Summary for acid pickling Discussion
Acid pickling for steel strips is the focus of this thread. Bipin asks about the defects and uses of hydrochloric acid (HCl) and sulfuric acid (H2SO4), and what would happen if H2SO4 were used instead of HCl. The reply notes that there may have been a language mix-up, but answers the practical point: sulfuric acid pickles steel very slowly unless it is used quite hot, while hydrochloric acid works well even at room temperature. Because of that, most small users prefer HCl for pickling. The thread does not list specific defects of either acid, but it does make clear that the main operational difference is speed and temperature requirement, with H2SO4 being the slower option unless heated.
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
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
Need quick confidential answers? $25
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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
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