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API-571 Real Exam Questions

Corrosion and Materials Professional

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Question 1 Single choice

Caustic corrosion is most often associated with:

  1. A

    Boilers and steam generating equipment

  2. B

    Caustic treaters

  3. C

    Caustic injections in crude units

  4. D

    Caustic storage tanks (non-postweld heat treated)

Show answer and explanation

Correct answer: C

Explanation

API RP 571, under "Caustic Corrosion" (also referred to as Caustic Stress Corrosion Cracking or Caustic Cracking), notes that this form of damage is: "Most commonly associated with the injection points of caustic (e.g., NaOH) in crude units, particularly upstream of desalter vessels and heat exchanger circuits."

"This damage occurs due to the combination of caustic environment and tensile stress, especially in carbon steel and low alloy steels."
"Stress relief heat treatment of welds can mitigate susceptibility."

References:
API RP 571, 3rd Edition, Section 4.2.2.3)
Thus, among the options, caustic injections in crude units are the most typical area of concern, making option C the correct answer.

Question 2 Single choice

____________ are characterized by a localized loss in thickness in the form of pits, grooves, gullies, waves, rounded holes and valleys. These losses often exhibit a directional pattern.

  1. A

    Erosion

  2. B

    Corrosion/Erosion

  3. C

    Environmental corrosion

  4. D

    Both A and B

Show answer and explanation

Correct answer: D

Question 3 Single choice

Corrosion under insulation mitigation is best achieved by:

  1. A

    Using low-chloride insulation

  2. B

    Maintaining process temperatures at the boiling point of water

  3. C

    Implementing a carefully planned, periodic inspection program

  4. D

    Using appropriate coatings

Show answer and explanation

Correct answer: D

Explanation

According to API RP 571 and API RP 583:
"The most effective mitigation of CUI is the use of appropriate coatings underneath the insulation, which are resistant to moisture and chloride ingress."
"Inspection and insulation selection are also important but are secondary controls."

References:
API RP 571, Section 4.3.4 - Corrosion Under Insulation
API RP 583)
Hence, option D is correct.

Question 4 Single choice

Stress levels and __________ are the critical factors causing carbonate stress corrosion cracking.

  1. A

    Temperature

  2. B

    Velocity

  3. C

    Water chemistry

  4. D

    None of the above

Show answer and explanation

Correct answer: C

Question 5 Single choice

Erosion-corrosion is a description for the damage that occurs when corrosion contributes to erosion by removing protective films or scales, or by exposing the metal surface to further ________ under the combined action of corrosion-erosion.

  1. A

    Stress

  2. B

    Corrosion

  3. C

    Oxidation

  4. D

    None of the above

Show answer and explanation

Correct answer: B

Question 6 Single choice

High temperature H?/ H corrosion damage is minimized by using alloys with high _________ content.

  1. A

    Carbon

  2. B

    Molybdenum

  3. C

    Chromium

  4. D

    Stainless

Show answer and explanation

Correct answer: C

Question 7 Single choice

Thermal fatigue cracks usually propagate _______ to the stress and they are usually dagger-shaped.

  1. A

    Parallel

  2. B

    Diagonal

  3. C

    Transverse

  4. D

    Across

Show answer and explanation

Correct answer: C

Question 8 Single choice

A form of corrosion that can occur at the junction of dissimilar metals when they are joined together in a suitable electrolyte is __________.

  1. A

    Galvanic corrosion

  2. B

    Anodic corrosion

  3. C

    Cathodic corrosion

  4. D

    All of the above

Show answer and explanation

Correct answer: A

Question 9 Single choice

Resistance to oxidation of steel is best provided by alloying with:

  1. A

    Molybdenum

  2. B

    Chromium

  3. C

    Nickel

  4. D

    Manganese

Show answer and explanation

Correct answer: B

Explanation

Comprehensive and Detailed From Exact Extract: According to, oxidation API RP 571 chromium is the most effective alloying element for improving resistance in steels. Chromium: Forms a stable, adherent chromium oxide (Cr#O#) scale Greatly reduces oxidation rates at elevated temperatures Is the basis for oxidation-resistant alloys and stainless steels Other alloying elements may provide secondary benefits, but chromium is the primary contributor to oxidation resistance.
Referenced Documents (Study Basis):
API RP 571 - Section on Oxidation and High-Temperature Corrosion

Question 10 Single choice

Carbonate SCC can occur at relatively low levels of ________ but usually occurs at welds that have not been stressed relieved.

  1. A

    Residual stress

  2. B

    Applied stress

  3. C

    Acid concentration

  4. D

    None of the above

Show answer and explanation

Correct answer: A