Neutralizing Browning Solutions

[bluenoser]

I have been neutralizing browning solutions with baking soda for many years with mixed results - with one exception.  Like many, I have a devil of a time neutralizing the LMF product.  Works great, but hard to kill.  I have scrubbed parts with baking soda, boiled them, soaked them in kerosene, sealed them with BLO and tried other approaches with poor to barely acceptable results.  I neutralized the last LMF browning job by soaking and scrubbing the parts in a strong household ammonia solution.  It worked well, but was most unpleasant to use in a closed environment.

The objective is to neutralize the acid in the browning solution with a base.  The PH scale goes from 0 to 14 with 0 being strongly acidic, 7 being neutral and 14 being strongly alkaline.  Baking soda is slightly alkaline with a PH of  8.4.  The PH of household ammonia is about 11, and that is why it was so much more effective.

While reading an article on household cleaners-of all things-I discovered the PH of washing soda is also 11.  Washing soda is a much more pleasant product to use and I intend to give it a try on my next browning job.
Here's hoping

[smylee grouch]

.OK, washing soda. Where do you buy it? I assume a supermarket. Are there any brand names to look for? 

[Frank]

Ammonia. Brush it on heavily with a small paint brush and rinse with fresh water.

[rich pierce]

I try to exhaust the acid as opposed to neutralizing it. I wash and card off the barrel after the final application and sweating, and sweat it once more with no browning solution added. My lame theory is that any remaining acid gets used up this way.

[bluenoser]

Sounds good in theory and boiling after the final application should equate to sweating, but that has not reliably done the trick for me when using LMF.
Washing soda should be available at just about any grocery store and Arm and Hammer is a well-known brand.  Look in the cleaning section.  Washing soda is also an excellent degreasing agent.

[smylee grouch]

Ok and thanks for the explanation. I had not heard of it called that before but actually use it myself. I have had that no stop rusting too.

[Sudsy]

.OK, washing soda. Where do you buy it? I assume a supermarket. Are there any brand names to look for? 

You'll see two items in the laundry area of the supermarket, Borax and washing soda
Borax has a PH of around 8
Washing soda around 11

I've used both as buffering solutions in my electrolysis tank - never thought to use them to neutralize browning solution !! (DOH !! insert image of me open palm smacking myself in the forehead)

[bluenoser]

I also use washing soda in the electrolyte when electrolytic cleaning.

[moleeyes36]

Ammonia. Brush it on heavily with a small paint brush and rinse with fresh water.

Frank's method has always worked for me as well.  However, do it outside because of the strong fumes.  I don't know if the fumes are toxic, but they certainly smell bad.

Don Richards

[Scota4570]

Can anyone confirm that LMF contains acid? 

I used to homebrew quick blues and browns.  They typically contain an oxidizers  and metallic chlorides.  These are salts.  Putting basic solutions on the metal will do nothing more than plain water to stop the rust.  Boiling it will stop the rust.  To me that is about dissolving the salts that are in the rust. 

I am fine the after rust.  IT stops in a week or two on it's own.  IT evens out the coverage so I do not make any special pains to prevent it.  After a trip or two to  the range I take it all apart and do a deep cleaning.  From then on it does not rust. 

[bluenoser]

That is an excellent question.  Perhaps someone has PH test strips or a test kit and could test it.
I assumed it is acidic since the only thing that seems to reliably kill it is a fairly strong base.  It really doesn't matter to me if it is an acid or a salt since I merely want to neutralize it and am in pursuit of the best and safest product to do the job.  The PH of both ammonia and washing soda is about 11.  Ammonia has already proven to be effective, but it is unpleasant to use and strong ammonia fumes are an irritant and can damage the eyes and respiratory system.  If washing soda proves to be equally effective, it will be a more pleasant and safer product to use.  In my opinion, after-rust is something to be avoided.

[Metalshaper]

Think it has hydrochloric acid in the mix, if I remember right? Helps it take its initial bite into the metal.. and HCL will rust the
the heck out of metal exposed to it's fumes..

Respect Always
Metalshaper/Jonathan

[Scota4570]

I did more looking around.  I checked the PH of LMF I have on hand.  It is acidic. 

We know it has copper in it based on it plating the substrate if you rub.  So, copper and acid.  OK, checking resources, Angier's book
p. 65 Aa 14 copper sulfate and hydrochloric acid, alcohol and water. 
Aa. 15 same but contains nitric acid too. 
Ab.1 adds zinc chloride.
Dunlap's book p.388  Hydrochloric acid, nitric acid, ferric chloride, copper sulfate, water. 

I have used old formulas that contained mercuric chloride (corrosive sublimate).  Do not do that, it is a potent neuro toxin.  I highly doubt that LMF uses any mercuric chloride. 

While experimenting with quick blue formulas, I found that stannous chloride and ammonia  nitrate (or potassium chlorate) in water made a good hot blue.  It worked like the old formula Birchwood Casey, which I understand contained mercuric chloride.  Also zinc chloride seems like a possible substation for MC. 

Based on the after rust, I think that hydrochloric acid is part of the formula.  I have a browning job in my near future.  I use LMF.  I will put the barrel in a piece of PVC pipe and flood it with warm water for a while and see what happens, then report back.