API 571 Corrosion Mechanisms

Question 1

What is the most common form of corrosion found in refinery equipment?

Accepted Answer

Uniform corrosion

Answer

Uniform corrosion is the most prevalent form in refineries, causing consistent metal loss across an entire surface.

Question 2

Which type of corrosion occurs at the interface between two dissimilar metals in a conductive electrolyte?

Accepted Answer

Galvanic corrosion

Answer

Galvanic corrosion occurs when two dissimilar metals are electrically connected in a corrosive electrolyte, with the more active metal becoming the anode.

Question 3

What environment best promotes crevice corrosion in process equipment?

Accepted Answer

Stagnant or low-flow areas with restricted oxygen access

Answer

Crevice corrosion thrives in tight, restricted spaces where stagnant solution creates localized oxygen depletion and anodic conditions.

Question 4

Pitting corrosion is characterized by which type of attack?

Accepted Answer

Localized attack forming small, deep cavities

Answer

Pitting corrosion creates small, deep cavities that concentrate at local anodic sites and is particularly damaging due to its localized, hard-to-detect nature.

Question 5

Which material is most susceptible to intergranular corrosion after sensitization in the 800–1500°F range?

Accepted Answer

304 austenitic stainless steel

Answer

Austenitic stainless steels like 304 precipitate chromium carbides at grain boundaries when heated in the sensitization range, depleting chromium and creating attack susceptibility.

API 571 - API 571 Corrosion and Materials Practice Test

API 571 - API 571 Corrosion and Materials Practice Test

API 571 Corrosion Mechanisms