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What are the benefits of electropolishing stainless steel

Stainless steel is not true to its name unless it has been electropolished. Stainless steel may satin and spot rust because of the Iron particles in the environment will start the oxidising process on the surface. This will usually only penetrate a short distance into the material as the Chromium levels are very high and this will resist the corrosion from penetrating further. Electro polishing stainless steel removes the iron from the surface and enhances the Chromium and Nickel content of the material and will draw this to the surface thus passivating the exposed surface.  Electro polishing will also remove the miro peaks that are on the surface of the stainless steel and polish it down to a smooth surface. This will provide a clean sterile surface that will then not hold onto Iron particles so the staining and rust process can’t start also bacteria is easily removed. The electro polishing finish will bring a mirrored lustre to the surface when finished.  At Fimar Polish we run a hospital grade process which involves the cleaning of the part, polishing of the part and passivation of the part. All this is done in a range of electro polishing tanks which are chemical Ph level checked and filled with reverse osmosis water so the finished electro polished product is medically clean. The use of tap water in electro polishing has the issue of you don’t know what contaminates are in that water and this will disrupt the process and finishing.

Passivation

Passivation is a critical process in maximizing essential corrosion resistance to parts and components that have been machined from stainless steel or have had steel components working on the part to bend or form into a shape. Passivation can make the difference between a part or component having superior performance or premature failure. If the passivation is processed incorrectly then this can lead to induced corrosion.

Passivation is a process that is not completely understood by all. Most think that it is just cleaning the surface. Passivation is a post-fabrication process that maximizes the inherent corrosion resistance of stainless steel. Passivation is not a scale removal treatment or like a coating of paint.

The mechanics of how the passivation really works is an unknown science at this point. It is certain that a protective oxide film is present on the surface of passivated stainless steel. The film is extremely thin and invisible to the naked eye. Passivation films are about 100,000 times thinner than a human hair.

Clean, tool polished or pickled stainless steel parts automatically acquire this film, but under controlled environments this would eventually cover the whole surface. If a complete passivation treatment is not done to parts, then free micro iron particles in the environment from machine tools or rusty nails on pallets etc or sulfides from the stainless steel may adhere to the surface and start the corrosion process before the environment has had time to naturally passivate the surface. Free machining stainless steel has sulfur added to improve machinability by improving the materials ability to form chips that break away. This sulfur once processed by machining turns into sulfides that maybe left on the surface of the material and can corrode the surface.

Passivating a surface will increase the corrosion resistance but over time the rough surface will pick up and hold contaminants thus reducing the resistance again. Stainless steel tubes, flat sheet or machined parts may look smooth with the naked eye but placed under a micro scope you will see all the micro valleys and peaks that will hold the micro iron or sulfide particles. Placing a part through a full cleaning, electro polishing and passivating system will make sure the part is free from oil and grease. Then electro polishing will then reduce the micro peaks and passivating will remove the contaminates from the surface. All this should be done with distilled water filled tanks so the contaminates are controlled in the process. This makes the part ready for use in the environment without corrosion starting or waiting for the passivation process to begin in the natural environment.

Fimar Engraving

Did you know!

Did you know Fimar Polish is a part of Fimar Group who also specialise in engraving and permanent marking.  Using the latest state-of-the-art advanced laser technology available. Follow link to Fimar Engraving to find out more.