API 510 Corrosion Assessment 4

Question 1

What type of corrosion involves the preferential attack of one phase in a multi-phase alloy, such as the removal of zinc from brass?

Accepted Answer

Dealloying (selective leaching)

Answer

Dealloying, or selective leaching, involves the preferential removal of one element from an alloy, such as dezincification of brass.

Question 2

According to API 510, how should a corrosion rate be established for a new vessel with no prior inspection history?

Accepted Answer

Use published data, experience from similar services, or process engineering estimates

Answer

For new vessels, API 510 allows use of published corrosion data, similar service experience, or process engineer estimates to establish an initial corrosion rate.

Question 3

Which condition is required for erosion-corrosion to be a significant degradation mechanism in a pressure vessel?

Accepted Answer

High-velocity flow, especially with entrained solids or vapors

Answer

Erosion-corrosion requires high-velocity flow that mechanically removes protective oxide layers, with entrained solids or phase changes accelerating the damage.

Question 4

What is the purpose of establishing a short-term corrosion rate in API 510 assessments?

Accepted Answer

To capture recent changes in process conditions that may differ from historical rates

Answer

Short-term rates reflect the most recent inspection interval, capturing changes in process conditions that may not be represented by historical long-term data.

Question 5

A pressure vessel inspector discovers blistering on the inner surface of a vessel in H2S service. What damage mechanism does this MOST likely indicate?

Accepted Answer

Hydrogen blistering

Answer

Hydrogen blistering occurs when atomic hydrogen diffuses into the steel and accumulates at inclusions, forming blisters visible on the surface.

(API 510) API 510 Inspector Certification Practice Test

(API 510) API 510 Inspector Certification Practice Test

API 510 Corrosion Assessment 4