Using Hydrochloric acid for etch on A8mod

Vardavak

Vardavak

Joined
Jan 5, 2023
Messages
11
Hello good people!
I want to start etching some blades (A8mod) and I can only get hydrochloric acid (30%) locally. I see that most search results give advice on ferric chloride acid and I know there are recipes on how to make this at home.
Is watered down hydrochloric acid a bad choice and why should I make/buy ferric instead? Any pros and cons?

Thank you in advance!
 
Back around 1990 I attended an ABS Damascus class in Washington Arkansas. We made Damascus blades and the instructor Charles Ochs taught us to etch the Damascus blades in full strength hydrochloric acid. I still do etch my Damascus blades in full strength hydrochloric acid. I etch for five minutes, then lightly sand with 800 grit sandpaper, then repeat till the etch is as deep as I want it to be.
Hydrochloric acid can be very dangerous. You should use it outside where there is good ventilation and you don't want to breath the fumes.
When I etch 26c3 steel to bring out the hamon I use Ferric Chloride. Ferric Chloride is much safer than Hydrochloric acid.
 
Use the Custom Search Engine in the Stickys and you can find many past threads on using hydrochloric (muriatic) acid for etching.
 
Stacy E. Apelt - Bladesmith said:
Use the Custom Search Engine in the Stickys and you can find many past threads on using hydrochloric (muriatic) acid for etching.
Click to expand...
Sorry for the wrong placement! I realized too late that muriatic acid is the same as hydrochloric acid (language 🚧). Thank you for moving my post to the right subforum!
 
Tom Lewis said:
Back around 1990 I attended an ABS Damascus class in Washington Arkansas. We made Damascus blades and the instructor Charles Ochs taught us to etch the Damascus blades in full strength hydrochloric acid. I still do etch my Damascus blades in full strength hydrochloric acid. I etch for five minutes, then lightly sand with 800 grit sandpaper, then repeat till the etch is as deep as I want it to be.
Hydrochloric acid can be very dangerous. You should use it outside where there is good ventilation and you don't want to breath the fumes.
When I etch 26c3 steel to bring out the hamon I use Ferric Chloride. Ferric Chloride is much safer than Hydrochloric acid.
Click to expand...
Thank you! On the same subject, neutralizing acid: I have natron/baking soda.
How strong should that be mixed? I have a 100g/3,5oz box, would a teaspoon pr liter/2,5 gallon be enough?
 
For neutralizing a strong acid, use a strong neutralizer.
The amount of baking soda (sodium bicarbonate) needed to make a gallon of neutralizing solution for a gallon of hydrochloric/muriatic acid is 5.5 pounds of baking soda (sodium bicarbonate) in one gallon of water.
If the knife was well rinsed first, a solution of 1 pound per gallon would work.
 
Stacy E. Apelt - Bladesmith said:
For neutralizing a strong acid, use a strong neutralizer.
The amount of baking soda (sodium bicarbonate) needed to make a gallon of neutralizing solution for a gallon of hydrochloric/muriatic acid is 5.5 pounds of baking soda (sodium bicarbonate) in one gallon of water.
If the knife was well rinsed first, a solution of 1 pound per gallon would work.
Click to expand...
Good morning, Satcy. Is that from memory or from a quick reference that I could share with the rest of our makerspace?

Not paying that close attention to cost, I typically put more baking soda than the 2-3 gallons of water will dissolve..🤔
 
"Not paying that close attention to cost, I typically put more baking soda than the 2-3 gallons of water will dissolve."
That is the normal way to make a saturated solution.

The numbers I gave are from a reference for neutralizing hydrochloric acid. You need as many moles of the base as there are moles of the acid to make a neutral salt. Excess baking soda is harmless, so just have a good size bucket for neutralizing blades.

Vardavak's mix of one tsp (6g.) per liter was far too weak to be a proper neutralizer (1/20 the normal strength used).

I buy baking soda in 15pound bags from Costo or Amazon. It is just a tad over $1/lb. I keep a bag on the bench for accidents like acid, FC, and plating liquid spills.

For the nerds:
Muriatic acid is considered a strong acid and has a pH of nearly 1.
Saturated sodium bicarbonate solution is a mild base. It has a pH of around 8.5.
This makes the basic solution safe to handle and have skin contact with, but it is active enough to neutralize the acid if the volume of base solution is greater than the acid. Since there is no harm to excess bicarbonate of soda, use it liberally to neutralize any acidic spills and then wash the residue and neutralized acid away with water.
If the sodium bicarbonate solution was splashed in your eyes it would be about the same as getting salt water in your eyes when swimming. Even the vapors from muriatic acid can blind you. If it contacts skin or other body tissue it will destroy whatever it gets on. Acid burns heal very slow and very poorly.
 
Thanks for satisfying my nerd brain, Stacy.

Wow, it's been a LONG time since high school chemistry...🥸
 
I used to think that muriatic acid (30% HCL) was diluted for the general market, that is only sort of true. It turns out that it is difficult to get it in concentrations over about 38%, so 30% is actually quite concentrated. You can get it a touch higher, but it winds up vaporizing into HCL gas. The fumes are mean.
en.wikipedia.org

Hydrochloric acid - Wikipedia

en.wikipedia.org en.wikipedia.org
 
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