Frequently Asked Questions
The electropolishing process reverses the plating process. As opposed to putting metal on a part, electropolishing removes a very fine outer layer. A combination of chemicals and electricity is used to accomplish this.
An electropolished surface can have a 50% improvement in finish. Electropolishing removes material and improves surface roughness at the same time. Often, dimensional tolerances are maintained by limiting process runtimes due to material removal. By allowing only a limited amount of material removal, roughness in the real world can be improved from 10% to 35%.
The process of electropolishing improves a surface on a microscopic level. An electropolished surface will only have a lustrous texture if there is a texture or scratch in the raw material.
The process of electropolishing treats the surface, not coats it. In this sense, an electropolished surface is just as susceptible to physical damage . An electropolished 316 stainless steel surface has the same strength and hardness properties as those published for 316 stainless steel. Due to the reflective finish produced by electropolishing, even the smallest surface scratch may be visible. Corrosion resistance of electropolished surfaces makes them more resilient in many corrosive environments.
A mechanical polishing process is mechanical while electropolishing is electrochemical. Mechanical polishing utilises abrasives to cut the surface of the stainless steel leaving microscopic contamination and pitting. Electropolishing is a surface treatment that removes material from the surface,
providing a smoother and contaminant free surface. The corrosion prevention surface oxide layer after electropolishing is much more robust.
The amount of material removed by electropolishing is directly related to the runtime and amp-minutes. As a result, electropolishing can be controlled to reduce the amount of material removed. A standard run typically removes only 0.003″ to 0.007″ of material. As much as 0.007″ of material may be removed from an electropolishing run with a longer runtime. A component’s dimensional tolerances should be reviewed before electropolishing.
Passivation is often misunderstood as a benefit of electropolishing, but it can also be achieved chemically without electropolishing. At Anopol, we passivate using Nitric or Citric Acid. Passivation is a chemical process used to remove free iron from parts. By electro-chemically removing metal from the surface, electropolishing improves micro-finish, provides deburring, enhances aesthetics and passivates remaining surface.
While passivation improves corrosion resistance, manufacturing leaves many imperfections behind that passivation cannot eliminate. During the process, heat tint and oxide scale created by welding and heat treating are not removed. Traditionally, pickling has been used to address this problem.
As electropolishing removes many surface imperfections and embedded contaminants left behind by machining operations, it is often used as a final step in manufacturing.
