Stainless steel finishing

[byblos]

Can any one recommend me with what is the best way to finish stainless steel besides mirror polish? The application will be used for food containers and anything related to food industry. What about sandblasting or chemical finish?

 

[kenvlach]

For sanitizing purposes, a microscopically smooth surface is desirable. The interiors of vessels and piping in the brewing, dairy, food processing, and pharmaceutical industries are often mechanically polished and then electropolished.
Electropolished piping is also used to ensure purities of gases and liquids used in the semiconductor industry.

Please see the article “Electropolishing” by Ken Hensel, which gives advantages of the process along with descriptions of the equipment and chemical solutions used:

http://www.metalfinishing.com/WZ/MetalFinishing/guidebooks/MetalGB_SurfaceTreatments/000013/show/

You can find some jobshops doing electropolishing at

http://www.finishing.com/Shops/index.html

Very good, illustrated descriptions of electropolishing are at these sites:

http://www.ableelectropolishing.com/electrop.htm

http://electromatic.com/

Electropolish Systems sells both chemicals and equipment:

http://www.ep-systems.com/index.html

 

[byblos]

Thanks for your reply.
My question is can electropolishing be dull looking? Instead of bright finishing?

 

[TEV]

A "dull looking" surface is dull because it is rough on a microscopic scale. The fine-scale roughness causes diffuse reflection, thus the dull appearance. The fine-scale roughness may not be apparent with a mechanical profilometer or visual examination, but will be apparent using optical interference surface measuring techniques or in the scanning electron microscope at high tilt angles.

This fine scale roughness will increase the surface area available for adsorption of contaminants, and provide greater potential for retention of microbes. You may be defeating your purpose.

You can generate a dull surface in stainless steel by etching in nitric acid with additions of etching salts, which are flourides.