Surface Finish Guide

Stainless steel is often chosen for its aesthetic appearance, so make sure to specify the surface finish you need. Finishes can be added to improve functionality and for aesthetic appearance. The most common is the shiny, silvery finish manufacturers refer to as “bright”; alternatively, you can request a “pickled” or dull finish. Polishing and centerless grinding operations can be performed as secondary processes to produce desired RMS (root mean square) finishes as needed.

Surface Finishing Services

Surface Finish Sand Blast

Production sandblasting center for achieving various degrees of matte surface finishes.

Sand Blasting – Produces a dull matte finish with various grit sizes. 60 / 100 / 180 / 220 / Glass Bead

Electropolishing – Produces a high, bright finish. Electropolishing is a process where the tubes are submerged in a tank and an electric current is used between a cathode and anode with the tubes in between. This electric current will then remove a small layer from the surface of the metal.

Belt Polishing – Produces a high luster finish using grits from 180 to 640. The material can have the smoothness/ brightness improved by conditioning the tubing using a belt polisher. The higher the number the finer the grit and the smoother the surface finish.

Black Oxide Finish – Minimizes light reflection

Centerless Ground Finish

Commercially Clean & Capped

Thermocouple Clean & Capped

Passivation (Chemical Cleaning) – Treatment of stainless steels after fabrication with oxidizing chemicals known as chemical cleaning or passivation. If iron particles or other substances have become embedded in the surface during fabrication or polishing operations, they must be removed. Otherwise, these minute particles may promote discoloration, rusting, or even pitting. Besides dissolving such particles, the oxidizing action of the bath also tends to enhance the corrosion resistance of stainless steel by fortifying the natural passive surface film.

This processing should be the final operation on a stainless steel part. It is generally done by immersing in a nitric or citric acid solution and then rinsing in clear deionized water and drying. If immersion of the stainless steel piece is impractical due to size, the acid solution may be applied with a suitable swab and removed by rinsing with water.

Nitric acid is recommended because it will dissolve any iron particles and leave the stainless steel unaffected. It is necessary that the surface of the steel be free of scale, heavy grease and oil if the chemical cleaning treatment is to be effective.

How is Surface Finish Measured?

RA (roughness average) and RMS (root mean square) both measure surface finish. They are analogous. They use a slightly different path but both arrive at the same conclusion.

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Eagle has the knowledge, the expertise, and the right equipment to give your finished parts the “look” you want. To inquire about a specific project or for any questions, please request a quote from us today.