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 circulation with Ferroquest FQ7101 (an acid cleaner containing editronic acid) promote the formation of an anodic film on the carbon steel surface to improve corrosion resistance. These treatments also help prevent flash rust, which can occur when clean carbon steel encounters any moisture between processing and installation or painting/coating. Other methods to minimize flash rust are using an alkaline, rust-inhibiting rinse, or applying a rust-preventing oil compound on a clean and dry carbon steel surface.
*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 Does | Astro Pak Does Not |
| Pickling | Conversion coat (parkerizing, phosphating, "bluing") |
| Descaling | Test for metals in cooling/wastewater |
| Passivation* | Install cathodic protection systems |
| Cleaning for Oxygen Service (CGA G-4.1, ASTM G93, etc.) | |
| Oil Flushing |
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
