API 653 Corrosion Assessment 2

Question 1

What type of corrosion occurs when two dissimilar metals are in electrical contact in the presence of an electrolyte?

Accepted Answer

Galvanic corrosion

Answer

Uniform corrosion

Answer

Crevice corrosion

Answer

Pitting corrosion

Question 2

According to API 653, what is the minimum shell thickness (t_min) formula used for corrosion assessment of existing tanks?

Accepted Answer

t_min = 2.6D(H-1)G / SE

Answer

t_min = 4.9D(H-1)G / SE

Answer

t_min = 2.6D(H-1)G / S

Answer

t_min = 4.9D(H-0.3)G / SE

Question 3

Which corrosion mechanism is characterized by localized attack beneath deposits, gaskets, or at crevices where oxygen is depleted?

Accepted Answer

Crevice corrosion

Answer

Erosion corrosion

Answer

Stress corrosion cracking

Answer

Intergranular corrosion

Question 4

When performing an internal inspection of a tank bottom, which measurement technique provides the most complete corrosion mapping?

Accepted Answer

Magnetic flux leakage (MFL) scanning

Answer

Spot ultrasonic thickness readings

Answer

Visual inspection only

Answer

Hammer testing

Question 5

What does a high cathodic protection current demand typically indicate when assessing tank bottom corrosion?

Accepted Answer

There is significant coating disbondment or bare metal exposure

Answer

The coating is in excellent condition

Answer

The tank has no external corrosion

Answer

The anode system is oversized

Question 6

Which factor most significantly accelerates microbiologically influenced corrosion (MIC) in aboveground storage tanks?

Accepted Answer

Stagnant water accumulation at the tank bottom

Answer

High ambient temperature

Answer

High-velocity fluid flow

Answer

Alkaline soil conditions

Question 7

What is the primary purpose of calculating the remaining corrosion allowance (RCA) during a tank inspection?

Accepted Answer

To establish the next inspection interval and fitness for service

Answer

To determine the cost of repairs

Answer

To select the appropriate coating system

Answer

To determine the tank's original design pressure