Stainless Steel passivation through electropolishing

Passivation is a process that helps protect metal alloys such as stainless steel from corrosion and rust. There are multiple ways to achieve passivation but electropolishing has been proven to be the most effective means of achieving passivation in a variety of metals including stainless steel. 

What is Stainless Steel Passivation?

Stainless steel passivation through electropolishing is a process that helps protect stainless steel surfaces from corrosion and rust. Stainless steel is considered “passivated” when it shows high resistance to corrosion in an environment where one would expect corrosion to take place. The passivation of stainless steel helps to ensure the longevity of stainless steel products, making them more reliable and safer for use in a variety of industries. But what exactly is stainless steel passivation, and how does it work? Lets take a closer look.

Understanding Stainless Steel Passivation

To understand the passivation of stainless steel, it helps to understand why stainless steel corrodes or rusts in the first place. The chromium in stainless steel forms a thin, oxygen-enriched, passive layer on the steel’s surface. This layer makes the metal inherently resistant to corrosion. However, manufacturing processes such as rolling, cutting, machining, laser cutting, welding, and other production steps disrupt the passive layer and embed “free iron” and impurities into the surface layer of the metal. When this free iron begins to react with elements from the environment such as salt water, chlorine and many other chemicals when combined with these impurities leads to corrosion. Stainless steel passivation works by removing any impurities or contaminants on the surface of the metal and restoring the chromium oxide layer that is normally present, thereby restoring the stainless steel’s inherent corrosion resistance.

Advantages of Stainless Steel Passivation through Electropolishing

There are multiple processes that can help to achieve passivation in stainless steel including nitric acid passivation and citric acid passivation. However, scientific studies have shown that stainless steel passivation through electropolishing is the most effective means of achieving passivation.

At NEE we agree; parts passivated through an abbreviated electropolishing cycle meet or exceed the corrosion resistance performance of parts passivated using a chemical method.

Passivation of stainless steel through electropolishing provides these key benefits:


The stainless steel passivation through electropolishing process is compliant with ASTM B 912-02 and ASTM A967-13, “Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts.”


Passivation through electropolishing removes all free iron from the surface of the work-piece, immediately eliminating free iron corrosion potential.

Electropolishing increases the chromium oxide layer to a greater degree than traditional passivation methods, thus enhancing the part’s corrosion resistance.
A mild electropolishing cycle removes a small amount of surface material, including additional free iron and deeply embedded impurities below the surface of the part.
Passivation through electropolishing increases the chromium oxide layer of stainless steel parts to a higher degree than chemical passivation methods, enhancing the part’s corrosion resistance.
All grades of stainless steel can undergo passivation through electropolishing, including: 301, 302, 303, 304, 316, 316L, 321, 17-4, 410, 416, 420, 431, 430, 440, 455, and F18.

How does the passivation of stainless steel work? 

Step One: Pre-Treatment/Cleaning:

Upon arrival to NEE all parts and components undergo a thorough pre-cleaning process to ensure surfaces are treated and prepared for the electropolishing process.

Step Two: Racking of parts:

Parts are either racked individually or combined in specially designed baskets for the electropolishing of bulk parts. Parts with restricted tolerances are individually racked for best results.

Step three: Electropolishing:

Once racked, parts are then submerged into an electropolishing bath which contains a calibrated blend of sulfuric acid and phosphoric acid. A positive electrical current is then applied to the solution.

Step four: Post-electropolishing procedures:

The post electropolishing procedure entails a multip step rinsing process which can include up to ten rinsing stations containing various acids or ionized water rinses. Parts are then dried utilizing various methods.

Step five: Testing:

Depending on the client’s needs, the performance of parts can be tested and analyzed through a variety of methods internally or through third-party laboratories.

Step six: Final Inspection/Shipping:

Once the electropolishing process has been completed, all parts undergo a final inspection from our quality control team.

What is the best way to passivate stainless steel? 

When it comes to ensuring the longevity, durability, and corrosion resistance of stainless steel, electropolishing emerges as the ultimate solution. This advanced passivation technique goes beyond the conventional methods, offering a transformative process that elevates stainless steel to new heights of performance.

Electropolishing involves immersing stainless steel components in an electrolyte bath and applying an electric current. This controlled electrochemical process meticulously removes surface material, eliminating impurities, contaminants, and micro-roughness. Unlike traditional passivation methods, electropolishing doesn’t just protect the surface; it enhances it. The result? A stainless steel surface that is not only free from impurities but also microscopically smooth, resistant to corrosion, and remarkably easy to clean.

This technique doesn’t merely offer superior passivation; it delivers a range of unparalleled benefits. Electropolished stainless steel exhibits enhanced resistance to rust, staining, and pitting, making it ideal for critical applications in industries such as pharmaceuticals, food processing, aerospace, and medical devices. Moreover, electropolishing imparts a brilliant, mirror-like finish, elevating the aesthetic appeal of stainless steel components.

In essence, electropolishing stands as the epitome of stainless steel passivation. It not only meets industry standards but exceeds them, providing a finish that is not only impeccably clean but also exquisitely polished. When you choose electropolishing, you’re not just passivating stainless steel; you’re enhancing its performance, aesthetics, and lifespan, ensuring your components endure the test of time in the most demanding environments.


In conclusion, the passivation of stainless steel is an important step in the manufacturing process for ensuring that your products remain safe and reliable over time by providing an extra layer of protection from corrosive elements present in the environment. It also provides improved aesthetics and makes cleaning parts easier too! With all these benefits of electropolishing in mind, it’s clear why many product engineers utilize electropolishing to achieve stainless steel passivation. To achieve passivation in stainless steel for your products, contact the experts at New England Electropolishing today. We offer a free sample part electropolished and shipped back to you at no cost.


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