Cathodic Protection

Question 1

Limitations of CP

Answer 1

Internal surfaces not protected Above ground surfaces not protected Electrical Shielding Stray Current Attenuation (gradual loss of current)

Question 2

Produce small amounts of current Cannot be adjusted No power source needed

Answer 2

Galvanic System

Question 3

Galvanic System Anodes

Answer 3

Aluminum, Zinc and Magnesium

Question 4

Produce any amount of current Can be adjusted Power source is needed

Answer 4

Impressed Current System

Question 5

Impressed Current Anodes

Answer 5

Graphite, High Silicone Cast Iron, Scrap Steel, Mixed Metal Oxide (MMO), Titanium-Niobium, Platinum, Lead-Silver

Question 6

Impressed Current Power Sources

Answer 6

Rectifiers Photovoltaic Solar Panels Thermo-Electric Gen Engine Generators Fuel Cells Wind Mill Power
Closed Cycle Vapor Turbo Gen Batteries

Question 7

Anode Backfill

Answer 7

Lowers contact with resistance to Earth; Enables anodes to consume uniformly; Lengthens the life of Impressed Anodes; Holds moisture for galvanic anodes; Must be designed to fit the ground-bed

Question 8

Reference Electrodes

Answer 8

Copper Copper/Sulfate Hydrogen Zinc Calomel Silver Silver/Chloride Antimony

Question 9

The positive terminal of an ICCP must be attached to the …..?

Answer 9

Ground bed

Question 10

Most common reference cell used for CP?

Answer 10

Copper/Copper-Sulfate

Question 11

What measurements are used most commonly as a criterion of protection for CP?

Answer 11

Potential

Question 12

Coated pipe lines polarize very ……; the better the coating the ……. the polarization?

Answer 12

Rapidly; Faster

Question 13

The lower the resistivity; the …… will be the corrosivity?

Answer 13

Higher

Question 14

The Wenner 4 pin test is used to measure ……. which is then utilized to calculate ………

Answer 14

Voltage (potentials), resistivites

Question 15

In tankers tanks that are filled with salt water for ballast after discharging cargo are suseptible to severe corrosion; …….. anodes are widely used to prevent corrosion?

Answer 15

Galvanic

Question 16

Metal that provides sacrificial protection to another metal that is more noble when electrically coupled in an electrolyte?

Answer 16

Galvanic Anode

Question 17

Ratio of an anode weight sacrificed for CP divided by total theoretical amperes hours or capacity of the material used.

Answer 17

Galvanic Anode Efficiency

Question 18

Ground bed anodes are not depended upon as a source of electrical energy. An external source of DC power is connected between ground bed anodes and structure.

Answer 18

Impressed Current CP (ICCP)

Question 19

Device that is powered by electrical utility system which converts high voltage AC to low voltage DC by means of step-down transformers.

Answer 19

Rectifier

Question 20

Change from open-circuit potential as a result of current across the electrode/electrolyte interface

Answer 20

Polarization

Question 21

3 Sources of DC stray current

Answer 21

DC Railway systems; Mining operations using DC power; DC welding Operations

Question 22

Closed interval potential survey is to record the potential profit of a pipeline over its entire length by taking potential readings at intervals of approximately M

Answer 22

CIPS

Question 23

Pearson Survey and DCVG survey have in common?

Answer 23

They are tests designed to locate coating defects in buried pipelines.

Question 24

Pearson Survey and DCVG survey are different?

Answer 24

Pearson Survey - no trailing wires and the defect gives a signal. No signal in DCVG means a defect.