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Pickling and roasting of semi-finished components of copper and cupro-nickel composition without the use of nitric acid and chromic acid
- Bundesministerium für Bildung und Forschung (BMBF)
Fertigung / produzierende Unternehmen, Umwelt- / Verfahrenstechnik
Surface oxides on metal products are removed in pickling plants in order to facilitate the further processing of the products concerned.
The objective of this investigation was to allow the replacement of the pickling agents nitric acid and chromic acid by a pickling agent which would be suitable for recirculation. Further objectives were the identification of pickling media which would ensure the adequate removal of oxide coatings, and the development of components for the continuous regeneration of the pickling solution.
For cupro-nickel alloys, the combination of pickling agents is as follows: H2SO4/Fe2(SO4)3/H2O2. H2SO4 is still used as a pickling medium for copper and low-alloy copper, albeit with modified flushing.
A test sequence has been developed for these two pickling agents using a spray flushing unit. This sequence has been tested in a pilot plant under experience-based conditions.
- Scope for the application of Fe2(SO4)3/H2SO4 pickling baths for cupro-nickel alloys has been demonstrated, together with reoxidation using peroxydisulphate/H2O2.
- The material flow chosen prevent that the production of waste water. Flushing water from the spray flushing unit is largely recycled, while sludge is separated using a hydrocyclone and a reversible flow filter.
- Copper is removed from the H2SO4 pickling bath by means of electrolysis, while the cupro-nickel pickling agent is processed by membrane electrolysis.
- Sludge from the pickling baths is removed and reprocessed in a recycling plant.
Autor/Projektleiter: no information
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