Galvanic Corrosion Prevention Options 1

[vbaldwin]

Hi everyone,

I'm currently working on a project where the client wants all 316 fasteners on a polyurethane bend restrictor. However, on the bend restrictor, on the droop line, we've added a clump weight made out of carbon steel (cost reasons) and I am trying to determine how to prevent galvanic corrosion. I plan on coating the clump weight and adding a welded on anode, but I'm trying to determine if this will be enough, AND what type of fasteners I should use. Any help is appreciated!

 

[SwinnyGG]

Are you saying the weight will be threaded and attached with stainless steel screws? Is this a subsea application? If so, that's probably a no-go unless it gets coated after assembly. If it's through bolted, you need to completely isolate the 316 from the carbon steel using washers/sleeves with good dialectric properties.

 

[Tmoose]

What are the dimensions of the " clump weight " and why ?

 

[dik]

even galvanising the carbon steel won't help...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[EdStainless]

Swinny has it, you can't thread the SS into the steel unless this is a short lived application.
You can pass the SS through the steel, but it must be fully isolated with non-conductive washers and sleeves.
Could you attach the weights with fiberglass bolts?

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P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

Does the clump weight require a specific weight? If not, you could make it larger and simply let it corrode.

 

[EdStainless]

Or make the weight concrete?

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P.E. Metallurgy, consulting work welcomed

 

[SwinnyGG]

Or make the weight from the same alloy as the bolts?

 

[SSCon]

Adding an anode is the correct approach. With the anode in place you need to ensure electrical continuity to the fasteners, as in remove paint underneath them. The anode will prevent any galvanic corrosion between the SS and CS. It will also prevent the 316L fasteners from corroding.