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De-greasing, pickling and passivation of stainless steel:

Your advantages at a glance:

  • We get your components completely scale-free using cutting-edge spray pickling technology.
  • If required, the fully automatic pickling plant can de-oil or de-grease your components in advance.
  • Even ground components can be pickled and retain their satin finish.
De-greasing, pickling and passivation of stainless steel:

Our Service

  • Contract pickling of customer-manufactured stainless steel components.
  • Complete cleaning by means of de-greasing/de-oiling, pickling and passivation.
  • Small components suspended as bulk goods in baskets, or individually in order to prevent drops/stains.
De-greasing, pickling and passivation of stainless steel:

Performance data

  • Component sizes up to 2800 x 2800 x 11000 mm
  • Unit weights up to 1000 kg
  • Only high-alloy stainless steels with at least 16% chromium can be pickled.
    In the case of ferritic steels, we recommend glass bead blasting.

1. Why do components need to be pickled?

The mechanical and thermal machining of stainless steel components causes damage to many areas of the protective passive layer (chromium oxide) e.g. as a result of grinding, brushing, laser-cutting, welding etc.

This causes contaminants, such as standard steel abrasions, welding residue, tarnishing, scale and rust film. The passive layer is then unable to form on the surface in these areas, which soon leads to corrosion.

2. What method of pickling does Modersohn use?

Our recently commissioned pickling plant sets new standards for the finishing of stainless steel. As a closed system with pickling chamber dimensions of 3 x 3 x 12 m, the system is able to de-grease and pickle large quantities of small production parts or large single workpieces in a single operation.

In fact, the whole system is rather like an oversized dishwasher! The components are placed in rail-mounted baskets, racks or supports for large components and moved into the chamber. After the de-greasing and pickling procedures, any remaining cleaning agent residue is removed and suctioned off in subsequent flushing operations. This dispenses with much of the manual work.

Key features of this machining process are:
- low consumption of pickle solution
- even and effective wetting of large and small components
- constant contact of pickle solution with oxygen
- and therefore more effective pickling results
... than with dip pickling.

3. What is passivation?

If requested by the customer, the components are finally sprayed with dilute nitric acid (an oxidising acid) and then rinsed again.

This additional operation - passivation - considerably accelerates the formation of the passive layer. It is particularly important if the workpieces are to be used in a harsh and low-oxygen environment just hours after manufacture.

If there are several days between the production process and deployment of the workpiece, the passive layer will form naturally, by contact with oxygen, on components that are "only" pickled.

4. Why do components need to be de-greased first?

Grease and oils adhere very tenaciously to surfaces. Without proper de-greasing and oil-removal agents, flushing will, at best, only displace these contaminants. Then they are often still located on the lower edge of a workpiece, where they form streaks that cannot be removed even with the pickle solution. The pickling procedure would be considerably less effective without a previous de-greasing procedure.

The passive layer will also be unable to form properly on areas that are affected by grease and oil streaks.