Mac26X Swing Keel Bracket and Pin Anti-Corrosion Sacrificial Aluminum Anode Washers

We have noticed that our Mac26X 304 SST swing keel bracket and pivot pin have suffered measurable galvanic pitting corrosion. While we have checked this over the years and throughly blended out the observed corrosion pitting it has repeatedly returned. We’ve also triple checked that there is not any form of active grounding or other circuit connected to the swing keel bracket assembly.

We tried using zinc washers but they proved to be difficult to find with a 3/8 inch diameter through hole. We also tried to self fabricate the zinc washers but they proved to be too brittle.

As we operate in both salt water, brackish and fresh water environments aluminum was determined to be a valid alternative to zinc.

We took 6061 baseline 2 inch wide x 1/8 inch thick aluminum strap to fabricate several 2”x2” square washers with 1/2” dia center holes.

We placed two of these sacrificial aluminum washers on either side of the swing keel and spaced apart by SST washers to maximize the water exposed surface area.

Aluminum is a lot more robust than zinc and still has good sacrificial anode capability, especially in salt and brackish water environments where we spend a good portion of our time and have incurred the most corrosion issues.

Best Regards,
Over Easy :-) :-)

For those not familiar with how a sacrificial anode material selection works here is a nice reference chart.
The ‘less’ noble metal will get consumed in an electrolytic environment before the ‘more’ noble metal.
So the further apart on the chart the metals are the more apt the ‘less’ noble metal will be consumed in an electrolytic environment.

As you can see Stainless Steel is at the bottom right as the ‘most’ noble metal on the chart.
As mentioned above zinc was too brittle and difficult to obtained… galvanized steel was out as after the (zinc) galvanizing is consumed the steel will rust (and making a Gawd Awful Mess in the process)…. So that is where Aluminum comes into play as a valid sacrificial anode.

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