API 571 Corrosion and Materials Practice Questions — 10 Free (2026)

Answer them, then check the reasoning and the clause each one comes from. No account, no card, nothing to dismiss.

10 CLOSED BOOK1 STANDARD

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Question bank: 2,425 questions
Mock papers: 3 full-length
Figures and exhibits: 35
This sample: 10 closed book

The ten questions below draw on API 571.

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10 QUESTIONS

CLOSED BOOKAPI 5711 / 10

Which percentage range of nickel in an alloy provides significantly better resistance to nitriding?

Worked answers

All ten API 571 Corrosion and Materials questions with the correct option, why it is correct and the paragraph it comes from. Attempt them above first — the reasoning is worth more than the key.

Show the ten answers and their references

Q1 · API 571 · Closed book
Which percentage range of nickel in an alloy provides significantly better resistance to nitriding?
- A. 5% to 15%
- B. 10% to 25%
- C. 30% to 80% ✓
- D. Exactly 100%
- E. 0.1% to 1%
Alloys containing 30% to 80% nickel are noted for their increased resistance to nitriding. API 571, 3.47.3(f)
Q2 · API 571 · Closed book
What is the primary mitigation strategy to prevent Caustic Stress Corrosion Cracking (Caustic Embrittlement) in carbon steel?
- A. Increasing the hardness of the welds
- B. Post-Weld Heat Treatment ✓
- C. Decreasing the nickel content
- D. Using high-sulfur fuel
- E. Applying a thermal spray aluminum coating
PWHT at 1150 °F (621 °C) minimum is the most effective way to reduce the residual stresses that drive caustic cracking. API 571, 3.14.6 (a)
Q3 · API 571 · Closed book
Installed anchor material obliges the contractor to do what?
- A. Direct attack of the nickel alloy by anhydrous hydrofluoric acid at elevated temperature
- B. Chloride contamination of the acid circuit from the upstream feed treating section
- C. Hydrogen charging of the alloy from the aqueous corrosion reaction at the surface
- D. Sensitization of the alloy by chromium carbide precipitation during welding operations
- E. Cupric fluoride formed by oxidation of cuprous fluoride ✓
Population density shifting, material and repair costs moving, downtime priced differently, law changing, the plan revised, or feed and operating conditions altered. API 571, 3.39.1
Q4 · API 571 · Closed book
Which specific organic acid is identified by API 571 as being among the "most corrosive" of the low-molecular-weight acids?
- A. Naphthenic Acid
- B. Formic Acid ✓
- C. Sulfuric Acid
- D. Carbonic Acid
- E. Butyric Acid
Formic and acetic acids are the most corrosive because they are highly soluble in naphtha and water. API 571, 3.7.3 (c)
Q5 · API 571 · Closed book
What do the L and H suffixes on austenitic stainless steels denote?
- A. Carbon held within set low and high bands ✓
- B. Low and high chromium content ranges within the alloy specification
- C. Low and high nickel content ranges controlled during manufacture
- D. Low and high hardness ranges achieved by the final heat treatment
- E. Low and high temperature service classifications for the material
That family takes in Types 304 and its L and H variants, 309, 310, 316 with its own L and H forms, 317 and others besides. API 571, Section 2
Q6 · API 571 · Closed book
In which specific location is localized pitting typically found within these systems?
- A. High-velocity headers
- B. Hot discharge lines
- C. Low-velocity areas ✓
- D. Fully aerated tanks
- E. Deaerator outlets
At reduced temperatures, localized pitting is commonly found in low-velocity or stagnant areas. API 571, 3.49.5
Q7 · API 571 · Closed book
In which temperature range does 885 °F (475 °C) embrittlement occur in susceptible stainless steels?
- A. 200°F to 500°F
- B. 600°F to 1000°F ✓
- C. 1100°F to 1500°F
- D. 400°F to 600°F
- E. Above 1800°F
The critical range for this metallurgical change is between 600°F (315°C) and 1000°F (540°C). API 571, 3.1.1
Q8 · API 571 · Closed book
What surface preparation may be needed to find fine chloride SCC by penetrant?
- A. Flapper wheel sanding to open deposits filling the tight crack openings
- B. Magnetization using a yoke placed across the suspected cracking direction
- C. Polishing or high-pressure water blast ✓
- D. Chemical etching with an acidic reagent to reveal the grain structure
- E. Application of a developer only, since no preparation is required at all
Penetrant will find chloride cracking, though very fine cracks may escape it and surface preparation has to be handled with care. API 571, 3.17.7
Q9 · API 571 · Closed book
Nickel alloy equipment in anhydrous HF service cracks after air ingress occurred during a turnaround. Which mechanism applies?
- A. Hydrogen stress cracking of high strength steels exposed to aqueous HF acid
- B. Dissimilar metal weld cracking at a carbon steel to Alloy 400 welded joint
- C. Cracking of the metal in that acid under stress ✓
- D. Chloride stress corrosion cracking requiring chloride ions and tensile stress
- E. Polythionic acid cracking requiring sensitized austenitic stainless steel
It follows from the type of mechanism, how fast it runs, whether it can be detected, and how much the item can take. API 571, 3.39
Q10 · API 571 · Closed book
In FCC overheads, what is the primary purpose of the water wash injection?
- A. Increase temperature
- B. Dilute corrodents ✓
- C. Add oxygen
- D. Remove catalyst
- E. Stop flow
Water wash dissolves and dilutes aggressive species like H2S and chlorides to manageable levels. API 571, 3.58.6(d)

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