Hello,

I have run into a problem while trying to passivate "new" (Unused, but they have been sitting for almost a year in a very dusty environment) stainless steel tanks. They are chinese tanks. I am running a rinse cycle, a caustic cycle at 140*F with 5% Chemstation 50177, rinse, acid at 140*F with 10% Chemstation 9917 nitric phosphoric blend, and a final rinse cycle. There is some type of dusty deposit on the tank that is visible. When the tank dries it looks exactly the same, none of the dirt has been removed. It does not seem like an oil as there is no beading of water on the surface after the caustic cycle. Where I can reach this residue it is easily wiped off with a paper towel. No scrubbing at all. In the pictures you can see the "clean stainless" and the residue which is a brownish color. Any insight or suggestions are greatly appreciated.

Thanks,

------------------------------
Darren McLean
Head Brewer
Pawleys Island Brewing
------------------------------

Stainless Steel requires >12% Chromium in order to protect it against rusting.  In the presence of oxygen Chromium forms a very thin layer of Chromium Oxide on the surface, protecting it against Ferric Oxide rust.  All Stainless Steel is not the same.  Obviously its less expensive to reduce the Chromium concentration in Stainless Steel and a takes a while to see the effect of cheap off shore product.  Buyers beware.

------------------------------
James Holden
Brewing Consultant
Retired but Busy
jholden007@hotmail.com
Canada/US/Mexico
------------------------------

​go in and scrub them down with down dish soap and a soft brush. that will remove the oil off the walls that is holding the dust. rinse, let dry and check before attempting the passivation again.
do you have spray balls or cleaning jets in the tank?
if there are any major rust spots you should remove them with a mechanical means and spot passivate with fluoric acid.
then you can bulk passivate the tank. they must air cure after treatment.

good luck but when you expand best to consider domestic tanks.

------------------------------
Ed Michalski
CEO
Pro Engineering and Mfg Inc
Milwaukee WI
(414) 362-1500
------------------------------

------Original Message------

​go in and scrub them down with down dish soap and a soft brush. that will remove the oil off the walls that is holding the dust. rinse, let dry and check before attempting the passivation again.
do you have spray balls or cleaning jets in the tank?
if there are any major rust spots you should remove them with a mechanical means and spot passivate with fluoric acid.
then you can bulk passivate the tank. they must air cure after treatment.

good luck but when you expand best to consider domestic tanks.

------------------------------
Ed Michalski
CEO
Pro Engineering and Mfg Inc
Milwaukee WI
(414) 362-1500
------------------------------

I've run into this a couple times and I feel your pain.  There are some residues that just don't want to let go of your tank wall.

My small piece of advice for you is to get better cleaning on the tank walls prior to the acid step.  The caustic that you're using doesn't have much detergency to help bind up and remove oils, grease, soils, and particulates.  The caustic is good at reacting with soils, but not very good at lifting those soils off the surface of the tank.  To combat this issue, I'll sometimes mix caustic at 2-3% titratable strength AND some powdered cleaner like PBW, BrewerEZ, etc.  If mixing chemicals isn't your favorite thing to do, you can also ask your chemical supplier to blend something for you.  Also - physical force like a beefy sprayball or manual scrubbing might also be necessary.  If the tank isn't clean prior to passivation, it'll never work properly.

Another quick note - does your water supply contain high levels of Manganese?  Manganese staining is really hard to remove and has caused me some heartache in the past.  It looks brown or black so folks usually assume it's an organic soil.  Cleaning with RO or softened water would be ideal, but that's not always an option.

Good luck.  Cheers,

------------------------------
Andy Hooper
Brewmaster
Seismic Brewing Company
Santa Rosa CA
------------------------------

Hi Darren - First, clean the tank with a 2% caustic (sodium hydroxide) cleaner at 120 to 160 degrees F for 30 minutes, rinse well and then use a liquid Citric or Nitric acid at 100 to 120 degrees F at 4 to 5% by volume and circulate for 30 minutes. Do not fall into the trap that more is better, these temperatures and percentages have worked well for many years. Too high a temperature and acid percentage will have the opposite effect and will release free iron which will result in what I suggest you are seeing. Drain and let the tank air dry overnight to form the Patina.

As Jim Holden correctly pointed out, you need an AISI 304 or higher specification stainless steel to ensure you have the correct Chromium and Nickel content in the stainless steel. If what I suggest does not work, then I'm afraid you have purchased a tank made with low grade stainless steel - What I call knife and fork stainless. Ideally, buy tanks Made in America, but If you insist on buying low cost Chinese stainless steel equipment, I suggest you purchase through a USA manufacturer who will certify and warranty what you purchase. 

Best,

------------------------------
Jeff Gunn
President & CEO
IDD Process & Packaging, Inc.
5450 Tech Circle
Moorpark, CA 93021
Tel: 805-529-9890
Fax: 805-529-9282
Cell: 805-444-3842
Toll Free: 800-621-4144
Email: idd2jeff@aol.com
Skype: jeffgunn50
Web: www.iddeas.com
------------------------------

The material looks like rust (iron oxide) but as others have said you need to remove all traces of organics/greases first. I suggest using a  chlorinated caustic (1-2% caustic with 60-80 ppm chlorine) - the chlorine will help oxidize the organics and the caustic will remove the soils.

Secondly, the acid that you are using may not be strong enough. One procedure that works, involves  20-25% nitric acid at 168F for 1-2 hr. This is not something that I would recommend unless you really know what you are doing - otherwise ask your chemical supplier for help. This procedure is effective because the nitric acid is an oxidizing agent and after removing the iron oxide will oxidize the chromium and nickel present to form a passive oxide layer. 

A less hazardous method uses 4-10% citric acid at ambient temperature. The citric acid is effective at removing the iron oxide but it is not an oxidizing agent so the formation of a passive layer is less predictable - it relies on natural air oxidation. Some companies recommend accelerating air flow using a fan for 24 hrs after the acid treatment.

However as James pointed out if your steel does not have much chromium or nickel then a passive layer will not form.





------------------------------
Richard Rench
Oakville ON
(416) 779-3908
------------------------------

------Original Message------

Hello,

I have run into a problem while trying to passivate "new" (Unused, but they have been sitting for almost a year in a very dusty environment) stainless steel tanks. They are chinese tanks. I am running a rinse cycle, a caustic cycle at 140*F with 5% Chemstation 50177, rinse, acid at 140*F with 10% Chemstation 9917 nitric phosphoric blend, and a final rinse cycle. There is some type of dusty deposit on the tank that is visible. When the tank dries it looks exactly the same, none of the dirt has been removed. It does not seem like an oil as there is no beading of water on the surface after the caustic cycle. Where I can reach this residue it is easily wiped off with a paper towel. No scrubbing at all. In the pictures you can see the "clean stainless" and the residue which is a brownish color. Any insight or suggestions are greatly appreciated.

Thanks,

------------------------------
Darren McLean
Head Brewer
Pawleys Island Brewing
------------------------------

Thanks you all for the responses. I guess I should've titled this thread differently. I am confident with the passivation process I am using and that the tanks are stainless, the problem is I cannot get the tank clean enough to passivate. There is some kind of grease or oil that can be wiped off but does not come off from the chemical cycles.

Mike, do you have any more info on cationic surfactants and quaternary ammonia? Is there a specific product you suggest? Or that anyone suggests for removing oil from stainless.

Thanks,

------------------------------
Darren McLean
Head Brewer
Pawleys Island Brewing Co.
Charleston SC
------------------------------

Original Message:
Sent: 07-13-2017 13:31
From: Mike Willis
Subject: Tank passivation wont remove this residue

There seems to be quite a few opinions on how to passivate stainless.  I go back to the ASTM procedure.  I think you have done the process correctly, however, my opinion is that straight Nitric at a higher concentration and without the phosphoric may be better, especially if corrosion products are visible.  I think I've seen the film you are referring to and have been looking for a solution.  One opinion is that it is left from the polishing processs.  The mineral oil and extreme pressure additives are not soluble in caustic or acid and must be removed with a cationic surfactant.  Quaternary Ammonia acts as such a surfactant and was suggested after a caustic wash to remove. 

I have seen an oily residue years back, I suspect it was from pneumatic oil and grinding dust.  Elbow grease was our solution before passivation.

------------------------------
Richard Michaels
Quality and Innovation Manager
F.X. Matt Brewing Co
Utica NY
(315) 624-2464
------------------------------

Original Message:
Sent: 07-13-2017 16:06
From: Darren McLean
Subject: Tank passivation wont remove this residue

Thanks you all for the responses. I guess I should've titled this thread differently. I am confident with the passivation process I am using and that the tanks are stainless, the problem is I cannot get the tank clean enough to passivate. There is some kind of grease or oil that can be wiped off but does not come off from the chemical cycles.

Mike, do you have any more info on cationic surfactants and quaternary ammonia? Is there a specific product you suggest? Or that anyone suggests for removing oil from stainless.

Thanks,

------------------------------
Darren McLean
Head Brewer
Pawleys Island Brewing Co.
Charleston SC
------------------------------

------Original Message------

Thanks you all for the responses. I guess I should've titled this thread differently. I am confident with the passivation process I am using and that the tanks are stainless, the problem is I cannot get the tank clean enough to passivate. There is some kind of grease or oil that can be wiped off but does not come off from the chemical cycles.

Mike, do you have any more info on cationic surfactants and quaternary ammonia? Is there a specific product you suggest? Or that anyone suggests for removing oil from stainless.

Thanks,

------------------------------
Darren McLean
Head Brewer
Pawleys Island Brewing Co.
Charleston SC
------------------------------

------Original Message------

Hi Darren,

Seems that you have a commun problem that we're seeing with new equipments before passivation.

Here is a procedure that can help you



Good Luck

------------------------------
Denis Blais
Technical support coordinator brewery & beverage
Ecolab Food & Beverage Canada
(450) 978-6644
------------------------------

​Darren, in passivation of new stainless you should not be final rinsing after your acid passivation step, the tank should be allowed to air dry, no rinse.  The air dry un-rinsed step, is when the oxide layer is formed rendering your tank "stainless", once the step is complete you would then rinse, sanitize and tank is ready for use.  wasn't sure from reading your post, if you are allowing for this step.  This may be why you are seeing a brown residue as it is actually the free iron rusting. The acid concentration recommended by my chemical supplier is 25% and I allow for 24-48 hours of air dry time.  Hope this helps.

------------------------------
Jeffrey Cooley
District Brewery Manager
McMenamin's
Portland OR
(971) 409-2971
------------------------------

​Darren

I'm in agreement with Denis, it appears that you have a static charged particles on the surface of the stainless that need to be removed.  Reference the information below.
On another note, we've seen this from time to time, it is important to follow all of the steps to prevent this issue from occurring....it only happens 1 out of 10 times, but when it does it is virtually impossible to go back.  It is quite possible that you oxidized the slag metal particles and have fixed them to the stainless steel---making it virtually impossible to remove.  If the cationic surfactant doesn't work, I'd recommend a local welding service to buff the interiors.  Once they are done, follow the steps for full slag removal, caustic cleaning, and ultimately passivation.

I hope this helps

Bob Klinetob

Master Brewer / Brewing & Beverage Specialist

Mobile: 570-881-2011

Email: bobklinetob@afco.net

www.afcocare.com

AFCO Program for Passivation of Stainless Steel

 

                     ( Isssued by Alex C. Fergusson – Revised November 2, 1998 )

 

 

The corrosion resistance of austentic stainless steels, the so called steels belonging to the ANSI 300 series (304, 304-L, 316-L, and 316-T) depends on the formation of a passive surface film composed of chromium and nickel oxide. If this passive film is not maintained, the steel is considered to be in a compromised state, and damage from corrosion may occur.

 

Establishing a passive surface film on austentic steels is essential to maximize the corrosion resistance that the metal offers. Stainless steel passive films occur naturally when exposed to an oxidizing environment. However, naturally occurring films occur very slowly and do not offer a uniform smooth oxidative layer.

 

Iron and chlorides are the two main culprits, which cause corrosion and resultant pitting in stainless surfaces. New stainless steel equipment will contain small iron particles on the surface left from the stainless manufacturing process. These surface iron particles will cause rusting of new stainless equipment with eventual corrosion and pitting if not removed with passivation. The process of passivation removes these iron particles using a strong oxidative acid.   Nitric Acid is recommended for this use.

 

Stainless steel weld joints on new or used equipment are particularly sensitive to corrosion and pitting. The slag left from the welding process must be removed or these weld joints will corrode and pit rapidly. Welding creates a rough surface and also destroys a passivation film. Therefore, weld joints are especially vulnerable to corrosion and should always be passivated before use.    

 

New stainless equipment that has been polished using an aluminum oxide grit requires a special cleaning procedure to assure removal of statically charges particles from the surface. It is very important to assure that the cleaning steps are kept in the proper sequence. If this static material is not removed prior to passivation a dark grey film will result which is very difficult to remove after treatment with Nitric Acid.

  

It is also important to note that an oily or soiled surface cannot be passivated, because oil and soil block the acid and oxygen from reaching the metal surface. The purpose of the caustic / surfactant solution cleaning is to render the surface clean and oil-free.

 

Used stainless equipment should be cleaned prior to passivation by doubling the normally used cleaning solution strength. A chlorinated cleaner may be necessary depending on the soil on used equipment. A thorough inspection of used equipment is recommended to determine if any soil films are present.

 

When to Passivate  

 

There are many ways that corrosion of stainless steel can occur. Processes involving high acid, high chloride containing products, especially if run at high temperatures have perhaps the highest potential. Some other common causes include:

 

1. Surface contamination from dissimilar metals.

            . Improper connections to water lines, cooling and heating lines etc.

            . Improper repairs to tanks and welds.

2. Water

            . Water supplies with high chloride levels

3. Chemical Corrosion

. Use of wrong chemicals

. Abuse of chemical concentrations

4. Food

. Salt content (chlorides) of certain foods combined with low pH

. Organic Acids

5. Bacteria

. Under certain static conditions anaerobic bacteria can cause corrosion

 

Most new stainless steel equipment has a protective coat applied to the surface of the vessel before shipment. The coating is applied to prevent high carbon tramp steel from causing rust spots during transport and storage. This coating can be mineral oil, silicone oil, or white plastic film.

 

Any film or foreign matter which may have accumulated and adhered to the stainless steel surfaces during shipment must be removed before passivation. The inside surface of new equipment vessels and pipe often contains high carbon tramp steel, fabricating lubricants, adhesive residues, air grinder oil, or other shop oils that were deposited during fabrication. This tramp steel and surface contaminants if not removed can lead to rusting and pit corrosion.

 

When polishing stainless steel some mills use aluminum oxide as a polishing dust. Statically charged micronic grinding particles result which cling to the stainless surface. If not removed prior to passivation these micronic sized particles will expand during passivation. These expanded particles will appear black in color when wiped with a clean white wiper

 

All manufacturing oils, EP additives and /or mineral oils must be completely removed prior to passivating to prevent stains, streaks, and future corrosion. If the stainless surface is not completely clean the oxidation process in inhibited and passivation will not be satisfactory.

 

 

 

 

New equipment must be thoroughly cleaned with compounds specifically formulated for this task. This requires pre-cleaning with a cationic surfactant followed with a cleaning solution containing caustic, wetting agents, and solvents for dissolving and removing these surface materials. The selection of the proper detergent formulation is dependent upon the makeup of the protective coatings or soils being removed.

 

For used equipment a chlorinated cleaner may be needed to assure removal of a protein film.

 

There are five major steps in The Passivation Process.

 

1. Pre-cleaning (Use of a cationic surfactant to remove static charge polishing dust)

Note: This step is not necessary with used equipment.

2. Caustic Cleaning (Use of caustic and solvents to remove grease, oil and films.)
3. Acid Wash (Use of Nitric Acid to provide an oxidizing atmosphere)
4. Final Rinse (Rinse using potable water free of chlorides and inorganic minerals)
5. Air Dry (For 24 – 48 hours to allow for a full passivation layer to develop.)

 

1. The first step (Pre-Cleaning) is designed to neutralize the statically charged

     micronic polishing particles resulting from polishing new stainless steel

     equipment. A cationic surfactant is used to free these particles to assure removal

     during the caustic wash.  

 

• The second (Caustic Wash) step is required to remove the polishing dust particles,

     dirt, oil, and grease. A water soluble detergent is used to accomplish this step. This

     detergent solution is composed of a solvent, wetting agent, and caustic cleaner.

 

3. The third step (Acid Wash) is to remove free iron, metallic residues, oxides, and other corrosive products from the surface of the metal. By dissolving these and providing an oxidizing atmosphere, the passive film is allowed to form.

 

4. The fourth step (the final rinse) is to flush the acid solution from the system until a neutral pH is achieved.

 

5. The fifth step (Air Dry) is to assure that the passivation layer is complete before use.

If possible allow the equipment to air dry for 24 to 48 hours before production use.

 

Note: Conduct a normal wash of the equipment prior to use. However, do not wash the equipment with a detergent before the air dry step is completed as formation of the chromium oxide layer may be interrupted prematurely.

 

The cleaning and passivation procedure can be modified to deal with a variety of soils, surface finish and weld conditions.

 

 

 

 

 

 

AFCO Chemicals Used for Passivation

 

1. R-2332 – Passivation Treatment is a cationic surfactant which is used to remove the  

     statically charged micronic grinding particles. Use the Passivation Treatment

     R-2332 to prepare a 10 % solution. No AFCO Test Kit is available to prepare this

     solution, thus mix it @ a 10 % by volume concentration.

     Note: A defoam additive (AFCO 1072) is recommended for use with this  

     product to control foaming in CIP and circulating systems.  

 

2. AFCO 5306 should be used in combination with available liquid caustic product.

     Recommend using AFCO 5306 at 10 % by volume and adding a caustic product

     to prepare a solution with a total causticity of 4 %. The 5306 will contribute approx.

     0.7 to 0.75 % alkalinity to the solution. Add additional alkalinity using available

     liquid caustic. Use the AFCO MiniCombo Kit to prepare this

     solution. AFCO 5232 or AFCO 5238 Liquid Caustic is recommended for use with

     this product.

 

3. AFCO 5294 (NoPhosCid) Nitric Acid is recommended as the preferred acid for

     passivation. AFCO recommends a solution strength of 7 to 10 % Acidity. This will  

     require approx. 28 gal.of AFCO 5294 (Nitric Acid) mixed with every 100 gal. of

     water. A special AFCO Acid Passivation Test Kit is available to control the proper

     mixing of the Nitric Acid solution.

------------------------------
Robert Klinetob
Regional VP/Brewing Technical Director
AFCO/Alex Fergusson Inc
Dallas PA
(570) 881-2011
------------------------------

Dear Darren:

The problem you are seeing is common these days as tanks are not properly finished, polished, cleaned and passivated prior to shipment to the customers.  The problem is also not isolated to Chinese tanks.  We have seen this problem with German, US, Canadian and other nations tanks as well, and sometimes just one tanbk is affected and other times all tanks.  The problem here is that the tank was not cleaned after polishing the welds and metal dust has attached itself electostatically to the non-passivated tank surface.  This metal dust will not come off using a standard routine passivation cycle and requires an additional step for removal.  Commonly, cationic compounds such as quaternary ammonium compounds are used to bind these metal dusts to the electrostaically charged chemical compound and remove it.  It almost works as two opposite magnetically charged magnets.  It is important that mechanical energy is also applied either via CIP sprayballs or brushes.

Once the cationic detergent has been rinsed out of the tank, I would recommend repeating the entire passivation cycle including caustic cleaning cycle.  A passivation cannot take place on any surface that has residual dirt or oils (from rolling and welding or just transport) still on it.  Then run the passivation cycle using Nitric Acid and you should be clear.  The absence of the dust can be checked using a white clean rag and rubbing vigorously over the stainless.  The cloth should be clean after rubbing.  If you see grayish/black deposits on the rag, you may need to repeat the passivation and cationic cleaning cycle.

As a general rule, any work with Hydrofluoric Acid (as suggested by some posters) requires both specialized equipment and specialized chemical handling knowledge.  Fluorine is one of the smallest molecules in chemistry and can penetrate quickly even chemical gloves and clothing not designed for fluorinated products.  In addition, it is one of the ten most toxic chemicals on the planet (T+) and quickly penetrates the skin to attack the bones and other vital organs.  NEVER use this product unless you have been trained to work with HF!!!  It may kill you.

There are additional products out there for the removal of the metal dust but this simple method will get the problem resolved in most cases.  Note that there are other metal problems such as contamination from rollers that may look similar and require different treatment.

I hope this helps and you can contact me directly if you have any other questions.



------------------------------
Dirk Loeffler
Technical Director
Loeffler Chemical Corp
Atlanta GA
(404) 629-0999
loeffler.dirk@loefflerchemical.com
------------------------------

Dirk,

Is there a recommended concentration for the quat solution? Suggested times? Temperatures?

We are having this issue in our brewery (new tanks that have sat for a long time and didn't come pre-"treated"). We have tried a 2-3% caustic followed by a 10% nitric/phosphoric acid wash both at 140-150°F followed by a 5% citric acid passivation cycle and the mill scale remains. They are 150bbl tanks with bottom manways so unfortunately a manual brush scrub would be extremely challenging.

Also, I have heard that quat can be tricky to deal with in a brewery setting and that the tank needs to be heavily rinsed and then caustic cleaned again after the quat cycle. Thoughts on that?

I appreciate yours (and everyone else's) feedback!

Cheers,

------------------------------
Chris Depew
Dean & Co. Brewing
La Junta, CO
------------------------------

Original Message:
Sent: 07-19-2017 12:20
From: Dirk Karl Robert Loeffler
Subject: Tank passivation wont remove this residue

Dear Darren:

The problem you are seeing is common these days as tanks are not properly finished, polished, cleaned and passivated prior to shipment to the customers.  The problem is also not isolated to Chinese tanks.  We have seen this problem with German, US, Canadian and other nations tanks as well, and sometimes just one tanbk is affected and other times all tanks.  The problem here is that the tank was not cleaned after polishing the welds and metal dust has attached itself electostatically to the non-passivated tank surface.  This metal dust will not come off using a standard routine passivation cycle and requires an additional step for removal.  Commonly, cationic compounds such as quaternary ammonium compounds are used to bind these metal dusts to the electrostaically charged chemical compound and remove it.  It almost works as two opposite magnetically charged magnets.  It is important that mechanical energy is also applied either via CIP sprayballs or brushes.

Once the cationic detergent has been rinsed out of the tank, I would recommend repeating the entire passivation cycle including caustic cleaning cycle.  A passivation cannot take place on any surface that has residual dirt or oils (from rolling and welding or just transport) still on it.  Then run the passivation cycle using Nitric Acid and you should be clear.  The absence of the dust can be checked using a white clean rag and rubbing vigorously over the stainless.  The cloth should be clean after rubbing.  If you see grayish/black deposits on the rag, you may need to repeat the passivation and cationic cleaning cycle.

As a general rule, any work with Hydrofluoric Acid (as suggested by some posters) requires both specialized equipment and specialized chemical handling knowledge.  Fluorine is one of the smallest molecules in chemistry and can penetrate quickly even chemical gloves and clothing not designed for fluorinated products.  In addition, it is one of the ten most toxic chemicals on the planet (T+) and quickly penetrates the skin to attack the bones and other vital organs.  NEVER use this product unless you have been trained to work with HF!!!  It may kill you.

There are additional products out there for the removal of the metal dust but this simple method will get the problem resolved in most cases.  Note that there are other metal problems such as contamination from rollers that may look similar and require different treatment.

I hope this helps and you can contact me directly if you have any other questions.



------------------------------
Dirk Loeffler
Technical Director
Loeffler Chemical Corp
Atlanta GA
(404) 629-0999
loeffler.dirk@loefflerchemical.com
------------------------------

Dear Chris:

The application is a little bit tricky since QAC products tend to foam.  If you run this in a CIP loop using a spray ball, I would recommend 3 - 5% by volume and run this solution ambient for about 20 - 30 minutes.  The solution is going to foam, so you may have to wait intermittently until the foam has settled and then continue running.  Listen for the pump cavitating, which is a good sign that the foam has taken over.

Rinse thoroughly with plenty of water until free of chemical.  Quaternary ammonium compounds (QAC) tend to have a distinct smell, so the absence is easy to detect.  We also have QAC test paper strips, which can be used to detect the residual presence of the QAC.  Sometimes is helps when you add a small amount of alcohol (0.5 - 1% Isopropanol) to the rinse water during the rinse cycle.  Be careful since the fumes may pose a flammability hazard depending on the environment in and around the tank. 

Please note that other problems may be present that look and appear similar, but require different products for removal.  If the QAC solution does not remove the dust, we may have to look into another form of treatment. Unfortunately, at times this can be a trial and error process.

I hope this helps and you can use our Lerasept^(tm) S 10 for the application of the QAC.

There is no need to run a second caustic cycle through your equipment after the QAC application.  The caustic only serves as a means to remove oils and organic deposits from the shipping and manufacturing process.  The dust is attached electrostatically to the tank surface and the caustic will work despite its presence during the first application.

Cheers,

------------------------------
Dirk Loeffler
Technical Director
Loeffler Chemical Corp
Atlanta GA
(404) 629-0999
loeffler.dirk@loefflerchemical.com
------------------------------

Original Message:
Sent: 07-21-2017 13:58
From: Chris Depew
Subject: Tank passivation wont remove this residue

Dirk,

Is there a recommended concentration for the quat solution? Suggested times? Temperatures?

We are having this issue in our brewery (new tanks that have sat for a long time and didn't come pre-"treated"). We have tried a 2-3% caustic followed by a 10% nitric/phosphoric acid wash both at 140-150°F followed by a 5% citric acid passivation cycle and the mill scale remains. They are 150bbl tanks with bottom manways so unfortunately a manual brush scrub would be extremely challenging.

Also, I have heard that quat can be tricky to deal with in a brewery setting and that the tank needs to be heavily rinsed and then caustic cleaned again after the quat cycle. Thoughts on that?

I appreciate yours (and everyone else's) feedback!

Cheers,

------------------------------
Chris Depew
Dean & Co. Brewing
La Junta, CO
------------------------------

Thank you all for your suggestions and helpful info. What ultimately ended up working was the fluorinated nitric acid, DART 191 suggested by Steve Gerloff. We tried the QAC method with no success. We ended up running a caustic cycle and then a Dart 191 cycle which removed most of the scale. We still had to get into every tank and scrub with a cloth to get the residue out of the polished areas at the seams and around probes and ports. We then proceeded with a standard passivation.

Thanks again for all the info everyone.

------------------------------
Darren McLean
Brewer
Pawleys Island Brewing Co
Charleston SC
------------------------------

Original Message:
Sent: 07-24-2017 11:38
From: Dirk Karl Robert Loeffler
Subject: Tank passivation wont remove this residue

Dear Chris:

The application is a little bit tricky since QAC products tend to foam.  If you run this in a CIP loop using a spray ball, I would recommend 3 - 5% by volume and run this solution ambient for about 20 - 30 minutes.  The solution is going to foam, so you may have to wait intermittently until the foam has settled and then continue running.  Listen for the pump cavitating, which is a good sign that the foam has taken over.

Rinse thoroughly with plenty of water until free of chemical.  Quaternary ammonium compounds (QAC) tend to have a distinct smell, so the absence is easy to detect.  We also have QAC test paper strips, which can be used to detect the residual presence of the QAC.  Sometimes is helps when you add a small amount of alcohol (0.5 - 1% Isopropanol) to the rinse water during the rinse cycle.  Be careful since the fumes may pose a flammability hazard depending on the environment in and around the tank.

Please note that other problems may be present that look and appear similar, but require different products for removal.  If the QAC solution does not remove the dust, we may have to look into another form of treatment. Unfortunately, at times this can be a trial and error process.

I hope this helps and you can use our Lerasept^(tm) S 10 for the application of the QAC.

There is no need to run a second caustic cycle through your equipment after the QAC application.  The caustic only serves as a means to remove oils and organic deposits from the shipping and manufacturing process.  The dust is attached electrostatically to the tank surface and the caustic will work despite its presence during the first application.

Cheers,

------------------------------
Dirk Loeffler
Technical Director
Loeffler Chemical Corp
Atlanta GA
(404) 629-0999
loeffler.dirk@loefflerchemical.com
------------------------------


Original Message:
Sent: 07-21-2017 13:58
From: Chris Depew
Subject: Tank passivation wont remove this residue

Dirk,

Is there a recommended concentration for the quat solution? Suggested times? Temperatures?

We are having this issue in our brewery (new tanks that have sat for a long time and didn't come pre-"treated"). We have tried a 2-3% caustic followed by a 10% nitric/phosphoric acid wash both at 140-150°F followed by a 5% citric acid passivation cycle and the mill scale remains. They are 150bbl tanks with bottom manways so unfortunately a manual brush scrub would be extremely challenging.

Also, I have heard that quat can be tricky to deal with in a brewery setting and that the tank needs to be heavily rinsed and then caustic cleaned again after the quat cycle. Thoughts on that?

I appreciate yours (and everyone else's) feedback!

Cheers,

------------------------------
Chris Depew
Dean & Co. Brewing
La Junta, CO
------------------------------


Original Message:
Sent: 07-19-2017 12:20
From: Dirk Karl Robert Loeffler
Subject: Tank passivation wont remove this residue

Dear Darren:

The problem you are seeing is common these days as tanks are not properly finished, polished, cleaned and passivated prior to shipment to the customers.  The problem is also not isolated to Chinese tanks.  We have seen this problem with German, US, Canadian and other nations tanks as well, and sometimes just one tanbk is affected and other times all tanks.  The problem here is that the tank was not cleaned after polishing the welds and metal dust has attached itself electostatically to the non-passivated tank surface.  This metal dust will not come off using a standard routine passivation cycle and requires an additional step for removal.  Commonly, cationic compounds such as quaternary ammonium compounds are used to bind these metal dusts to the electrostaically charged chemical compound and remove it.  It almost works as two opposite magnetically charged magnets.  It is important that mechanical energy is also applied either via CIP sprayballs or brushes.

Once the cationic detergent has been rinsed out of the tank, I would recommend repeating the entire passivation cycle including caustic cleaning cycle.  A passivation cannot take place on any surface that has residual dirt or oils (from rolling and welding or just transport) still on it.  Then run the passivation cycle using Nitric Acid and you should be clear.  The absence of the dust can be checked using a white clean rag and rubbing vigorously over the stainless.  The cloth should be clean after rubbing.  If you see grayish/black deposits on the rag, you may need to repeat the passivation and cationic cleaning cycle.

As a general rule, any work with Hydrofluoric Acid (as suggested by some posters) requires both specialized equipment and specialized chemical handling knowledge.  Fluorine is one of the smallest molecules in chemistry and can penetrate quickly even chemical gloves and clothing not designed for fluorinated products.  In addition, it is one of the ten most toxic chemicals on the planet (T+) and quickly penetrates the skin to attack the bones and other vital organs.  NEVER use this product unless you have been trained to work with HF!!!  It may kill you.

There are additional products out there for the removal of the metal dust but this simple method will get the problem resolved in most cases.  Note that there are other metal problems such as contamination from rollers that may look similar and require different treatment.

I hope this helps and you can contact me directly if you have any other questions.



------------------------------
Dirk Loeffler
Technical Director
Loeffler Chemical Corp
Atlanta GA
(404) 629-0999
loeffler.dirk@loefflerchemical.com
------------------------------

Darren,

I'm a little late to the party, but I just saw this post. The procedure that I follow to proper clean and passivate is Caustic wash at 10% by volume at 150F for 60 minutes 
Passivate with Nitric/Phos Acid blend product at 50% by volume at 140F for 60 minutes.
Rinse.
Allow to dry for 72 hours, then perform regular caustic wash before use.
Works every time!


------------------------------
Michael Peeples
Account Manager
Ecolab
Loganville GA
(919) 302-8180
------------------------------

Original Message:
Sent: 08-08-2017 11:49
From: Darren McLean
Subject: Tank passivation wont remove this residue

Thank you all for your suggestions and helpful info. What ultimately ended up working was the fluorinated nitric acid, DART 191 suggested by Steve Gerloff. We tried the QAC method with no success. We ended up running a caustic cycle and then a Dart 191 cycle which removed most of the scale. We still had to get into every tank and scrub with a cloth to get the residue out of the polished areas at the seams and around probes and ports. We then proceeded with a standard passivation.

Thanks again for all the info everyone.

------------------------------
Darren McLean
Brewer
Pawleys Island Brewing Co
Charleston SC
------------------------------


Original Message:
Sent: 07-24-2017 11:38
From: Dirk Karl Robert Loeffler
Subject: Tank passivation wont remove this residue

Dear Chris:

The application is a little bit tricky since QAC products tend to foam.  If you run this in a CIP loop using a spray ball, I would recommend 3 - 5% by volume and run this solution ambient for about 20 - 30 minutes.  The solution is going to foam, so you may have to wait intermittently until the foam has settled and then continue running.  Listen for the pump cavitating, which is a good sign that the foam has taken over.

Rinse thoroughly with plenty of water until free of chemical.  Quaternary ammonium compounds (QAC) tend to have a distinct smell, so the absence is easy to detect.  We also have QAC test paper strips, which can be used to detect the residual presence of the QAC.  Sometimes is helps when you add a small amount of alcohol (0.5 - 1% Isopropanol) to the rinse water during the rinse cycle.  Be careful since the fumes may pose a flammability hazard depending on the environment in and around the tank.

Please note that other problems may be present that look and appear similar, but require different products for removal.  If the QAC solution does not remove the dust, we may have to look into another form of treatment. Unfortunately, at times this can be a trial and error process.

I hope this helps and you can use our Lerasept^(tm) S 10 for the application of the QAC.

There is no need to run a second caustic cycle through your equipment after the QAC application.  The caustic only serves as a means to remove oils and organic deposits from the shipping and manufacturing process.  The dust is attached electrostatically to the tank surface and the caustic will work despite its presence during the first application.

Cheers,

------------------------------
Dirk Loeffler
Technical Director
Loeffler Chemical Corp
Atlanta GA
(404) 629-0999
loeffler.dirk@loefflerchemical.com


Original Message:
Sent: 07-21-2017 13:58
From: Chris Depew
Subject: Tank passivation wont remove this residue

Dirk,

Is there a recommended concentration for the quat solution? Suggested times? Temperatures?

We are having this issue in our brewery (new tanks that have sat for a long time and didn't come pre-"treated"). We have tried a 2-3% caustic followed by a 10% nitric/phosphoric acid wash both at 140-150°F followed by a 5% citric acid passivation cycle and the mill scale remains. They are 150bbl tanks with bottom manways so unfortunately a manual brush scrub would be extremely challenging.

Also, I have heard that quat can be tricky to deal with in a brewery setting and that the tank needs to be heavily rinsed and then caustic cleaned again after the quat cycle. Thoughts on that?

I appreciate yours (and everyone else's) feedback!

Cheers,

------------------------------
Chris Depew
Dean & Co. Brewing
La Junta, CO


Original Message:
Sent: 07-19-2017 12:20
From: Dirk Karl Robert Loeffler
Subject: Tank passivation wont remove this residue

Dear Darren:

The problem you are seeing is common these days as tanks are not properly finished, polished, cleaned and passivated prior to shipment to the customers.  The problem is also not isolated to Chinese tanks.  We have seen this problem with German, US, Canadian and other nations tanks as well, and sometimes just one tanbk is affected and other times all tanks.  The problem here is that the tank was not cleaned after polishing the welds and metal dust has attached itself electostatically to the non-passivated tank surface.  This metal dust will not come off using a standard routine passivation cycle and requires an additional step for removal.  Commonly, cationic compounds such as quaternary ammonium compounds are used to bind these metal dusts to the electrostaically charged chemical compound and remove it.  It almost works as two opposite magnetically charged magnets.  It is important that mechanical energy is also applied either via CIP sprayballs or brushes.

Once the cationic detergent has been rinsed out of the tank, I would recommend repeating the entire passivation cycle including caustic cleaning cycle.  A passivation cannot take place on any surface that has residual dirt or oils (from rolling and welding or just transport) still on it.  Then run the passivation cycle using Nitric Acid and you should be clear.  The absence of the dust can be checked using a white clean rag and rubbing vigorously over the stainless.  The cloth should be clean after rubbing.  If you see grayish/black deposits on the rag, you may need to repeat the passivation and cationic cleaning cycle.

As a general rule, any work with Hydrofluoric Acid (as suggested by some posters) requires both specialized equipment and specialized chemical handling knowledge.  Fluorine is one of the smallest molecules in chemistry and can penetrate quickly even chemical gloves and clothing not designed for fluorinated products.  In addition, it is one of the ten most toxic chemicals on the planet (T+) and quickly penetrates the skin to attack the bones and other vital organs.  NEVER use this product unless you have been trained to work with HF!!!  It may kill you.

There are additional products out there for the removal of the metal dust but this simple method will get the problem resolved in most cases.  Note that there are other metal problems such as contamination from rollers that may look similar and require different treatment.

I hope this helps and you can contact me directly if you have any other questions.



------------------------------
Dirk Loeffler
Technical Director
Loeffler Chemical Corp
Atlanta GA
(404) 629-0999
loeffler.dirk@loefflerchemical.com