API 571 High Temperature Corrosion 2

Question 1

The Couper-Gorman curves extend McConomy curves by accounting for what additional factor?

Accepted Answer

Effect of hydrogen partial pressure on H2S corrosion rates

Answer

Couper-Gorman curves account for the accelerating effect of hydrogen partial pressure on H2S corrosion rates in hydrogen-containing environments.

Question 2

In which type of steel does sigma phase embrittlement occur, and at what temperature range?

Accepted Answer

Austenitic and duplex stainless steels between 600–1000°F

Answer

Sigma phase forms in austenitic and duplex stainless steels during long-term exposure in the 600–1000°F range, causing severe embrittlement that manifests at ambient temperature.

Question 3

885°F (475°C) embrittlement is a damage mechanism primarily affecting which steel family?

Accepted Answer

Ferritic and duplex stainless steels

Answer

Ferritic and duplex stainless steels with high chromium content undergo alpha-prime phase precipitation near 885°F, causing severe ambient-temperature embrittlement.

Question 4

Which inspection method is most effective for detecting High Temperature Hydrogen Attack (HTHA)?

Accepted Answer

Advanced ultrasonic testing (TOFD or phased array)

Answer

HTHA creates internal fissures and decarburization that require advanced volumetric UT methods like TOFD or phased array UT to reliably detect.

Question 5

Temper embrittlement in Cr-Mo steels occurs primarily during which condition?

Accepted Answer

Slow cooling or extended hold in the 700–1050°F range

Answer

Temper embrittlement occurs when Cr-Mo steels are held or slowly cooled through the 700–1050°F range, causing tramp elements to segregate to grain boundaries and reduce toughness.

API 571 - API 571 Corrosion and Materials Practice Test

API 571 - API 571 Corrosion and Materials Practice Test

API 571 High Temperature Corrosion 2