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. According to API 510, when calculating remaining life using both short-term and long-term corrosion rates, which rate should be used for the next inspection interval?

    Answer: The more conservative (higher) of the two rates

    API 510 requires using the more conservative (higher) corrosion rate between short-term and long-term calculations to ensure adequate safety margin in remaining life assessments.

  2. What is the primary purpose of installing corrosion-resistant alloy (CRA) cladding or weld overlay on the internal surface of a pressure vessel?

    Answer: To provide a corrosion-resistant surface while using lower-cost base material

    CRA cladding or weld overlay provides corrosion resistance at the wetted surface while the lower-cost carbon or low-alloy steel base material provides structural integrity.

  3. Erosion-corrosion in a pressure vessel causes wall loss that is typically characterized by which appearance?

    Answer: Directional grooving or horseshoe-shaped depressions aligned with flow

    Erosion-corrosion produces directional damage — grooves, horseshoe pits, and streamlined depressions — that reflect the local flow pattern and turbulence direction.

  4. Which monitoring technique directly measures electrochemical corrosion rate in real time by applying a small voltage perturbation to a probe in a conducting electrolyte?

    Answer: Linear polarization resistance (LPR) monitoring

    LPR monitoring applies a small polarization to a probe and measures the current response to calculate instantaneous corrosion rate based on the Stern-Geary relationship.

  5. In sour service (H₂S-containing) environments, which steel hardness level is specified in NACE MR0175/ISO 15156 as the maximum to prevent sulfide stress cracking (SSC)?

    Answer: 22 HRC (237 HBW) maximum

    NACE MR0175/ISO 15156 limits carbon and low-alloy steel hardness to 22 HRC (approximately 237 HBW) to prevent SSC in H₂S-containing environments.

  6. A vessel inspector notices orange-brown tubercles on the internal surface of a carbon steel water storage vessel. What corrosion mechanism do these indicate?

    Answer: Microbiologically influenced corrosion (MIC) with iron-related bacteria

    Orange-brown tubercles are characteristic of MIC involving iron-oxidizing or iron-reducing bacteria, which create mounds of corrosion product over active pit sites beneath.

  7. What is the significance of the 'critical pitting temperature' (CPT) for stainless steels used in pressure vessel applications?

    Answer: The temperature below which pitting corrosion cannot initiate in a given chloride environment

    The CPT is the minimum temperature at which pitting corrosion can initiate and propagate in a specific chloride-containing environment, used to select appropriate alloys for service.