API 571 Corrosion Mechanisms 3

Question 1

Naphthenic acid corrosion primarily occurs above what temperature threshold?

Accepted Answer

450°F (232°C)

Answer

200°F (93°C)

Answer

300°F (149°C)

Answer

700°F (371°C)

Question 2

The Total Acid Number (TAN) of crude oil is used to assess risk of which damage mechanism?

Accepted Answer

Naphthenic acid corrosion

Answer

Sulfide stress cracking

Answer

Hydrogen embrittlement

Answer

Creep damage

Question 3

Chloride stress corrosion cracking (Cl-SCC) in austenitic stainless steel requires what combination of conditions?

Accepted Answer

Tensile stress, chlorides, and temperature above ~140°F

Answer

Compressive stress, chlorides, and low temperature

Answer

Dry chloride environment without moisture

Answer

Chlorides alone at any temperature

Question 4

Which alloy provides the best resistance to naphthenic acid corrosion in high-temperature crude service?

Accepted Answer

316L stainless steel with molybdenum

Answer

Carbon steel

Answer

5Cr-0.5Mo low alloy steel

Answer

9Cr-1Mo steel

Question 5

How does corrosion fatigue differ from pure mechanical fatigue?

Accepted Answer

A corrosive environment eliminates the normal fatigue endurance limit

Answer

It requires no cyclic loading to occur

Answer

It occurs only in high-alloy materials

Answer

It has a well-defined safe stress range

Question 6

What corrosion rate threshold typically triggers increased inspection frequency under API 510?

Accepted Answer

Greater than 0.010 in/yr

Answer

Greater than 0.001 in/yr

Answer

Greater than 0.005 in/yr

Answer

Greater than 0.050 in/yr