Passivation of carbon steel, exposure of the material to acids that have particular functions

Passivation of carbon steel is a very important process that contributes to extending the life of this material.

What does it consist of

Carbon steel is, among other metals, the most vulnerable to weathering, including air and water.

Unlike stainless steel, it does not have a natural covering layer of chromium oxides and hydroxides to protect it from corrosion.

The passivation of carbon steel therefore intervenes artificially to cover the metal to allow its use in different contexts.

Carbon steel alloys in the industrial context are used in a wide variety of contexts. Normally, carbon steel requires a protective coating that can be given by painting or galvanic coating treatments.

When this is not possible or practicable, a chemical passivation is performed that is always preceded by a pickling, mechanical or chemical action. Passivation treatment is mainly carried out on products such as prefabricated pipes or bars, inside tanks, exchangers or valves.


Products to use

Bama Carbopass and Bama Fosfiron are two examples: the first is a liquid product with a passivating action specific for carbon steel.

The second, instead, is a degreasing, decontaminating and passivating liquid and is therefore characterized by a dual action of cleaning and passivation carbon steel, able to eliminate the residues of grease and salts and to create a protective film anticorrosive.


The procedure of passivation carbon steel consists in the exposure of the material to alkaline solutions based on sodium salts or acid-based phosphating agents that have the particular function - once in contact - to create the passive layer through chemical reactions.

This can be achieved by immersing the object in a tank containing acids or manually by spraying, depending on the characteristics of the object and its size.

However, it should be remembered that passivation on carbon steel is not eternal.

The non stainless alloy will tend by its nature in contact with oxygen to rust. For this reason, in order to better preserve the surface of the product before it enters into operation, protective oils of different formulations are applied at the request of the customer depending on the type of product and the service that the latter must perform.

If the surface must be free of any organic protective product, such as in applications for oxygen use, special ammonia-based papers are used to reduce and absorb the residual moisture inside the pipes or tanks.

Where required, Bama is also able to provide for nitrogen preservation of the treated items.

The substances used by Bama for the passivation of carbon steel are of its own production and fully comply with international standards on the subject.




For passivation treatments in stainless steel, aluminium, carbon steel, copper, nickel, zirconium and titanium, Bama uses a substance called passivating, which differs according to the material being treated.