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API-571 Exam Questions
- Topic 1: Terms, Definitions, and Acronyms: This domain covers the key terminology, standard definitions, and commonly used acronyms related to corrosion and materials. It ensures a clear understanding of technical language used throughout the API-571 body of knowledge.
- Topic 2: Damage Mechanisms: This domain explains various corrosion and damage mechanisms, including their characteristics, affected materials, causes, and visual appearance. It also covers where damage occurs, along with methods for prevention, mitigation, inspection, and monitoring.
Free API API-571 Exam Actual Questions
Note: Premium Questions for API-571 were last updated On Apr. 22, 2026 (see below)
(Amine stress corrosion cracking is found primarily in the:)
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
(What steel alloy is no longer recommended for services susceptible to HTHA?)
Comprehensive and Detailed Explanation From Exact Extract:
According to API RP 571 and API RP 941 (Nelson Curves), 1 Cr--0.5 Mo steel is no longer recommended for services susceptible to High-Temperature Hydrogen Attack (HTHA).
API RP 941 documents industry experience showing that 1 Cr--0.5 Mo steels have suffered HTHA damage below previously assumed safe operating limits, due to insufficient carbide stability. As a result, this material has been removed from the Nelson Curves as an acceptable choice for new construction in hydrogen service.
By contrast:
Mn--0.5 Mo, C--0.5 Mo, and 1.25 Cr--0.5 Mo steels retain higher resistance due to more stable carbide structures.
Referenced Documents (Study Basis):
API RP 571 -- Section on High-Temperature Hydrogen Attack
API RP 941 -- Updated Nelson Curves and Material Recommendations
Which of the following weldments is most susceptible to dissimilar metal cracking when operating at high temperatures?
Dissimilar Metal Cracking (DMC) is a form of high-temperature cracking that frequently occurs in weld joints between carbon steel and austenitic stainless steel (such as Type 316 SS) due to differences in thermal expansion coefficients and mechanical properties.
From API RP 571 Section 5.2.3.1 (Dissimilar Metal Weld Cracking):
''Cracking frequently occurs in weld joints between ferritic and austenitic materials such as carbon steel to 300 series stainless steels due to thermal expansion mismatch during high temperature operation.''
Therefore, Option D (Carbon steel to 316 stainless steel) is the most susceptible combination and the correct answer.
Erosion and erosion-corrosion metal loss is characterized by:
Erosion and erosion-corrosion are mechanical degradation mechanisms enhanced by fluid motion, and typically result in directional or flow-oriented metal loss patterns.
According to API RP 571 Section 5.4.2 (Erosion and Erosion/Corrosion):
''Erosion typically results in localized thinning, often described as grooves, gullies, or horseshoe-shaped patterns... The metal loss is directional and may occur in elbows, tees, reducers, and pumps.''
Hence, Option C (grooves and gullies) most accurately describes erosion and erosion-corrosion characteristics.
(Which three residual alloy elements are of most concern when it comes to corrosion of carbon steel in HF Alkylation process units?)
Comprehensive and Detailed Explanation From Exact Extract:
In HF Alkylation units, API RP 571 identifies certain residual alloying elements in carbon steel that can significantly increase corrosion rates in HF acid service.
The most detrimental residual elements are:
Chromium (Cr)
Copper (Cu)
Nickel (Ni)
These elements:
Disrupt formation of protective iron fluoride films
Increase general and localized corrosion rates
Are tightly controlled in carbon steel specifications for HF service
Referenced Documents (Study Basis):
API RP 571 -- Section on Hydrofluoric Acid Corrosion
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