Can I Monitor the Composition of my Pickling Bath?

Relevant for steel, aluminium, semiconductors, electronics

Pickling bath monitoring

Pickling baths for steel are typically filled with sulfuric acid (H2SO4) or hydrochloric acid (HCl) to remove scale from the surface. Phosphoric acid (H3PO4) and other acidic mixtures are used in special cases, such as for pickling stainless steel or aluminum. Pickling baths are commonly used whenever removing of impurities, scale, rust or contaminants is necessary. Similar solutions are provided in the semiconductor and electronics industry for etching processes.

Over time the metal ion concentration of the pickling bath increases and the acid concentration decreases. This can be corrected to a certain extent by adding fresh acid to the bath. The acid concentration of the pickling bath is a decisive factor for achieving a clean surface without etching the basic material.

Inline monitor with L-Dens 7400 Version Tantalum and conductivity sensor

The inline monitor from Anton Paar, equipped with the density sensor L-Dens 7400 Version Tantalum, a conductivity sensor and an mPDS 5 evaluation unit, continuously monitors and displays the acid and iron salt concentration of a pickling bath. The use of Tantalum for all wetted parts ensures complete resistance against all usually used acids in pickling baths. The acid monitor achieves a measuring accuracy of ± 0.3 %, depending on the used acid, temperature range, measuring range and contamination.

The maintenance free construction allows operating times for many years. These benefits are combined with high accuracy and a wide temperature range.


  • Reduced acid, neutralization and cleaning fluid consumption
  • Reduced risk of etching the base metal
  • Optimized pickling time
  • Optimized pickling result

Learn more about the L-Dens 7000 Density Sensors Series

Learn more about the mPDS 5


Specifications L-Dens 7400 Version TAN

Measuring range:max. 3000 kg/m³
Process temp. range: -40 °C to 125 °C
Repeatability: 0.02 kg/m³