Coating of Subsea 316 SS Valve Sealant Injection Piping? 2

[Naijatium]

Hi,

I have found valuable information on this forum and this is my first time here.

I'm working on a project involving fabrication of flowlines and subsea structures. We have a valve sealant injection Piping made of 316 SS. There has been a back and forth on "coating and not coating" of the 316 piping. My question is does the coating provide extra protection for the 316 SS considering the seabed (burial conditions), seawater and 30 yrs design life? Also, would the coatings help prevent the occurence of hydrogen embrittlement since we have welds on the piping and cathodic protection of the whole subsea structures?. Thanks for your help.

 

[jbknudsen]

Coating the 316SS may offer additional protection however there are many factors that will coinside with the Hydrogen embrittlement, ie, levels at sea floor, temp, region the equipment is deployed.
We manufacture equipment designed for 20yrs that operate at 10-15 ksi and are designed and tested for 10,000 feet of water depth. All of our control lines are 316SS. We have never coated the lines, nor do we plan to. We have not had any type of corrosion, or cracking on any of the lines.

I dont have any firm scientific evidence for you, however i can state we do not coat SS fittings or control lines for our sub sea equipmeht.

i hope this helps,


Jay

 

[Naijatium]

Jay,

Thanks for your response. The debacle is there have been reports of recent corrosion of 316 SS for subsea applications (not sure of actual operating temp and process data). Will there be a form of crevice or galvanic corrosion if the 316SS piping are buried on the seafloor with the flowlines? the conditions are 125 - 270 ft depth, temp at seabed is between 38.7 - 46.9F and max operating temp of the flowlines and subsea system is 57F.
Again, thank you for your help.

 

[SJones]

316L is an austenitic alloy and not prone to CP generated hydrogen embrittlement unless something has gone badly wrong! If there is a good CP design which accounts for the piping being uncoated, then the pipe can be left bare as its only real purpose will be to reduce the CP current demand.

To settle the argument, refer to EEMUA 194, subclause 11.2.1

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[Naijatium]

Thanks SJones for the reference guideline. It clears the air on the issue. Thank you all for your input, I do appreciate them.

 

[EdStainless]

You can't get HE failures in austenitic alloys, it just doesn't happen.
Pitting or crevice corrosion are another matter.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[Naijatium]

EdStainless, I agree that 316 SS would be immuned to HE. My other question was the possibility of crevice corrosion if the 316 SS was buried?