Formulation of pickling paste for stainless steel

A. There are commercial products for local passivation of stainless steels after welding. Try asking at a local welding shop. I know that Avesta, a stainless steel company, is one supplier of a passivation paste product.

A. You can perhaps gel the nitric acid with Fumed Silica [affil links].

My prejudice is I dislike gelled acid for safety reasons. Further, since acids function by reacting with metal, and the gel impedes fresh solution flow to the surface, I think they are less effective than liquid acids. But I would think that you can just follow the regular passivation spec (QQ-P-35C [link is to free spec at Defense Logistics Agency, dla.mil]) for nitric or nitric-chromic passivation.

Is it impractical to just repassivate the whole welded structure?

A. Chris, You could use Brush Electroplating to selectively passivate the areas that need to be done. Depending on the size of the areas it could go fairly quick.

A. Dear all,

For thickening weak or strong acids you can use Ethomeen C12 from Akzo or Cecajels from Ceca. Cecajel 210 for many Weak and Strong acids (HF, Phosphoric, Citric); Cecajel 300 for Sulfamic acid; Cecajel 250 for Hydrochloric acid.

Hope this helps.

A. Thanks Ron for doing what you could. Sergio asked for the chemical names of raw materials and I think fumed silica and barium sulphate are the most common generic thickeners, although maybe not the equal of commercial products :-)

I suspect, but don't know, that fumed silica would be unsatisfactory for mixes that contain hydrofluoric acid. Regards,

A. Hi Rajendran. The more common thickening agents will not work because the HF will attack Fumed Silica [affil links] and the HNO₃ will attack cellulose thickening agents. Sorry, I don't know the answer. One thing you could do is review expired patents on the subject, or you could buy some and reverse engineer them.

A. The thickener is barium sulphate.

Dear Mr.Sun,

It will be some really mad person who will disclose its proprietary chemistry to you and the world. You may better go to some Chennai five star hotel and ask the recipe of their speciality cuisine and get same feedback from them.

---

March 18, 2009

Calcium Gluconate
for HF acid burns

on eBay or

Amazon

(affil links)

Hi, Jenny. You're right, of course, that proprietary knowledge won't be shared. Still, there is a constant & continuing shift between what constitutes proprietary chemistry versus what is generic info that is discussed in technical conferences, journal articles, and industry websites. The worldwide patent system, with patents having a limited life of 20 years, was established with the specific goal of encouraging progress through ideas becoming public knowledge after a time.

Some people may consider the thickening agent for gelled acids to be proprietary information but, as you see, some other people consider at least some thickeners to be just generic info.

Users must make sure they have the calcium gluconate first-aid antidote on hand at all times, and a clear plan for proper follow-up medical treatment before even getting near hydrofluoric acid.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. This is a very difficult task.

adv.
We have successfully developed green" pickling pastes without nitric acid for stainless steel, carbon steel, titanium. We are currently working on eliminating hydrofluoric acid also. However work is not completed yet.

A. Anal,

Gels production for pickling, passivation for stainless steel, carbon steel, titanium - are proprietary.

adv: If you want to buy the recipes - no problem - contact me. But free advice - sorry, we cannot.

A. Not enough barium sulphate. Keep adding until it is the consistency you want.

A. Hi akshata. As you see, we added your posting to a thread where the question was already answered. But please be aware that when you jellify this very dangerous acid, allowing it to be placed onto surfaces and just sit there where people can potentially be unknowingly exposed to it, you drastically increase its dangers. Please make sure you that are a highly responsible steward for the risks you will be creating by creating a failsafe plan for its removal before anyone can touch it. Thanks for your understanding.

Regards,

A. Hi Gokay. We appended your inquiry to a thread which should answer your questions, but feel free to continue the discussion. Good luck.

Readers, please search the site before starting a topic. When you start a topic there is zero search engine coverage for the world to even find your question, and Google penalizes us for duplicative topics, so it will never appear on search engines even when answered :-( Plus, people who have already answered the question repeatedly are unlikely to do so yet again :-)

Luck & Regards,

Hi Gokay,

Preparing pickling paste does not involve mixing with organics. The proprietary know-how has been sold to Bama technologies, Italy many years ago. Thanks to in-house mixing, Bama won numerous contracts for maintenance cleaning of large vessels for bio and food industries.

The gels compositions can be altered for summer temperature, for carbon steel, stainless steel, titanium. It is possible to mix 'green" gels, gels for passivation only.

adv.
Contact us if you are serious in obtaining gel technology. aff