4.2 Chemical Removal Methods

Methods of chemical removal

There are different options for chemical removal, each of which will be described below.

These options can be used separately or, where necessary, in combination with one another.

There are different options available for chemical removal, each of which will be described below.

These options can be used separately or, where necessary, in combination with one another.

4.2.1 Chemical Pickling

Chemical pickling

  Pickling is an intensive chemical treatment of stainless steel surfaces that is reserved for specialist companies. One of the benefits of this method is that it can dissolve even smaller-scale inorganic impurities and systematically clean them off of surfaces. As a rule, all pickling agents cause a minimum amount of material abrasion (from 1 to 3 µm) during the cleaning process. The chemicals used for this purpose are typically based on hydrofluoric acid and nitric acid in aqueous solution, and can be used in the form of baths, pastes and sprays. The acids essentially react in the following two-stage process:

➡ (1) Metal oxidation, and

➡ (2) Dissolution of the metal oxide/reaction forming a typical metal fluoride salt 

    Pickling is an in intensive chemical treatment of stainless steel surfaces that is reserved for specialist companies. One of the benefits of this method is that it can dissolve even smaller-scale inorganic impurities and systematically clean them off of surfaces. As a rule, all pickling agents cause a minimum amount of material abrasion (from 1 to 3 µm) during the cleaning process. The chemicals used for this purpose are typically based on hydrofluoric acid and nitric acid in aqueous solution, and are available in the form of baths, pastes and sprays. The acids essentially react in the following two-stage process:

➡ (1) Metal oxidation, and

➡ (2) Dissolution of the metal oxide / reaction forming metal fluoride as a typical metallic salt

  Before the pickling process can be carried out, anything covering the surface (e.g., label adhesive) must be removed to ensure that the treatment chemicals can reach the surface without any hindrance at the same time.

    Before the pickling process can be applied, anything covering the surface (e.g., adhesive labels) must be removed to ensure that the treatment chemicals can reach the surface at the same time without any hindrances.

Depending on various different standards, select a suitable pickling agent and a suitable pickling method, as well as the correct parameters:

➡What type of stainless steel or what grade of alloy is to be pickled?

➡What is the extent of the layer to be removed?

➡What surface requirements must the parts being pickled meet (e.g., final roughness Ra/Rz in accordance with DIN EN 4288)?