API-571 Exam Dumps - Corrosion and Materials Professional

API RP 571 states under Chloride Stress Corrosion Cracking (Cl-SCC):

“Nickel contents above approximately 35% provide significant resistance to chloride stress corrosion cracking. Alloys such as Alloy 625 and Alloy 825 exhibit excellent resistance.”

“Austenitic stainless steels with lower nickel contents, such as 304 and 316, are more susceptible to Cl-SCC.”

Hence, option C (35%) is correct.

API RP 571 on Chloride Stress Corrosion Cracking (Cl-SCC) clearly states:

“Austenitic stainless steels such as 304 and 316 are highly susceptible to Cl-SCC when subjected to tensile stress and exposed to chloride-bearing environments.”

“Susceptibility is greatest in non-stress-relieved weldments or cold-worked areas.”

Brass and carbon steels are not typical Cl-SCC candidates; low alloy steels such as 1.25Cr-0.5Mo are also not commonly affected.

Thus, option C is the correct answer.

Comprehensive and Detailed Explanation From Exact Extract:

Reheat cracking is explicitly defined in API RP 571 as cracking that occurs during postweld heat treatment or elevated temperature exposure due to stress relaxation in the heat affected zone of welded components.

Key characteristics per API RP 571 include:

Occurs during PWHT or high-temperature service

Associated with creep-strength-enhanced steels (e.g., Cr-Mo steels)

Driven by stress relaxation and grain boundary weakness

Most common in heavy wall sections

Why the other options are incorrect:

Option A (PWHT cracking) is a non-specific term; API classifies this mechanism as reheat cracking.

Option B (Thermal fatigue) requires cyclic temperature changes, not stress relaxation.

Option D (Temper embrittlement) does not cause cracking during PWHT.

API RP 571 uses reheat cracking as the correct classification.

Referenced Documents (Study Basis):

API RP 571 – Section on Reheat Cracking

API Welding Metallurgy Study Guide

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API RP 571 on HTHA states:

“Acoustic emission testing is not currently a proven or reliable method for identifying HTHA in refinery components.”

“HTHA typically occurs internally, not as surface blisters, and is not limited to welds. Austenitic (300 series) stainless steels are generally resistant at normal refinery conditions.”

(Reference: API RP 571, Section 4.2.1.3 – High Temperature Hydrogen Attack)

Thus, option A is the most accurate statement.

API RP 571 details that:

“Sulfide Stress Cracking (SSC) susceptibility increases significantly with increased hardness of the steel.”

“NACE MR0175/ISO 15156 provides hardness limits for carbon and low-alloy steels to avoid SSC in sour environments. These are typically limited to 22 HRC or 248 Brinell.”

“High hardness promotes crack initiation under tensile stress in sour environments (i.e., containing H₂S).”

(Reference: API RP 571, Section 4.2.2.1 – Sulfide Stress Corrosion Cracking)

While hydrogen-induced cracking (HIC) and blistering are related to hydrogen charging, SSC is the only mechanism directly and critically impacted by hardness, making option B correct.