Electropolishing, sometimes described as reverse electroplating, is an electrochemical process that removes a controlled layer of surface material to eliminate defects and improve the finish of metal parts. Using an electrolyte bath and a dc current, the process dissolves microscopic peaks on the surface, reducing roughness and leaving a smooth, corrosion-resistant finish.
Why this matters for electric vehicles? It’s a matter of material performance.
“A lot of people don’t realize that you can electropolish nearly any material except for precious metals,” shares Scott Potter, VP of Sales, ABLE Electropolishing. “You’ve got brass and of course you’ve got copper, so it does improve the corrosion resistance greatly.”
Electropolished components are increasingly used in automotive and EV manufacturing, where smooth, corrosion-resistant metal surfaces improve conductivity, durability, and assembly precision.
That versatility is critical in EVs, where copper and aluminum dominate busbars, connectors, and battery enclosures, and stainless steel appears in fasteners, housings, and structural components.
A smoother, contamination-free surface helps maintain conductivity and corrosion resistance in high-voltage systems, reducing long-term degradation from oxidation and vibration.
By refining the micro-finish of these materials, electropolishing enhances electrical stability and mechanical durability in demanding EV environments. In short, it provides a controlled way to improve both mechanical and electrical performance without adding coatings or altering base material properties.
Electropolishing versus passivation
Electropolishing differs from traditional passivation in that it electro-chemically removes metal and surface contaminates. The result is smoother and chemically cleaner. Passivation, in comparison, is a chemical process that typically uses nitric or citric acid to remove free iron and encourage the growth of a thin, protective oxide layer on the surface.
While passivation improves corrosion resistance, it does not alter surface texture or remove microburrs. Electropolishing achieves both outcomes. It dissolves iron and embedded impurities, increases the chromium-to-iron ratio on stainless steel, and produces a stable passive oxide film with greater corrosion resistance than untreated or mechanically polished surfaces.
Potter explains, “We can improve the micro-inch finish, lowering the Ra value by up to 50%. In addition, we provide micro-deburring, which can eliminate problems with arcing.”
The micro-inch improvement directly enhances the electrical and mechanical reliability of EV components. A smoother surface reduces localized stress points that can lead to fatigue cracking in parts such as brackets and hinges.
In conductive components, improved surface uniformity minimizes high-current arcing, which refers to small electrical discharges that occur when voltage jumps across tiny gaps or sharp edges, and lowers contact resistance at junctions. The process removes microscopic burrs and raised features that can initiate electrical discharge, adding a critical layer of safety in compact, high-voltage assemblies.
Finishing operations
Electropolishing can also replace several downstream finishing operations. Because it deburrs and cleans at the same time, it can eliminate the need for tumbling, pickling, and manual deburring. The resulting surface is bright, uniform, and passive, slowing down further oxidation, which may eliminate the need for additional coating or plating.
Unlike plating or painting, the finish will not crack, peel, or delaminate. For stainless components in structural or decorative locations, that durability can be critical over a vehicle’s lifetime.
“We can also give an ultra-clean finish, which keeps the part in an extremely passive state,” he says. “You’ve got parts that have been electropolished and there are no platings or coatings on them. It’s just the base metal, and it’s bright and corrosion resistant.”
In EV design, electropolishing is finding growing use in parts that require a combination of electrical performance, corrosion resistance, and dimensional precision.
Examples include:
- Copper and aluminum busbars and connectors, where surface uniformity improves current distribution and minimizes localized heating.
- Stainless fasteners, clamps, and hinges, which benefit from lower friction, longer fatigue life, and better corrosion protection.
- Battery module frames and coolant manifolds, where electropolishing removes machining residues and surface cracks that could expand under thermal cycling.
- Sensor housings and enclosures, which gain from the ultra-clean, passive surface that resists contamination.
Potter notes that the process works across a wide range of alloys. “You can electropolish nearly any material except for precious metals,” he says. “That includes aluminum, copper, brass, and stainless. Each one reacts differently, but with the right electrolyte and current control, you can get a consistent result.”
Before and after electropolishing: the untreated copper part (left) shows surface roughness and oxidation, while the electropolished part (right) has a bright, uniform finish that enhances conductivity and corrosion resistance.
This flexibility is valuable in multi-metal systems, where different alloys must coexist in the same environment. By adjusting parameters such as current density, bath temperature, and electrolyte composition, engineers can achieve uniform surface removal without etching and erosion.
The functional gains extend beyond appearance. By removing micro-defects and leveling surface topography, electropolishing reduces friction, mitigates stress risers, and extends the fatigue life of loaded components.
For conductive surfaces, it helps prevent partial discharge under high voltage, an issue that becomes more critical as modern EV architectures exceed 800 volts. Since the process leaves parts in a naturally passive state, it can also simplify production and assembly.
Components can move directly from polishing to packaging or installation with minimal handling, reducing contamination risks. For stainless steels and nickel alloys, the enhanced passive layer supports longer service life in harsh conditions, including underbody systems or thermal management assemblies exposed to road salt and moisture.
As EV platforms continue pushing higher current densities, tighter tolerances, and longer life cycles, electropolishing offers a controlled and repeatable way to enhance surface integrity, improve reliability, and reduce the failure risk of even the smallest components.
“You can see a whole variety of different parts from aluminum, copper, brass, and stainless,” adds Potter. “The finish is bright and clean, but more importantly, it’s consistent across every material. Uniformity is what gives these parts long-term reliability in demanding environments.”
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