Joe I got dizzy just reading your post. And you confirmed my worst fear. I could hire a professional and watch him spend hours searching for the needle in the hay stack.
Mike C&C 37 K/CB Shoal draft Persuasion Stormont Yacht Club From: Della Barba, Joe via CnC-List Sent: August 13, 2018 10:04 AM To: cnc-list@cnc-list.com Cc: Della Barba, Joe Subject: Re: Stus-List Galvanic corrosion You can have grounds places you don’t expect. The VHF radio may ground negative to the chassis that connects to the coax shield that connects to the body of the antenna loading coil that connects to the mount that connects to the mast. Almost any SSB has the coax shield connected to negative that may have DC connectivity through the tuner. Submersible centrifugal bilge pumps (Rule etc.) can have the metal pump shaft connected to DC negative, or even worse DC positive if you wire it backwards and it will pump just fine wired backwards. Battery chargers can be a link between DC ground and the AC green wire bus outside of the intended connection. Engines more or less carry DC ground to underwater metal. If the engine ground connection is bad, starting the engine will raise the underwater metal above DC ground voltage and so will battery charging. Anything AC like an air conditioner is effectively connected to DC ground. Etc etc Back in the day I could spend hours and hours at $60/hr with meters and cables tracking this stuff down. Joe Coquina From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Persuasion37 via CnC-List Sent: Saturday, August 11, 2018 1:42 PM To: cnc-list@cnc-list.com Cc: Persuasion37 <persuasio...@gmail.com> Subject: [EXTERNAL] Re: Stus-List Galvanic corrosion Thanks Joe I think I’m suffering from stray current corrosion. I’m on a ball at the yacht club and as said earlier, the only time I’m connected to AC is when Persuasion is on the hard. I’ve started eliminating different devices looking for the leak. A very slow process. Mike PERSUASION C&C 37 K/CB Long Sault On Aug 10, 2018, at 3:16 PM, Della Barba, Joe via CnC-List <cnc-list@cnc-list.com> wrote: I am a bit late to this, but FYI: Galvanic corrosion is caused by two different types of metal in water that are electrically connected. The “less noble” metal is the one that corrodes, which is why we use zincs (or magnesium or aluminum). There has to be a path between the metals for this to happen. This can get much much worse when on shorepower because all the boats in the marina end up wired together via the green ground wire connection. If no one buys new zincs but you, guess who supplies the entire marina with anode material? YOU DO! Galvanic isolators are 100% needed for any boat on shore power for this reason. The other form of corrosion is stray current corrosion. This does not need different metals to work, just electricity flowing through the water. The current moves metal from one place to the other, this is how electroplating works. This can be very complicated to track down and can do a vast amount of damage very quickly. There are a lot of different ways this can happen, but imagine a boat with the keel connected to the ground bus, a negative ground engine, and a SSB ground plate with DC connection through to the radio. We now have 3 different underwater metals connected to the negative side of the DC system. If the onboard ground bus and wiring are not perfect, some current will flow through the water too. Joe Coquina _______________________________________________ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
_______________________________________________ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray
