Hastelloy C-276 and Sodium Hypochlorite

[Angsi]

Location: Offshore Platform
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I understand Hastelloy C-276 reacts with sodium hypochlorite which is used on offshore platforms to prevent marine growth/fouling of pipework. 2 ppm is what we will normally specify for continuous dosing and for intermittent shock dosing, 4 ppm.

Can someone please advise me if these dosage rates will adversely affect the Hastelloy materials?

Thanks in advance.

 

[monaco8774]

I should start by saying I am not a metalurgist, however I do operate dozens of vessels equipped with hypochlorite injection systems to control marine life and have stainless steels of different types aboard. Firstly we use 0.5 ppm for continuous and 2ppm for batch and it keeps marine life in check. So your dosages seem high. Secondly of the choices Hastelloy is about the best, we have always had horror stories in the design phase for crevice corrosion at temperatures above 40°C but actually we come out of some of our exchangers at 80°C + and never seem to have any crevice corrosion. We do have problems with 316 SS and dont use that anymore and we do have problems with duplex stainless steels if we get our welding wrong, but of we do that correctly we dont get any problems.

 

[Ashereng]

You should contact a metal specialist. Maybe try moving this posting to the steel/stainless steel forum.

I have found EdStainless to be a very good source of metal answers.


One of my experiences with sodium hypochlorite application was at temperature, and most of the Hastelloy B and C we were looking at were for the most part okay chemically, but not temperature wise.

I recall Hastelloy C4 being the final choice. But, you need to talk to someone who specialize in metal.

 

[EdStainless]

Monaco is right on with the dosage numbers. A lot of power plants use 0.5ppm cont. with periodic burst levels of 2-5ppm. The higher levels are for 1 hour every other day or so.

The only C276/hypo problems that I have ever seen are at the injection quill itself. You have to be careful there.

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