API 653 Cathodic Protection Systems

Question 1

What is the minimum negative potential criterion for adequate cathodic protection of a steel tank bottom, as measured against a copper/copper sulfate reference electrode (CSE)?

Accepted Answer

-850 mV

Answer

API 653 and NACE SP0193 specify a minimum potential of -850 mV (vs. CSE) as the criterion for adequate cathodic protection of steel tank bottoms.

Question 2

Which of the following is a type of cathodic protection system used on aboveground storage tank bottoms?

Accepted Answer

Sacrificial anode (galvanic) system

Answer

Sacrificial anode (galvanic) systems and impressed current systems are the two primary types of cathodic protection; sacrificial anode systems use more active metals such as magnesium or zinc that corrode in place of the tank steel.

Question 3

In an impressed current cathodic protection (ICCP) system for a tank bottom, what is the function of the rectifier?

Accepted Answer

To convert AC power to DC current for the CP circuit

Answer

The rectifier in an ICCP system converts alternating current (AC) from a power source into direct current (DC), which is then applied to the tank bottom to provide cathodic protection.

Question 4

According to API 653, when should cathodic protection be considered for the external bottom of an aboveground storage tank?

Accepted Answer

When corrosion on the tank bottom is detected or anticipated

Answer

API 653 states that cathodic protection should be considered when corrosion on the external bottom is detected or anticipated based on soil corrosivity, inspection findings, or operating history.

Question 5

What reference electrode is most commonly used for measuring cathodic protection potentials in soil environments?

Accepted Answer

Copper/copper sulfate electrode (CSE)

Answer

The copper/copper sulfate electrode (CSE) is the standard reference electrode used for measuring CP potentials in soil environments due to its stability and reliability.

(API 653) API 653 Aboveground Storage Tank Inspector Certification Practice Test

(API 653) API 653 Aboveground Storage Tank Inspector Certification Practice Test

API 653 Cathodic Protection Systems