• T-38 Main Landing Gear Piston made of Ferrium S53
  • QuesTek Governmental  Clients

Ferrium® S53®


Ferrium S53 (AMS 5922, MMPDS) is an ICME-designed, corrosion resistant, ultra-high strength steel for structural aerospace and other applications where 300M (BS S155) and 4340 are typically used, but S53 steel provides: much greater resistance to general corrosion and to stress corrosion cracking (SCC); excellent resistance to fatigue and to corrosion fatigue; and high hardenability. Its resistance to general corrosion is similar to that of 440C stainless steel, but it has much greater fracture toughness.

S53 steel is double vacuum melted (i.e., vacuum induction melted and then vacuum arc remelted or "VIM/VAR") for high purity, leading to much greater fatigue strength.

Because of its high resistance to corrosion and ultra high strength and toughness combination, S53 steel is being used in demanding landing gear and helicopter rotor shaft applications without the use of toxic cadmium coatings.

The figures below demonstrate the significant corrosion resistance improvement of Ferrium S53 alloy versus 300M. The images show performance after expsoure to 1000 hr salt fog test per ASTM G49.

Improved S53 Steel Properties versus Incumbent Materials

A comparison of typical properties is shown in the table below:

Additional S53 steel property data is available in the CINDAS LLC Aerospace Structural Materials Data demo (under "Typical Material PDF Files) and more info can be found on Carpenter's Ferrium S53 page.

Want greater toughness, higher SCC resistance, and can accept lower corrosion resistance? See Ferrium M54.


According to a SERDP/ESTCP released article, S53 exceeds conventional steels in terms of corrosion protection and other properties, without the need for a hazardous cadmium coating. There are a number of exciting ongoing flight-critical S53 steel applications including:

  • S53 steel is being used for numerous flight-critical components on orbital class rocket programs.
  • S53 steel landing gear have been flying on a T-38 aircraft since December 2010. At the 19 month point of service, QuesTek’s S53 steel landing gear (in service without toxic cadmium plating) were inspected and found to be performing better than the incumbent steel that requires toxic cadmium plating for additional corrosion resistance.
  • S53 steel landing gear have been flying on an A-10 aircraft since August 2012.
  • S53 steel truck beam landing gear assemblies have been in service on the KC-135 aircraft since 2015.
  • S53 steel roll pins have been in service on the C-5 aircraft since 2014.

S53 steel should be considered for any applications where 300M, 4340 or Maraging steels are used but are experiencing corrosion issues. Other applications can include driveshafts, rotorshafts, fasteners, and other highly-loaded components that can benefit from increased resistance to corrosion, corrosion fatigue and SCC.


Benefits of using S53 steel vs. 300M, 4340 and other incumbent materials can include:

  • Eliminate or reduce the need for toxic cadmium plating, in order to reduce EHS impact and expenses for both initial installation and on-going re-application. A primer and paint protection scheme on S53 steel performs comparably to that of a cadmium, chromate, primer and paint protection scheme on 4340 or 300M after 500 hours of salt fog testing per ASTM B117 (see below).
  • Reduce general corrosion and related expenses for part condemnation and equipment/system failure.
  • Reduce the occurrence of difficult-to-predict SCC failures, and related expenses for part condemnation and equipment failure/downtime.
  • Improve resistance to fatigue and corrosion fatigue.
  • Reduce specific manufacturing costs, because the high hardenability of S53 steel permits less severe quench conditions for a given part section size and typically results in less part distortion during heat treatment.

Forging, Machining, Heat Treatment and Finishing Processes

Processing of S53 steel is similar to other quench and tempered martensitic secondary-hardening steels. Vacuum heat treatment and vacuum tempering is recommended to avoid surface decarburization. After quenching to room temperature S53 steel is subjected to cryogenic treatment to assure a complete martensitic transformation. S53 steel is typically double-step tempered around 900°F (482°C).

For detailed information about forging, machining, heat treating and finishing processes of S53 steel, please refer to our Manufacturing and Thermal Processing of S53 Steel document.

S53 Steel Availability and Pricing

Carpenter Technology produces and typically keeps an inventory of S53 steel in round bar form of the following sizes, usually with immediate shipment and no minimum order: 0.625", 1", 2", 5.25" and 7.25" OD.

Other sizes will be added in time, and they can produce custom diameters, round corner square and octagon, although longer lead times and minimum orders in the range of 800 lbs or more are likely.

For pricing, inventory availability and lead time please contact Carpenter Latrobe facility by phone (800-241-8527) or e-mail at service@cartech.com. You may also contact the Reading facility by phone (800-572-2800 or 800-245-5030) or e-mail at sales@cartech.com

Technical Assistance

If you have a specific application engineering or technical question that is not answered by by the processing document above, then feel free to Contact Us.

Design and Development Background

We computationally designed S53 steel in direct response to and with the financial support of the U.S. Strategic Environmental Research and Development Program (http://www.serdp.org), in order to help reduce the use of toxic cadmium on 300M landing gear in the DoD and elsewhere. We won a "Pollution Prevention Project of the Year" Award from SERDP/ESTCP for designing S53 steel. The article in Advanced Materials and Processes magazine attached below provides significant additional background information.

In 2011 we co-authored a technical paper that evaluated protection schemes for ultrahigh-strength steels (including S53 steel) for landing gear applications. The paper concluded that a primer and paint protection scheme on S53 steel is comparable to that of a cadmium, chromate, primer and paint protection scheme on 4340 or 300M, after 500 hours of salt fog testing per ASTM B117; comparative data for zinc-nickel protection schemes was also presented (see below).

In 2008 the A- and B-basis design allowables were included in MMPDS.

In 2008 SAE International issued AMS 5922 specification for S53 steel.

Relevant files


Material Data Sheets


  • AA&S 2011

    Design, Development, Qualification and Insertion of Corrosion-Resistant, Ultra-High Strength Ferrium® S53® Steel for Aircraft Sustainment and Airworthiness - April 19, 2011

  • AeroMat 2007

    Probabilistic Property Prediction of Ultra High Strength Corrosion-Resistant Steel - A presentation detailing QuesTek's use of AIM to predict Ferrium® S53® properties 

  • American Helicopter Society 2014

    Design, development and qualification of computationally designed alloys - May 20, 2014

Press Releases