API-510 Exam (571 Section) MCQs Exam Questions and Answers (Latest Update 2026).docx

API-510 Exam (571 Section) MCQs
Exam Questions and Answers (Latest
Update 2026)
Which materials are susceptible to brittle fracture?
A. Carbon steels
B. Low alloy steels
C. 400 Series SS
D. All of the above -
correct answer ✅D. All of the above
Ref: API 571, 3.11.2


Which material is not susceptible to caustic corrosion?
A. Carbon steel
B. 400 Series SS
C. 300 Series SS
D. Low alloy steel -
correct answer ✅B. 400 Series SS
Ref: API 571, 3.14.2


Caustic SCC can be prevented by PWHT at what temperature?
A. 1100º F
B. 1150º F

,API-510 Exam (571 Section) MCQs
Exam Questions and Answers (Latest
Update 2026)
C. 1200º F
D. 1250º F -
correct answer ✅B. 1150º F
Ref: API 571, 3.15.6 (a)


Cracking can occur at low caustic levels if a concentrating
mechanism is present. Concentrations of how many ppm are
sufficient to cause cracking?
A. 50-100
B. 100-150
C. 150-200
D. 200-250 -
correct answer ✅A. 50-100
Ref: API 571, 3.15.3 (c)


300 Series SS, 400 Series SS, and duplex SS are subject to pitting
and localized corrosion under insulation. Additionally, which alloy is
subject to SCC if chlorides are present?
A. Duplex SS
B. 300 Series SS

,API-510 Exam (571 Section) MCQs
Exam Questions and Answers (Latest
Update 2026)
C. 400 Series SS
D. Low alloy steels -
correct answer ✅


Critical factors for chloride stress corrosion cracking (Cl SCC) include
all EXCEPT:
A. Chloride content
B. pH & temperature
C. Alloy composition
D. Stress & presence of CO2 -
correct answer ✅D. Stress & presence of CO2
Ref: API 571, 3.17


300 Series SS, 5Cr, 9Cr, and 12Cr alloys are not susceptible to
__________ at conditions normally seen in refineries.
A. Cl SCC
B. SOHIC
C. HTHA
D. HTLA -
correct answer ✅C. HTHA

, API-510 Exam (571 Section) MCQs
Exam Questions and Answers (Latest
Update 2026)
Ref: API 571, 3.36.2(b)


Due to HTHA considerations, what steel alloy is no longer
recommended for new construction in hot hydrogen services?
A. Mn ½ Mo
B. 1¼ Cr ½ Mo
C. 1Cr ½ Mo
D. C - ½ Mo -
correct answer ✅D. C - ½ Mo
Ref: API 571, 3.36.6(c)


Blistering, HIC, and SOHIC have been found to occur between
ambient and _________.
A. 250º F
B. 300º F
C. 350º F
D. 400º F -
correct answer ✅B. 300º F
Ref: API 571, 3.67.3(f)1