Neutralizing Ferric Chloride

[Centaur]

I know that an alkaline neutralizes an acid, and vice versa. In my job, I used to work with some pretty nasty acids. I've never worked with alkalines.

Would using vinegar be the best way to neutralize ferric chloride? Since I don't have any litmus strips, what would the ratio be for neutralization? How many fluid ounces of vinegar to neutralize one fluid ounce of FeCl?

Thanks in advance

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Glen AKA Centaur
"If I have seen further, it is by standing on the shoulders of giants."
- Isaac Newton

 

[Nathan House]

Hi, I just used baking soda in warm water
iI just dumped some in a boket no exact
amount and fill it with teh water,I stuck my blades in the ferrice to get the color I wanted then dipped them in the baking soda water,and it stop the ferric acid from going any farther.no rust on my blades and it has been 2 weeks and the steel is 1095
one of the worst for rusting.

 

[Jerry Hossom]

Devin Thomas recommends Trisodium Phosphate to neutralize the Ferric Chloride when etching his Damascus. Nathan's Baking Soda probably works fine too. A good washing with soap and water and a soft brush is likely best of all, since it will reach those little nooks and crannies that water alone won't get to.

After that, a good coat of light oil will displace any water that's left. (do this only after you are done with the handle and the epoxy is well cured. Bet you can't guess who learned that the hard way?)

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Jerry Hossom
www.hossom.com

 

[Walt Welch]

Centaur; you are correct that acids and bases neutralize each other. Actually, they form salts and water. You can tell whether an aqueous solution of a salt will be acidic or basic (alkaline) by looking at what the reactants were.

Take ferric chloride. This is a salt formed from ferric oxide and hydrochloric acid (or could be just Fe and HCl). The point is that ferric oxide (rust) is not a very strong base, but hydrochloric acid is a very strong acid; that is to say HCl is nearly completely dissolved into H+ and Cl- ions in water.

Thus, ferric chloride is a salt formed from the reaction of a weak base and a strong acid. You would expect this salt to be acidic if dissolved in water, and you would be right. Therefore, you would need a base to neutralize the salt, NOT an acid such as acetic acid (vinegar).

Thus, sodium bicarbonate, a weak base (formed from the reaction of sodium hydroxide, a strong base, and carbonic acid, a weak acid), would do the job of neutralizing the ferric chloride.

Nathan House; I believe you mispoke yourself when you said 'ferric acid.' You meant, I believe, to say an aqueous solution of ferric chloride. Although I must admit it is an acidic solution, and does have ferric ions in it.

I would agree emphatically with the suggestion to use a small amount of detergent in with the sodium bicarbonate. This would lower the surface tension of the solution so that it would penetrate the pores of the steel better. Gentle brushing with an old tooth brush wouldn't hurt either.

Hope this helps; I hate to think that I spent all that time in the mid '60's in chemistry classes and didn't learn ANYTHING!

Walt

 

[Centaur]

Thanks for all the replies, and Walt: E-Chem 101! Outstanding!

I guess I was a little confused after reading the final etch reference in Jim Hrisoulas' "The Pattern-Welded Blade." He refers to "Low-Acidic" (as opposed to Aqua Regia) and "Alkaline Based" reagants in the same section. So re-read it more carefully.

I also got some pool water analysis strips and verified that, yes, Ferric Chloride is acidic.

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Glen AKA Centaur
"If I have seen further, it is by standing on the shoulders of giants."
- Isaac Newton

 

[Pete Peterson]

Just spray a little windex with ammonia on it. Works ok for me.


;D

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old pete

[This message has been edited by Pete Peterson (edited 05-25-2000).]

 

Sodium or potassium carbonate or bicarbonate will do the trick, But they produce CO2, which may be a nuisance. Using dilute ammonia works the same, without "bubling" (no gas production) neutalisation products are "harmless"=> iron hydroxyde (rust) and sodium/potassium/ammonium chloride.
Remember sodium chloride is just "table salt". Happy etching

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D.T. UTZINGER

 

[Jim Harvey]

I use straight ammonia after the etch. Then I use hot water and regular dishwashing liquid and rub / wash the blade with my fingers. After all is done, a light coat of oil ( I use Break Free) and I'm done.