The Benefits of Electropolishing for 440C Stainless Steel | Able

The Benefits of Electropolishing for 440C Stainless Steel

October 4, 2022

If you’re manufacturing parts with 440C stainless steel and relying on passivation to get the finish you need, you may be overlooking an opportunity to dramatically improve the corrosion resistance of your parts.


Electropolishing provides stainless steel parts with up to 30x the corrosion resistance of passivation alone. And electropolishing leaves parts in a passive state at the same time. It’s a one-stop finishing method used by manufacturers of a wide variety of critical metal parts and a wide variety of alloys, including 400 series stainless steels.

Enhanced Corrosion Resistance Makes Electropolishing the Right Choice 

Enhanced corrosion resistance is a key reason for specifying electropolishing for parts where durability and life cycle are critical concerns.

While 440C has high mechanical strength and hardness, its lower chromium content makes it more susceptible to corrosion. It is commonly used in the manufacture of parts that do not require the highest level of corrosion resistance, including ball bearings, cutlery, molds and dies and some surgical instruments.

As other forms of stainless have risen in price, the use of 440C stainless has grown.

440C Stainless Steel Corrosion Resistance Case Study

When a customer in the hydraulics and pneumatics industry came to Able with a machined 440C stainless part used inside a valve assembly where friction was involved, corrosion resistance was a primary concern. The customer did not want the risk of corrosion impeding the valve function. Since 440C’s elemental composition makes it susceptible to flash attack under passivation, the customer opted to try electropolishing. Passivation can also leave parts made of 440C stainless steel with a scaly, gray texture or turn them black.

Able’s customer corrosion tested an electropolished part against a passivated and a raw “control” part. All three parts were placed in a pan lined with aluminum foil in an oven at 190° F for 8 hours a day, while spraying the parts with water a few times per day. The test ran for 7 days. After the test was completed the raw and passivated parts both showed obvious red rust while the electropolished part remained clean. (See photo at top right.)

Additional Benefits of Electropolishing for 440C Stainless

Electropolishing’s other benefits include:

Your Partner for High Quality Finishing of 440C Stainless Parts

At Able Electropolishing, we have decades of experience electropolishing a wide variety of metal parts, including 440C stainless steel. Our processes yield precise and consistent material removal that leaves parts defect free, more durable and with improved fit, finish and function.

Watch our video to learn more about the electropolishing process or reach out to one of our team members. You can also take advantage of our free sample process to see the results of electropolishing on your part.

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