N.B.Oler

Electropolishing

Tech Tuesday
Electropolishing
Rick Batten, 9/1/2020

How it works

Electropolishing is a method of obtaining a smooth, sanitary surface finish that is superior to mechanical polishing. The basic idea is to immerse the component in an electrolyte bath consisting of an acidic solution—such as sulfuric or phosphoric acid—where electrical current is applied. The component to be polished be attached to the positive terminal of a power supply, acting as the anode. The component’s micro-peaks have greater current density, liberating positively charged metal cations that move from the stainless steel to the negatively charged cathode. This typically removes 20-40 micrometers of material on stainless steels, resulting in an aesthetically pleasing smooth, sanitary finish.

Electropolished stainless weld

Advantages Over Mechanical Polishing

Mechanical polishing can be aggressive, which causes excessive heat and can embed abrasive material into the surface of the component or cause deformation. Electropolishing has proved very useful for polishing irregularly shaped components where mechanical abrasives are impractical. Mechanical preparation prior to electropolishing may be essential in most cases where the surface finish is coarser than 220 grit. Electropolishing can also eliminate the fine directional lines left behind from mechanical polishing, as well as deburr small imperfections. The microscopically smooth finish from electropolishing discourages bacterial growth resulting in a superior sanitary finish. The electropolishing process removes surface iron on stainless which results in greater nickel and chromium concentration on the surface, which further improves the component’s resistance to corrosion. Welded joints can be problematic if the weld has hidden voids and poor penetration, but top-quality welds can be electropolished without issue. Considering the solvent tanks at N.B.Oler are welded prior to electropolishing, that means our welds are of high quality.

Industries That Utilize Electropolishing

Electropolishing is necessary for stainless applications in the cannabis industry considering the products are meant for human consumption, meaning it must have a sanitary surface finish. This also applies to fields such as medical, dental, and food/beverage industries. It is also used where improved resistance to corrosion is preferred, such as aerospace and automotive components.

References/Further Reading

Cutchin, Johnson H. “Electropolishing Applications and Techniques.” The Fabricators, 2015, www.thefabricator.com/tubepipejournal/article/finishing/electropolishing-applications-and-techniques.

Delstar Metal Finishing, Inc. “Electropolishing vs Mechanical Polishing.” Electropolishing, Passivation & Metal Finishing, 2015, www.delstar.com/electropolishing-vs-mechanical-polishing.

Electropolishing, New England. “Electropolishing & Reverse Plating of Stainless Steel: New England Electropolishing.” Stainless Steel Electropolishing Company - New England Electropolishing, 2020, neelectropolishing.com/resources/electropolishing-basics/.

Glo, Electro. “7 Industries That Depend On Electropolishing: Electro-Glo Distribution.” Electro, 31 Mar. 2019, www.electro-glo.com/7-industries-that-depend-on-electropolishing/.

Visit nobler.com or contact N.B. Oler at info@nboler.com for products, technical documents, SOPs, and more.

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