Pickling achieves an intensive cleaning and activation of metal surfaces, through the removal of a thin layer of the material processed. The result is a metallically pure surface, free of oxides and contamination of other metals. Pickling attacks primarily the grain boundary of the metal structure and gives the surface a matt to satin gloss appearance.
Pickling can be carried out either chemically or electrolytically (anodically). Pickling chemicals usually contain mineral acids and an oxidation chemical as well as additives to improve the result and reduce pollutants.
Several methods are available for the pickling process:
- Immersion pickling for immersing, sprinkling or through-pumping
- Spray pickling involves spraying on an adhesive pickling paste onto free-standing areas
- Brush pickling for local treatment by painting the chemicals e.g. onto welding seams
Non-rusting steels, nickel-based alloys and titanium are usually pickled following processing, in order to create a good starting point for the further processing or creating an intact passive layer as a precondition for corrosion resistance.
Normal steel, copper materials and aluminium are pickled for cleaning purposes or pre-treatment before electropolishing, chemical deburring, polishing, anodizing or galvanizing.
Rinsing water and used pickling chemicals must be treated and disposed of in accordance with the legal regulations.
POLIGRAT processes and products
Stainless steel and nickel-based alloys
Chemical immersion pickling:
- POLINOX B with additives to prevent nitrous gases, nitrite and chromates
- POLINOX NF nitrate-free
- POLINOX UB (patented) free from mineral acids, environmentally friendly, can also be applied anodically
- POLINOX VA 100 (patented) free from nitrates, sulphates or phosphates. For all stainless steels, optionally with or without metal removal, can also be operated without waste water in a closed system.
Electrolytic immersion pickling (anodic):
- POLINOX AB
- POLINOX UB
- POLINOX FL Dispers
- POLINOX FL Aktiv
- POLINOX P Rapid
- POLINOX P Retard
Titanium and titanium alloys (immersion pickling)
- POLINOX TB 100
Carbon steel (immersion pickling)
- POLINOX BESTA (pickling inhibitor)
- POLINOX BESTA S (without hydrochloric acid, no hydrogen embrittlement)
Aluminium and aluminium alloys
- POLINOX AT 100