Corrosion Prevention & Protection Flashcards
7 cards from real SPED 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 Prevention & Protection flashcards as text
What is the primary corrosion mechanism in pipelines transporting CO2-rich fluids (sweet corrosion)?
Answer: Formation of carbonic acid (H2CO3) when CO2 dissolves in water
CO2 dissolves in produced water to form carbonic acid, which lowers pH and directly attacks steel — this is known as sweet corrosion or CO2 corrosion.
In the context of pipeline coatings, what does 'cathodic disbondment' mean?
Answer: Loss of coating adhesion caused by cathodic protection current generating hydroxyl ions at holidays
Cathodic disbondment occurs when cathodic protection current at coating defects generates hydroxyl ions, raising local pH and destroying adhesion between the coating and pipe surface.
Which alloy addition to carbon steel most significantly improves resistance to CO2 corrosion in oil and gas pipelines?
Answer: Chromium (Cr)
Chromium additions (even 1-3% Cr in low-alloy steels or 13% in martensitic stainless steels) significantly improve CO2 corrosion resistance by stabilizing a protective passive film.
What is the purpose of a 'close-interval potential survey' (CIPS) on a cathodically protected pipeline?
Answer: Obtain continuous pipe-to-soil potential readings along the pipeline to identify CP deficiencies
A CIPS provides continuous pipe-to-soil potential profiles along the pipeline route to identify areas of inadequate cathodic protection, coating holidays, and current interference.
Stray current corrosion on a buried pipeline is most commonly caused by which external source?
Answer: DC transit systems (railways/subways) or other DC electrical infrastructure
DC stray currents from transit systems (trams, subways, DC rail) flow through the earth and onto buried pipelines, causing accelerated corrosion where current leaves the pipe.
What does PHMSA require for pipeline operators regarding corrosion control records under 49 CFR Part 192/195?
Answer: Records of cathodic protection tests and inspections must be maintained for the life of the pipeline
49 CFR Parts 192 and 195 require operators to maintain cathodic protection records and corrosion control documentation for the life of the pipeline to demonstrate regulatory compliance.
Which method is used to determine the degree of cathodic protection provided when IR drop error cannot be eliminated from an instant-off measurement?
Answer: The 100 mV polarization shift criterion
The 100 mV polarization shift criterion (net protective current causes at least 100 mV of cathodic polarization) is used as an alternative CP criterion when IR-free potentials cannot be reliably measured.