Corrosion Mechanism Question

[ab1999]

We have an electrical connector in a piece of equipment installed in a subsea well (around 3V and 4mA passing through connector). Electrical connector is made of super duplex material with HNBR elastomer seal and Inc 718 metal seal and is threaded into 8630 body. We seem to be suffering minor corrosion in the 8630 which has failed the seals of the electrical connector allowing fluid encroachment which has shorted out the connector. The fluid around the connector ended up being pure methanol.

Is there anything we are missing in the system regarding material compatibility between the connector and main body that could be causing the corrosion. The corrosion is minor, but still enough to fail seals, and not what I would expect to see for crevice corrosion. Galvanic or general surface corrosion perhaps?

 

[EdStainless]

Have you replicated this in the lab?
The 8630 is failing where it is in contact with what other material?

I used to fill submerged connectors with Krytox grease. It is a mess and a pain, but it saved my butt.

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Rust never sleeps
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[TVP]

Is there any type of coating on the 8630 body? This will obviously be the weak link in a system with stainless steel and nickel alloy 718.

 

[ab1999]

I am catching up on what was done at initial installation (~7 yrs ago), but I believe there was a dry-moly spray applied to the bore which was likely removed by the connector manufacturer at installation.

As for lab testing, I am trying to get a hold of some of the same 8630 material from the manufacturer to perform lab testing.

My current plan is to assume that the corrosion is causing my seal failure and to clean out corrosion and apply a brush nickel repair to the sealing surfaces as well as look to apply some grease in and around the sealing areas to provide another barrier to fluid ingress. This should allow me to continue to use the same component (ie. get the seal bore in tolerance for diameter and surface finish) and reduce the corrosion potential between the duplex connector and mating body.