API-571 Exam Dumps : Corrosion and Materials Professional

API RP 571 – Polythionic Acid Stress Corrosion Cracking:

“Polythionic acid SCC may be mistaken for wet H₂S damage because both involve cracking in austenitic stainless steels under certain conditions.”

Thus, option D is correct.

Comprehensive and Detailed Explanation From Exact Extract:

Per API RP 571, sulfidation corrosion rates are significantly accelerated by the presence of hydrogen. Hydrogen promotes:

Breakdown of protective sulfide scales

Increased diffusion of sulfur into the metal

Higher metal loss rates

This phenomenon is often referred to as hydrogen-assisted sulfidation and is commonly observed in refinery process units.

Moisture is more closely associated with oxidation mechanisms rather than high-temperature sulfidation.

Referenced Documents (Study Basis):

API RP 571 – Section on Sulfidation and High-Temperature Corrosion

According to API RP 571 Section 5.1.2.6 (Carbonate Stress Corrosion Cracking - CSCC):

“The cracking is usually intergranular and is most commonly detected using wet fluorescent magnetic-particle testing (WFMT) after surface cleaning. PT may not be sensitive enough to detect fine cracks formed by this mechanism.”

Because CSCC cracks are typically surface-connected and very fine, WFMT offers the best visibility, especially after proper surface prep.

Therefore, Option D is correct.