Caustic Stress Corrosion Cracking (Caustic Embrittlement)

Explore this topic

Caustic Stress Corrosion Cracking, also referred to as Caustic Embrittlement, is a form of degradation that is caused when a component operates in a caustic environment. It is one of the most prevalent afflictions in the industry and one of many environmental cracking mechanisms that typically occur in carbon steel equipment, but it can also afflict low alloy and austenitic stainless steel equipment. Caustic environments (those that contain high amounts of NaOH & KOH) cause cracking most commonly in weldments because of high residual stresses, but can also affect base metal with high residual stresses.

When inspecting for cracks caused by caustic cracking it is difficult to follow a strict set of guidelines. These cracks can follow the heat-affected zone (HAZ) or they can be transverse through the weld. They can sometimes be small and difficult to find even with penetrant testing, or they can be so large and visible that they can be detected using a simple visual inspection. On the outside surface though, it’s not uncommon to see white crystalline deposits of caustic where a leak has occurred due to caustic cracking.

A number of factors can contribute to whether caustic cracking will affect a particular piece of equipment. Steaming out non-post-weld heat treated (PWHT) equipment can make it more vulnerable to caustic cracking. Similarly, inadequate PWHT can also create higher residual stresses and thus higher susceptibility to caustic cracking. Injecting concentrated caustic into process environments is another big problem. Caustic carry-over or concentration in steam systems is also incredibly dangerous and needs to be prevented by continuous, high quality control of boiler feed water treatment and operating controls. Finally, pipe bends, bellows, or coils that have high levels of residual stresses and are exposed to hot caustic containing fluids are also quite susceptible.

This topic is covered in more detail in API RP 571 - Damage Mechanisms Affecting Fixed Equipment in the Refining Industry.

Related Topics

Topic Tools

Share this Topic

Contribute to Definition

We welcome updates to this Integripedia definition from the Inspectioneering community. Click the link below to submit any recommended changes for Inspectioneering's team of editors to review.

Contribute to Definition
Articles about Caustic Stress Corrosion Cracking (Caustic Embrittlement)
March/April 2022 Inspectioneering Journal

This article provides an overview of some of the more common forms of stress corrosion cracking (SCC) with a focus on effective inspection methods for detecting these forms of cracking.

May/June 2020 Inspectioneering Journal

There are many places where brittle fracture risk can sneak into your plant and many reasons why a new or revised brittle fracture assessment may be required when reviewing your pressure systems. Don’t overlook this dangerous failure mechanism.

Authors: Greg Garic
January/February 2003 Inspectioneering Journal

I already mentioned this common affliction in the introduction. Caustic cracking was long called caustic embrittlement, but since no embrittlement actually occurs that name is fading away.

Authors: John Reynolds
Partner Content

Download Pinnacle's Economics of Reliability Report - Refining to see how reliability is affecting profitability.

    Downloads & Resources related to Caustic Stress Corrosion Cracking (Caustic Embrittlement)

      Inspectioneering Journal

      Explore over 20 years of articles written by our team of subject matter experts.

      Company Directory

      Find relevant products, services, and technologies.

      Talent Solutions

      Discover job opportunities that match your skillset.

      Case Studies

      Learn from the experience of others in the industry.


      Inspectioneering's index of mechanical integrity topics – built by you.

      Industry News

      Stay up-to-date with the latest inspection and asset integrity management news.


      Read short articles and insights authored by industry experts.

      Expert Interviews

      Inspectioneering's archive of interviews with industry subject matter experts.

      Event Calendar

      Find upcoming conferences, training sessions, online events, and more.


      Downloadable eBooks, Asset Intelligence Reports, checklists, white papers, and more.


      Watch educational and informative videos directly related to your profession.


      Commonly used asset integrity management and inspection acronyms.