Hydrofluoric and Nitric Acid

[willynilly]

Have you used this on your SS?

Cut the tubing for my new SS stand today, it is getting TIG welded on Thursday and then getting a Hydrofluoric and Nitric Acid bath, have any of you done this?

It removes all discoloration so that the steel, welds, everything are pure and clean and the SS looks like one piece, as it is all one color and sheen. No heat discoloration, nothing...

Have any of you done this on your stands? How did it turn out?

 

[kmack747]

I use nitric acid all the time. Some wonderfully nasty stuff

 

[GlenF]

just be careful with the "boneseeker"

 

[Gfei]

Yeah, HF is some nasty stuff

 

[Loweface]

Anybody who works with HF who isn't activly trying to stop using it should be stopped from using it on safety grounds... Trust me I won't be using it again.

 

[willynilly]

Well, this place has to use it, it is a requirement of their customers, I am getting it done free...

They work for major food and pharma companies doing sanitary SS work.

 

[Gfei]

Anybody who works with HF who isn't activly trying to stop using it should be stopped from using it on safety grounds... Trust me I won't be using it again.

I don't think I would go that far, I've used the stuff quite a bit in the past. Proper PPE and attention to what you're doing and it's fine... and plenty of calcium gluconate just in case.

 

[android]

i heard on a podcast today that nitric acid can help repassivate SS. i have some minor rust on the inside of the welds on my keggles. obviously taking the necessary safety precautions, would i be able to scrub/brush off the rust and then apply some nitric acid to the weld to repassivate?

 

[kmack747]

i heard on a podcast today that nitric acid can help repassivate SS. i have some minor rust on the inside of the welds on my keggles. obviously taking the necessary safety precautions, would i be able to scrub/brush off the rust and then apply some nitric acid to the weld to repassivate?

Yes A 10% solution for 15 to 20 min will passivate very nicely. Just remove all corrosion first.

 

[Loweface]

I don't think I would go that far, I've used the stuff quite a bit in the past. Proper PPE and attention to what you're doing and it's fine... and plenty of calcium gluconate just in case.

Sure use it if nessicary, but if you find an alternative use it...

It's when you get complacent that it'll bite you...

 

[android]

Yes A 10% solution for 15 to 20 min will passivate very nicely. Just remove all corrosion first.

sweet! we just happen to have a huge bottle of it in my lab.

 

[willynilly]

Yeah, without proper ventilation in their old shop, the fumes alone corroded every single piece of carbon steel in the place. They finally had to move to another shop with proper ventilation when my buddy refused to accept this work from their sales dept. It took them a few years of bitching and finally a visit from their corporate pres. to get the new shop. They had to replace nearly everything made of carbon steel in the old shop before they moved out... pipes, hangars for the drop ceilings etc... it was all trashed.

Now they have the proper facilities to build brew stands... I mean do customer work We are thinking of maybe building custom stands for some guys in the area.

 

[willynilly]

Before the HF wash...

https://www.t-mobilepictures.com/myalbum/photos/photo17/af/ca/146a5013ffcd__1268913538000.jpeg

https://www.t-mobilepictures.com/myalbum/photos/photo15/b0/44/25aee9f47772__1268913563000.jpeg

After the HF wash...

https://www.t-mobilepictures.com/myalbum/photos/photo01/c5/51/0427c7305300__1269013069000.jpeg

Just have to mount the control box, RIMS, pumps and apply the custom safety decals...
The stand ran about $1200 before my discount, final price $475

It was 100% TIG fusion welded, VERY clean work.

 

[kezgin]

i heard on a podcast today that nitric acid can help repassivate SS. i have some minor rust on the inside of the welds on my keggles. obviously taking the necessary safety precautions, would i be able to scrub/brush off the rust and then apply some nitric acid to the weld to repassivate?

some bar keepers friend, a green scrub pad and a little elbow grease will work too

 

[Cliff897]

Have you used this on your SS?

Citric is easier cheaper and safer.

TIG welded on Thursday and then getting a Hydrofluoric and Nitric Acid bath, have any of you done this?

First question you ought to be asking is why?
I mean to say: What purpose is it you hope to accomplish by invoking a passivation process after welding?

If it is to restore the passive chrome oxide layer you have a more pressing issue which you must address first.

After welding temperatures the surface of SST will have undergone a molecular change.

All (or mostly all) the Chrome in the upper layer of metal will have migrated to the surface and deposited itself at the surface. It does not establish a good bond to the metal so it can be invades and stripped by corrosives.

However, some SST does not do this so dramatically as others. 304 being the most user friendly in that respect.

If you want to address this chrome super deposition issue you need to re heat the metal and anneal it by lowering the temperature slowly over time.
Another anneal for SST is a fast quench in water.
SST and copper are unique in the world of metals in that a fast water quench can anneal them.

To know which anneal you need ( if any) you need to know what the consumable used to weld it was, what the temp it was welded at, whether the weld was done all at once and what grade of SST you started out with.
(sorry to end the sentence with a preposition)

Only after you address the chrome migration between the boundary layers can you then consider whether passivation is an issue.

Remember: SST will instantly produce the passive Chrome oxide layer whenever the chrome at the first mole layer is at 10.2% or higher.
Since all SSt has this percentage it's really all about whether you have changed the molecular structure of the steel or not.

But since it's a pot and since your welder is probably a skilled tradesman (and not a freaking G.D. professional) you are probably golden.

Never let a professional anywhere near you steel. Only tradesmen.

If all you want is to get rid of the rainbow effect use a SST or brass wire brush or some abrasive followed by the SST wire Brush.

Never use a plain steel wire brush.

 

[GlenF]

Just listen...be SUPER careful when using nitric and HF acids. My brew buddy and I were cleaning up his keggle and having some homebrew. It was an old barleywine...needless to say we got a bit "careless" after a few. This is where the tragedy starts. So we were cleaning, drinking, and shooting the ****. My bud sets his beer down near the beaker of acid. He goes to take a drink of barleywine and accidentally DRINKS THE ACID!!! I couldn't drive, so we had to call an ambulance to get him to the hospital. Unfortunately, he died shortly after he arrived.





They even made a beer in his honor:

 

[Schnitzengiggle]

This may be slightly off-topic, but when it comes to kegs would using Hydroflouric or Nitric acid be necessary for cleansing and repassivating kegs?

I have a decent source of near new, if not new, kegs that have been sitting for 5+ years, and after inspection some of them are under vacuum, they look great, but have product in them, and who the hell knows waht may or may not be growing in them, as they are coming from a winery that seems to have used them for wine storage/lab test batches.

I understand that Muriatic acid may be used, but the SS must be repasivated to avoid rust, but I do not understand the chemistry behind it, is there a better caustic to use that is more "friendly" for the homebrewer.

Sorry for the semi-hijack, I am interested in understanding the cleansing, and re-passivation process.

Passiviation is really something I would like to understand when it comes to SS. I havethe basics with aluminum, but not SS.

 

[Schnitzengiggle]

Just listen...be SUPER careful when using nitric and HF acids. My brew buddy and I were cleaning up his keggle and having some homebrew. It was an old barleywine...needless to say we got a bit "careless" after a few. This is where the tragedy starts. So we were cleaning, drinking, and shooting the ****. My bud sets his beer down near the beaker of acid. He goes to take a drink of barleywine and accidentally DRINKS THE ACID!!! I couldn't drive, so we had to call an ambulance to get him to the hospital. Unfortunately, he died shortly after he arrived.





They even made a beer in his honor:

Super messed up...brings a story to my mind about some ******* who drank some degreaser when I worked at McD's as a teenager, all I could think of was...*******.

 

[kladue]

For the cleaning of the science projects in the kegs, powder dishwasher soap or washing soda in water heated to 180 degrees and left for an hour. Passivation 1/4 cup Ascorbic acid+1/4 cup citric acid in water, heat to 180 and let cool, and rinse with water. The citric/ascorbic acid method is used in food, beverage, and pharmeceutical line passivation these days, nitric acid prep is increasingly uncommon these days because of the nature of the acid and waste products.

 

[willynilly]

Well it is 304 SS

The HF was done by a company that uses it all the time.

It was free

It looks FABULOUS!!!!!

 

[pickles]

For the cleaning of the science projects in the kegs, powder dishwasher soap or washing soda in water heated to 180 degrees and left for an hour. Passivation 1/4 cup Ascorbic acid+1/4 cup citric acid in water, heat to 180 and let cool, and rinse with water. The citric/ascorbic acid method is used in food, beverage, and pharmeceutical line passivation these days, nitric acid prep is increasingly uncommon these days because of the nature of the acid and waste products.

Can you recommend a source for ascorbic and citric acids? How many gallons of water for the amounts stated?

 

[oceanselv]

Well it is 304 SS

The HF was done by a company that uses it all the time.

It was free

It looks FABULOUS!!!!!

Well then lets see a picture.

 

[oceanselv]

Pickles try a company like McMaster Carr or any other industrial supply house.
Here is what McMaster charges:
Citric Acid, Granular 5-lb. Pail 3190K624 32.55
25-lb. Pail 3190K625 132.78

 

[kladue]

Do a search on Amazon.com for Ascorbic acid powder in 1Lb container, and same for citric acid. For water quantity fill pot or kettle and add powdered acid, heat, let stand at 180 degrees then cool down. This gives the acid blend time to remove surface iron and chrome and re oxidize the chome surface. In industrial applications the solution is circulated at 180 degrees and tested to determine soluble iron content. When iron levels plateau the solution is drained and lines are flushed as passivation was finished.

 

[willynilly]

My all SS (down to the last screw and nut) Brutus "20".

*9000W Blichman Boil Kettle

*9000W RIMS heater

*15G Blichman MLT with "AutoSparge"

*(2) LG 3-MD-HC pumps

*BCS wireless control (is it catching on!)

*"The Brain", a 12" x 12" x 6" self contained control box that controls all brew functions, processes and temperatures. It contains 10 SSRs, 8 heatsinks, distribution block, grounding bar and fuses. Also houses the BCS 460 web based controller as well as the wireless bridge to provide wireless control. Utilizes a 105 CFM 220VAC muffin fan for ventilation.

I give you, DIGIBREW...

In testing (ran all components on test stand before mounting to SS stand) it has been found to bring 12 gallons of 50F water to a rolling boil in 33 minutes! The LG pumps will pump through the current plumbing configuration at a rate of approx. 6 gallons/min.

 

[Ohio-Ed]

Hey willy... I know you're a proud new papa, but this is the third thread I have seen with the same message and pics. Why not start a new build thread to show off your new baby .

LOOKS VERY NICE BTW...

Ed

 

[willynilly]

Hey willy... I know you're a proud new papa, but this is the third thread I have seen with the same message and pics. Why not start a new build thread to show off your new baby .

LOOKS VERY NICE BTW...

Ed

I had started two threads, one concerning the welds, one concerning the HF cleaning of the SS. I just cut and pasted the post to each thread to show the stand and welds when it was complete, to complete the threads.

Sorry, no interest in doing a build thread.