Passivation

A clean stainless steel surface will generate its own passive oxide layer when exposed to oxygen. It is this oxide layer that gives stainless steels their corrosion resistant qualities.

However, it is possible to accelerate the formation of this layer by chemical passivation.

Passivating

Chemical passivation is not always necessary, but is important where surfaces are possibly starved of oxygen, for example in the case of pipework or enclosed vessels. Where items are pickled and likely to be exposed to corrosive atmospheres, such as chemical processing plants or marine and coastal locations, chemical passivation following pickling is highly recommended. Additional passivation following electropolishing is not necessary due to the excellent oxide layer formation present after electropolishing.

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Pickling and passivation of stainless steel

Pickling and passivating of stainless steels is not restricted to immersion in treatment tanks, although this method is widely used. Where fabrications are too large for immersion or require treatment in-situ, Anopol spray-on systems can be employed. The results are compatible with the finish obtained by immersion methods.

Where only localised areas require treatment, for example heat affected surfaces resulting from welding, Anopol pickling paste products can be applied with a brush.

Anopol has extensive pickling and passivating facilities at its Birmingham and Bordon, Hampshire facilities. Additionally, Anopol can supply all the necessary equipment, including water treatment, together with the necessary chemicals, to those companies wishing to carry out their own pickling and passivation.

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Special metals

Cleaning, pickling and passivating products are available in liquid and paste form.

Anopol also markets the Weldkleen machine, an environmentally friendly way of removing weld burn. We can also supply passivation services for a series of special metals, including; Titanium, Tungsten, Molybdenum, Aluminium, Cobalt Alloys, Nickel & Nickel Alloys, Copper & Copper Alloys, and Zirconium.

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More from metal processing

Electropolishing is simply electroplating in reverse, removing a surface layer, typically 20 – 40 micrometres in depth.

Learn about Electropolishing

Correct Pickling, in a formulated solution of dilute acids, produces a uniform matt grey finish – the effect of chemical micro-etching.

Learn about Pickling

At Anopol, we understand the challenges our customers may face within our industries. We provide practical and pragmatic solutions to these obstacles. See our case studies to see these solutions in action.

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