Hastelloy C22 corrosion on ambient temperature HCL duty (36%) 1

[Ryza00]

Hi we have been using a dry break coupling on a tanker offload facility where we offload 36% HCL at ambient temperatures.

The dry break coupling has been in service for approximately 1 year and the material of construction is hastelloy C22. We had a PMI test carried out to confirm this. The coupling recently started leaking and we disconnected it and found that it was corroded inside, see attached images.

When we specified this we did not see any issues with using C22 on HCL duty at these conditions and did not expect it to fail after 1 year in operation.

Has anyone had any experience with corrosion of hastelloy C22 at ambient temperatures? We will be sending this to a metallurgist to further investigate but was looking for other opinions as to the cause.

Thanks

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[ehbadger]

My book says for C-22 in ambient temp HCl at 36% to expect 5 mpy corrosion. Which isn't a lot, but would definitely be noticeable on the surfaces.

book: Materials Selector for Hazardous Chemicals (MTI Publication MS-3)

anecdotally, we use fluoropolymer lined equipment for all HCl offloading.

 

[moltenmetal]

Does this component stay immersed in acid continuously, or is it exposed to the atmosphere for part of its lifecycle?

Same here- I wouldn't mess with alloy components in a concentrated acid environment at room temperature. Polymeric materials and linings are just far more likely to last long term.

 

[Ryza00]

I believe the line is drained after offloading so the coupling will be exposed to the atmosphere after each offload.

I'm not sure why Hastelloy was specified as all other equipment we have on HCL duty is lined but I wouldn't have expected them to fail after only 1 year in service.

 

[EdStainless]

Because the line is drained, and then filled with air the part is exposed to all concentrations from 36% down to near zero. This variation will allow different forms of attack, and greatly shorten service life.
I would not use metal in HCl service where there is any option.

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P.E. Metallurgy, Plymouth Tube