API 571 Corrosion Mechanisms 2

Question 1

What pH range is generally associated with aggressive acid corrosion in refinery process systems?

Accepted Answer

Below 4

Answer

Acid corrosion becomes significant at pH below 4, where hydrogen ion concentration is high enough to drive aggressive metal dissolution.

Question 2

Atmospheric corrosion is most severe in which type of environment?

Accepted Answer

Marine or coastal environment

Answer

Marine environments combine high relative humidity with chloride ions from sea spray, dramatically accelerating atmospheric corrosion rates.

Question 3

Corrosion under insulation (CUI) is primarily driven by what mechanism?

Accepted Answer

Moisture penetrating insulation and concentrating corrosive species against the pipe

Answer

CUI occurs when water infiltrates degraded insulation and remains in contact with the metal surface, concentrating chlorides and other corrosives.

Question 4

What is the primary damage mechanism for carbon steel in amine treating systems?

Accepted Answer

Amine corrosion from degradation products and stress corrosion cracking

Answer

Carbon steel in amine service suffers general corrosion from degraded amine compounds and is susceptible to SCC if residual welding stresses are present.

Question 5

Microbiologically influenced corrosion (MIC) is most commonly caused by which organisms?

Accepted Answer

Sulfate-reducing bacteria (SRB)

Answer

Sulfate-reducing bacteria produce hydrogen sulfide as a metabolic byproduct, directly attacking metal surfaces and promoting pitting corrosion.

API 571 - API 571 Corrosion and Materials Practice Test

API 571 - API 571 Corrosion and Materials Practice Test

API 571 Corrosion Mechanisms 2