Rudder pitting?

[croakz]

Hi,

We just had a survey done on a R25SC and one of the finding was,

"Pitting and dezincification was noted on the bronze rudder, most likely from galvanic corrosion. The rudder has lost some of its structural integrity and will need to be replaced."

They didn't say this was an immediate thing, so is pitting something that can be stopped with rudder anodes or will it continue to deteriorate? It seems like a rudder replacement is a pretty significant cost, so I'm wondering if I need to do it now, or in a couple years.

Thanks.

- tom

 

[scross]

Others have reported the same pitting issue on this forum - though not to the point of structural compromise that I remember.
One solution to galvanic corrosion is to install pancake zincs directly to the rudder. These need to be monitored and replaced as needed.
A second method, one that I use, is to spray the rudder (and prop) with a zinc heavy paint like Pettit's Prop Coat Barnacle Barrier 1792. If my boat was in the water full time I’d check the protection every few months. Since my boat is not in the water most of the year, I only apply the zinc paint every year or even every other year as needed.
A third solution is bonding the rudder. For my boat the rudder is tied to the boats bonding system. A big common sacrificial zinc below the waterline on the stern is connected to all bonded components.

PS: I even have a set of pancake zincs tied to the bonding system on a copper wire cable that I drop out into the water from the cockpit at places I consider to be “hot” marinas.

PPS: Just in case the problem is caused by “prop burn” rather than galvanic corrosion you might want to review this thread.
viewtopic.php?f=2&t=6818&hilit=Rudder+pitting

 

[ohioan55]

I'd also look into adding a galvanic isolator to your electrical system, if you don't already have one.

 

[GaylesFaerie]

On my 2012 R27 there is a braided metal strap connected to the rudder assembly under the stern seat. That strap should be connected to the bonding system. On my boat the strap itself is showing significant wear and corrosion and is in need of replacement which I will do this coming winter.

Search the forums for: "Braided Strap on rudder".

Once tied into the bonding system you'll be relying on the prop acorn anode for corrosion protection. As noted multiple times on this forum that anode can and often does "come off" and there are multiple solutions to keeping it in place.

See: http://www.tugnuts.com/viewtopic.php?f=6&t=20122&hilit=+anode&sid=058c17c2f8ae7168ba07d21afb265612

I also backed up my entire bonding system by installed a donut transom zinc tied direction to the bonding bus bar and the prop shaft.

Search the forums for: "Need Shaft, Prop & Rudder Bonding Advice".

HTH, Gary

 

[Captain Mike]

Agree with the puck zinc attached directly to the rudder.
After my last haul out, while i did not have a pitting issue, there were barnacle issues. boat yard recommended a product called "prop Speed". Not cheap but two years later, both the prop and the rudder are clean as a whistle. No barnacles and no pitting.
Seems like $300 well spent.

 

[ohioan55]

I have also applied prop speed, and like the product. I actually picked up a little speed.