Concentrations used in preparing chemical etchants
Concentrations used in preparing chemical etchants
(OP)
Hello all,
I work for a bowling manufacturing company and we are looking to install a materials failure analysis addition to our engineering test lab. I have been looking online everywhere for chemical suppliers (and have finally found one or two good ones) but I wasn't sure what concentrations we should purchase.
For example, in preparing nital, I understand that it is about 2 parts nitric acid and 98 parts alcohol - but what original concentration of nitric acid do you use to mix with the alcohol?
The idea is, we are trying to buy just a few key chemicals (glycerin, nitric, hydrochloric, hydrofluoric, & ethanol) so we can keep the cost down, but at the same time have the ability to create a variety of etchants. Let me know if you have any suggestions. Thanks,
Kyle
I work for a bowling manufacturing company and we are looking to install a materials failure analysis addition to our engineering test lab. I have been looking online everywhere for chemical suppliers (and have finally found one or two good ones) but I wasn't sure what concentrations we should purchase.
For example, in preparing nital, I understand that it is about 2 parts nitric acid and 98 parts alcohol - but what original concentration of nitric acid do you use to mix with the alcohol?
The idea is, we are trying to buy just a few key chemicals (glycerin, nitric, hydrochloric, hydrofluoric, & ethanol) so we can keep the cost down, but at the same time have the ability to create a variety of etchants. Let me know if you have any suggestions. Thanks,
Kyle





RE: Concentrations used in preparing chemical etchants
Principles of Metallographic Laboratory Practice
by George L Kehl
RE: Concentrations used in preparing chemical etchants
Your safety people may not allow you to use picric acid because of concerns about explosion. I fought that battle and eventually lost.
There are several choices for suppliers, I use Fisher Scientific www.fishersci.com.
RE: Concentrations used in preparing chemical etchants
HCl 36.5 %
HNO3 70 %
H2SO4 96 %
HF 50 %
I have used picric acid at every lab I have been in over the last 17 years. Your mileage may vary.
RE: Concentrations used in preparing chemical etchants
Using 1 part nitric, 2 parts glycerol and 3 parts hydrochloric, does it matter what specific concentrations you use for the individual components? I haven't been able to find anything online that says so (although I understand that nitric is unstable in certain solutions - like alcohol, if you're preparing nital - past 5% conc.). I can buy concentrated solutions and dilute them, but if I need to, say, dilute the hydrochloric acid for this "recipe", is there a specification (or just a rule of thumb) that says how much to dilute it?
RE: Concentrations used in preparing chemical etchants
I guess it's just a etchant-to-etchant basis.
Thanks again for all your help.
Kyle
RE: Concentrations used in preparing chemical etchants
Normally there will be a don't store label if the enchant is at all unstable. Glyceriga falls into the don't store category. I've never seen a need for Nital to be over 5% in 46 years in and around metallurgical laboratories.
You need to get the book referenced by Arunmrao or any book that has all the enchants and directions.
Or you can subscribe to a database like the one at the Kaker site.
http://www.kaker.com/etch/etch.html
RE: Concentrations used in preparing chemical etchants
RE: Concentrations used in preparing chemical etchants
The book that unclesyd mentioned was once the bible of metallography, but it is long since out-of-print. George Vander Voort's book Metallography: Principles and Practice published by ASM International is probably the best reference if you want a thorough source on techniques, lab practices, etc. ASM HANDBOOK Volume 9 Metallography and Microstructures is also an authoritative reference. Buehler and Struers also have a lot of excellent information on techniques, etchants, failure analysis, etc. on their sites. Here are some links for more information:
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