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I work on a commercial diving vessel in the Persian Gulf. We have equipment that regularly goes sub sea. On occasion this equipment springs a gas leak, the gas leaking is a mixture of oxygen and helium (Heliox), usually somewhere between 8% to 18% oxygen. When a small leak occurs and goes unnoticed for some time there is a white buildup aroud the leak area. These buildups can grow quite significant in size compared to the leak and, in the odd case, self seal the leak!

The best way I can describe it is a calcification, it is brittle and breaks off quite easily into granule not unlike sand. The metal components involved are 316 stainless steel and Tungum, which is a brass alloy with aluminium in it, but the buildup occurs anywhere there is a leak, so I don't think the metals are relevant.

I am hoping someone here could explain this phenomenon to me, if this is not the right place for a question like this I apologies and ask if you could point me in the right direction.

Image of buildup on leaking pipework

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Is that deposit everywhere, or only below water? If under water, likely some marine organisms are taking advantage of a steady O2 supply. Examine the deposit under a microscope. If the ship is engaged in petroleum exploration, there might be a petroleum geologist aboard who would be familiar with foraminifera, likely colonizers.

For a citation, "Species of benthic foraminifera presumably colonized the bacteria- and diatom-rich biofilms on the metallic surfaces of... petroleum platforms soon after their emplacement."

The heliox mix should not leave a residue, by itself -- one wouldn't want to breathe anything that left deposits like that!

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    $\begingroup$ Hi Dr Pippik, thank you for the reply. Yes the equipment is subsea for prolonged periods of time so marine growth does make sense. Although we are in the oil and gas industry we do not have a geologist or a microscope onboard. That would have been interesting to see. The deposit (or growth) is not negatively effecting any operations, in fact it makes leaks easy to identify and correct, just interested in causes. Thank you again for your reply. $\endgroup$
    – Dalmain
    Jun 13, 2023 at 15:41
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    $\begingroup$ @Dalmain, it might be worthwhile using a pair of magnifying glasses, or an inexpensive USB microscope, to take a look. Some of these critters shells are incredible: paleonerdish.wordpress.com/2013/06/17/… $\endgroup$ Jun 13, 2023 at 15:47
  • $\begingroup$ Could you comment the image displayed in the first question ? What is the red light ? What is the white stuff near the junction ? Is it the result of corrosion? Why is there a junction ? Has water entered the gas tubing ? Why don't we see any bubbles around ? $\endgroup$
    – Maurice
    Jun 13, 2023 at 20:14

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