Development, testing and optimisation of process technology for the pickling/etching of composite metals with the minimal loss of material

The application of the patented in-situ regeneration process developed has generated savings of some 25,000 euros per annum in the etching of composite metals, based upon a 90% reduction in the consumption of process and neutralisation chemicals and in the production of sludge.


Before workpieces of composite metal construction can be galvanised, their surfaces must be subject to preliminary treatment by electrolytic etching and pickling. A hydrochloric acid bath is the preferred medium for etching. To date, the replacement of the hydrochloric acid has been necessary, even where it contains only limited quantities of abraded metals, in order to prevent the impairment of quality. Thereafter, it has been necessary to neutralise the discarded hydrochloric acid in the waste water treatment system.

The objective of the project was to achieve a drastic reduction in the high consumption of hydrochloric acid and neutralising agents and to allow the recovery of metals removed in a materially useful form.


  • The regeneration of hydrochloric acid has been achieved by the introduction of air – this required only the technically straightforward installation of an injection device in the process bath.
  • The copper sludge produced is extracted from the base of the container using a membrane pump, then collected in a buffer tank, filtered using a chamber filter press and recovered for reuse.
  • The filtrate (hydrochloric acid) is recirculated in the production process.
  • In addition to the reduction in environmental pollution associated with the reduced consumption of chemicals and the reduction in sludge production, this in-situ regeneration process also generates cost savings of the order of 25,000 euros per annum.

There have been no problems in the incorporation of this procedure into the production process.

A patent has been granted in respect of the process technology developed.

Project Participants

Implementing Institution

Kolbenschmidt Gleitlager GmbH

More Project Informations

Project title:  Development, testing and optimisation of process technology for the pickling/etching of composite metals with the minimal loss of material

Project number:  01RK9617/0

Project period:  1996 - 1999

Project region:  Germany (Lower Saxony)

Project contact:

Herr Dipl.-Ing. Rehbock

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++ 49 / 4961 / 986 - 116

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Source: German National Library of Science and Technology Hannover (TIB)