With the shaft and prop both stainless and the boat on a mooring I wouldn't expect the zincs to disappear very fast. Probably very close to the ideal situation.
A galvanic isolator would gain you nothing if not connected to shore power.
Should I replace these zincs?
- Thread starter Rich Stidger
- Start date
- Status
A galvanic isolator would gain you nothing if not connected to shore power.
The Zinc caper...the rest of the story
Today I tackled my prop and shaft. The first thing I did was to measure the resistance between the two zincs from last season and the corresponding shaft and prop.
The 1.25" CAMP zinc that showed very little erosion measured 17 ohms to the shaft. This brand of zinc has the two copper balls on the inside to presumably make better contact with the shaft.
The 3/4" Martyr zinc (Canadian Metals) that showed more normal erosion measured to be under 0.2 ohms to the prop. This zinc has no copper balls inside.
See the pictures below- Where the 1.25" CAMP zinc was located on the shaft there was significant white deposits, while the mounting area of the Martyr zinc showed much less white deposits. More deposits appears to cause a higher resistance. The higher resistance, 17 ohms vs 0.2 ohms, may likely be the reason that the larger 1.25" zinc was not eroded very much.
Taking a look at the inside of these two zincs, the 1.25" CAMP zinc has lots of white deposits inside that corresponds to the deposits on the shaft. The 3/4" Martyr zinc has much less deposits on the inside.
You can see a flat spot on the copper ball in the CAMP zinc and a corresponding blemish mark on the shaft that suggests the zinc was in good contact with the shaft- but the resistance was higher and the erosion was less. Go figure.
So, inquiring minds probably want to know what I did. Well, I installed two new zincs, both of them Martyr brand and neither of them have the internal copper balls. I measured the resistance after installation and found both to measure "zero". I did give them a good whack with a hammer although I think that I remembered that a whack was not necessary for the Martyr ball-less design.
The bottom line is that I believe that my low erosion of last seasons 1.25" zinc was due to a poor connection to the shaft. However I would have expected that the erosion of the other zinc might have been more to compensate, but that doesn't seem to be the case. In any event maybe we don't need zincs with balls.....
Today I tackled my prop and shaft. The first thing I did was to measure the resistance between the two zincs from last season and the corresponding shaft and prop.
The 1.25" CAMP zinc that showed very little erosion measured 17 ohms to the shaft. This brand of zinc has the two copper balls on the inside to presumably make better contact with the shaft.
The 3/4" Martyr zinc (Canadian Metals) that showed more normal erosion measured to be under 0.2 ohms to the prop. This zinc has no copper balls inside.
See the pictures below- Where the 1.25" CAMP zinc was located on the shaft there was significant white deposits, while the mounting area of the Martyr zinc showed much less white deposits. More deposits appears to cause a higher resistance. The higher resistance, 17 ohms vs 0.2 ohms, may likely be the reason that the larger 1.25" zinc was not eroded very much.
Taking a look at the inside of these two zincs, the 1.25" CAMP zinc has lots of white deposits inside that corresponds to the deposits on the shaft. The 3/4" Martyr zinc has much less deposits on the inside.
You can see a flat spot on the copper ball in the CAMP zinc and a corresponding blemish mark on the shaft that suggests the zinc was in good contact with the shaft- but the resistance was higher and the erosion was less. Go figure.
So, inquiring minds probably want to know what I did. Well, I installed two new zincs, both of them Martyr brand and neither of them have the internal copper balls. I measured the resistance after installation and found both to measure "zero". I did give them a good whack with a hammer although I think that I remembered that a whack was not necessary for the Martyr ball-less design.
The bottom line is that I believe that my low erosion of last seasons 1.25" zinc was due to a poor connection to the shaft. However I would have expected that the erosion of the other zinc might have been more to compensate, but that doesn't seem to be the case. In any event maybe we don't need zincs with balls.....
Attachments
Rich,
Interesting that the spot on the shaft where the copper ball was is perfectly clean - as is the flat on the copper itself. So, obviously the ball was doing its job in making contact with the SS shaft to the extent it remained proud of the zinc as witnessed by the corrosion between shaft and zinc..
Would be interesting to know if the ball was actually making contact with the zinc???
Interesting that the spot on the shaft where the copper ball was is perfectly clean - as is the flat on the copper itself. So, obviously the ball was doing its job in making contact with the SS shaft to the extent it remained proud of the zinc as witnessed by the corrosion between shaft and zinc..
Would be interesting to know if the ball was actually making contact with the zinc???
Donalex- Good thought! I have saved the zincs and I will measure them later this week and post the result.
Today is a steady rain, gray, and only about 60F. I am scheduled to launch later today but I still have outside work to do. Maybe I will launch tomorrow when it is supposed to be nice. I feel bad, the yard has jumped through hoops to clear all the boats between me and the water.....
Today is a steady rain, gray, and only about 60F. I am scheduled to launch later today but I still have outside work to do. Maybe I will launch tomorrow when it is supposed to be nice. I feel bad, the yard has jumped through hoops to clear all the boats between me and the water.....
Donalex,
I measured the resistance of the copper ball to the zinc on both halves and found the resistance is be "0".
So I guess the mystery is still - "Why didn't this zinc have a good connection?"
I measured the resistance of the copper ball to the zinc on both halves and found the resistance is be "0".
So I guess the mystery is still - "Why didn't this zinc have a good connection?"
- Status