Re: Stus-List [EXTERNAL] Re: Galvanic corrosion (Della Barba, Joe)
I was going to replace with Marlon but elected to not do so for two reasons: 1) they are not as robust as bronze thru-hulls as you noted; and 2) unlike the Marlon thru-hulls I considered, the replacement bronze thru-hull was identical in size so the flange fit perfectly in the existing cavity in the hull surface. It was a remarkably easy repair (for a change). I never did determine the source of electric current which caused the thru-hull to erode. In any event, re-installing the ground wire appears to have resolved the issue. From: Bill Coleman via CnC-List Sent: Wednesday, August 15, 2018 11:06 AM To: cnc-list@cnc-list.com Cc: Bill Coleman Subject: Re: Stus-List [EXTERNAL] Re: Galvanic corrosion (Della Barba, Joe) Now you’re really spinning my head. This would lead you to believe you should use Marlon, but I absolutely hate those thru hulls. I have another boat with them, and I expect they are going to break when I turn the valves, and one is actually leaking around a point where it necks down, leading me to believe it is about to break. I will stick with Bronze. Or SS. Bill Coleman C&C 39 Erie, PA ___ 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
Re: Stus-List [EXTERNAL] Re: Galvanic corrosion (Della Barba, Joe)
Now you’re really spinning my head. This would lead you to believe you should use Marlon, but I absolutely hate those thru hulls. I have another boat with them, and I expect they are going to break when I turn the valves, and one is actually leaking around a point where it necks down, leading me to believe it is about to break. I will stick with Bronze. Or SS. Bill Coleman C&C 39 Erie, PA From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Matthew L. Wolford via CnC-List Sent: Tuesday, August 14, 2018 4:24 PM To: cnc-list@cnc-list.com Cc: Matthew L. Wolford Subject: Re: Stus-List [EXTERNAL] Re: Galvanic corrosion (Della Barba, Joe) Not so fast, Bill. I replaced a bronze thru-hull when doing extensive core repair about six years ago. There was a ground wire connected to the original thru-hull that we did not re-connect. About two years ago, I discovered that the thru-hull had been substantially eaten away. The flange on the outside was about half gone and greenish-blue in color. I replaced the thru-hull with an identical bronze unit and re-connected the ground wire. Haven’t had a problem since. From: Bill Coleman <mailto:cnc-list@cnc-list.com> via CnC-List Sent: Tuesday, August 14, 2018 2:43 PM To: cnc-list@cnc-list.com Cc: Bill Coleman <mailto:colt...@verizon.net> Subject: Re: Stus-List [EXTERNAL] Re: Galvanic corrosion (Della Barba, Joe) Well, Joe, you have just thrown some weight to a very weighty question in my head. I have read where these thru hulls are to be grounded, and then I read where you shouldn’t , so I think over the years some I have re-done some grounds, then I read the other way, and I don’t connect them, so half mine are grounded, and the other half are not, just because I don’t know what to do! Are a couple drinks a day good for you, or bad for you? Depends on the latest study you read! So, I am going with you, no grounds on any thru-hulls! Thanks for clearing my head. (At least until I read another article.) Bill Coleman C&C 39 Erie, PAanimated_favicon1 From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Della Barba, Joe via CnC-List Sent: Tuesday, August 14, 2018 2:08 PM To: cnc-list@cnc-list.com Cc: Della Barba, Joe Subject: Re: Stus-List [EXTERNAL] Re: Galvanic corrosion (Della Barba, Joe) I am still not clear on how the voltage is being measured and between what points. I have bronze thru-hulls that are not wired to anything. If I measured between them and the lead keel or the engine with the stainless shaft, I am sure I would read a voltage, they are dissimilar metals in salt water. Absent me wiring up the voltmeter, the thru-hulls have no connection to anything else and would not corrode. If you do have all these thru-hulls wired to ground, as is done on some boats, you now have a battery. You need to be sure there is a zinc involved in there somewhere and it had better have a good connection so that the zinc is the part of the battery corroding. IMHO and also the article referenced in another post, I like to make sure my seacocks and thru-hulls are NOT grounded. This eliminates the issue of poor contact to zincs and prevents the boat wiring from being a path for leakage between boats on one side of you and boats on the other, which is something a zinc will have a hard time saving you from. Joe Coquina From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Michael Brown via CnC-List Sent: Tuesday, August 14, 2018 1:53 PM To: cnc-list@cnc-list.com Cc: Michael Brown Subject: [EXTERNAL] Re: Stus-List Galvanic corrosion (Della Barba, Joe) You could try reading current with your multimeter instead of voltage. Small stray voltages likely exist when measuring between lead and SS even in fresh water but I doubt they will sustain much current. Just as an example of magnitude very roughly if there was a current of 1 amp continuously in normal soil it would corrode about 20 lbs of steel in a year. If you are reading less than 0.5 milliamp I would say those two surfaces are not going to have much corrosion between them. If you are seeing over a milliamp then there is an issue. The circuit requires two paths, the dissimilar metals in water and then something on the boat connecting them together. Some advice has been to connect the mast, standing rigging and keel together but do not ground them to the boats electrical system. That may be difficult if items like the VHF antenna is mounted to a metal bracket on the mast. You can test for this by measuring the resistance between the mast and ship's ground. Anything under 10 ohms would indicate a connection. Michael Brown Windburn C&C 30-1 Date: Tue, 14 Aug 2018 13:41:43 + From: "Della Barba, Joe" Voltage readings between what and what? Joe Della Barba Coquina Sent: Monday, August 13, 2018 7:25 PM
Re: Stus-List [EXTERNAL] Re: Galvanic corrosion (Della Barba, Joe)
Not so fast, Bill. I replaced a bronze thru-hull when doing extensive core repair about six years ago. There was a ground wire connected to the original thru-hull that we did not re-connect. About two years ago, I discovered that the thru-hull had been substantially eaten away. The flange on the outside was about half gone and greenish-blue in color. I replaced the thru-hull with an identical bronze unit and re-connected the ground wire. Haven’t had a problem since. From: Bill Coleman via CnC-List Sent: Tuesday, August 14, 2018 2:43 PM To: cnc-list@cnc-list.com Cc: Bill Coleman Subject: Re: Stus-List [EXTERNAL] Re: Galvanic corrosion (Della Barba, Joe) Well, Joe, you have just thrown some weight to a very weighty question in my head. I have read where these thru hulls are to be grounded, and then I read where you shouldn’t , so I think over the years some I have re-done some grounds, then I read the other way, and I don’t connect them, so half mine are grounded, and the other half are not, just because I don’t know what to do! Are a couple drinks a day good for you, or bad for you? Depends on the latest study you read! So, I am going with you, no grounds on any thru-hulls! Thanks for clearing my head. (At least until I read another article.) Bill Coleman C&C 39 Erie, PA From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Della Barba, Joe via CnC-List Sent: Tuesday, August 14, 2018 2:08 PM To: cnc-list@cnc-list.com Cc: Della Barba, Joe Subject: Re: Stus-List [EXTERNAL] Re: Galvanic corrosion (Della Barba, Joe) I am still not clear on how the voltage is being measured and between what points. I have bronze thru-hulls that are not wired to anything. If I measured between them and the lead keel or the engine with the stainless shaft, I am sure I would read a voltage, they are dissimilar metals in salt water. Absent me wiring up the voltmeter, the thru-hulls have no connection to anything else and would not corrode. If you do have all these thru-hulls wired to ground, as is done on some boats, you now have a battery. You need to be sure there is a zinc involved in there somewhere and it had better have a good connection so that the zinc is the part of the battery corroding. IMHO and also the article referenced in another post, I like to make sure my seacocks and thru-hulls are NOT grounded. This eliminates the issue of poor contact to zincs and prevents the boat wiring from being a path for leakage between boats on one side of you and boats on the other, which is something a zinc will have a hard time saving you from. Joe Coquina From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Michael Brown via CnC-List Sent: Tuesday, August 14, 2018 1:53 PM To: cnc-list@cnc-list.com Cc: Michael Brown Subject: [EXTERNAL] Re: Stus-List Galvanic corrosion (Della Barba, Joe) You could try reading current with your multimeter instead of voltage. Small stray voltages likely exist when measuring between lead and SS even in fresh water but I doubt they will sustain much current. Just as an example of magnitude very roughly if there was a current of 1 amp continuously in normal soil it would corrode about 20 lbs of steel in a year. If you are reading less than 0.5 milliamp I would say those two surfaces are not going to have much corrosion between them. If you are seeing over a milliamp then there is an issue. The circuit requires two paths, the dissimilar metals in water and then something on the boat connecting them together. Some advice has been to connect the mast, standing rigging and keel together but do not ground them to the boats electrical system. That may be difficult if items like the VHF antenna is mounted to a metal bracket on the mast. You can test for this by measuring the resistance between the mast and ship's ground. Anything under 10 ohms would indicate a connection. Michael Brown Windburn C&C 30-1 Date: Tue, 14 Aug 2018 13:41:43 + From: "Della Barba, Joe" Voltage readings between what and what? Joe Della Barba Coquina Sent: Monday, August 13, 2018 7:25 PM Hi Alan The readings I posted are at anchor in the Thousand Island area. I almost never plug in during the cruising season. I only use shore power to charge the batteries during winter layup when the solar and wind are removed, every 6 to 8 weeks So today I did more testing. I disconnected the positive cable for the start battery and I still saw 0.02V at the prop shaft. So I ruled out that as an issue. I disconnected the battery charger and still saw voltage. Next I took the wind generator out of the equation and the results were the same. Next I disconnected the windlass, same results. Next I moved inside and checked for voltage on the tube for the centre board pendant. Saw 0.25 V. I removed the positive cable to the house elect
Re: Stus-List [EXTERNAL] Re: Galvanic corrosion (Della Barba, Joe)
I also am of the convention of none of the overboards that have plastic/rubber inboard should be grounded. When I first got the boat in 1980 we were eating zincs, one every other month. I read an article at the time that basically said that if you have a copper base paint you were setting up eddy currents between the overboards and the prop zinc. I remove all the grounds from the overboards and have had the zinc last the whole season (May-Oct), since then. My two cents Don Kern /Fireball /12708 C&C 35 MK2//(1974)/ / On 8/14/2018 2:43 PM, Bill Coleman via CnC-List wrote: Well, Joe, you have just thrown some weight to a very weighty question in my head. I have read where these thru hulls are to be grounded, and then I read where you shouldn’t , so I think over the years some I have re-done some grounds, then I read the other way, and I don’t connect them, so half mine are grounded, and the other half are not, just because I don’t know what to do! Are a couple drinks a day good for you, or bad for you? Depends on the latest study you read! So, I am going with you, no grounds on any thru-hulls! Thanks for clearing my head. (At least until I read another article.) Bill Coleman C&C 39 Erie, PAanimated_favicon1 *From:*CnC-List [mailto:cnc-list-boun...@cnc-list.com] *On Behalf Of *Della Barba, Joe via CnC-List *Sent:* Tuesday, August 14, 2018 2:08 PM *To:* cnc-list@cnc-list.com *Cc:* Della Barba, Joe *Subject:* Re: Stus-List [EXTERNAL] Re: Galvanic corrosion (Della Barba, Joe) I am still not clear on how the voltage is being measured and between what points. I have bronze thru-hulls that are not wired to anything. If I measured between them and the lead keel or the engine with the stainless shaft, I am sure I would read a voltage, they are dissimilar metals in salt water. Absent me wiring up the voltmeter, the thru-hulls have no connection to anything else and would not corrode. If you do have all these thru-hulls wired to ground, as is done on some boats, you now have a battery. You need to be sure there is a zinc involved in there somewhere and it had better have a good connection so that the zinc is the part of the battery corroding. IMHO and also the article referenced in another post, I like to make sure my seacocks and thru-hulls are NOT grounded. This eliminates the issue of poor contact to zincs and prevents the boat wiring from being a path for leakage between boats on one side of you and boats on the other, which is something a zinc will have a hard time saving you from. Joe Coquina *From:*CnC-List [mailto:cnc-list-boun...@cnc-list.com] *On Behalf Of *Michael Brown via CnC-List *Sent:* Tuesday, August 14, 2018 1:53 PM *To:* cnc-list@cnc-list.com *Cc:* Michael Brown *Subject:* [EXTERNAL] Re: Stus-List Galvanic corrosion (Della Barba, Joe) You could try reading current with your multimeter instead of voltage. Small stray voltages likely exist when measuring between lead and SS even in fresh water but I doubt they will sustain much current. Just as an example of magnitude very roughly if there was a current of 1 amp continuously in normal soil it would corrode about 20 lbs of steel in a year. If you are reading less than 0.5 milliamp I would say those two surfaces are not going to have much corrosion between them. If you are seeing over a milliamp then there is an issue. The circuit requires two paths, the dissimilar metals in water and then something on the boat connecting them together. Some advice has been to connect the mast, standing rigging and keel together but do not ground them to the boats electrical system. That may be difficult if items like the VHF antenna is mounted to a metal bracket on the mast. You can test for this by measuring the resistance between the mast and ship's ground. Anything under 10 ohms would indicate a connection. Michael Brown Windburn C&C 30-1 Date: Tue, 14 Aug 2018 13:41:43 + From: "Della Barba, Joe" mailto:joe.della.ba...@ssa.gov>> Voltage readings between what and what? Joe Della Barba Coquina Sent: Monday, August 13, 2018 7:25 PM Hi Alan The readings I posted are at anchor in the Thousand Island area. I almost never plug in during the cruising season. I only use shore power to charge the batteries during winter layup when the solar and wind are removed, every 6 to 8 weeks So today I did more testing. I disconnected the positive cable for the start battery and I still saw 0.02V at the prop shaft. So I ruled out that as an issue. I disconnected the battery charger and still saw voltage. Next I took the wind generator out of the equation and the results were the same. Next I disconnected the windlass, same results. Next I moved inside and checked for voltage on the tube for the centre board pendant. Saw 0.25 V. I removed the positive cable to t
Re: Stus-List [EXTERNAL] Re: Galvanic corrosion (Della Barba, Joe)
Well, Joe, you have just thrown some weight to a very weighty question in my head. I have read where these thru hulls are to be grounded, and then I read where you shouldn’t , so I think over the years some I have re-done some grounds, then I read the other way, and I don’t connect them, so half mine are grounded, and the other half are not, just because I don’t know what to do! Are a couple drinks a day good for you, or bad for you? Depends on the latest study you read! So, I am going with you, no grounds on any thru-hulls! Thanks for clearing my head. (At least until I read another article.) Bill Coleman C&C 39 Erie, PAanimated_favicon1 From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Della Barba, Joe via CnC-List Sent: Tuesday, August 14, 2018 2:08 PM To: cnc-list@cnc-list.com Cc: Della Barba, Joe Subject: Re: Stus-List [EXTERNAL] Re: Galvanic corrosion (Della Barba, Joe) I am still not clear on how the voltage is being measured and between what points. I have bronze thru-hulls that are not wired to anything. If I measured between them and the lead keel or the engine with the stainless shaft, I am sure I would read a voltage, they are dissimilar metals in salt water. Absent me wiring up the voltmeter, the thru-hulls have no connection to anything else and would not corrode. If you do have all these thru-hulls wired to ground, as is done on some boats, you now have a battery. You need to be sure there is a zinc involved in there somewhere and it had better have a good connection so that the zinc is the part of the battery corroding. IMHO and also the article referenced in another post, I like to make sure my seacocks and thru-hulls are NOT grounded. This eliminates the issue of poor contact to zincs and prevents the boat wiring from being a path for leakage between boats on one side of you and boats on the other, which is something a zinc will have a hard time saving you from. Joe Coquina From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Michael Brown via CnC-List Sent: Tuesday, August 14, 2018 1:53 PM To: cnc-list@cnc-list.com Cc: Michael Brown Subject: [EXTERNAL] Re: Stus-List Galvanic corrosion (Della Barba, Joe) You could try reading current with your multimeter instead of voltage. Small stray voltages likely exist when measuring between lead and SS even in fresh water but I doubt they will sustain much current. Just as an example of magnitude very roughly if there was a current of 1 amp continuously in normal soil it would corrode about 20 lbs of steel in a year. If you are reading less than 0.5 milliamp I would say those two surfaces are not going to have much corrosion between them. If you are seeing over a milliamp then there is an issue. The circuit requires two paths, the dissimilar metals in water and then something on the boat connecting them together. Some advice has been to connect the mast, standing rigging and keel together but do not ground them to the boats electrical system. That may be difficult if items like the VHF antenna is mounted to a metal bracket on the mast. You can test for this by measuring the resistance between the mast and ship's ground. Anything under 10 ohms would indicate a connection. Michael Brown Windburn C&C 30-1 Date: Tue, 14 Aug 2018 13:41:43 + From: "Della Barba, Joe" Voltage readings between what and what? Joe Della Barba Coquina Sent: Monday, August 13, 2018 7:25 PM Hi Alan The readings I posted are at anchor in the Thousand Island area. I almost never plug in during the cruising season. I only use shore power to charge the batteries during winter layup when the solar and wind are removed, every 6 to 8 weeks So today I did more testing. I disconnected the positive cable for the start battery and I still saw 0.02V at the prop shaft. So I ruled out that as an issue. I disconnected the battery charger and still saw voltage. Next I took the wind generator out of the equation and the results were the same. Next I disconnected the windlass, same results. Next I moved inside and checked for voltage on the tube for the centre board pendant. Saw 0.25 V. I removed the positive cable to the house electrical panel. Still saw voltage. Am I doing this right. My memory tells me that the way I?m testing might be creating some kind of battery but my memory might be tricking me. Could really use some help from any electricians or corrosions specialist out there. Mike C&C 37 K/CB Shoal draft Persuasion Stormont Yacht Club ___ 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
Re: Stus-List [EXTERNAL] Re: Galvanic corrosion (Della Barba, Joe)
I am still not clear on how the voltage is being measured and between what points. I have bronze thru-hulls that are not wired to anything. If I measured between them and the lead keel or the engine with the stainless shaft, I am sure I would read a voltage, they are dissimilar metals in salt water. Absent me wiring up the voltmeter, the thru-hulls have no connection to anything else and would not corrode. If you do have all these thru-hulls wired to ground, as is done on some boats, you now have a battery. You need to be sure there is a zinc involved in there somewhere and it had better have a good connection so that the zinc is the part of the battery corroding. IMHO and also the article referenced in another post, I like to make sure my seacocks and thru-hulls are NOT grounded. This eliminates the issue of poor contact to zincs and prevents the boat wiring from being a path for leakage between boats on one side of you and boats on the other, which is something a zinc will have a hard time saving you from. Joe Coquina From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Michael Brown via CnC-List Sent: Tuesday, August 14, 2018 1:53 PM To: cnc-list@cnc-list.com Cc: Michael Brown Subject: [EXTERNAL] Re: Stus-List Galvanic corrosion (Della Barba, Joe) You could try reading current with your multimeter instead of voltage. Small stray voltages likely exist when measuring between lead and SS even in fresh water but I doubt they will sustain much current. Just as an example of magnitude very roughly if there was a current of 1 amp continuously in normal soil it would corrode about 20 lbs of steel in a year. If you are reading less than 0.5 milliamp I would say those two surfaces are not going to have much corrosion between them. If you are seeing over a milliamp then there is an issue. The circuit requires two paths, the dissimilar metals in water and then something on the boat connecting them together. Some advice has been to connect the mast, standing rigging and keel together but do not ground them to the boats electrical system. That may be difficult if items like the VHF antenna is mounted to a metal bracket on the mast. You can test for this by measuring the resistance between the mast and ship's ground. Anything under 10 ohms would indicate a connection. Michael Brown Windburn C&C 30-1 Date: Tue, 14 Aug 2018 13:41:43 + From: "Della Barba, Joe" mailto:joe.della.ba...@ssa.gov>> Voltage readings between what and what? Joe Della Barba Coquina Sent: Monday, August 13, 2018 7:25 PM Hi Alan The readings I posted are at anchor in the Thousand Island area. I almost never plug in during the cruising season. I only use shore power to charge the batteries during winter layup when the solar and wind are removed, every 6 to 8 weeks So today I did more testing. I disconnected the positive cable for the start battery and I still saw 0.02V at the prop shaft. So I ruled out that as an issue. I disconnected the battery charger and still saw voltage. Next I took the wind generator out of the equation and the results were the same. Next I disconnected the windlass, same results. Next I moved inside and checked for voltage on the tube for the centre board pendant. Saw 0.25 V. I removed the positive cable to the house electrical panel. Still saw voltage. Am I doing this right. My memory tells me that the way I?m testing might be creating some kind of battery but my memory might be tricking me. Could really use some help from any electricians or corrosions specialist out there. Mike C&C 37 K/CB Shoal draft Persuasion Stormont Yacht Club ___ 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
