Stress Corrosion Cracking


Stress corrosion cracking (SCC) is a fracture process that involves the combined and simultaneous action of a tensile stress and a corrosive environment. SCC occurs when the tensile stress and a specific environment are able to cause failure by their combined action, but are insufficient to cause failure by either one acting alone. In fact, the tensile stresses are usually below the metal’s yield strength. Furthermore, the metal would suffer only minimal corrosion in the absence of the applied stress.
There are three requirements for SCC to occur:

  1. A susceptible metal.
  2. Tensile stresses applied to the metal.
  3. A specific environment containing an aggressive species that promotes SCC.

Elimination of any of these three factors will prevent SCC.

SCC occurs in specific combinations of metals and environments. The number of metal environment combinations that promote SCC is fewer than the number of metal environment combinations that will result in corrosion. Other environmental factors, such as pH and temperature, can also influence the severity of SCC.

See metallurgy courses & webinars
Need help with a failure analysis?

The source of the tensile stress may be externally applied stress or residual stresses. Externally applied stresses arise from applied mechanical loads such as tensile or bending loads. Residual stress is an internal stress that exists in a metal without an external load being applied. Residual stresses can result from cold working, heat treating, or welding.

Other than metal composition and the specific corroding species in the environment, other factors that influence SCC include total tensile stress on the metal, metal microstructure, and metal yield strength.

Increasing the yield strength of a metal is one way to improve its resistance to SCC because the threshold stress for SCC increases as the yield strength increases. The yield strength can be increased through alloying, heat treating, cold-working, and combination of these approaches. There is one very important consideration when increasing the yield strength. The increase in strength must not be accompanied by a significant reduction of the metal’s toughness, because decreasing the toughness will have a detrimental effect on a metal’s resistance to SCC and on its fracture toughness.

SCC can be controlled by any of the following three approaches: 1) design, which includes selection of the mechanical and materials aspects of components, 2) controlling the materials, 3) and controlling the environment.

Take our Corrosion of Metals course if you’d like to learn more about stress corrosion cracking and how to prevent it from occurring. Also, the books Corrosion and Corrosion Control (4th edition) by R.W. Revie and H.H. Uhlig and Corrosion: Understanding the Basics by ASM International are good resources for information about the SCC and the different corrosion mechanisms.

  • "A group of us took several courses (Principles of Metallurgy, Metallurgy of Steel, Corrosion of Metals) to become more knowledgeable about the science of metals to avoid problems. For me, the biggest impact of the training was on working with suppliers. I feel more confident asking questions and I now know the suppliers which know their stuff and which ones don’t. And it was great being able to get the training when it was convenient for me."

    Sam Bloodgood, VP Process Improvement, Hydraforce, Inc.
  • "I oversee several operations, including steel heat treating and laser welding. However, my background was in the construction materials industry. Principles of Metallurgy gave me the knowledge to have meaningful discussions with my engineers and be able to ask them better questions."

    Tom Parkman, Plant Manager, Simonds International.
  • “Principles of Metallurgy exceeded my expectations. The content was straightforward enough not to be burdensome, yet deep enough to provide a practical review of fundamental principles. I recommend this course to any engineer or technical person who has been out of school and working in industry for several years, but not necessarily having been focused on metallurgy.”

    Andy Jacobs, Staff Engineer, DePuy Orthopaedics, Inc.
  • “The Principles of Metallurgy course is broke up into convenient length modules that can be fit into the busiest schedule. The course is a good review for engineers who had a materials class ten or more years ago.”

    Paul Flury B/E Aerospace
  • “This is an excellent course (Metallurgy of Steel Heat Treating) for learning basic heat treating practices. The course introduces and covers a broad range of processes. I would recommend it for anyone in the steel business.”

    Jim Marks, Magellan Corporation
  • “This course has given me more confidence in my job and given me a better understanding of some of the heat treatments used in the business.”

    Mark Winter, Abbey Forged Products

Have more questions? Email or call 847.528.3467

Why Industrial Metallurgists?

  • Practical, up-to-date content.
  • Metallurgy expertise and 20+ years of experience.
  • Courses designed for non-metallurgists.
  • Training accessible from anywhere with internet access.
  • Engaging content.
  • Convenience. Learn when it suits your schedule.
  • Avoid being overwhelmed with too much information at one time. Set your own pace.