Sealing surface, surface treatment 1

[HenHen]

Hi everyone!

I have a cylindrical enclosure with lids and radial O-ring seals in both ends, which will be submerged in seawater.
Ø approx 300mm. The enclosure is filled with dielectric oil, and it is pressure compensated(internal pressure and seawater ambient pressure is equalized)
The cylinder itself is coated in norsok sys 7, and also has sacrificial anodes attached.
I'm unsure of how to handle the sealing surfaces. Applying coating to the sealing surfaces might make the surfaces too rough
for the O-rings to seal properly, and not applying coating to the sealing surfaces seems like a bad idea, seeing as the cylinder material is S355..

Anyone have any experience on the topic? Surface treatment of radial sealing surfaces of non stainless steel.. Pressure equalized.

Nothing has been made yet, still beeing designed.

 

[Compositepro]

Suitable submersible grease should aid sealing and provide corrosion protection.

 

[adamgnt]

I take it only the outer surface on the cylinder is being coated then?

I think your two options here would be a material change (out of curiosty what drove the decision of S355 instead of 316L?) or else trust your zincs to do their jobs as the components will be electrically linked. A cursory search yields that Norsok Sys 7 leaves a 50-85 micron finish which substantially rougher than the ~32 usually specced on an o-ring seal. You may get away with it with enough o-ring squeeze, but keep in mind that your seal should outprioritize your corrosion protection.

My vote would be to switch material, but that's mainly due to all past pressure vessel experience being either Bronze alloys, Ti, SS or anodized 6061 AL.

Also agree with Compositepro, grease the hell out of those bad boys regardless.

 

[HenHen]

Thank you for the replies! I have changed the material to 316L. The outer surfaces will be coated yes, the internal ones will only be primed, to give some additional protection should the oilfilled enclosure become waterfilled enclosure=| The sealing surfaces will not be coated.
I had to go with radial O-ring seals due to size restrictions, but I am concerned about crevice corrosion in the sealing area. Does anyone have any experience with how well 316L is protected from cervice corrosion when connected to CP?