Can You Passivate Carbon Steel?

Stainless steel is an ubiquitous material for process equipment in high purity industries.  Its predecessor, carbon steel is an even more popular material and found in some capacity at any manufacturing environment.  Plain carbon steel has far less corrosion resistance than its stainless derivative. However chemical techniques do exist that can maintain surface cleanliness and surface resistance in mildly aggressive environments.

The Science Behind Carbon Steel Oxidation

Like stainless steel, carbon steel also forms a passive oxide surface.  Stainless steel’s passive layer is predominantly chromium oxide. For this oxide layer to form, a critical threshold of chromium content, commonly agreed to be 10.5% by weight, must be present in the alloy.  Typically, the total alloying elements in carbon steel is less than 10.5%.  Although a chromium oxide layer does not form on carbon steel, it can still oxidize a well-adhering, resistant layer.

Astro Pak has experience processing carbon steel systems in the following industries and applications:

·       Aerospace

·       Metal Production

·       Battery Manufacturing

·       Oil and Gas Refining

·       Data Centers

·       Turbines and Power Generation

·       Hydraulic and Lube Oil Piping

·       Wastewater

·       Industrial Manufacturing Piping

·       Water Treatment

Deciphering Carbon Steel Treatment Techniques

Astro Pak has procedures for descaling hard water deposits, pickling heavy weld oxidation or heavy corrosion product, and enhancing corrosion resistance with oxidizing agents or corrosion inhibitors.  Treatments like sodium nitrite oxidation or etidronic acid (1-Hydroxyethylidene-1,1-diphosphonic acid, HEDP) promote the formation of an anodic film on the carbon steel surface to improve corrosion resistance.  *These processes have an effect similar to passivating stainless steel, but they are not by definition passivation processes.  Keep in mind, these “passivating” treatments provide strongest results when continually applied and maintained in the carbon steel system

What Astro Pak Can and Cannot Do

The table below shows Astro Pak’s offerings relative to carbon steel systems.

Astro Pak DoesAstro Pak Does Not

Conversion coat

(parkerizing, phosphating, “bluing”)

DescalingTest for metals in cooling/wastewater
Passivation*Install cathodic protection systems

Cleaning for Oxygen Service

(CGA G-4.1, ASTM G93, etc.)

Oil Flushing 
Pipeline Pigging/Dewatering 
Oil Coating 
Pressure Testing 

Ready to elevate your carbon steel system? Request a quote today and let Astro Pak be your trusted partner ensuring your carbon steel system performs as designed

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Picture of Bradley Hostetler

Bradley Hostetler

Bradley Hostetler has joined Astro Pak filling the role of senior metallurgist in Astro Pak’s Technical Services Group. Bradley holds a Bachelor’s degree in Materials Engineering from California Polytechnic State University, San Luis Obispo and a Master’s in Materials Science from Carnegie Mellon University. He comes from the metal production industry and has both research and work experience in steel and specialty alloy melting. Bradley has experience participating and presenting at various AIST (Association for Iron and Steel Technology) and NACE (National Association of Corrosion Engineers) conferences during his time as a student.

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