC --- In mailto:Sabresailboat%40yahoogroups.com, Dave Lochner <davelochner@...> wrote: > > RC, > > Thanks for chiming in. Amazon now has one less copy of The Boatowners Guide to Corrosion. Cheap at $13. > > Dave > > > On Dec 14, 2012, at 5:31 PM, mainecruising wrote: > > > Hi All, > > > > I would strongly urge anyone to not make any "bonding" changes to their boat without first having a very, very good understanding of your boats electrical & bonding systems and how these pieces interact with such things a bilge water etc.. You also have lightning bonding which should not be confused with the bonding of your submersed metals, nor should it be disconnected. Without a reference cell, proper tools and a good understanding of corrosion tackling bonding issues can be as risky as going to Vegas.. > > > > I would only recommend "un-bonding" after a thorough corrosion survey and at the very least buying and reading Everett Colliers book "The Boatowner's Guide To Corrosion",. Read this book until it makes sense to you. This is not some Don Casey "Corrosion for Dummies" book it is science and one of the best marine books out there IF you get it..... Everett's book is the best on the subject.. > > > > IMHO, as a marine electrical systems specialist, I feel WM has done a great disservice to the boating community as a whole by publishing that article. > > > > This is not because un-bonding is always bad, my own vessel is not bonded, but because when people who don't understand such complexities as marine corrosion, begin to "cherry pick" what they believe to now be an ultimate truth, bad things can happen. I am the one who see's the results of articles like the WM article.. > > > > Can you get lucky or possibly stop an "issue". Sure but the root cause of the issue may still be there and your luck with becoming your own corrosion doctor may be about as good a Vegas odds.. > > > > Corrosion issues are simply not as easy as "I read the WM article I think I will un-bond and go sailing.". I wish it was, and WM makes it seem that way, but it is not. > > > > I have attended many, many, many hours of both on-line and classroom corrosion training. I would like to write some articles for my own web site but the subject simply requires multiple hundreds of pages of real estate to give it any true benefit. > > > > I've studied nearly every book, done the ABYC classes, had seminars with every "guru" in the industry and I can assure you the WM article barely even skims the surface. Heck the "guru's" and guys who have devoted entire careers to this don't even agree on all aspects of corrosion.... > > > > Suffice it to say the WM article leaves a LOT of room for error and a real potential for the proverbial can of worms. Corrosion understanding CAN NOT be written into a WM Advisor article. It is rather sad they think it can... > > > > Rant over.... > > > > -RC > > > > --- In mailto:Sabresailboat%40yahoogroups.com, "Ken Jenkins" <kjenk3@> wrote: > > > > > > Nick, > > > > > > The same non-response occurred the last time I mentioned the West Marine > > > article on grounding so evidently there is no experience of having tried > > > seperating the lightning/keel ground system from the engine and DC ground on > > > this board. I am more and more leaning to the idea that the keel is the > > > source of much of the zinc consumption, but for now my low zinc use is > > > stopping me from trying to split the grounds. > > > > > > I did come across a few things that might help you in using your DVM. There > > > is a good discussion of using a "silver half cell" here > > > > > > http://yachtwork.com/report-corrosion.htm > > > > > > When I had an electrical survey done, this is what the surveyor used. > > >
> > > Also, if you do decide to separate grounds notice that the West Marine > > > article mentions a "DC Inner Outer Block" for the VHF coax. This is because > > > the outer shield of the coax is grounded to the mast at the whip mouning > > > point. The block is a coax device that can be mounted on the output of the > > > vhf radio. Here's an example > > > > > > http://www.e-meca.com/specs_dc_block/specs_dc_block.php?dcID=3 > > > <http://www.e-meca.com/specs_dc_block/specs_dc_block.php?dcID=3&dcSpecsID=28 > > > > &dcSpecsID=28 > > > > > > Good luck, Ken > > > > > > > > > > > > > > > > > > _____ > > > > > > From: mailto:Sabresailboat%40yahoogroups.com [mailto:mailto:Sabresailboat%40yahoogroups.com] > > > On Behalf Of Nick Sands > > > Sent: Tuesday, December 11, 2012 12:24 PM > > > To: mailto:Sabresailboat%40yahoogroups.com > > > Subject: RE: [SabreSailboat] Re: stray current and electrolysis > > > > > > > > > > > > > > > > > > All, > > > > > > > > > > > > So it sounds like "bonding everything metal together is the thing to do, > > > until it isn't" . I wonder if there is a way to tell if something is awry > > > (without waiting for the metal to be chewed away and the paint to blister > > > off) .. I have a DVM and I know how to use it ;) > > > > > > > > > > > > Something along the lines of measuring current through a bonding connection, > > > or measuring voltage across a disconnected bond? > > > > > > > > > > > > Nick > > > > > > > > > > > > From:ymailto="mailto:Sabresailboat%40yahoogroups.com">mailto:Sabresailboat%40yahoogroups.com [mailto:mailto:Sabresailboat%40yahoogroups.com] > > > On Behalf Of Ken Jenkins > > > Sent: Tuesday, December 11, 2012 10:47 AM > > > To: mailto:Sabresailboat%40yahoogroups.com > > > Subject: RE: [SabreSailboat] Re: stray current and electrolysis > > > > > > > > > > > > > > > > > > Allison, > > > > > > That is consistent with the advice given in the West Marine advisor article > > > on Marine Grounding Systems. They advise! isolating the thru hulls rather > > > than bonding them. They also advise DC isolation between the engine and the > > > keel. > > > > > > I am puzzled though. If you only broke one of the bonding connections you > > > would still have the other thru hulls connected to the keel and thence to > > > the engine. I would think that you would need to break more than one bond to > > > get a dramatic change in zinc consumption. Can you tell us exactly what > > > connection was broken? > > > > > > Thanks, Ken > > > > > > > > > > > > _____ > > > > > > From: mailto:Sabresailboat%40yahoogroups.com [mailto:mailto:Sabresailboat%40yahoogroups.com] > > > On Behalf Of Allison Lehman > > > Sent: Tuesday, December 11, 2012 10:11 AM > > > To: mailto:Sabresailboat%40yahoogroups.com > > > Subject: Re: [SabreSailboat] Re: stray current and electrolysis > > > > > > > > > > > > > > > > > > Hi Nick, > > > > > > My husband spent a year chasing what we thought was stray current. We went > > > thru zincs quickly and blew off paint on the bottom of our keel as well as > > > around some thru hulls. We also have a sacrificial zinc hung overboard. > > > Finally as an experiment, he disconnected one of the bonding wires to break > > > the circuit. All problems stopped. > > > > > > > > > > > > Back in '97 when I sold 362 to client, he had terrible problems. I believe > > > he did the same, with the same results. After all lightning is not too > > > common her! e. > > > > > > > > > > > > Allison > > > > > > > >