NACE - National Association of Corrosion Engineers Cathodic Protection Principles Questions and Answers

Question 1

According to NACE SP0169, which of the following is the most commonly accepted minimum protective potential for carbon steel in soil or water, when measured with respect to a copper-copper sulfate electrode (CSE)?

Accepted Answer

-850 mV

Answer

-550 mV

Answer

+850 mV

Answer

0 mV

Question 2

An engineer is designing a cathodic protection system for a large, poorly coated, cross-country pipeline with high current requirements. Which type of CP system is generally more suitable and cost-effective for this application, and why?

Accepted Answer

Impressed Current Cathodic Protection (ICCP), because it can provide a higher, adjustable current output.

Answer

Sacrificial Anode Cathodic Protection (SACP), because it requires no external power source.

Answer

Sacrificial Anode Cathodic Protection (SACP), because it eliminates the risk of stray current interference.

Answer

Impressed Current Cathodic Protection (ICCP), because its anodes are always consumed slower than sacrificial anodes.

Question 3

Which of the following anode materials is most commonly used in a sacrificial anode cathodic protection (SACP) system for a steel structure in a high-resistivity soil environment?

Accepted Answer

Magnesium

Answer

Zinc

Answer

Aluminum

Answer

Mixed Metal Oxide (MMO)

Question 4

A technician measures a structure-to-electrolyte potential of -950 mV CSE on a pipeline protected by an ICCP system while the rectifier is operating. Immediately after interrupting the current source, the potential reading shifts instantly to -750 mV CSE. What does this instantaneous voltage shift represent?

Accepted Answer

IR drop error

Answer

Cathodic polarization

Answer

Anodic depolarization

Answer

Telluric current effect

Question 5

In an impressed current cathodic protection (ICCP) system, what is the primary function of the rectifier?

Accepted Answer

To convert alternating current (AC) to direct current (DC).

Answer

To serve as the consumable anode that protects the structure.

Answer

To measure the structure-to-electrolyte potential.

Answer

To create a dielectric shield between the anode and the structure.

Question 6

Which of the following conditions is a primary cause of "cathodic shielding," a phenomenon that can prevent protective current from reaching the underlying metal surface?

Accepted Answer

A disbonded coating that remains intact and shields the steel from the electrolyte.

Answer

High soil resistivity that limits the overall flow of current.

Answer

Using a sacrificial anode material with a very high driving voltage.

Answer

Stray DC currents from a nearby transit system interfering with the CP system.