Galvanic Corrosion Solutions

Garrett Green · Sep 8, 2022

I am designing Liquid Petroleum dividers and I am very worried about galvanic corrosion. The blocks will be made from Aluminum but the hose fittings will be brass. My first reaction was to anodize the aluminum but I already know I will be asked if we can avoid this to save a few bucks. I have looked at a few samples from other companies and none of their dividers are anodized and they are using brass fittings. This may be that they are fine putting out low quality where we will not.

My question is, Is there a thread sealant that will insulate enough to prevent galvanic corrosion? I feel like this would be impossible because while the sealant fills in the cracks the aluminum and brass threads will still be in contact. Hopefully someone smarter than me can let me know if I am way off base [bigsmile]

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Thank you,

EdStainless · Sep 8, 2022

Which Al and which brass? Alloy will matter.
What will cause corrosion? Is there water in the system?

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P.E. Metallurgy, consulting work welcomed

Garrett Green · Sep 8, 2022

The current plan is 6061 T6511 Aluminum, and obviously that will or will not be anodized based on the conclusion from this thread.
I do not know the Brass alloy yet but have reached out to the manufacturer for that information.

There will be propane in the lines and these will be installed on RV's so they will be exposed to the elements and will even have snow and salt sprayed up on them while driving down the road.

TugboatEng · Sep 8, 2022

Hard anodizing, type 3, holds up well in this environment.

For thread sealants, Loctite 545 is good for small diameter threads, 577 is good for all diameter threads. These are my go to sealants for petroleum applications. I don't know if you are expecting cryogenic temperature and I don't know if these sealants are acceptable for extreme low temperatures.

Garrett Green · Sep 8, 2022

is there a reason you suggest type 3 over type 2 in this case?

From what I know type 2 has plenty of corrosion resistance its just doesn't penetrate as deep and it doesn't harden the aluminum like type 3 does. I don't think either of those extra features are necessary here because they shouldn't see impacts or scratches that would compromise the type 2 anodizing.

I appreciate the suggestions for Loctite, 577 looks like it would be great for my application! These would have no effect at slowing down galvanic corrosion though correct?

EdStainless · Sep 8, 2022

Not directly, but a sealant will prevent corrosive fluid from getting into the threads.
The corrosion is often worse in these tight crevices.

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P.E. Metallurgy, consulting work welcomed

TugboatEng · Sep 8, 2022

Type 3 is thicker and will provide longer lasting protection in a salty environment. Type 2 is good for open air corrosion resistance while type 3 will provide more protection against galvanic corrosion.

Garrett Green · Sep 8, 2022

Thank you both for your help with this. I will plan on getting the blocks anodized. We get our hydraulic manifolds anodized with type 2 and those seem to hold up in roughly the same location these will be so I will plan to do that. However if we start seeing any issues I will look into switching to type 3 for more protection!

Thank you again.

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Galvanic Corrosion Solutions

Garrett Green

Mechanical

EdStainless

Materials

Garrett Green

Mechanical

TugboatEng

Marine/Ocean

Garrett Green

Mechanical

EdStainless

Materials

TugboatEng

Marine/Ocean

Garrett Green

Mechanical

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