Practice Test Geeks(API 510) Certified Pressure Vessel Inspector Practice Test
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Corrosion Mechanisms and Monitoring 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.

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  1. What type of corrosion occurs when two dissimilar metals are in electrical contact in the presence of an electrolyte?

    Answer: Galvanic corrosion

    Galvanic corrosion occurs when dissimilar metals are electrically connected in an electrolyte, causing the more anodic metal to corrode preferentially.

  2. Which monitoring technique uses the rate of change in electrical resistance of a metal probe to measure corrosion rate?

    Answer: Electrical resistance (ER) probes

    Electrical resistance (ER) probes measure corrosion rate by detecting changes in the probe's cross-sectional area as metal is lost to corrosion.

  3. Polythionic acid stress corrosion cracking (PTA SCC) primarily affects which material in refineries?

    Answer: Sensitized austenitic stainless steel

    PTA SCC affects sensitized austenitic stainless steel when exposed to polythionic acids formed from sulfur compounds, water, and oxygen during shutdowns.

  4. What is the primary driving force for under-deposit corrosion in pressure vessels?

    Answer: Concentration of aggressive species beneath accumulated solids

    Under-deposit corrosion is driven by the concentration of corrosive species (chlorides, acids, sulfur compounds) trapped beneath deposits, creating a localized aggressive environment.

  5. In API 510 inspection practice, which corrosion mechanism is most commonly associated with crude oil distillation overhead systems?

    Answer: Hydrochloric acid (HCl) dew point corrosion

    HCl dew point corrosion is the dominant mechanism in crude distillation overhead systems, where HCl condenses from hydrolyzed chloride salts and attacks carbon and low-alloy steels.

  6. Which parameter is most critical in determining the susceptibility of carbon steel to wet H₂S damage (hydrogen blistering)?

    Answer: pH of the aqueous phase and H₂S partial pressure

    Wet H₂S damage susceptibility depends primarily on the pH of the water phase and H₂S partial pressure, with damage most severe at low pH and elevated H₂S concentrations.

  7. A pressure vessel inspector finds localized deep pits on the internal surface of a carbon steel vessel in cooling water service. What corrosion mechanism is most likely responsible?

    Answer: Microbiologically influenced corrosion (MIC)

    MIC in cooling water systems commonly produces localized deep pitting due to the action of sulfate-reducing or acid-producing bacteria creating aggressive microenvironments.