The processes of cutting, bending, machining, and polishing stainless steel during fabrication usually leave iron, silica, and other abrasive particles embedded within the surface of the metal. Finishing helps in removing these surface impurities, strengthening the properties of the metal, and improving its appearance. Electropolishing and passivation are two common techniques used in finishing stainless steel metal.
Both of these techniques are distinct regarding the processes involved and outcome. It is essential to understand their characteristics and differences so you can choose the ideal one for your application.
Stainless steel electropolishing
Electropolishing is an electrochemical technique that uses an electrolyte bath and an electric current to dissolve impurities such as carbon, silica, and free iron on the surface of stainless steel. Since electropolishing removes surface metal, the final result is a smooth surface that's free of burrs and crevices that could otherwise attract and trap impurities. Before the weld is electropolished, it is deburred, ground, and inspected for any mechanical defects that could affect the quality of the finished metal.
Electropolishing is an effective technique for achieving a smooth stainless steel surface with no impurities and contaminants. In addition, it offers the following benefits to stainless steel.
- It increases resistance to corrosion. Impurities on the surface of stainless steel metal disrupt the formation of a naturally occurring corrosion resistant oxide layer. When they are eliminated, the metal's ability to form the oxide is improved, hence enhancing its corrosion resistance properties.
- It reduces surface adhesion and friction. Electropolishing creates a smooth and less adhesive surface that is easy to clean and handle.
- It improves the appearance of stainless steel as there are no fine directional lines that are usually present after abrasive polishing.
- It improves maintenance and sterilization of stainless steel used for food, pharmaceutical, and chemical processing equipment.
Stainless steel passivation
Just like electropolishing, stainless steel passivation involves submerging metal into a temperature controlled chemical solution for a specified period of time. However, this process does not make use of an electric current. The main aim of passivation is to get rid of surface contaminants such as iron and silica. Before passivation, the metal must be cleaned to get rid of dirt, grease, coolant, machining chips, and other debris that could compromise the quality of the final product.
The process of passivation provides the following benefits to stainless steel.
- It eliminates surface contaminants and impurities, hence improving the corrosion resistant properties of the metal.
- It creates a smooth and uniform appearance of the metal surface.
- It extends the usable life of stainless steel.
The downside of passivation is that it does not change the aesthetics of stainless steel metal. It is suitable for applications that require stainless steel with no surface impurities and contaminants.
For more info on on these and other fabrication and finishing techniques, talk to a metal fabrication company near you.
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