In short, electropolishing is a process that removes steel and free irons from 200, 300, 400, Al6xn, Duplex’s and Inconel series stainless steel as well as from 17-4 and 15-5 stainless steel and brings the nickel and chrome to the surface of the product/part providing a passive part with a mirror finish.
Electropolishing systems require rinse water to remove solution from the parts after each chemical operation. These rinses usually go to a holding tank for batch treatment before discharge to waste and are subject to Federal, State, and Local regulations affecting discharge to public sewer treatment systems. Most modern electropolishing systems Incorporate evaporative recovery and/or multiple rinse technologies to minimize the amount of rinse water used.
High Performance Metal Finishing meets or surpasses DEQ, EPA, OSHA, and Michigan State regulations regarding electropolishing pre-treatment and electropolishing baths. Most electropolishing companies have small to moderate sized tanks and can only handle small to moderate sized parts. HPMF has large sized tanks which allow us to handle bigger parts. Our largest tank size is 10’ x 10’ x 20’. These tanks are also used for smaller parts. Because of this, we can provide our customers faster service at a more competitive price; meaning fast turn-around times and, in most cases, with no premium charge.
Following is a brief description of our electropolishing process:
Our proprietary electropolishing process is accomplished with a series of wet processing steps using specially designed tanks that are similar to electroplating and/or anodizing. The parts to be polished are mounted on a rack or jig that is moved from tank to tank. The three major process steps of the electropolishing system are as follows:
- Metal Preparation (Pre-clean): To remove all oils, lubricants, shop dirt, oxides, fingerprints, and any other contaminants from the surface of the part. There are many suitable methods that can be used in this cleaning process. These include vapor degreasing, solvent immersion, alkaline and/or acid soak cleaning, spray washing, abrasive blasting, wire brushing, as well as other types of mechanical finishing steps.
High Performance Metal Finishing uses a pre-clean method that includes degreasing, then deoxidizing to loosen and/or remove weld scale and discoloration.
- Electropolish: To smooth, brighten, deburr, passivate, improve surface
profile, stress relief, hygienically clean, reduce friction, and increase corrosion resistance.
- Post Treatment : To remove chemical residues or by-products of the electropolishing process and to assist in drying.
- Clean Room: Parts are then moved to our state-of-the-art clean room to finish the drying process.
Each of the major operations requires a number of steps and may require one or more tanks to accomplish the desired result.
Below is a flowchart of the general electropolishing process.
Benefits of Electropolishing
Most mechanical finishing systems can smear, bend, or stress the metal surface to achieve a smooth polished surface. In severe cases it can actually fracture the metals surface. Obviously, this is not an acceptable means to an end. However, stainless steel electropolishing removes metal from the surface leaving no surface pattern which is free from occlusions and stress; it is highly reflective and microscopically smooth.
A truly superior benefit of electropolishing is that bacteria cannot multiply on a surface that has been electropolished because electropolishing makes the part devoid of hydrogen as well as the surface shows no directional lines. Therefore, electropolishing is widely used in the food, medical, pharmaceutical, and surgical industries just to name a few.
Following is a summary of electropolishing attributes:
- Burr Removal
- Sharpening of Instruments for industries such medical, pharmaceutical, and food
- Total Passivation
- Oxide and Tarnish Removal
- Removal of Scale and Discoloration
- Reduction in Surface Profile
- Removal of Surface Occlusions
- Increased Corrosion Resistance
- Increased Ratio of Chromium to Iron
- Improved Adhesion in Subsequent Plating
- Reduced Buffing and Grinding Costs
- Removal of Directional Lines
- Radiusing of Sharp Edges
- Reduced Surface Friction
- Stress Relieved Surface
- Removal of Hydrogen
- Superior Quality Surface Cleaning
- Highly Reflective Surface
- Less Corrosion
- Improved Smoothness
- Improved Sealing
- Reduced Out-Gassing
- Reduced Galling
- Reduced Bacterial Buildup
- Other Alloys