Pickling baths are used downstream of the hot rolling process, but also in many other fields of the metal-working industry to remove, modify, passivate or clean surfaces in a defined manner. To this end, pickling solutions are employed, mainly consisting of mineral acids, like hydrochloric acid.
The concentration of these acids decreases during the pickling process, whereas the degree of disturbing components such as contaminations and carry-over increases.
Pickling removes impurities from the steel surface. However, the acid also attacks the iron oxide on the metal surface and ferrous salts are generated (e.g. iron (II)). It is therefore of great importance to precisely control all process-relevant parameters, such as dwell time, bath temperature and bath composition. Only in this way, pickling bathes can be operated in an economic and resource-saving manner.
|Carbon Steel/Mild Steel/Wrought Iron||Hydrochloric Acid (HCl)|
|Stainless Steel||Phosphoric Acid (H3PO4), Nitric Acid (HNO3), Hydrofluoric Acid (HF)|
|Aluminium||Nitric Acid (HNO3), Caustic Soda (NaOH), Phosphorous Acid (H3PO4)|
|Copper Alloys||Sulphuric Acid (H2SO4)|
|Brass||Sulphuric Acid (H2SO4), Sodium Chloric (NaCl), Soot|
The measuring system LiquiSonic® 40 allows the parallel detection of two physical quantities, such as sonic velocity and conductivity, and therefore the determination of the HCl concentration in the pickling bath as well as the iron content. This leads to the elimination of expensive laboratory analysis.
The LiquiSonic® analyzer provides a precise inline bath concentration measurement with real-time monitoring and permanent data logging. This allows the process to be automatically controlled in the optimal concentration range with stable, sufficient pickling results. LiquiSonic® is used to avoid a underdosage or overdosage of HCl.
LiquiSonic® reduces extensive lab measurements and replaces the time-consuming sampling process:
LiquiSonic® saves costs by reduction of hydrochloric acid consumption (ROI for 30 m3 plant: 7,5 m3/h acid consumption):