Carbon Steel and 304 SS performance in chloride solution

[bbakes]

Howdy, Eng-Tip users,

I have a de-commissioned plant that we are trying to re-use at a different site; however the new feed stream has ~2000 ppm Cl-.
The CS steel tanks will see a solution pH of ~10, while the 304SS will see ~ 3-5. The entire process will be at ambient temperature (assume 20°C).

My initial thought is that both the CS and the 304SS tanks will need a passive coating applied to them. Anyone out there with evidence to the contrary? Failing that, any recommended coatings for the CS and 304SS tanks?

Thanks in advance,
Cheers,
Brent Baker

 

[davefitz]

If the operating temperature is low enough , you may want to get an estimate to replace the tanks with FRP or polypropylene tanks.

Also, the corrosion issue is not limted to tanks- piping,valves, pumps etc have cossion issues as well.

 

[stanweld]

bbakes,
Without more info re pressure and feed stream make up, it's impossible to provide meaningful answers to your post.

 

[bbakes]

Thanks for the replies so far.

I'll try and answer some of the queries.

Pressure: the carbon steel tanks are all open top, so therefore will operate at ambient pressure. The 304SS tanks are operated under a negative pressure, sealed and vented to a scrubber.

Feed make up: Unfortunately, I don't have an ICP analysis of the feed stream. I only know it is a BLS from a gold plant. So it will contain CN, be about a pH of 9.5, and contain Cu, Ag, and Au. It shouldn't contain much Fe2+ or Fe3+.

Piping and valves: most of the piping/valving from this plant is PVC, so no worries on that front. Just interested in re-using the steel tanks.

Cheers,
Brent

 

[unclesyd]

What is the size of your CS tanks?

 

[EdStainless]

304 will suffer serious pitting at that pH and Cl.

Line the CS tanks with resin.
Don't use 304 in 2,000ppm Cl, even with liner.

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