What is Electropolishing?
Electropolishing is an electro-chemical process performed primarily on stainless steel. It is similar to electroplating, but is anodic in nature, meaning it is exactly the reverse. During the process, metal is selectively removed under controlled conditions of temperature, amperes and time.
Microscopic high points of the metal surface are removed at a faster rate than the low points to create a smoother surface as material is removed. These high and low points are called micro and macro projections and depressions. A current is applied and forms a polarized film on the part’s surface, which allows the metal ions to diffuse through the film. The high current density areas (high points and burrs) are dissolved away at a greater rate to smooth, level and deburr the surface. At the same time, the process produces a brighter, reflective finish known as anodic luster.
The surface finish obtained by electropolishing is mainly a function of the surface quality and finish before processing. Increasing time, the temperature and or the current density also increases the amount of metal that is removed from high current density areas to achieve a brighter finish. The process details are particularly important to consider when dimensions are of critical tolerance.
During the process, the cathode produces hydrogen and the anode generates oxygen, leaving a transparent chromium oxide film on the surface. The film causes partial passivation and improves corrosion resistance. Unlike plating, the problem of hydrogen embrittlement, which makes the material brittle, does not occur with electropolishing. Complete passivation is an additional step that must be performed after electropolishing if it is needed.
The surface finish, in micro-inches, is usually reduced from 33 to 66 percent. However, as the values become lower before the process, the improvement percentage decreases proportionally. Fine-grained deposits are most important for true reflective finishes.
The greatest contributing factors toward poor results include:
The Benefits of Electropolishing
Electropolishing offers a variety of benefits over passivation and other polishing processes. It is frequently used for deburring, micro-finishing, increasing corrosion resistance, and improving the appearance of the surface.
Electropolishing results in a smooth, uniform surface that is completely free of imperfections. The microscopic smoothness of an electropolished surface reduces contamination and adhesion to promote cleanability, sterilization, and ease of maintenance.
Surface contaminants disrupt the inherently corrosion-resistant oxide layers of stainless steel, titanium, aluminum, and other metal alloys. Electropolishing removes embedded particles and inclusions to improve the chemistry of the metal surface. This improved surface forms a thicker and more consistent oxide layer with enhanced corrosion resistance properties.
The most visibly noticeable benefit of electropolishing is the resulting surface brightness, or anodic luster. Because electropolishing is not an abrasive or mechanical process, it does not make directional lines or marks of any kind. It is scratch-free, deformation-free, and directionless, and it reveals the true metal color.
What Materials Can Be Electropolished?
Electropolishing is often associated with stainless steel, but most metal alloys can be electropolished, including aluminum, brass, bronze, copper, steel, titanium, precious metals and more. For metals such as aluminum and copper, electropolishing is an effective pre-treatment for anodizing or plating. The most notable benefits are electropolishing for titanium and stainless steel applications.
Can You Electropolish Titanium?
Titanium is one of many alloys that can achieve excellent results from electropolishing. Electropolishing improves the performance of titanium parts and makes them last longer. Due to its light weight, high tensile strength, high corrosion resistance, and ability to withstand high temperatures, titanium is commonly used to produce parts for aerospace and medical applications. The aerospace industry uses titanium to produce compressor blades, landing gear, hydraulic systems, rotors, valves, and other parts. Titanium is ideal for use in a wide variety of medical applications, from joint replacement and dental implants to surgical instruments and wheelchairs. Electropolishing titanium eliminates microsurface imperfections, debris, and embedded contaminants that improve corrosion resistance and biocompatibility.
Electropolishing Stainless Steel
Electropolishing stainless steel has many benefits for sanitary applications in biotechnology, cosmetics, food and beverage processing, and life sciences. Instruments, containers, tubing and vessels that work in the most sanitary conditions and must comply with specific industry regulations. Constant cleaning and decontamination are necessary to ensure impurities are not present in critical processes. Stainless steel is non-toxic and resistant to moisture, organic compounds, acids, and bases, making it a desirable choice for sanitary applications. Electropolishing stainless steel enhances its corrosion resistance and the ability to clean surfaces frequently and more thoroughly with harsh sterilizing cleaning agents.
Electropolishing in Massachusetts
Electropolishing is a science that is often the last step in a sequence of manufacturing processes, so there is a lot of time and money at risk. Experts have many years of experience with varied materials, shapes, and sizes, and well-kept documentation on the results. For each distinct part, the process is adjusted to achieve the desired results or specifications. As an electropolishing company with ISO 9001:2000 certification and more than 40 years of experience, you can trust AMF Technologies with your medical components and devices, biotechnology and pharmaceutical applications and more.