API-580 Corrosion Mechanisms

Question 1

Which type of corrosion occurs in the heat-affected zone (HAZ) of welded equipment?

Accepted Answer

Intergranular corrosion

Answer

Uniform corrosion

Answer

Galvanic corrosion

Answer

Erosion corrosion

Question 2

What is the primary driver of stress corrosion cracking (SCC)?

Accepted Answer

The combination of tensile stress, a susceptible material, and a corrosive environment

Answer

High operating pressure alone

Answer

Cyclic loading at low temperatures

Answer

Exposure to atmospheric oxygen

Question 3

What is the mechanism behind microbiologically influenced corrosion (MIC)?

Accepted Answer

Bacteria create localized corrosive conditions on metal surfaces

Answer

Microbes directly consume metal atoms

Answer

Fungi grow through metal grain boundaries

Answer

Algae produce electrical currents in pipelines

Question 4

Which corrosion mechanism is most common in carbon steel piping carrying acidic crude oil?

Accepted Answer

Naphthenic acid corrosion

Answer

Chloride stress corrosion cracking

Answer

Ammonia stress corrosion cracking

Answer

Caustic cracking

Question 5

What is hydrogen-induced cracking (HIC) and where does it typically occur?

Accepted Answer

Cracking caused by hydrogen atoms diffusing into steel, common in wet H2S environments

Answer

Cracking from hydrogen gas pressure in storage tanks

Answer

Fractures caused by hydrogen embrittlement at high temperatures

Answer

Corrosion from hydrogen peroxide cleaning solutions

Question 6

What distinguishes pitting corrosion from uniform corrosion?

Accepted Answer

Pitting creates localized holes while uniform corrosion affects the entire surface evenly

Answer

Pitting occurs only at high temperatures

Answer

Uniform corrosion is more dangerous than pitting

Answer

Pitting only affects non-metallic materials