Frequently Asked Questions
- Electropolishing FAQs
- How large/small of an order will you accept?
- What is the largest size piece that you can electropolish?
- How smooth of a surface can electropolishing produce?
- How durable is an electropolished surface?
- What is the difference between electropolishing and mechanical polishing?
- What is the difference between electropolishing and electroplating?
- What is the difference between Ra and RMS?
- How much material is removed by electropolishing?
- What electropolishing/passivation standards does your process comply to?
- How large/small of an order will you accept?
- New England Electropolishing has ten electropolishing lines operating on a daily basis. We have
tremendous capacity to push out high-volume orders. That said, NEE welcomes orders from 1 unit to 500,000 units. No job is too big or small.
- What is the largest size piece that you can electropolish?
- New England Electropolishing has capacity and expertise to electropolish and passivate fabrications up to 9 feet long by 5 feet in diameter. NEE’s staff members are skilled at designing and fabricating custom cathodes that are often critical to processing large parts to specification.
- How smooth of a surface can electropolishing produce?
- The electropolishing process may improve a surface finish by up to 50%. The electropolishing reaction removes material while it improves surface roughness. Because of the material removal, process
runtimes are often limited to maintain dimensional tolerances. Limited runtimes result in real world su
rface roughness improvements from 10 to 35%. In is important to keep in mind that electropolishing improves a surface on the microscopic level. If a raw material has a texture or surface scratch, electropolishing will only result in a lustrous texture or lustrous scratch.
- Electropolishing is a surface treatment, not a surface coating. Thus, an electropolished surface can be physically damaged or degraded in the same way as its base material can be damaged or degraded. An electropolished 316 stainless steel surface has the same strength and hardness properties as those published for 316 material. Note however, because electropolishing may produce such a lustrous finish,
even the finest surface scratch may be visible. Electropolished surfaces possess increased corrosion
resistance and as a result are more resilient in many corrosive environments.
- Electropolishing is an electrochemical process while mechanical polishing is a mechanical process. Electropolishing is a surface treatment that can improve surface finish as it dissolves material from the surface. Mechanical polishing, like machining, alters a surface by cutting material away from the surface. Electropolishing can improve a surface finish on a microscopic level, mechanical polishing improves
a surface finish on a macroscopic level.
- Electropolishing removes material while electroplating adds material. Electropolishing and electroplating
have similar setups, but they involve opposite reactions. Both are electrochemical reactions,
however, in electropolishing the work-piece is charged anodically (thus loses ions) and in electroplating
the work-piece is charged cathodically (gains ions).
- The amount of material that is removed by electropolishing is directly proportional to the runtime
and the amp-minutes that pass through the piece. Given this, the amount of material removed by electropolishing may be controlled. Often, during a standard run, total material removal is only to
0.0003" to 0.0007". If the goal of an electropolishing run requires a longer runtime, as much as
0.003" of material may be removed. It is always important to review the dimensional tolerances of a component before it is electropolished.
- Ra and RMS are both representations of surface roughness, but each is calculated differently. Ra is calculated as the Roughness Average of a surfaces measured microscopic peaks and valleys. RMS is calculated as the Root Mean Square of a surfaces measured microscopic peaks and valleys. Each value
uses the same individual height measurements of the surfaces peaks and valleys, but uses the measurements in a different formula. The formulas are shown above. One can infer from examination
of the formulas, that a single large peak or flaw within the microscopic surface texture will effect
(raise) the RMS value more than the Ra value.
- Listed below are common industry specifications that either detail or incorporate the surface treatments performed by New England Electropolishing:
- Electropolishing:
- ASTM B912, "Standard Specification for Passivation of Stainless Steel Using Electropolishing"
- ASME BPE, "Bioprocessing Equipment"
- Passivation:
- ASTM A967, "Standard Specification for Chemical Passivation Treatments for Stainless Steal Parts”
- ASTM A380, "Standard Practice for Cleaning, Descaling, and Passivation of Stainless
Steel Parts, Equipment, and Systems" - QQ-P-35C, Federal Specification: "Passivation Treatments for Corrosion-Resistant Steel" (replaced by ASTM A967)
- ASTM B912, "Standard Specification for Passivation of Stainless Steel Using Electropolishing"