For industries that include aerospace, medical manufacturing, food and beverage manufacturing, automotive, electronics, semiconductor, and more, electropolishing is the premier finishing process for improved finish, fit and function of critical metal parts.
Electropolishing, sometimes described as “reverse electroplating” is an electrochemical process that removes a precise and consistent level of surface material to eliminate defects and enhance the surface quality of metal parts. This process uses a combination of an electrolytic solution and an electrical current.
While often compared to passivation, electropolishing is a distinct procedure. Both techniques improve the corrosion resistance of metal and include the use of a chemical bath; however, electropolishing uses an electrical current to achieve its effects, which include significantly enhanced corrosion resistance and the removal of surface defects like microburrs and microcracks. Electropolishing also leaves parts in a passivated state and can eliminate the need for additional finishing processes like manual deburring, tumbling, pickling, and cleaning.
Watch the video below to see the process first-hand:
In electropolishing, the chemical bath and electrical current work together to dissolve a uniform layer of surface material. A meticulous process of quality control ensures the consistently high-quality results that electropolishing delivers. Steps include:
Upon arrival, parts are entered in our ERP system and inspected for defects that include scratches and nicks and to determine that the correct parts have been received, are dimensionally in range, and that cartons show no sign of loss or damage to contents. The parts then undergo pre-cleaning to remove any impurities that could affect the electropolishing outcome. This includes degreasing and alkaline reverse treatments to ensure the surface is free of lubricants and other insulators.
Cleaned parts are submerged in a bath containing a phosphoric-acid-based electrolyte, essential for the electrochemical reaction.
An electrical current is applied, causing gassing in the form of oxygen to occur on the part's surface. This facilitates the removal of material from the surface peaks, smoothing out microscopic imperfections.
Electropolishing offers precise material control with removal controlled to +/- .0002”, allowing for targeted reduction in surface flaws without compromising the integrity of the part.
Post-electropolishing, parts are rinsed to remove any residual chemicals and dried to prevent oxidation.
The finished parts are visually inspected for surface anomolies, measured to confirm proper dimensions and, if required, tested for surface finish using a profilometer.
Electropolishing effectively removes iron and other embedded impurities that can lead to corrosion, enhancing the chromium-to-iron ratio on the surface of stainless steels and improving their passive oxide layer.
Electropolishing significantly improves metal surface finish, reducing roughness by leveling micro-peaks and valleys. This enhances both functional and aesthetic qualities of the part.
Electropolishing is highly effective for removing microburrs, mircrocracks and other surface defects left behind by machining processes. These defects can cause mechanical and assembly issues.
Beyond deburring and smoothing, electropolishing provides an ultraclean and shiny finish that is aesthetically pleasing and ideal for visible components.
By removing surface imperfections that can serve as initiation points for stress corrosion and cracking, electropolishing can significantly extend the fatigue life of metal parts.
By deburring the threads on metal fasteners, electropolishing can reduce the risk of adhesion between two mating surfaces – known as galling – which can cause material between the surfaces to deteriorate and seize up when parts are pressed together.
Passivation uses nitric or citric acid in a chemical process that does not remove material but rather treats the surface of stainless steels and other alloys to enhance corrosion resistance. Passivation is often confused with electropolishing as both processes improve corrosion resistance; however, passivation does not alter the metal's appearance or surface finish.
Pickling removes surface impurities such as stains, inorganic contaminants, and rust from metals using chemical solutions. The primary purpose of pickling is to prepare the metal for further processing like painting or electroplating by creating a clean surface. While effective for removing scale and other surface impurities, pickling does not enhance the metal’s intrinsic properties.
While electropolishing provides both aesthetic improvements and increases corrosion resistance, pickling is best used for removing scale before further processing, and passivation is ideal for enhancing corrosion resistance without removing any surface material.
For a detailed guide on these processes and to determine which might be best suited for your application, read our full guide: Passivation, Pickling or Electropolishing: Which Metal Finishing Process is Right for Your Parts?
As the world’s largest electropolishing specialist, and a pioneer of the process for commercial applications since 1954, Able has collaborated with engineers in a wide array of industries over the decades, honing the applications where electropolishing has become a critical step in the production of parts with no room for error.
In aerospace manufacturing, electropolishing is used for many flight critical components for its ability to significantly improve corrosion resistance and for eliminating surface defects like microburrs and microcracks that can create added friction and stress in parts that must withstand extreme conditions.
The result is a defect-free and ultrasmooth finish for improved performance and enhanced fatigue life. Electropolishing’s consistency and precision helps ensure the reliability and safety of flight critical parts.
Electropolishing of both interior and exterior automotive parts reduces the threat of lingering metal shavings, burrs and embedded contaminants that can compromise a vehicle’s performance. The process removes a precise amount of surface metal to brighten, deburr, improve corrosion resistance, and remove imperfections and contaminants left behind by stamping, machining and other manufacturing processes. In addition, electropolishing of aluminum and copper parts for EV battery manufacturing improves conductivity and battery performance.
Electropolishing is the finishing method of choice for food and beverage manufacturers for its ability to create smooth, clean surfaces that have been shown to inhibit the growth of bacteria and other pathogens, as well as the enhanced corrosion resistance that enables stainless steel food production equipment to stand up to frequent and harsh cleaning processes. Food manufacturers also prize the bright, shiny finish that electropolishing imparts, creating a clean, aesthetically-improved appearance and leaving parts easier to sanitize.
Semiconductor manufacturers rely on electropolishing to meet the demanding requirements of the industry including an ultraclean surface finish and precise, consistent and gentle treatment of delicate components. Due to the corrosive nature of the liquids and gases used in the manufacturing processes, the industry has developed rigid specifications for acceptable finish quality, including SEMI F19, which defines the wetted surface characterization requirements and finish acceptance criteria for electropolished stainless steel components.
Electropolishing's ability to remove a microscopically precise surface layer leaves critical metal parts for medical manufacturing with an ultraclean and ultrasmooth surface that inhibits the growth of pathogens and makes reusable devices easier to clean, without burrs, microcracks and other surface imperfections that can trap liquids and debris and give harmful bacteria a place to hide.
Electropolishing is ideal for fragile parts and commonly used medical alloys including titanium and Nitinol.
Fasteners, the screws and structural bolts used for transportation, waterworks and steel fabricated buildings, among other applications, gain enhanced function and durability from the defect-free surface finish that electropolishing provides. The corrosion resistance advantage of electropolishing also makes it a critical finishing process for fasteners that must withstand constant exposure to the elements, including saltwater. By removing a uniform layer of surface metal, electropolishing is also effective for deburring fastener threads and minimizing the risk of galling.
Industry standards for quality control of electropolishing include:
For a deeper understanding of how electropolishing can transform your metal parts, schedule a part review consultation or sign up to attend a private electropolishing 101 webinar.
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