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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 Jun. 23, 2026 (see below)
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.
(Cooling water corrosion usually increases with decreasing:)
Comprehensive and Detailed Explanation From Exact Extract:
According to API RP 571, corrosion in cooling water systems often increases at low flow velocities due to:
Stagnation
Deposit formation
Increased risk of underdeposit corrosion and MIC
Higher velocities tend to:
Sweep away deposits
Maintain protective films (within erosion limits)
Therefore, decreasing velocity is strongly associated with increased corrosion risk.
Referenced Documents (Study Basis):
API RP 571 -- Section on Cooling Water Corrosion
(Typically, surface decarburization will have what effect on steel components in high temperature service?)
Comprehensive and Detailed Explanation From Exact Extract:
According to API RP 571, surface decarburization is a metallurgical degradation mechanism that occurs when carbon is removed from the surface layers of steel due to exposure to oxidizing environments at elevated temperatures. This results in a carbon-depleted surface layer.
Carbon is a primary strengthening element in carbon and low-alloy steels. When carbon is lost from the surface:
Hardness and tensile strength are reduced
Creep resistance and load-carrying capability decrease
The component becomes more susceptible to plastic deformation and failure under stress
API RP 571 states that decarburization leads to loss of mechanical strength, especially critical in high-temperature service, where components already operate close to material limits.
Why the other options are incorrect:
Option A: Stress cracking is not the primary effect; loss of strength is.
Option C: Decarburization does not directly accelerate oxidation or sulfidation, although both may coexist.
Option D: This is incorrect; decarburization is considered detrimental in high-temperature applications.
Referenced Documents (Study Basis):
API RP 571 -- Section on Decarburization and Metal Dusting
API Corrosion and Materials Study Guide
In steam-generating equipment, caustic corrosion is best prevented through:
From API RP 571 Section 5.3.3.2 (Caustic Corrosion):
''Caustic corrosion, also known as caustic gouging, occurs in boiler systems when caustic concentrates in under-deposit areas or due to improper steam drum and boiler water design. Good design and water treatment practices are key preventive measures.''
Temperature control or acid injection are not practical or effective mitigation techniques. Design considerations---such as proper water flow, material selection, and minimizing deposits---are essential.
Hence, the correct answer is Option C.
(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
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