Reliance or Sea Shield are excellent. Camp is the worst, IMHO.
Navalloy's by Performance Metals
The Hatt had a lot of zincs involved, including four shaft zincs, four small trim tab zincs, two big rudder zincs and one for the thruster, and we had occasion to visit some fairly "active" harbors, so this was something I paid a fair amount of attention to.
Could be....even using the right type for the conditions (zinc alloy, aluminum alloy, or magnesium alloy) can be a struggle to get right.OK, got the zinc content piece as a benchmark, George. Is that it or are there other factors? I've heard people gripe about "bad zincs that rapidly deteriorate" - seems to me that's an indicator that the zinc is doing its job in an active situation - not a defect. Am I right, so far?
Given the number of zincs that you replace every year, I would tend to listen to your opinion.
That is a bit of an apples to oranges kind of comparison since Performance Metal's Navalloy is an aluminum alloy anode material, not zinc. I was looking at their anodes a while ago and at least their marketing materials are well done. They make a good argument for Navalloy, at least to me (who knows nothing and is easily swayed).
I am likely going to be putting on a bunch of zincs today at the survey. To be honest, I have never paid a lot of attention to zincs in the past other than to replace them or have them replaced as needed. I only have three on my current boat and other than the Autoprop zinc, they are all very inexpensive. I was impressed and surprosed by simply the weight of the box that I got from Boatzincs.com for the zincs for this new boat.
However, I would think that judging zinc performance would be tough. If a zinc is used up quickly is it because it is poor quality, or that it is doing a better job of protecting your boat? The converse is true if the zincs last a long time.
OK, got the zinc content piece as a benchmark, George. Is that it or are there other factors? I've heard people gripe about "bad zincs that rapidly deteriorate" - seems to me that's an indicator that the zinc is doing its job in an active situation - not a defect. Am I right, so far?
What PS said: IOW Zinc.
Beyond that it's all smoke and mirrors
A nice independent study link would be interesting.
The only experience I have professionally with galvanic protection and measuring the effectiveness of zinc is to measure the difference in protection once zinc is attached to see if the metal is properly protected. Using the silver-silver chloride probe and a multimeter.
Corrosion Reference Electrode Product Specifications
The rate at which a zinc dissipates may have little to do with it's quality...and the perceived quality over protection...it's all about protection in the long run.
What PS said: IOW Zinc.
Beyond that it's all smoke and mirrors