API API-571 Online Practice Questions and Exam Preparation

API API-571 Online Questions & Answers

• Question 411:

  ________ has been a major problem on coke drum shells.

  A. Thermal fatigue
  B. Stress cracking
  C. Erosion
  D. Temper embrittlement
  A. Thermal fatigue

• Question 412:

  Which of the following would be utilized in prevention or mitigation strategies against hydrochloric acid corrosion?

  A. Nickel-based alloys
  B. Duplex stainless-steel materials
  C. 300 series stainless steel materials
  D. Copper-based materials
  A. Nickel-based alloys

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  Comprehensive and Detailed From Exact Extract:

  Hydrochloric acid (HCl) corrosion, particularly in crude unit overhead systems, is aggressive toward carbon steel and stainless steels.

  According to,, such as Monel (Ni-Cu alloys), exhibit API RP 571 nickel-based alloys excellent resistance to hydrochloric acid corrosion and are commonly used for: Overhead piping Injection quills High-risk corrosion zones Why the other options are incorrect:

  Duplex and 300 series stainless steels are highly susceptible to chloride corrosion and SCC. Copper-based materials alone lack sufficient resistance and structural strength in refinery HCl environments.

  Referenced Documents (Study Basis): API RP 571 - Section on Hydrochloric Acid Corrosion

• Question 413:

  What damage mechanism can occur in wet H#S environments and is sometimes confused with wet H#S damage?

  A. Ammonia cracking
  B. HCl cracking
  C. Amine cracking
  D. Polythionic cracking
  D. Polythionic cracking

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  API RP 571 -Polythionic Acid Stress Corrosion Cracking:

  "Polythionic acid SCC may be mistaken for wet H#S damage because both involve cracking in austenitic stainless steels under certain conditions."

  Thus, option D is correct.

• Question 414:

  Regular and controlled carbon grades of stainless steels such as types 304/304H and 316/316H are particularly susceptible to sensitization in the weld HAZ. Low carbon "L" grades are less susceptible and usually can be welded without sensitizing. The "L" grades will not sensitize provided long term operating temperatures do not exceed about __________.

  A. 700?F
  B. 750?F
  C. 800?F
  D. 900?F
  B. 750?F

• Question 415:

  (Corrosion fatigue can be distinguished from stress corrosion cracking because the fatigue:)

  A. Mechanism is unrelated to environmental conditions
  B. Failure is highly dependent upon the fatigue load limit
  C. Failure occurs only in low-alloy steels
  D. Cracks exhibit little or no branching
  D. Cracks exhibit little or no branching

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  Comprehensive and Detailed From Exact Extract: According to, results from the combined action of a cyclic stress and a API RP 571 corrosion fatigue corrosive environment. One of the most important distinguishing features between corrosion fatigue and SCC is crack morphology. Corrosion fatigue cracks are typically transgranular and show little or no branching Stress corrosion cracking is characterized by extensive crack branching Therefore, the absence of significant branching is a key diagnostic feature of corrosion fatigue. Referenced Documents (Study Basis): API RP 571 - Section on Corrosion Fatigue

• Question 416:

  Severe internal grooving corrosion is found at the bottom of a 4-inch (101.6 mm) carbon steel piping system in steam condensate service. Which of the following is the most likely cause?

  A. Carbon dioxide corrosion
  B. Carbonate corrosion
  C. Ammonium bisulfide corrosion
  D. Erosion-corrosion
  A. Carbon dioxide corrosion

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  API RP 571 explains under Condensate Corrosion (CO# Corrosion):

  "In condensate systems, carbon dioxide dissolves in the water forming carbonic acid, which leads to localized corrosion, including grooving and under-deposit attack, especially at low points like the bottom of horizontal piping."

  "This is most commonly observed in steam condensate return lines, and the damage is localized due to stratification."

  This matches the scenario described, where internal grooving at the bottom of steam condensate piping is characteristic of CO#-induced corrosion. Hence, option A is correct.

• Question 417:

  High strength steels are susceptible to LME when they come in contact with molten ________.

  A. Cadmium
  B. Zinc
  C. Lead
  D. Both A and C
  D. Both A and C

• Question 418:

  The form of corrosion most often caused by sulfidation is typically described as:

  A. General or uniform corrosion
  B. High-temperature corrosion
  C. Localized erosion-corrosion
  D. Sulfide cracking corrosion
  A. General or uniform corrosion

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  API RP 571 -Sulfidation:

  "Sulfidation generally results in uniform thinning of iron-based alloys at temperatures above 500癋 (260?

  C)."

  "It is classified as a form of general corrosion, although it can be accelerated in turbulent flow areas."

  So, option A is correct.

• Question 419:

  Proactive and retroactive positive material identification programs are especially useful for services exposed to:

  A. Caustic embrittlement
  B. Ammonia stress corrosion cracking
  C. Sulfidation
  D. Sour water
  C. Sulfidation

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  API RP 578 (Material Verification Program), referenced in API RP 571, specifically calls out sulfidation failures as a major driver for Positive Material Identification (PMI):

  "PMI programs are particularly important in services prone to sulfidation where incorrect alloying elements (e.g., carbon steel used in place of low Cr alloy) have led to catastrophic failures."

  "Many failures have occurred when carbon steel was mistakenly installed in place of specified Cr-alloys in

  sulfidation-prone environments."

  API RP 578 and API RP 571, Section 4.2.1.1 - Sulfidation) Thus, option C is the most appropriate answer.

• Question 420:

  (Sulfidation is known to be accelerated by the presence of:)

  A. Hydrogen
  B. Chlorides
  C. Amines
  D. Moisture
  A. Hydrogen

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  Comprehensive and Detailed From Exact Extract:

  Per, rates are significantly accelerated by the presence of hydrogen.

  API RP 571 sulfidation corrosion

  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