Passivation is a chemical surface treatment method that creates or strengthens the protective passive layer on stainless steel surfaces.
The process removes free iron and other impurities from the surface that weaken corrosion resistance. At the same time, a uniform, permanent chromium oxide layer forms on the surface, effectively protecting the steel against rust and pitting corrosion.
Passivation improves the natural corrosion resistance of stainless steel by removing metallic impurities created during manufacturing and strengthening the passive layer. The process restores the steel's original corrosion protection without altering the part's dimensional accuracy or surface structure.
It is suitable for all stainless, acid-resistant and duplex steels, as well as many types of manufactured components whose corrosion resistance needs to be ensured. Passivation is an especially important procedure for components exposed to moisture, chemicals or demanding environmental conditions.
Most commonly used standards: ASTM A967, ASTM A380, ISO 16048.
The surface contains visible or invisible impurities: free iron, scale, oil residues and metal particles from mechanical processing. These significantly reduce the steel's corrosion resistance and can cause pitting corrosion in a short time.
The passive layer is uneven or incomplete, which exposes the steel to rusting, especially in humid or chemically demanding conditions.
After passivation, the surface is clean of impurities, and a uniform, protective chromium oxide layer has formed on the surface.
The process removes free iron and other metallic impurities through a chemically controlled reaction. The result is a technically optimal surface that effectively resists corrosion and maintains the natural protection of stainless steel.
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CEO, Sales
INOX Finland Oy
Passivation should always be performed when impurities have accumulated on the stainless steel surface during manufacturing or when the best possible corrosion resistance needs to be ensured.
Passivation is an especially critical procedure in the pharmaceutical, food, chemical and offshore industries, where corrosion resistance and cleanliness are essential.
Both are chemical surface treatments, but their purpose and effect differ from each other.
Pickling is a more powerful process that removes oxide layers, heat tints and scale from the steel surface. It restores the steel's original surface and creates a new passive layer. Pickling is especially suitable for treating welded components.
Passivation, on the other hand, is a lighter and more refined process that focuses on removing free iron and metallic impurities while strengthening the existing passive layer. Passivation does not remove oxide layers as effectively as pickling, but it significantly improves corrosion resistance without aggressive surface impact.
For the most demanding applications and to achieve optimal corrosion resistance, we recommend a combination treatment, where both processes are performed sequentially:
This two-stage treatment ensures the best possible result, especially for welded components, critical parts and applications where corrosion resistance is of paramount importance. Combination treatment is a recommended solution for components in the pharmaceutical, food, offshore and chemical industries, for example.
Benefits of combination treatment:
INOX Finland optimises the properties of stainless steel with chemical treatments. We specialise in bringing up the best in stainless steel. By selecting the right materials and optimising their qualities, we are able to produce the most outstanding results.