Free API-571 Exam Dumps October 2026

Same as above. Sigma phase formation is a microstructural phenomenon and not typically detected by NDE methods like magnetic particle or surface hardness testing.

Therefore, metallographic testing remains the definitive detection method, confirming option D again as the correct answer.

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.

As per API RP 571 Section 5.1.4.2 (Metal Dusting):

''Metal dusting is a type of carburization attack that typically occurs in high carbon activity environments, with temperatures generally between 900F and 1200F (480C to 650C), although damage has been reported as low as 600F (315C).''

Therefore, the commonly accepted operational range is best described by Option A: 600F--1200F (315C--650C).

API RP 571 under Oxidation:

''Carbon steels and low alloy steels, such as 9 Cr, have poor oxidation resistance at temperatures above 1000F (540C), rapidly losing thickness.''

''Stainless steels with higher Cr and Ni content (like 310) have superior oxidation resistance.''

Thus, 9 Cr steel will corrode fastest at 1350F, making option D correct.

From API RP 571, brittle fracture prevention measures include:

''Postweld Heat Treatment (PWHT) reduces residual stresses in the heat affected zone and base metal, thus lowering susceptibility to brittle fracture.''

''PWHT is particularly effective when applied to pressure-containing components fabricated from carbon steel or low-alloy steel that will experience low-temperature service.''

(Reference: API RP 571, Section 4.2.1.2 -- Brittle Fracture)

Therefore, while other measures may reduce stress or detect flaws, PWHT directly targets one of the root causes: residual stress. Thus, option D is the best prevention method.

According to API RP 571 Section 5.3.2.3 (Spheroidization):

''Spheroidization is a microstructural degradation that occurs in carbon steels and low alloy steels when exposed to elevated temperatures for long periods, typically beginning at temperatures as low as 650F (345C). It involves the transformation of lamellar pearlite into spherical cementite particles, reducing strength and hardness.''

Thus, Option A (650F / 345C) is the minimum threshold temperature for spheroidization to begin.

Comprehensive and Detailed Explanation From Exact Extract:

According to API RP 571, amine stress corrosion cracking (Amine SCC) is a form of environmentally assisted cracking that occurs in alkanolamine systems (e.g., MEA, DEA, DGA) used for acid gas treating. The cracking mechanism requires the simultaneous presence of tensile stress, susceptible microstructure, and an amine environment.

API RP 571 clearly states that Amine SCC occurs primarily in the weld heat affected zone (HAZ) of carbon and low-alloy steels. The reasons include:

The HAZ contains high residual stresses from welding.

The microstructure in the HAZ is metallurgically altered, making it more susceptible than base metal.

Cracks often initiate adjacent to welds, not in the weld metal itself.

Why the other options are incorrect:

Option A (Weld fusion line) is not the primary cracking location.

Option C (Weld metal) generally has different chemistry and lower susceptibility.

Option D (Base metal) typically has lower residual stress and is less prone.

API RP 571 specifically identifies the weld HAZ as the dominant cracking location for Amine SCC.

Referenced Documents (Study Basis):

API RP 571 -- Section on Amine Stress Corrosion Cracking

API Corrosion and Materials Study Guide