Refurbishing a Zinc Anode

[Kenomac]

At $65 for a new primary anode, I decided it was worthwhile to spend 15 minutes refurbishing the old one using a grinder.

[hpeer]

I do the same.

[SVRocinante]

Good day

First, I don't KNOW a darn thing about anodes, so please excuse the question if it's completely off base.

It was my understanding that an anode works by sacrificing it's less noble metal in order to save the more "important" metal parts on your boat.

Does grinding away the parts that have started to get "eaten up" prolong the overall life of the anode?

Thanks!

[Kenomac]

Sometimes anodes become pitted and appear much worse than they really are. In the case of the one pictured above, after grinding off the calcium deposits or corrosion to expose new shiny zinc, there was still more material left on the old zinc than on the new replacement anode. So rather than throwing it out because it looked bad, I can probably get another 2-3 years service out of the thing.

[barnakiel]

Yep. This one looks perfectly fine to live on.

Some say replace when 50% gone.

Cheers,
b.

[a64pilot]

Originally Posted by SVRocinante

Good day

First, I don't KNOW a darn thing about anodes, so please excuse the question if it's completely off base.

It was my understanding that an anode works by sacrificing it's less noble metal in order to save the more "important" metal parts on your boat.

Does grinding away the parts that have started to get "eaten up" prolong the overall life of the anode?

Thanks!

I don’t believe so, as long as the metal is there, there is protection.
However when most of the metal is gone, likely so is a lot of the protection.
If your really getting five years or so out of an anode, you could almost say it isn’t needed. I’m hoping to get six months, I used to be lucky to get 90 days. My only anode is the prop anode.

I had an anode on my Mercury Verado that was lasting almost forever, it was just getting calcium covered like the one in the photo, turns out it didn’t have an electrical connection to the motor, once I removed the glossy paint that had it insulated, it started wasting at the same rate as the others.
If your getting years out of an anode, I’d strongly suspect it may not be in electrical contact with the ships grounding system, and may just be a lump of metal underwater.

[seasick]

In the course of my summer's commercial salmon trolling in Alaska, I use to take the time to visit many tidal grids around Southeast AK and pick up literally tons of used zincs that had been discarded on the sand. During the winter months I would melt these down and recast them in bread pans and other molds.

[mikemilt]

[Dan_K]

The chemical composition of the zinc anode is critically important. Iron needs to be limited to 0.025 weight percent of the anode. With a high iron content the zinc will form a crust and cease to be a sacrificial anode. I did a failure analysis of a very large steel ship that suffered millions of dollars damage due to pitting of the hull. To "save" money they bought anodes made in someone's basement that contained much higher iron than the specification allowed. All the zincs formed this crust and allowed the pitting to occur. Please be very careful with your zincs.

[savoir]

I'm not too sure that grinding an anode does anything to extend its life. On the other hand it will look nice.

[meirriba]

Originally Posted by SVRocinante

Good day

First, I don't KNOW a darn thing about anodes, so please excuse the question if it's completely off base.

It was my understanding that an anode works by sacrificing it's less noble metal in order to save the more "important" metal parts on your boat.

Does grinding away the parts that have started to get "eaten up" prolong the overall life of the anode?

Thanks!

No need to grind or clean the eaten area as long as the metal in this area is zinc. If any area of the anode is covered by any foreign substance then you help by removing the deposit and exposing the zinc.
By the way, if the anode is covered, e.g. by calcium deposit or anything else it will "prolong" its life as the anode will cease to function...

[northwestsailor]

As an aside. Does anyone know of a commercial operation in the Bay Area that will re-cast zincs to order. I have 6 zincs which I hang over the side in suspect marinas but several are near the end of there useful life.

[buzzstar]

What am I missing? Is there any reason to replace an anode based upon looks? I think they are solid, more or less pure metal (zinc) and there was no reason to replace them until they were sufficiently used up to reduce their effectiveness or affect the structural/attachment strength. To that I have added an annual (more or less) inspection and convenient opportunity.

[Rough Magic]

They also depend on the amount of surface area to have the proper amount of electrical effect for protection. Hence the good advise to replace after 50% gone. For me, for what it costs to repair electrolysis damage, just not worth taking a chance.

[FabioC]

This may also be a stupid question, but I am confused...
Why do you need to grind the anode? If there is still enough material for the anode to work, then it will continue to work regardless (calcium accumulation is not an issue, the anode work with calcium on it as well), if there is not enough material, then it is gone regardless...
What am I missing?
Cosmetically, I can see that used anodes look horrible, but they are very hard to see, so I am not sure it is worth to get them out and put them back on just for cosmetic reason.