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Acid pickling

Q. We are working on steel strips. We do pickling of steel strips. We use HCl as medium for this purpose. I know that we can use h2so4 also for the same but can you please tell me what are the defects and uses of HCl and h2so4 respectively. What if I use h2so4 instead of HCl for that.

Bipin
- Hyderabad, Andhra Pradesh, India
2003

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You requested that this inquiry be posted in our Kindergarten to Grade 12 school projects section, Mr. Bipin,but I am beginning to suspect that there was a language problem and you are actually an industrialist. In any event, the short answer is that sulfuric acid works very slowly unless quite hot, so most small users opt for hydrochloric acid because it functions well even at room temperature.

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

HCl emits chlorine gas when in use and even a little bit when not in use. This tends to rust anything within 100 feet if you do not have a good exhaust system that runs all of the time.

James Watts
- Navarre, Florida
2003

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HCl & H2SO4 are both capable to clean steel. HCl has been preferred here in the states due to availability/price and it's ability to result in a brighter surface.

H2SO4 is able to get it clean, but tends to have a slightly darker surface and could even develop a smut layer (which can be wiped/brushed away) if over-pickled.

Amanda Glass
- Springboro, Ohio, USA
July 7, 2011