API API-571 Online Practice Questions and Exam Preparation

API API-571 Online Questions & Answers

• Question 501:

  Corrosion from oxygen in boiler feed water usually creates:

  A. Uniform corrosion.
  B. Isolated pitting.
  C. Intergranular cracking.
  D. Transgranular cracking.
  E. Hard and brittle zones.
  B. Isolated pitting.

• Question 502:

  _________ is the main concern during start-up, shutdown and/or hydro testing for equipment/piping operating at elevated temperatures. This event can also occur in an auto refrigeration event in units processing light hydrocarbons.

  A. Stress fracture
  B. Carburization
  C. Spheroidization
  D. Brittle fracture
  D. Brittle fracture

• Question 503:

  A condition where steel loses strength due to the removal of carbon and carbides leaving only an iron matrix is called decarburization. This occurs during high temperatures, during PWHT and from exposure to fires. Which of the following materials is not affected by this?

  A. Low alloy steel
  B. Duplex SS
  C. Carbon steel
  D. None of the above
  B. Duplex SS

• Question 504:

  Which of the following does not increases the likelihood of atmospheric corrosion?

  A. Bird poop
  B. Increasing annual rainfalls
  C. Locations where moisture is trapped
  D. Increasing operating pressures
  E. Increasing amounts of airborne contaminates
  D. Increasing operating pressures

• Question 505:

  Non-stressed relieved __________ is susceptible to stress corrosion cracking when in contact with moist HF vapors in the presence of oxygen.

  A. Carbon steel
  B. Alloy 400
  C. 300 Series SS
  D. 400 Series SS
  B. Alloy 400

• Question 506:

  Aggressive ammonium chloride corrosion often occurs:

  A. When the salts precipitate from high-temperature streams as they cool.
  B. In the absence of a free water phase.
  C. When excess water washing dissolves too much ammonium chloride.
  D. When dry salts are exposed to a small amount of free water.
  D. When dry salts are exposed to a small amount of free water.

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  According to API RP 571:

  "Ammonium chloride corrosion is most aggressive when dry salts are exposed to a small amount of free water. This condition allows the formation of a concentrated acidic aqueous solution, which is highly corrosive to carbon steel."

  "The corrosion mechanism is activated especially during startup and shutdown when condensation may occur on salt deposits."

  API RP 571, Section 4.3.3.1 - Ammonium Chloride Corrosion)

  Hence, while salt deposition begins as temperatures drop, the most aggressive corrosion happens when water is introduced to dry salt, making option D correct.

• Question 507:

  (Chloride stress corrosion cracking of 300 series stainless steel initially becomes a concern at a metal temperature above:)

  A. 100 癋 (38 癈)
  B. 140 癋 (60 癈)
  C. 180 癋 (82 癈)
  D. 212 癋 (100 癈)
  B. 140 癋 (60 癈)

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  Comprehensive and Detailed From Exact Extract: According to, austenitic (300 series) stainless API RP 571 chloride stress corrosion cracking (Cl-SCC) of steels becomes a credible concern when: Chlorides are present Tensile stress exists Metal temperatures exceed approximately 140 癋 (60 癈) Below this temperature, Cl-SCC is far less likely, while susceptibility increases rapidly above this threshold. Referenced Documents (Study Basis): API RP 571 - Section on Chloride Stress Corrosion Cracking

• Question 508:

  (Concentration Cell Corrosion is best described as corrosion:)

  A. Where deposits form within piping or equipment
  B. In the presence of dissimilar metals in electrical contact in a corrosive environment
  C. At high temperatures in the presence of sulfur compounds
  D. By mechanical stress and fatigue in metal structures
  A. Where deposits form within piping or equipment

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  Comprehensive and Detailed From Exact Extract:

  Concentration Cell Corrosion is defined in API RP 571 as a form of electrochemical corrosion driven by differences in concentration of corrosive species, most commonly oxygen, under deposits or within crevices. This type of corrosion typically occurs: Beneath deposits, scale, or fouling In stagnant zones or crevices Where oxygen concentration differs between adjacent areas The area with lower oxygen concentration becomes anodic and corrodes preferentially, while the oxygen-rich area becomes

  cathodic.

  Why the other options are incorrect:

  Option B describes galvanic corrosion, not concentration cell corrosion.

  Option C refers to high-temperature sulfidation, unrelated to concentration gradients.

  Option D describes mechanical damage mechanisms, not electrochemical corrosion.

  API RP 571 clearly categorizes concentration cell corrosion as being associated with deposits or crevice conditions, making Option A the correct description.

  Referenced Documents (Study Basis):

  API RP 571 - Section on Concentration Cell and Crevice Corrosion

  API Corrosion Fundamentals Study Guide

• Question 509:

  ______ is most likely found in hard welds and heat affected zones and in high strength components.

  A. SOHIC
  B. HIC
  C. Carburization
  D. SSC
  D. SSC

• Question 510:

  (The signature mark of a mechanical fatigue failure is a "clam shell" type fingerprint:)

  A. With intergranular cracking
  B. With microvoid coalescence
  C. That has nonconcentric rings
  D. That has concentric rings
  D. That has concentric rings

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  Comprehensive and Detailed From Exact Extract:

  Per, beach marks or clam shell API RP 571 mechanical fatigue failures are identified by the presence of patterns on the fracture surface. These features:

  Appear as concentric rings

  Represent successive crack growth increments

  Radiate outward from the crack initiation site

  This "clam shell" or "beach mark" appearance is one of the most recognizable signatures of fatigue failure.

  Referenced Documents (Study Basis):

  API RP 571 - Section on Mechanical Fatigue