Surreal illustration of stainless steel decaying under intense heat.

The Silent Thief: How Aging Impacts Stainless Steel and What You Can Do

Mira Elwood in Tech & Innovation August 2025 • 4 min read.

"Uncover the hidden effects of short-term aging on lean duplex stainless steel and discover strategies to protect your investments."

Stainless steel is known for its strength and resistance to corrosion, making it essential in industries ranging from oil refining to pharmaceuticals. Duplex stainless steels, in particular, offer an enhanced combination of strength and corrosion resistance compared to standard austenitic stainless steels. Lean duplex stainless steels (LDSSs) offer a cost-effective alternative without sacrificing significant performance, balancing affordability with the necessary durability for various applications.

However, even the toughest materials have their vulnerabilities. Exposing lean duplex stainless steel to temperatures between 400 and 1000 °C during manufacturing or welding can cause significant changes in its structure. This process, known as short-time aging, can lead to the formation of unwanted phases that compromise the material's integrity. Understanding these changes is crucial for maintaining the reliability and safety of equipment and structures built with LDSS.

This article explores how short-time aging impacts the pitting corrosion behavior and mechanical properties of a novel lean duplex stainless steel (LDSS) 2002. By understanding the underlying mechanisms and potential consequences, you can take proactive steps to protect your investments and ensure long-term performance.

What Happens When Stainless Steel Ages?

Surreal illustration of stainless steel decaying under intense heat.

When LDSS 2002 is exposed to high temperatures, it undergoes microstructural changes that affect its resistance to pitting corrosion and its mechanical strength. The main culprits are the formation of secondary phases, such as Cr2N and M23C6, which precipitate along the ferrite-austenite grain boundaries. These precipitates deplete chromium from the surrounding areas, making the steel more susceptible to corrosion and reducing its toughness.

To understand the effects of aging, researchers conducted potentiostatic critical pitting temperature (CPT) tests and Charpy impact tests on LDSS 2002 samples aged at different temperatures. The results revealed a significant degradation in both pitting corrosion resistance and toughness, particularly at 650 °C. At this temperature, the CPT decreased by 28 °C, and the impact energy dropped dramatically from 69 to 29 J/cm² compared to the solution-annealed sample.

Here’s a quick look at the key changes observed during aging:

Formation of Secondary Phases: Precipitation of Cr2N and M23C6 along grain boundaries.
Chromium Depletion: Reduced chromium concentration in areas surrounding precipitates.
Decreased CPT: Lower resistance to pitting corrosion.
Reduced Impact Energy: Lower toughness and increased brittleness.

The most significant reduction in CPT and impact energy occurred concurrently at 650 °C, highlighting the critical impact of this temperature range on the material's properties. Transmission electron microscopy (TEM) confirmed that the main precipitates formed at this temperature were Cr2N and M23C6, which accumulated along the ferrite-austenite grain boundaries.

Protecting Your Stainless Steel Investments: Practical Steps

Understanding how short-time aging affects LDSS 2002 is the first step in mitigating its impact. While the changes at a microstructural level may seem daunting, several practical strategies can help maintain the integrity and extend the lifespan of your stainless steel components. By implementing careful heat treatment protocols, controlling the welding environment, and choosing appropriate operating temperatures, you can minimize the risks associated with aging and ensure the continued reliability of your materials.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1007/s40195-018-0829-y, Alternate LINK

Title: Effect Of Short-Time Aging On The Pitting Corrosion Behavior Of A Novel Lean Duplex Stainless Steel 2002

Subject: Industrial and Manufacturing Engineering

Journal: Acta Metallurgica Sinica (English Letters)

Publisher: Springer Science and Business Media LLC

Authors: Tian-Yi Sun, Yan-Jun Guo, Yi-Ming Jiang, Jin Li

Published: 2018-10-09

Everything You Need To Know

What is the primary concern when lean duplex stainless steel 2002 is exposed to high temperatures?

The main concern is the microstructural changes that occur in lean duplex stainless steel 2002 when exposed to temperatures between 400 and 1000 °C, known as short-time aging. These changes involve the formation of secondary phases like Cr2N and M23C6, which precipitate along the ferrite-austenite grain boundaries. This process depletes chromium from the surrounding areas, making the steel more susceptible to pitting corrosion and reducing its mechanical strength and toughness.

How does short-time aging affect the pitting corrosion resistance of LDSS 2002?

Short-time aging significantly reduces the pitting corrosion resistance of lean duplex stainless steel 2002. The formation of secondary phases, particularly Cr2N and M23C6, leads to chromium depletion in the areas around the precipitates. This depletion weakens the steel's protective layer, making it more vulnerable to pitting corrosion. The potentiostatic critical pitting temperature (CPT) tests on aged samples show a decrease, indicating a lower temperature threshold at which pitting corrosion initiates.

What are the specific mechanical property changes observed in LDSS 2002 due to short-time aging?

Short-time aging causes a significant reduction in the mechanical properties of LDSS 2002. The primary effect is a decrease in toughness, leading to increased brittleness. This is indicated by a drop in impact energy, as observed in Charpy impact tests. For instance, at 650 °C, the impact energy dropped dramatically. Additionally, the material's resistance to pitting corrosion decreases, making it more susceptible to failure under corrosive conditions. These changes are a direct result of the formation of secondary phases and chromium depletion.

What practical steps can be taken to mitigate the effects of short-time aging on LDSS 2002?

Several practical strategies can help to protect the integrity and lifespan of LDSS 2002. Implementing careful heat treatment protocols is crucial to control the temperature exposure during manufacturing and welding. Controlling the welding environment, such as using appropriate shielding gases, can minimize the formation of detrimental phases. Furthermore, selecting appropriate operating temperatures that avoid the critical range of 400 to 1000 °C can also help to prevent aging. These proactive measures will help to maintain the material's durability and reliability.

Why is understanding short-time aging in LDSS 2002 important for industries using stainless steel?

Understanding short-time aging in lean duplex stainless steel 2002 is crucial for industries that rely on the material's strength and corrosion resistance, such as oil refining and pharmaceuticals. This understanding allows engineers and manufacturers to anticipate potential failures, implement preventive measures, and ensure the long-term performance and safety of equipment and structures. By recognizing how secondary phases like Cr2N and M23C6 affect the material's properties, industries can make informed decisions about material selection, heat treatment, welding procedures, and operating conditions. This knowledge helps to extend the lifespan of stainless steel components and reduces the risk of costly failures or safety hazards.