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Water Treatment Laboratory Corrosion
5

Water Treatment Laboratory Corrosion

Water Treatment Laboratory Corrosion

(OP)
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.

RE: Water Treatment Laboratory Corrosion

How are they polishing?
Have they acid cleaned (passivated) everything?
Why on earth didn't they use non-metallics?
This room is 100%RH 100% of the time with water being splashed on items carrying whatever is in it.
I am sorry that someone told them that 316 would stand up to this.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Water Treatment Laboratory Corrosion

You can pickle in place with gel solutions such as Wonder Gel. https://www.derustit.com/products/wonder_gel.php It would be worth trying it before tossing everything. Wash with a caustic cleaner first to remove residues from the polishing compounds.

The pickling will give significantly more corrosion resistance but the procedure may have to be repeated occasionally over the lifetime, ideally just spot repairs.

Do you use chlorides in your water treatment?

Your application is indifferent from a natatorium of which there are many resources for design and maintenance.

https://www.nickelinstitute.org/media/1805/stainle...

RE: Water Treatment Laboratory Corrosion

(OP)

Quote (EdStainless (Materials))

How are they polishing?
Have they acid cleaned (passivated) everything?
Why on earth didn't they use non-metallics?
This room is 100%RH 100% of the time with water being splashed on items carrying whatever is in it.
I am sorry that someone told them that 316 would stand up to this.

Polished with with Bar Keepers Friend Stainless Steel Cleaner & Polish and Iron Out Rust Stain Remover.

Don't know if acid cleaned (passivated) everything.

The laboratory is air conditioned, don't know what the RH is. New HVAC system.

The laboratory was remodeled. The stainless steel backsplash was 50 years old and the reused backsplash is not rusting.

The inside of the trough sink is not exhibiting rust like the outside.

This water is potable drinking water from a clarifier. The water has been treated with alum to remove solids, plus chlorination. The water is fresh water from Lake Michigan and is considered to be good quality, low TDS water.





RE: Water Treatment Laboratory Corrosion

(OP)
Does the 316L-2B stainless steel need to be passivated prior to use?

The other components (eye wash, faucet, and hood) are 316 and also show rust, but not as bad as the trough sink.

The 316L-2B stainless steel was supplied by Outokumpu.

RE: Water Treatment Laboratory Corrosion

any high chloride concentrations?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

RE: Water Treatment Laboratory Corrosion

(OP)

Quote (dik (Structural))

any high chloride concentrations?

Chloride averages 20 mg/L.

RE: Water Treatment Laboratory Corrosion

Start here, I implore you:

https://www.mcmaster.com/#8554T11

The price seems to have skyrocketed, I paid the same for a full gallon last year. But it's a cheap test. Passivate the metal and if the corrosion doesn't come back your problem is solved.

Also, make sure nothing stays in contact with any surfaces for more than a few hours (don't leave containers standing on the surfaces) and rinse everything down with water regularly. As the water evaporates it concentrates the chlorides so regular rinsing will help prevent corrosion. Treat it like a commercial kitchen.

RE: Water Treatment Laboratory Corrosion

Can you do the same with a nitric acid wash?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

RE: Water Treatment Laboratory Corrosion

From my project notes:

STAINLESS STEEL
-ALL STAINLESS STEEL SHALL CONFORM TO AISI [S304L | S316].
-STAINLESS STEEL BOLT SPECIFICATION TO ASTM A193, GRADE 8B CLASS 2. NUTS SHALL CONFORM TO ASTM A194, GRADE 8. WASHERS SHALL CONFORM TO AISI S 304L. THREADS CAN BE INCLUDED IN THE SHEAR PLANE.
-STAINLESS STEEL WELDING SHALL CONFORM TO ANSI/AWS D1.6-2017.
-WELDING ELECTRODES MAY BE 308L.
-IN THE ABSENCE OF FACTORY PASSIVATION, ALL STAINLESS STEEL WELDING SHALL BE PASSIVATED BY IMMERSION IN A 20% SOLUTION OF NITRIC ACID FOR 4 HOURS. ATTACHMENTS SHALL BE FLUSHED CLEAN AND DRIED.
-INSTALLATION OF STAINLESS STEEL FABRICATIONS SHALL USE NON-FERRIC TOOLS.
-WELD MATERIAL CHARACTERISTICS SHALL MATCH THE PROPERTIES OF THE BASE MATERIALS.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

RE: Water Treatment Laboratory Corrosion

I don't believe nitric acid alone posseses the properties to passivate the more corrosion resistant alloys such as 316. There needs to be some hydrofluoric acid in the mix to pickle type 316. If immersion is possible, the passivation can be done using citric acid and electrical current.

RE: Water Treatment Laboratory Corrosion

Thanks... will look into this.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

RE: Water Treatment Laboratory Corrosion

Straight Nitric will passivate fine at 30-40% concentration.
First a light cleaning with a fine abrasive, like the abrasive ScotchBrite pads.
Then wash with a caustic degreaser (make sure that it doesn't have any corrosion inhibitors in it).
And then acid wash.
If we were worried about heat tint or scale then we would want to pickle. That is where you need HF in the acid solution.
All that we are concerned about is removing embedded iron from the surface, and straight Nitric will do that. There are also systems that use a brush or pad with a DC power supply. They are often used to descale welds, but with weaker solutions work great for passivation.
I suspect that in production (or more likely fabrication) iron (steel) has been embedded in the surface of this material.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Water Treatment Laboratory Corrosion

Thanks, Ed...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

RE: Water Treatment Laboratory Corrosion

For clarity, I always emphasize the caustic cleaning first because acids can't penetrate through oil residues that maybe present on surfaces.

RE: Water Treatment Laboratory Corrosion

Thanks, Tug... I've added the caustic cleaning to my project notes... It's a 400K text file with information added to it over the last 3 decades that I use for project notes for projects. The last edition to this part of the notes was the inclusion of using Head and Shoulders 'white' shampoo for trace iron content.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

RE: Water Treatment Laboratory Corrosion

(OP)
I was called into this project at the punch list stage representing the owner.

The lab supervisor stated that the previous sinks were all some type of stainless steel and didn't exhibit the corrosion stains. As stated previously, the stainless steel backsplashes haven't been changed nor the faucets. Don't know why the trough sinks were changed.

The room humidity is 67%

RE: Water Treatment Laboratory Corrosion

Thanks, bimr... I'm not into materials, but that is some of the worst SS corrosion, I've seen.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

RE: Water Treatment Laboratory Corrosion

(OP)

Quote (EdStainless (Materials))

I suspect that in production (or more likely fabrication) iron (steel) has been embedded in the surface of this material.

Do you think that this equipment can be saved or is it recommended to propose non-metallic sinks? The trough sinks with the worst corrosion are used as just potable water sampling with no other reagents used. 70% of the inside of the sinks have no corrosion. The worst corrosion is on the outside. It looks like the splashing water may be evaporating leaving salts behind or the splashed surface is absorbing corrosive fumes from the lab. The lab does clean glassware with HCl but not in these trough sinks. The lab uses other chemicals such as sulfuric acid.

The lab supervisor stated that the previous sinks were all some type of stainless steel and didn't exhibit the corrosion stains. As stated previously, the stainless steel backsplashes haven't been changed nor the faucets. Don't know why the trough sinks were changed. For the most part, the backsplash and faucets do not have extensive corrosion, but do have some water scale on them.

This operation operates 24/7. Can the chemical treatments for passivation be conducted safely in a working laboratory?






RE: Water Treatment Laboratory Corrosion

If your corrosion were concentrated around the welded areas I would suspect carbide precipitation and that would likely require replacing the equipment. This does not seem to be your case. In 2 of your pictures there appears to be blisters of rust which indicates pitting so you may want to replace those pieces (only if they fail again after cleaning).

The acid cleaning an be done online, the process takes minutes. Just work small areas at a time. This will minimize the fumes produced. Ventilation and respirators will allow workers to be in the space during the cleaning process. The gel type cleaners can be applied by brush and may help facilitate online cleaning. The same gel cleaners can be used to touch up future corrosion areas that may arise.

RE: Water Treatment Laboratory Corrosion

Give some of the worst area an abrasive cleaning (flap wheel or scotchbrite) and see how deep the pitting is.
If there is not deep pitting (only a few thousandths of an inch) then cleaning properly (abrasive, caustic, acid, rinse) should work.
Be careful with the alkaline cleaner though, and commercial pre-packaged ones have corrosion inhibitors in the intended for use on steels. Residue from these will interfere with the passivation.
I agree with your conclusions that the splashing is what makes it worse. This is common with SS.
At least inside the sinks get rinsed off.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Water Treatment Laboratory Corrosion

(OP)
You did not mention passivation?

The sampling sinks are supposed to be made of 316SS. There is a smaller sink fabricated from 430SS. 430SS seems to be more suitable for a commercial food establishment than a laboratory.

RE: Water Treatment Laboratory Corrosion

The passivation should occur naturally after the acid wash provided and the surface is clean and exposed to air.

RE: Water Treatment Laboratory Corrosion

(OP)

Quote (TugboatEng (Marine/Ocean))

The passivation should occur naturally after the acid wash provided and the surface is clean and exposed to air.

This is a 24/7 operation. How long does this equipment have to sit idle for passivation to occur naturally?

RE: Water Treatment Laboratory Corrosion

Passivation of SS means to acid clean in order to remove embedded iron on the surface.
The forming of a passive surface film is a natural process in these alloys and does not need any chemical assistance beyond a good clean surface.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Water Treatment Laboratory Corrosion

(OP)
Thanks everyone for the comments, have a good weekend.

RE: Water Treatment Laboratory Corrosion

Aside from the corrosivity issues, better drainage would help matters.

I basically agree with EdS though, 316SS is not up to the task of resisting everything flowing over it in a lab like this one.

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

RE: Water Treatment Laboratory Corrosion

(OP)
There are test procedures to determine if there is contamination. Would you have to remove the rust spots before you do this contamination test?

RE: Water Treatment Laboratory Corrosion

Ed may have something else to say but as far as I know there are no procedures to test. This is a case where you need to follow the procedures to prepare the surface. Everything with stainless is about processing and handling. The damage can be done at any step and it won't become apparent until the material is placed in service.

I implore you, get a container of the pickling gel. McMaster stocks it and will have it in your mailbox within 24 hours. Use it on a small area. You're risking all of $100. I think you'll be pleased with the results.

RE: Water Treatment Laboratory Corrosion

(OP)
I wish it were so simple. I am representing the Owner. I have an engineering who specified this mess. I have a Contractor who installed it.

The problem is that the existing stainless steel fascia has performed well for over 40 years with scant rust. This new stainless steel rusted and stained within a week. I don't know the specifications on the existing material.

One of the things that I have to determine is if there is contamination of the new stainless steel. There is e Ferroxyl test to do this. ASTM A 380 Ferroxyl Test for Free Iron.

The first thing that I need to do is to positively identify the problem. The problem is likely the contamination, but that needs to be confirmed so that I can provide the path forward.

RE: Water Treatment Laboratory Corrosion

You are fortunate that your problem shows itself in such short time. That will help identify and prove the solution rapidly. You can do the acid cleaning tomorrow and have results in a week. That's likely faster and more conclusive than any lab test. I understand the desire to follow the more traditional route but the cause of your problem seems very obvious (assuming the correct alloy was used).

As this seems to be warranty work, and you're providing the solution, perhaps the engineer will cover the cost of the solution as well as your time finding it? I know it never works this way, insurance makes nothing simple.

RE: Water Treatment Laboratory Corrosion

It'll be done before you have the lab results... no harm trying... just hit 'petty cash'.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

RE: Water Treatment Laboratory Corrosion

It could also be related to the surface getting smeared when they did the final 'polish' and trapping stuff in the smears. Anything that traps moisture on this surface will aggravate this issue, in addition to iron contamination.
I always recommend that people do an abrasive treatmetn first, it helps open up any smears and it helps remove other surface contamination.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Water Treatment Laboratory Corrosion

I'm going to throw out something totally different: When I've seen damage like that in 316, I've found the corrosion is really from stress corrosion cracking that formed from chloride exposure. The SCC exhibited in the form of localized pitting when observed macroscopically. I note that the sink outside surface as well as all of the new hardware all exhibit significant corrosion damage while the inside is largely free of it, probably from the constant rinsing away of the sink interior during use.

An alternate explanation is the grade of steel is not 316L but a grade much less resistant to pitting corrosion in a water lab. Given the degree of damage, is it possible to remove some of the corroded material and send it to a lab to investigate? They could examine corrosion mode (i.e. SCC or pitting, for example), look for contaminants like chlorides that would drive corrosion, and confirm base material.

RE: Water Treatment Laboratory Corrosion

(OP)

Quote (mrfailure (Materials))

I'm going to throw out something totally different: When I've seen damage like that in 316, I've found the corrosion is really from stress corrosion cracking that formed from chloride exposure. The SCC exhibited in the form of localized pitting when observed macroscopically. I note that the sink outside surface as well as all of the new hardware all exhibit significant corrosion damage while the inside is largely free of it, probably from the constant rinsing away of the sink interior during use.

An alternate explanation is the grade of steel is not 316L but a grade much less resistant to pitting corrosion in a water lab. Given the degree of damage, is it possible to remove some of the corroded material and send it to a lab to investigate? They could examine corrosion mode (i.e. SCC or pitting, for example), look for contaminants like chlorides that would drive corrosion, and confirm base material.

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

Mill provided information that shows this material is 316L.

Somebody kept telling me that the original sink that was installed for 60 years did not have corrosion like this. I wasn't here so I went back and found some pictures. Well surprise, surprise.



EdStainless mentioned it in his first post. Not a good application for stainless. Why would a consultant specify the same material when it is clearly not suited for the application?

RE: Water Treatment Laboratory Corrosion

Quote (bimr)

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

The issue with exposed surfaces is that as the water evaporates away, the concentration of chlorides increases substantially.

RE: Water Treatment Laboratory Corrosion

As TBE said, the spots that form when water drops evaporate will be 26% salt. Wet/dry is the killer application for SS.
There are special aggressive corrosion tests where you warm the sample and then apply drops of low concentration salt water, waiting just long enough so that it almost drys between drops.
If there are visible scratch lines in the polish they should run up and down to assist drainage.
I have seen people wax SS to prevent this, but it takes maintenance. I don't know how one of the newer hydrophobic auto polishes with ceramic in it would work. It should help.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Water Treatment Laboratory Corrosion

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.

RE: Water Treatment Laboratory Corrosion

Did it rust through in those 60 years, or is this a cosmetic problem? In my experience, stainless steel is miss-named. It stains easily, but resists serious corrosion.

RE: Water Treatment Laboratory Corrosion

stevenal,
The 'steel' component of stainless steel came from the Engineering Dept.
The 'stainless' component came from the Marketing Dept.

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

RE: Water Treatment Laboratory Corrosion

Quote (bimr)

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."

RE: Water Treatment Laboratory Corrosion

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.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Water Treatment Laboratory Corrosion

Quote (mrfailure)

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."

RE: Water Treatment Laboratory Corrosion

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."

RE: Water Treatment Laboratory Corrosion

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.

RE: Water Treatment Laboratory Corrosion

(OP)

Quote (ironic metallurgist (Materials))

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.

RE: Water Treatment Laboratory Corrosion

And?

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

RE: Water Treatment Laboratory Corrosion

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

RE: Water Treatment Laboratory Corrosion

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.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Water Treatment Laboratory Corrosion

What is a lab without chemicals?

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

RE: Water Treatment Laboratory Corrosion

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

RE: Water Treatment Laboratory Corrosion

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."

RE: Water Treatment Laboratory Corrosion

(OP)

Quote (ironic metallurgist (Materials))

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.

RE: Water Treatment Laboratory Corrosion

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

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

RE: Water Treatment Laboratory Corrosion

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

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Water Treatment Laboratory Corrosion

(OP)

Quote (ironic metallurgist (Materials))

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

Maybe something ironic.

RE: Water Treatment Laboratory Corrosion

Thanks EdStainless for a rational response as always.

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

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