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Muriatic solution uses in a metallurgical setting

I am a student learning/researching corrosion and have a question regarding 5% muriatic solution. From what I can gather, muriatic solution is Hydrochloric acid, so how (or for example 2 good uses) and why would this be used in a metallurgical setting?

Mandy Yasinski
- Calgary, Alberta, Canada
2003

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2003

Hi Mandy,

What a weird request! ... in a metallurgical setting!

Go and ask any distributor of stainless steel for a corrosion chart ... try the Web, too ... just type down corrosion resistance, for example ...and add to that, maybe, steel, stainless, aluminum, etc ...

HCl = hydrochloric acid = muriatic acid.

5% solution is pretty tame but still will chew up stainless in time. It's a reducing acid and loves chrome.

See # 12044 in the archives, if you wish.

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).

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I've been looking at Mandy's inquiry, Freeman, and I think what she means by "in a metallurgical setting" is "within the context of the study of metals". Muriatic acid would be used to remove rust and mill scale from steel, as one example, and to strip coatings like zinc plating as a second example.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003

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2003

Well, Ted, I dunno.

After all, when one uses a long word (which I can hardly spell) and mentions HCl, obviously I find the context somewhat hilarious.

What would you say if someone said 'Rainwater in a Metallurgical Setting'?

I am reminded of the answer a medical student gave to the judge (for some minor infraction) ... he said that he was recuperating from the traumatic perroninivitis of the flexor dignatorium sublimus in the metacarphogal joint... (please excuse the spelling) ...i.e. he had a sore finger.

I like precise, concise unadulterated English, s.v.p.

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).

To add to the information that Ted provided, a solution of 5% HCl and 95% ethanol (called Nital) is a very common etchant for iron and magnesium base alloys. When preparing metallurgical samples (section, grind, polish) the final step is usually etching, which selectively removes material to reveal the microstructural constituents, e.g. grain boundaries, different phases, etc.

Toby Padfield
- Troy, Michigan
2003

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For shame, Toby! Nital is NITric acid plus ALcohol, not hydrochloric. I'm not aware of a cute lab name for a simple HCl solution in water or alcohol.

muriatic acid ⇦this on eBay or Amazon [affil links] is a trade name for Hydrochloric when in industrial purity for things like swimming pool pH control or etching concrete. Lab grades are higher purity.

"In a metallurgical setting" HCl is used, usually along with other chemicals, in various weak solutions for final etching, and is also used in strong and hot solutions (20-50% by volume) for deep etching. This gives a severe surface attack that reveals grain flow and discontinuities in forged or rolled steels.

Paul Tibbals, P.E.
gas & electric
San Ramon, California, USA
(My opinions are not related to nor a statement of my employer's)
2003

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Paul,

Thanks for the clarification. I can't believe I goofed on that. My brain must have been somewhere else...

Toby Padfield
- Troy, Michigan
2003