Corrosion Assessment Flashcards
7 cards from real API 510 practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Corrosion Assessment flashcards as text
Which type of corrosion produces a series of small, deep cavities penetrating into the metal while leaving surrounding areas relatively unaffected?
Answer: Pitting corrosion
Pitting corrosion is a localized form that creates deep, narrow cavities while surrounding metal remains largely intact, making it particularly dangerous and hard to detect.
High-temperature hydrogen attack (HTHA) in pressure vessels primarily causes which type of damage?
Answer: Decarburization and fissuring of the steel
HTHA causes decarburization as hydrogen reacts with carbides in the steel, forming methane gas that creates fissures and significantly degrades mechanical properties.
What is the most reliable method for an API 510 inspector to distinguish between active pitting corrosion and old, inactive pits?
Answer: Comparison of pit depth measurements between inspection intervals
Comparing pit depth measurements from successive inspections reveals whether pits are growing (active) or stable (inactive), providing direct evidence of activity.
Under API 510, which assessment method may be used to evaluate pressure vessels with localized metal loss that does not meet minimum thickness requirements?
Answer: API 579 Fitness-for-Service (FFS) assessment
API 579 FFS assessment provides analytical methods to evaluate whether vessels with local metal loss can continue safe operation despite falling below nominal design thickness.
A carbon steel vessel operating in a caustic (NaOH) service exhibits cracking along welds. Which corrosion mechanism is MOST likely responsible?
Answer: Caustic stress corrosion cracking (caustic embrittlement)
Caustic embrittlement is the preferential cracking of carbon steel in NaOH environments, particularly at welds where residual tensile stresses are high.
When applying the ASME Section VIII Division 1 formula for minimum required shell thickness under internal pressure, which variable directly represents the corrosion allowance?
Answer: C (corrosion allowance added to t_min)
The corrosion allowance C is added to the calculated minimum thickness t_min to establish the nominal design thickness, accounting for expected metal loss over the vessel life.
Which non-destructive examination (NDE) method is BEST suited for detecting hydrogen-induced cracking (HIC) damage in a vessel shell plate?
Answer: Ultrasonic testing (UT) with straight beam or phased array
UT with straight beam or phased array can detect the internal, subsurface planar flaws characteristic of HIC without requiring surface access to the damage plane.