I received a very interesting and rather informative message from Matt Esser in response to my post regarding excessive zinc anodes on Skiron. I asked for his permission to post his comments here and, rather than tacking it onto the end of my post, decided that it was worthy of a separate blog entry. Here are his comments…..
Good morning. I’m writing to you, because an item from your blog appeared on the Professional Hull Divers’ FB page this morning. After reviewing the mess with which you were greeted on hauling out your vessel at KKMI, I thought it prudent to share some observations.
Based on what I saw in your photos, the symptoms point to over-and/or under-protection. The symptoms of both can be identical to include blistering/flaking paint on and around hardware.
This photo shows a newly-installed, aluminum anode on a properly-prepped, clean surface, though you can clearly see what was happening to the paint around the old anode.
Additionally, zinc is problematic in our waters here in the Bay Area. In water that is less than ocean-level salinity, zinc anodes crust over in a matter of 3-4 weeks with a zinc-oxide layer which renders them inactive. So, even though you have too much anode on your boat to begin with, after a few weeks, it’s as though you have little or no anode protecting your metals.
Seeing growth on an anode is an excellent indicator that the anode is inactive
The anodes we use for our clients’ vessels are aluminum. The aluminum anodes don’t crust over when left untouched, rather the anodes foam over. This foam is still permeable to the transmission of electrons, which allows the anodes to continue doing their job.
Additionally, the aluminum anodes have a higher driving potential than their zinc counterparts, so one needs less “total anode mass” on the bonding system to offer the same level of protection. Aluminum anodes are significantly lighter and also generally cost a little less than zinc.
In a subsequent communication Matt recommended that I have a marine electrician evaluate the boat……
“I thought of something which I neglected to mention. In a case where this sort of issue has occurred, I would bring in a marine electrician to do a bonding system assessment. While the symptoms point to an over-and/or under-protection issue, it is also possible that there are faulty connections/wiring in the bonding system which could easily exacerbate the situation.”
Here is a link that Matt has provided regarding their services…..