February 21, 2013 | by Ben Lee
I recently sat down with Shane McCall of Emerald City Diving to talk about non-zinc anodes and get his take on the effectiveness of the aluminum alternatives to zincs. Here’s what we talked about:
CBF: Thanks for your time here, Shane. I’m just going to ask you a few questions to get your professional diver perspective on how these non-zinc anodes are working in Puget Sound waters. First of all, how are these aluminum anodes comparing to the more traditional zinc anodes?
Shane: The aluminum anodes are actually working just as good, if not better, than zincs.
CBF: Okay, cool – that’s good to hear! Where are most of the boats that you dive on?
Shane: My shop is in Ballard but we’ve got a boat at Elliott Bay Marina. Most of our work is there at ElliottBay but we do get some work on boats in the Ship Canal and on Lake Union.
CBF: What anodes are you putting on boats in the fresh water of the Lake/Canal?
Shane: Honestly, I feel good about putting aluminum anodes on boats on the Canal, too. They say that aluminum anodes are best for salt or brackish water and magnesium anodes are best for fresh water, but a lot of the boats on the Canal go back and forth, through the locks, between fresh and salt water. The magnesium anodes would dissolve pretty quickly [in a matter of weeks, according to the manufacturer] in salt water. There doesn’t seem to be any problem for the aluminum anodes going back and forth from salt to fresh, like there is for the old zincs [ie. developing a permanent zinc oxide crust while in fresh water].
CBF: What kinds of hulls do you feel comfortable installing aluminum anodes on?
Shane: I put them on everything, including aluminum hulls.
Shane: Yes. The aluminum anode isn’t just a hunk of aluminum – it’s an electrically more active alloy mixture. It’s more active than the aluminum hull material, protecting even those boats.
CBF: Interesting. I’ve heard that aluminum anodes tend to wear away differently than zincs.
Shane: Yep – zincs wear away by finer grains, resulting in a smoother surface. Aluminum anodes wear away a little differently – more even over the whole anode and looking a little more pitted, kind of like pumice. But the aluminum anodes, from what I’ve seen, are lasting just as long as the old zincs. And they’re about half the weight.
CBF: Wow. Do you see any downsides to aluminum anodes?
Shane: Not at all in their performance. The only thing that’s kind of a pain about them, as a diver, is in their fastener system. The nuts on the aluminum anodes are free and so they’re not the easiest to work with underwater. Installing them while hauled out would take that issue away, though.
CBF: Alright, thanks a lot for your time, Shane. How can boaters get in touch with you if they need some diving services?
Shane: No problem. They can go to my website at http://emeraldcitydiving.com/ or give me a call at 206-789-8000.
We’ve got some photos of aluminum anodes here if you’re curious to see how they wear away differently than the more traditional zinc anodes.
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