Stainless steel combines desirable mechanical properties with a known and proven level of corrosion resistance. Stainless Steel is one of the most popular alloys to electropolish because it enhances its corrosion resistance properties. The performance of stainless steel alloys are well known and fully documented, and despite these known properties and use within an appropriate environment, stainless steels can still fail from corrosion.

All stainless steels are iron-based alloys (minimum 50% iron) and have at least 10.5% chromium. The chromium content is the key to stainless steel's basic corrosion resistance. When the chromium is exposed to oxygen, it spontaneously forms a passive oxide layer. This passive oxide layer is very thin, yet it prevents further diffusion of oxygen into the base material and thus prevents corrosion. Stainless steel electropolishing enhances the passive oxide layer by making it thicker, and therefore more resistant to harsh environments. Further details can be found in our discussion of electropolishing stainless steel and other metals.

Corrosion resitance is not the only advantage that is improved when electropolishing stainless steel. An electropolished surface also repairs surface finish, makes the material easier to clean, and gives the material a striking finish.

Common Electropolished Stainless Steel Alloys

• 304 Stainless Steel
• 316 and 316 L Stainless Steel
• 400 Series Stainless Steels
• 17-4 pH
• 2205 Duplex Stainless Steel
• Other Duplex Stainless Steels

Mechanical Finishes Common to Stainless Steel

1. #4 finish is one of the many generally accepted, mechanical finishes which are often used in the metal finishing industry. Both the NiDi No. 9012 and previous revisions of ASME BPE specificationsinclude a list that describes various mechanical surface finishes for stainless steel. A few common finishes include:
2. #4 finish - A widely used, general purpose finish produced by finishing with a 120-150 mesh abrasive. This finish is commonly found on architectural panels and stainless steel kitchen appliances and sinks.
3. #2B finish - A bright, cold-rolled finish. This finish is a standard finish for raw sheet metal and is produced at the mill.
4. #8 finish - A highly polished, highly reflective, "mirror like" surface . This finish is produced by polishing with successively finer abrasives followed with extensive buffing.

Electropolishing is an electrochemical process by which surface material is removed by anodic dissolution. Electropolishing removes surface material, beginning with the high points within the microscopic surface texture. By removing these points, the electropolishing process will improve the surface finish, leaving a smoother and more reflective surface.

Electropolishing Process

Electropolishing is accomplished by creating an electrochemical cell in which the material to be polished is charged anodically. A cathode is formed to mirror the geometry of the work-surface and the two are submerged in a heated electrolyte bath. When a DC current is applied, the electrical charge forces metal ions to be dissolved from the stainless steel work-surface.

Prior to Electropolishing

The key to the electropolishing process is the difference in current density across the surface. Within the microscopic surface profile, the current density is greater at the high points and lesser at the low points. The rate of the electropolishing reaction is directly proportional to the current density. The increased current density at the raised points forces the metal to dissolve faster at these points and thus tends to level the surface material. After the electropolishing treatment, the work-piece is passed through a series of steps to neutralize, rinse, clean and dry the surfaces.

Electropolishing Benefits

Electropolishing delivers a smoother, more reflective surface that reduces product adhesion and improves surface cleanability. Perhaps more importantly, electropolishing preferentially dissolves free iron, inclusions, and embedded particles from the surface of the work-piece. This process improves the near surface chemistry of the material, and promotes the formation of an improvedcorrosion resistant surface layer. Please see the full description of each of electropolishing's benefits.

i. Improved Corrosion Resistance:

All forms of corrosion begin on or near the surface. Unfortunately all fabricating and handling practices invariably degrade surface conditions and surface properties. Surface contaminants, including grease, dirt, iron, and other metallic particles are inherent to machining, welding and fabrication processes. Mechanical cutting, machining, handling and polishing will leave iron and abrasive particles embedded within a material surface. These surface contaminates disrupt the formation of stainless steels' naturally occurring corrosion resistant oxide layer and are often the origin site of corrosion. Electropolishing removes surface material and surface contaminants. Electropolishing dissolves free iron, inclusions, and embedded particles from the surface of the material surface.

Electropolishing improves the near surface chemistry of stainless steel. Not only does it remove embedded particles and inclusions, it also improves the atomic ratios of the materials alloying elements. Figure 1 is an Auger Electron Spectroscopy (AES) analysis of an electropolished stainless steel. It shows the effect of electropolishing to the near surface atomic composition of stainless steel. Electropolishing preferentially dissolves Iron (Fe) from the material matrix and leaves the surface with a higher relative concentration of Chromium (Cr). This improved surface will form a thicker and more uniform oxide layer with enhanced corrosion resistance properties. The improved oxide layer resulting from electropolishing will have a Chromium to Iron ratio greater than 1.5 and a Chromium oxide to Iron oxide ratio greater than 2.0. The oxide layer will be thicker than 30 Angstroms.

Electropolished stainless steels are better suited to resist the onset of pitting corrosion, crevice corrosion, localized galvanic corrosion, stress corrosion cracking and microbiologically influenced corrosion.

Figure 1: Spectroscopic analysis of an electropolish 316L Stainless Steel

ii. Improved Surface Finish:

Improved microfinishes can do more than improve the appearance of a part. Superior microfinishes can improve seals, lower friction, reduce real surface area, allow for easier sanitation, and improve heat and light reflection.
The roughness of a surface can be measured and quantified by a profilometer. A profilometer is an instrument that measures roughness by moving a diamond tipped stylus across a surface. A profilometer will produce a reading of the surface roughness in either micro-inches (µin) or micrometers (µm). The electropolishing process may improve a surface finish reading by up to 50%. Because electropolishing is not a surface coating, there is no risk of the surface distorting or peeling over time. (See more on our FAQ page: How smooth of a surface can electropolishing produce?)

iii. Reduced Product Adhesion & Ease of Cleaning:

The improved microfinish produced by electropolishing can reduce product adhesion and contamination buildup. Reduced adhesion can limit product build up and significantly lengthen duty cycles. When cleaning is necessary, cleaning operations can be completed in less time and with less effort.

Electropolishing facilitates sterilization and maintenance of hygienically clean surfaces. Research by the USDA has indicated that electropolishing reduces the buildup of bacterial biofilms.

Electropolishing reduces the appearance of rouging on the inside surfaces of distillation columns, storage vessels, and distribution systems for hot purified water and clean steam.

iv. Deburring:

Electropolishing is naturally suited for deburring. During the electropolishing process, the current density is greater at high points and lesser at the low points within the surface profile. The rate of the electrochemical reaction is directly proportionate to the current density. The increased current density at the raised points forces the material to dissolve faster at these points and thus tends to level the surface. Electropolishing will simultaneously deburr and polish the surface.

Grinding, vibration and tumbling techniques are often not suited for highly detailed or fragile parts. An properly controlled electropolishing process can remove burrs from such components. Because electropolishing is a non-mechanical process, there is no risk of distortion and the material hardness has no bearing on the processing time or cost.

Burr removal by electropolishing is limited to burr sizes of 0.002" or less. Larger burrs require a longer process time to achieve the adequate material removal. These material removal levels may affect critical dimensions of the component. Large burr removal can be accomplished by first mechanically polishing the component then electropolishing.

v. Appearance:

The most striking benefit of electropolishing is the resulting lustrous surface. Electropolishing is a non-mechanical process. No tools come in contact with the piece so there is no risk of creating directional polishing lines. The material is treated electrochemically, leaving a microscopically smooth surface that is highly lustrous.

specialize in electro polishing and related activities for corrosion resistant high purity process equipments. We have an in house, fully equipped electro polishing unit and trained staff for the processes.

We offer electro polishing of stainless steel equipments like valves, fittings, pumps, pipes and fabricated vessels.

Our electro polishing process gives benefits like enhanced resistance to corrosion, improved finishing, easy of cleaning, attractive appearance of equipment etc.

Description / Specification of Electropolishing Services

We are involved in offering a wide range of Electropolishing Services to our most valued clients. Our range of these are widely appreciated by our clients which are situated all round the nation. We offer our range of it at most affordable prices.

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Description / Specification of Steel Polishing Service

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Description / Specification of Ss Tube Electropolishing Service

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Description / Specification of Stainless Steel Electropolishing

We are involved in offering a wide range of Stainless Steel Electropolishing to our most valued clients. Our range of these are widely appreciated by our clients which are situated all round the nation. We offer our range of it at most affordable prices.

We introduce ourselves as an eminent trader and supplier of an extensive array of  Stainless Steel Electropolishing. Prior to dispatch, our quality controllers run numerous tests on the entire range on various parameters of quality and durability. The offered equipment is manufactured using superior quality components with the aid of sophisticated techniques at the vendors' end. Moreover, our precious clients can purchase it in different technical specifications at reasonable price from us within promised time frame.
Features:

Sturdy design
Highly durable
Application specific design