API 571 Corrosion Mechanisms

Question 1

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

Accepted Answer

Uniform corrosion

Answer

Pitting corrosion

Answer

Crevice corrosion

Answer

Galvanic corrosion

Question 2

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

Accepted Answer

Galvanic corrosion

Answer

Erosion corrosion

Answer

Crevice corrosion

Answer

Intergranular corrosion

Question 3

What environment best promotes crevice corrosion in process equipment?

Accepted Answer

Stagnant or low-flow areas with restricted oxygen access

Answer

Open, high-flow systems

Answer

High-temperature dry gas streams

Answer

Strongly alkaline solutions

Question 4

Pitting corrosion is characterized by which type of attack?

Accepted Answer

Localized attack forming small, deep cavities

Answer

Uniform metal loss across the surface

Answer

Grain boundary dissolution

Answer

General surface thinning

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

Carbon steel

Answer

Aluminum alloys

Answer

Copper alloys

Question 6

Erosion-corrosion is primarily accelerated by which condition?

Accepted Answer

High fluid velocity with entrained particulates

Answer

Low fluid velocity and laminar flow

Answer

Static stagnant conditions

Answer

Cathodic protection currents