Ideas for preventing galvanic corrosion on rudder quadrant

[JPE]

Hey guys, I'm new here. Just wanted to see if anyone had any thoughts about a rudder quadrant I'm making for a friend's boat. The OEM rudder quadrant was cast aluminum, connected with one stainless through-bolt to a stainless rudder post. It corroded badly and is near failure. I am going to fab up a new rudder quadrant, and want to avoid future galvanic corrosion problems if I can. I'll be making the new quadrant out of aluminum, but putting a delrin sleeve between the stainless post and the bore through the quadrant. My question is about the through bolt. If I use a stainless through-bolt, I'm expecting to have at least some continued corrosion issues. I was considering a monel or bronze fastener, but now I'm wondering if that will just make my problems worse by introducing another metal to the mix. Does anyone have any clever ideas about how to through-bolt an aluminum rudder quadrant onto a stainless rudder post without creating a galvanic cell?

[tkeithlu]

Welcome to the forum, JPE.

Galvanic cells require an electrolyte. Where is the salt water coming from? Can you stop it?

Where are the anodes? A zinc should help you if it is nearby.

Absent substantial sources of salt water, galvanic problems are not as great as they might seem. I have bronze seacocks in a steel hull, but lots of anodes.

Bedding the bolts in a non-conductive material also helps.

Congratulations on your substantial project.

[thinwater]

Corrosion is bad, but I would give very careful consideration before placing a plastic sleeve on the shaft. This will reduce the grip on the shaft, place more load on the bolt, and increase the risk of loosing steering. Loosing steering is one of the leading causes of loosing a boat.

Is there really any risk of loosing the replacement quadrant to corrosion within the useful life of the boat or rudder shaft? I doubt it.

Keep it dry. Wash out the salt once in a while. I'd go with Duralac.

[Fuss]

Originally Posted by thinwater

Corrosion is bad, but I would give very careful consideration before placing a plastic sleeve on the shaft. This will reduce the grip on the shaft, place more load on the bolt, and increase the risk of loosing steering. Loosing steering is one of the leading causes of loosing a boat.

Is there really any risk of loosing the replacement quadrant to corrosion within the useful life of the boat or rudder shaft? I doubt it.

Keep it dry. Wash out the salt once in a while. I'd go with Duralac.

Yes, use Duralac, don't overthink it, It corroded due to a direct connection to the stainless in a salty environment. Clean and repair then use plenty of duralac between alu and stainless including a new bolt.

[double u]

second the Duralac, & how about painting with a good Epoxi after assembly?

[Gaia]

Good question, excellent answers. My first reaction was much like tkeithlu. Galvanic corrosion does not occur without an electrolyte. So if the area is dry no corrosion. But things on boats are not always dry. Add salt aerosols and condensation and presto, corrosion. I too second durable. We have had good success with lanolin as well. And Titanium bolts but I cannot remember off hand where it is on the scale nobility wise.

Jim sv Gaia

[zstine]

My quadrant is bronze. Why use Aluminum if it corrodes?

[Capt. Lace]

Originally Posted by JPE

Hey guys, I'm new here. Just wanted to see if anyone had any thoughts about a rudder quadrant I'm making for a friend's boat. The OEM rudder quadrant was cast aluminum, connected with one stainless through-bolt to a stainless rudder post. It corroded badly and is near failure. I am going to fab up a new rudder quadrant, and want to avoid future galvanic corrosion problems if I can. I'll be making the new quadrant out of aluminum, but putting a delrin sleeve between the stainless post and the bore through the quadrant. My question is about the through bolt. If I use a stainless through-bolt, I'm expecting to have at least some continued corrosion issues. I was considering a monel or bronze fastener, but now I'm wondering if that will just make my problems worse by introducing another metal to the mix. Does anyone have any clever ideas about how to through-bolt an aluminum rudder quadrant onto a stainless rudder post without creating a galvanic cell?

I would change to a stainless rudder. Get 316 ss for better corrosion resistance

[Searles]

Must be a lot af salt and water to cause that much of a problem ,if it’s a twohalfs Edison type quadrant do not put any thing between the alu and the ss rudder stock ,part of this system relies on the friction fit of the two faces ,the bolt usually only locates the quadrant vertically on the rudder stock there may also be a long key in the system ,spray with lanotec or similar should keep corrosion at bay for many years ,remember check your chain and cables these bont last forever and failure can ruin your whole day ⛵️��

[JPE]

Thanks for the thoughtful responses! I ended up doing a quick calculation on the effects the delrin sleeve would have on the friction between the rudder stock and the quadrant. Looks like adding the delrin would mean it would only hold to about 150 ft-lbs which I decided wasn't enough. I scrapped the delrin sleeve and we're just going to go with an aluminum stock on the steel rudder post with some duralac in the joint.

The original cast aluminum quadrant lasted nearly 50 years, so I'm hopeful this one will sustain the useful life of the boat. I did end up using a bit of stainless hardware in other places on the build, so I'm going to take a suggestion someone made here and seal it with a bit of epoxy to hopefully give a little bit more resistance to corrosion.

If anyone's curious, here are some pictures of the build from this weekend. Thanks again for the good suggestions!

https://imgur.com/a/s53NMrt