Pickling and electropolishing of stainless steel. 
The parts that are to be delivered are especially budget-priced, if mechanical treatment precedes delivery, welding connections are required or components can be manufactured using our water-jet cutting installation. 
Reasons for electropolishing of metals
The surface finish of a metal component will determine its appearance, function and service life.Electropolishing improves the crucial metallic surface properties considerably.

The Process Principle
Electropolishing is, in principle, a reversal of the electroplating process. Metal is removed by applying a dc current to the anodically connected work piece submerged in a special acid electrolyte. Removal takes place without inducing stress and preferentially affects the surface micro-roughness. The surface becomes smooth and bright, with burrs, edges and corners being removed.

What Materials can be Electropolished?
All kinds of chromium-nickel steel.
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Electropolished surfaces are distinguished by:
•  Free from burrs, fragments and particles
•  Improved corrosion resistance and durability
•  Reduced friction and wear
•  Easier cleaning, reduced build-up of products on the surface, reduced bacterial growth
•  Reduced pumping times to achieve high vacuum
•  Reduced radioactive contamination
•  Improved adhesion of plating deposits
•  Optimum reflectivity
•  Bright and decorative
•  Chemically passive

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The Process Results
Electropolished and mechanically produced metal surfaces have fundamental differences. Mechanical operations such as lathing, drilling, grinding and polishing will all adversely affect the structure and properties of the material surface. Contamination resulting from tool abrasion and contact with coolants can lead to corrosion and wear. Dependent upon the degree of the manufacturing forces applied, the surface structure can be affected to a depth of 50 microns.In contrast to this, electropolishing will removed metal from the component without any mechanical, thermal or chemical transformation. Electropolishing will eliminate damaged surface layers and allow the original properties of the material to be fully utilised again.

The processes and the electropolished surfaces produced by these processes have been employed in practically all fields of engineering and industry: 

  Food and beverage industries

  Electrical and electronic engineering

  Machine and tool manufacturing

  Textile and paper industries

  Automotive and vehicle manufacturing

  Aviation and aerospace engineering

  Nuclear research and nuclear industry

  Vacuum and cryogenic engineering

  Ornaments and fancy metal shapes

  Architecture and interior decoration

  Household and catering equipment

  Medical-technical products


Why the pickling of metals?
Pickling cleans and restores the corrosion resistance of components manufactured from stainless steel and thus considerably influences their service life and usefulness.
The corrosion resistance of stainless steel is primarily based upon the presence of at least 13% chromium in the alloy. In combination with oxygen, the chromium forms a dense layer of chromic oxide which is chemically resistant and protects the surface against corrosion.
Unfortunately, every mechanical treatment will damage the surface layer by contamination with ferritic matter, e.g. by changes to the microstructure. In addition, any heat treatment, such as annealing and welding, will lead to scaling and discolouration. These aspects not only diminish the visual appearance of the components, but in particular reduce their corrosion resistance.

A dense passive layer of chromic oxide can only form on a metallically pure surface. Professionally pickled stainless-steel surfaces and welding seams
• are metallically pure and free of scaling and discolouration
• have full corrosion resistance
• have a decorative satin metallic appearance


How to Pickle
Depending upon size and shape, the components that are to be pickled are either immersed in a pickling bath or the pickle solution is applied to their surface. The process is allowed to take effect at least for a few minutes, but also up to a few hours at room temperature. Afterwards the pieces are fully rinsed with water.
The active chemicals consist of mixed acids that cause a removal of the surface layer of the component from 1 to 3 microns. Discolouration, ferritic matter and surface contamination are preferentially attacked and removed. The final passive film is formed while rinsing with water and upon exposure to air.

The environment
All processes used by BIOTECHNIK pay due consideration to the relevant health and safety issues as well as the safe disposal of wastewater.

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