Zinc Usage

[Pete]

Last year this time our 48 LRC was going back in the water after 7 weeks on the hard getting a new barrier coat, bottom paint, balanced wheels, and zincs. Installed two diver plates, three zincs per shaft, 1 each on rudders, and bow thruster zincs. Yesterday, had a diver clean the bottom, check for blisters, and prepared to change zincs. First GREAT news is no blisters that he could see after a year. Second unexpected news was all zincs were at least 80% still in place. The boat spent 3 months on the Chesapeake, another month of assorted salt water trips, and 8 months behind our house in brackish, 90 degree plus summer temperature, acidic water (yes, acidic enough that it eats concrete bulkheads). This performance is much better than in the past. Usually after a year all but the diver plates are ready for change. So, what did it? I do not know.

But I did change out the hot water heater. When I did that, I decided that I did not like the 240 heating element as hot water thermostats are all single pole switches. This leave one side of the coil at 120 volts to ground at all times. I know the theory that AC does not cause electrolysis. But I went for a 120 volt/1500 watt heating element so it would switch off all power to the coil when not heating water (only the white wire neutral is attached to the coil in idle state). Did this help? Again, I do not know.

Just some facts for a Sunday morning.

Pete

[REBrueckner]

Good news for unexplained reasons is unusual...here are a few possible contributing factors:
If you added additional zinc mass last time that could explain part of the extended life;if the boat was kept in different locations in the past, say more salt water or a lot more running or both, that could also be a factor; Maybe a neighbor rewired THEIR dock and eliminated a source of stray currents in the water; was there a lot more rain the last year..more fresh water?? (would that add or decrease acidity??)

Your hot water tank comment is interesting....If your description is correct (single pole thermostat switch) it could definitely be a contributing factor because while ac current isn't as damaging as dc, it does have some effect....