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Chemical reactions.
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Booshway
Picture of Josh Crain
posted
I got a question for those of a scientific mindset out there. I use a mixture of coal dust and water to age my blades. I mix water and dust into a thick, sloppy pudding and then burry the knife in it overnight. Now here's my question: what is the chemical reaction between the water and the coal that creates a corrosive agent? It works beautifully, pitting the blade, and darkening the steel. In fact I've accidently left a project in there for two days, and when I remembered it, there were tiny holes corroded right through the steel. Does anyone know what the chemistry behind this is? Just curious.


"Return unto me, and I will return unto you," saith the Lord of hosts.
~Malachi 3:7b
 
Posts: 297 | Location: MI | Registered: 18 August 2012Reply With QuoteReport This Post
Factor
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My guess would Carbonic acid eating on the carbon steel


Beer is proof that God loves us,and wants us to be happy-B. Franklin
 
Posts: 2014 | Location: Oreegun Territory | Registered: 24 March 2013Reply With QuoteReport This Post
Booshway
Picture of MountainRanger
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I think it might depend in part on the type...anthracite, bituminous etc. which would determine the specific chemistry. There is some sulfur content in all coal and it sort of sounds like what you are seeing is an evolution into mild sulfuric acid and that might be what is giving you the effect want: etching your blades.


Sua Sponte
 
Posts: 460 | Location: SW Virginia (New River Valley) | Registered: 13 August 2014Reply With QuoteReport This Post
Factor
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Agreed, I think it's the sulfur in the coal that's doing the trick. Coal is hardened peat, and peat bog are one of the most acidic environments around, so acidic that corpses from 2400 years ago were found mummified (well they were really tanned). Check out Tollund Man.

LD


It's not what you know, it's what you can prove
 
Posts: 3843 | Location: People's Republic of Maryland | Registered: 10 November 2004Reply With QuoteReport This Post
Booshway
Picture of Josh Crain
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So, in essence, adding water just recreates the peat bog environment? Interesting.


"Return unto me, and I will return unto you," saith the Lord of hosts.
~Malachi 3:7b
 
Posts: 297 | Location: MI | Registered: 18 August 2012Reply With QuoteReport This Post
Factor
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*scratches head* umm,ok? Sounds good to me....


Beer is proof that God loves us,and wants us to be happy-B. Franklin
 
Posts: 2014 | Location: Oreegun Territory | Registered: 24 March 2013Reply With QuoteReport This Post
Booshway
Picture of MountainRanger
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Josh, you can probably change the dilute factor of your acid bath by varying the density of the crushed coal. The finer the crush and the soupier the stew, and if you change the environment it sits in while you're waiting for it to be done, (seal the container, cook it, etc) I think you will find some changes in how dilute/strong the mix is. That can vary the kinds of patterns you can get in your etching. Sounds like a fun project.


Sua Sponte
 
Posts: 460 | Location: SW Virginia (New River Valley) | Registered: 13 August 2014Reply With QuoteReport This Post
Booshway
Picture of Josh Crain
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Thanks! I never thought of that. =D


"Return unto me, and I will return unto you," saith the Lord of hosts.
~Malachi 3:7b
 
Posts: 297 | Location: MI | Registered: 18 August 2012Reply With QuoteReport This Post
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