In the passivation process, a protective layer is created on the surface of a metallic material that prevents or greatly slows down the oxygen corrosion of the base material.
Protection and repair
The passivation process removes foreign particles (alloy components, oxide layers) from the component surface. At the same time, the passive layer on the component surface is strengthened. Since the process does not result in any significant metal removal, close-fitting surfaces with tolerances ≥ 2 μm can be treated.
Treatment of boreholes and interior areas
Natural passive layer
The passivation process is a purely chemical process. As a result, boreholes and interior areas are also treated. Surface layers with tarnish or oxides are chrome-depleted. Here, the natural passive layer is only weakly developed. Such surfaces must be pickled before passivation. Stainless steels automatically form a natural passive layer in the atmosphere. However, an artificially created passive layer is significantly denser and thicker than the natural one. Passive layers have a self-healing effect, i.e. after damage they form again by themselves on contact with atmospheric oxygen. Steels with a high chromium, nickel and molybdenum content are suitable for passivating stainless steel.
Passivation gives stainless steel surfaces very good corrosion resistance. It is used on new surfaces as well as for repair and restoration of corroded surfaces. Weld seams and scaled surfaces can be passivated by pickling or blasting without prior treatment.
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