Water Treatment Laboratory Corrosion 5

[bimr]

Does anyone have an explanation for this corrosion?

This application is a remodel of a water treatment laboratory. The equipment is all new. The trough sampling sinks are made from Gauge 316L-2B stainless steel. The other items like the drawer pulls and safety eyewash are 316 stainless steel.

The trough sinks are used for water quality control and the water runs continuously. The trough sinks have the worst corrosion. As you move farther away in the room, the corrosion on the other fixtures lessems.

October 2020, photos were taken of new rusting stainless-steel products in the Control Lab. New stainless-steel eyewashes, new stainless-steel tub sink, and new stainless-steel cabinet handles were all showing significant signs of rust.

March 8th – 10th, 2021 the new stainless steel trough sinks were installed and were not cleaned or polished at that time. Within a week, these items began showing signs of
rusting.

On April 5th, 2021, the new stainless steel trough sinks were cleaned and polished along with other existing stainless-steel products. Within a week, they began showing signs of rusting again.
On May 27th, 2021, Owner polished the new stainless-steel trough sinks. Within a week, they began showing signs of rusting again and photos of the current condition of the new stainless steel trough sinks are included.

 

This is potable water with 20 mg/L of chlorides. Not significant chlorides.

That is more than enough to cause SCC when you add a bit of temperature.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[EdStainless]

I would not be too worried about CSCC in this application.
I have seen it in very high stress hot water applications, but I doubt that they get a sink hot enough.

It certainly is Stain-less steel. Not stain-proof or even as the Germans say rust-free.

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P.E. Metallurgy, consulting work welcomed

 

Take note of what Ed and Tugboat said. Easiest way to know if you do have high chloride content is to have a lab do EDS analysis on a removed sample, if you can spare one.

EDS is probably not capable of that. A wet chemistry lab can give you a quantitative measure of anion content in a water sample at very low cost. Refineries have water samples tested there daily, and I've used them numerous times for just the same purpose when investigating failures.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

No need to offer speculations into all the ways 316SS can be attacked. There were only ever two possibilities:

1) With all the nasty stuff dumped into these sinks on an hourly basis, 316 is not up to the task. A useful bit of directly applicable evidence is the material that was previously used to do the same job.

2) 316SS is up to the task, but this equipment arrived in a compromised condition, leading to very rapid corrosion over a wide surface area.

Rather than analyze case #2 to death, I would research whether #1 is the case.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[mrfailure]

EDS actually is quite capable. I usually find significant chlorine peaks when analyzing SCC-related failures in 304/316. This confirms the material was exposed to high concentrations during service.

 

[bimr]

No need to offer speculations into all the ways 316SS can be attacked. There were only ever two possibilities:

1) With all the nasty stuff dumped into these sinks on an hourly basis, 316 is not up to the task. A useful bit of directly applicable evidence is the material that was previously used to do the same job.

2) 316SS is up to the task, but this equipment arrived in a compromised condition, leading to very rapid corrosion over a wide surface area.

Rather than analyze case #2 to death, I would research whether #1 is the case.

Read the posts carefully. These sampling sinks only have potable water running into the sampling sinks. The previous sampling sinks were the same material.

 

And?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[bimr]

So there is no "nasty stuff dumped". And the "material that was previously used to do the same job" is the same.

 

[EdStainless]

When I have had to show this effect to customers I use a very simple test.
Mark off a few place 12" x 12'.
Get some clean lab wipes (texwipe or similar).
And some very high purity water.
And some sip seal bags.
Wet one wipe and put it into a bag labeled 'blank'
Then dampen another wipe and thoroughly wipe area #1, put into bag #1.
Repeat as often as you like with other areas.
Send them our for Cl analysis. This is very straight forward.
I have seen SS material with serious surface corrosion and only 5 micorgrams/sqft of total Cl.
Wet dry is the real killer combined with less than optimal surface condition.

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P.E. Metallurgy, consulting work welcomed

 

What is a lab without chemicals?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[bimr]

There are other (non-metallic) sinks beside this sampling sink where the "nasty stuff (is) dumped".

 

Hey bimr,
are you trying to solve me or solve the original question?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[bimr]

Hey bimr,
are you trying to solve me or solve the original question?

No, I am the one that posted the original question. In case you hadn't noticed, EdStainless has posted the most rational response.

 

So...what's the alternative to 'rational'?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[EdStainless]

The alternative is;
What they have now .....

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P.E. Metallurgy, consulting work welcomed

 

[bimr]

So...what's the alternative to 'rational'?

Maybe something ironic.

 

Thanks EdStainless for a rational response as always.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."