Integripedia Topic
Polythionic Acid Stress Corrosion Cracking (PASCC)

Explore this topic

Polythionic Acid Stress Corrosion Cracking (PASCC) is a type of intergranular stress corrosion that affects sensitized stainless steels in refineries processing feedstocks containing sulphur. This damage mechanism primarily affects standard and high carbon stainless steels, but low carbon and chemically stabilized stainless steels may also be vulnerable under certain conditions. PTA SCC typically does not occur during normal processing, but rather, after the equipment is shutdown and opened up for inspection (i.e. when moist air contacts the surface of equipment that has been exposed to sour hydrocarbons in service).

A common form of "prevention" is to perform a soda acid wash of the equipment before or right after it is exposed to air and moisture. PTA SCC can also be prevented by removing oxygen from the environment by performing a dry nitrogen purge or removing moisture by performing a dry air purge.

This damage mechanism is covered in greater detail in API RP 571, Damage Mechanisms Affecting Fixed Equipment in the Refining Industry. It includes a general description of the damage mechanism, susceptible materials of construction, critical factors, inspection method selection guidelines, and control factors. PTA SCC is also covered by NACE Standard RP0170-97, Protection of Austenitic Stainless Steels and Other Austenitic Alloys from Polythionic Acid Stress Corrosion Cracking During Shutdown of Refinery Equipment, which lists several methods for preventing or mitigating PTA SCC and details some of its causes.

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 Polythionic Acid Stress Corrosion Cracking (PASCC)
    News related to Polythionic Acid Stress Corrosion Cracking (PASCC)

      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.