Electropolishing

Electropolishing is an electrochemical finishing process. While electroplating deposits a layer of metal onto the surface of a substrate, electropolishing removes a thin microscopic layer and cleans the metal’s surface of any minerals or other impurities. Typically done on stainless steel and other alike alloys, electropolishing provides a clean, shiny, and streamlined finish to its substrates.

The Electropolishing Process

Parts are racked and placed into a chemical tank. The tank contains an electrolytic solution which then has a positive electric current run through it. The current causes the surface of the metal to become oxidized, removing impurities and irregularities from the surface of the substrate. Due to the strength of the electrolytic solution, electropolishing is typically a quick process. To control the amount of surface removal, the following elements must be accounted for and adjusted:

• Solution Composition
• Solution Temperature
• Time of Exposure
• Electric Current Density
• Substrate Composition

• Clean and Bright Finish: One of the more obvious benefits of electropolishing is the sleek and aesthetically pleasing finish the process provides. Since the process strips a metal’s surface of stains, small abrasions, and thermal wear, it leaves components looking brand new. On top of aesthetic benefits, the intense cleaning process can also improve seals, reduce surface resistance, and increase thermal reflection.
• Corrosion Resistance: Corrosion of metal surfaces can be caused through handling alone. From machining to fabricating, every process can have a varying effect on the corrosion of a metal’s surface. These processes leave excess grease and foreign metal deposits on the surface of a metal. These foreign metal deposits are an especially a problem for stainless steel as they can disrupt its naturally anti-corrosive properties. Electropolishing removes these impurities before they can cause corrosive damage. In the case of stainless steel, electropolishing is especially useful as it changes the chemical composition of stainless steel. The process dissolves iron ions in stainless steel, causing its material matrix to contain higher amounts of chromium. This shift in the surface’s atomic composition causes electropolished stainless steel to be chemically stronger than its non-polished counterparts.
• Increased Smoothness: Many metal manufacturing processes can cause deformities on the surface of metals. Processes like welding and stamping can cause microscopic peaks to form on the surface of a metal, which can lead to complications further down the manufacturing process. Electropolishing can remove these peaks, allowing for a smoother finish and more even geometries. These qualities are highly useful in the production of valves and gears. 
• Deburring Delicate Components: Oftentimes, due to the varying mechanical processes within the metal manufacturing industry, components will have varying physical surface imperfections called burrs. These burrs can be removed physically, through a variety of different tumbling, grinding, or vibrating techniques. However, if a part is too fragile to be physically deburred, electropolishing is an effective chemical alternative. Since the process uses an electric current and chemical bath, it is a safer alternative for smaller and more delicate components. 
• Surface Preparation: Since Electropolishing is an extremely effective way to clean the surface of certain metals and metal alloys, it is often used as a cleaning procedure before additional plating or other metal finishing processes. The even surface also makes it easier to paint, as there won’t be uneven build up. The smooth surface and elimination of microscopic metals make for an easy and worry-free plating or anodizing process.

At AOTCO, we provide metal finishing services to an array of highly specialized clients, customers, and industries. Of those industries, many have found effective uses for our electropolishing services. Here are some of the most common industry applications for electropolishing:

Electropolishing in the Medical Industry

Since Electropolishing provides an even surface finish to its components, this makes it great for sanitation control. Irregularities on the surface of medical tools can lead to the build-up of bacteria, dirt, or other foreign substances, even after being properly sanitized. These microscopic build ups can potentially contaminate patients and disrupt an entire medical process. Electropolishing removes these surface pockets, preventing any microscopic build up, allowing for successful sanitization.

Electropolishing in the Aerospace Industry

The anti-corrosive properties of electropolishing are utilized throughout the aerospace manufacturing process. Electropolishing provides a precise deburring process that leaves its substrates with a fully even and smooth finish. In an industry where the margin for error is nonexistent, absolute surface uniformity is a necessity in the aerospace industry. Electropolishing is commonly used on aircraft components such as turbine blades, struts, landing gear, and vacuum chambers.

Since the process is chemical, there is no threat of potentially damaging the parts. This quality makes electropolishing especially useful on delicate or intricate aerospace parts that can’t be physically deburred or altered.

Electropolishing in the Defense Industry

Electropolishing is frequently used in the military and defense industries to improve the strength and functionality of their equipment. Much like the aerospace industry, many military aircraft will use electropolish as the finish to their landing gear and vacuum chamber components. Electropolish is also often used to improve the inner ballistics of military weaponry. Rifle and canon barrels will sometimes be electropolished to reduce friction and improve the longevity of the weapon.

At AOTCO, we provide Electropolishing and Passivation spec: AMS-B912

For more information, see the full list of AOTCO plating specifications