Corrosion, Welding & Material Defects 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, Welding & Material Defects flashcards as text
What is the primary purpose of a corrosion allowance specified in the original design of a pressure vessel?
Answer: To allow for predictable metal loss over the vessel's intended service life
The corrosion allowance is extra wall thickness deliberately included in the design to accommodate expected corrosion over the vessel's intended service life without falling below the calculated minimum required thickness.
Which weld discontinuity is described as non-metallic material, such as flux or oxide, trapped within the weld metal?
Answer: Slag inclusion
Slag inclusions are non-metallic solid materials (flux residue, oxides) entrapped in the weld metal or between weld passes, typically caused by inadequate interpass cleaning or improper welding technique.
Hydrogen blistering in pressure vessels typically occurs in which environment?
Answer: Wet hydrogen sulfide (H2S) or other sour service environments
Hydrogen blistering occurs in sour (wet H2S) service where atomic hydrogen generated by the sulfide corrosion reaction diffuses into the steel and combines at internal voids or laminations to form H2 gas, causing blisters.
According to API 510, which organization's welding standards are typically referenced for repair welding procedures on pressure vessels?
Answer: ASME Section IX
API 510 specifies that repair welding must be performed in accordance with ASME Section IX, which governs welding and brazing qualifications including procedure and performance qualifications.
What type of corrosion damage is characterized by small, deep, cup-shaped cavities on the metal surface while the surrounding metal remains relatively unattacked?
Answer: Pitting corrosion
Pitting corrosion creates localized, deep cavities (pits) on the metal surface while surrounding areas remain largely unaffected, making it particularly dangerous because the small surface area masks the true depth of attack.
A weld with 'overlap' or 'cold lap' is a condition where:
Answer: The weld metal extends beyond the weld groove but is not fused to the base metal
Overlap (cold lap) occurs when weld metal rolls over onto the base metal surface without fusing to it, creating a mechanical notch at the weld toe that acts as a stress concentrator.
Which damage mechanism is associated with wet hydrogen sulfide service and involves crack propagation through steel driven by hydrogen pressure?
Answer: Hydrogen-induced cracking (HIC)
Hydrogen-induced cracking (HIC) in wet H2S service occurs when atomic hydrogen diffuses into the steel and recombines as molecular H2 at traps (inclusions, laminations), building pressure that causes internal cracks to initiate and propagate.