Electropolishing for Industrial Use


Posted on: July 15th, 2020

By Ashley Belliveau

Electropolishing is an increasingly common method for smoothing, polishing, and deburring ferrous and nonferrous metals. Also referred to as electrochemical polishing, anodic polishing, or electrolytic polishing, this method is especially useful for polishing and deburring metal parts that are fragile or have complex shapes. Learn more about the electropolishing process and its uses.

How Does Electropolishing Work?

SDC EP10 Electropolishing MachineBefore the electropolishing process can begin, the metal surface must first be cleaned to remove any contaminants. Contaminants, such as oil and grease, need to be removed to ensure the electropolishing process creates a uniform surface finish on the metal without any fine lines.

Once the metal is cleaned, the electropolishing system works by submerging the metal part in an electrolytic bath, typically consisting of sulfuric acid and phosphoric acid, that’s connected to a power supply. When the power supply is activated, the metal part becomes anodic (+) while another metal, usually lead, copper, or stainless steel, is used as a cathode (-).

The direct current flows from the anode to the cathode, removing high points on the metal surface at a controlled rate, while producing a uniform, high luster. The amount of metal removed is dependent on the specific bath, temperature, speed, and alloy being electropolished. This same process is used for micro- and macro-deburring, as this reverse plating process selectively removes metal ions from high points on the surface without etching it.

After completing the electropolishing process, post treatment is crucial to prevent staining. Any residual electrolyte and chemical by-products, such as phosphates and sulfates, must be removed to ensure a consistent finish. Failure to rinse the metal of these acid residues can cause white spots to appear on the metal surface after drying.

Benefits of Electropolishing

There are many benefits to using electropolishing compared to other mechanical finishing systems. Unlike conventional mechanical finishing systems, this process does not smear, bend, stress, or fracture the crystalline metal surface to achieve smoothness or luster.

Instead, electropolishing removes metal from the surface while producing a unidirectional pattern that is stress- and occlusion-free, microscopically smooth, and often highly reflective. In addition, electropolishing can improve corrosion resistance and passivity on many ferrous and some nonferrous alloys.

Types of Metals That Can Be Electropolished

Although nearly any metal can be electropolished, stainless steel tends to be one of the most popular alloys to electropolish because it can enhance its corrosion resistance properties. Other metals that are compatible with electropolishing include:

  • 200, 300, 400 Series Stainless Steel
  • Low Carbon Steel
  • High Carbon Steel
  • Low-Alloy Steel
  • Nickel
  • Nickel-Silver
  • Certain Non-Silicon Aluminum Casting Alloys
  • Wrought Aluminum Alloys
  • Copper
  • Beryllium-Copper Alloy
  • Brass
  • Bronze
  • Inconel
  • Monel

What is Electropolishing Used For?

Electropolishing is a common finishing procedure used by manufacturers within a number of industries. For example, a medical device manufacturer may use electropolishing for stents, while an automaker might electropolish gears and fuel lines to reduce friction and increase the part’s longevity. Some examples of metal parts commonly electropolished include:

  • Piping and Tubing
  • Fasteners
  • Springs
  • Wire Racks
  • Blades
  • Stents

Electropolishing Equipment for Industrial and Medical Parts

Electropolishing machines produce a uniform, luster surface that surpasses the quality of standard mechanical polishing. For a repeatable, automatic electropolishing system, Steven Douglas Corp. (SDC) offers a cost-effective solution to improve your standard of quality. Our complete, stand-alone, proprietary electropolishing system’s small size, advanced controls, and proven durability is designed and built to produce a corrosion-resistant, high-polished surface for precision metal parts.

Our team of experts will design and build your electropolishing system upon request and to your specific application. Contact SDC today to discuss your upcoming electropolishing equipment needs.