651 - P1 (50Q)

Question 1

A commercial carbonaceous backfill material.

Answer 1

coke breeze

Question 2

An electrochemical cell the electromotive force of which is due to a difference in air (oxygen) concentration

Answer 2

differential aeration cell

Question 3

The change from the open-circuit potential of an electrode as a result of current across the electrode/electrolyte interface.

Answer 3

polarization

Question 4

Differing oxygen concentrations between areas on a steel surface may generate __________.

Answer 4

differences in potential.

Question 5

________________ and other factors interact in a complex fashion to influence corrosion.

Answer 5

Moisture content, pH, oxygen concentration,

Question 6

The most common, and potentially the most

damaging, stray currents are __________.

Answer 6

direct currents.

Question 7

Sand is often installed by loose lifts in maximum layering of_________ thickness.

Answer 7

6 in. – 8 in. (15 cm – 20 cm)

Question 8

rolling is suggested to be done for each layer to achieve compaction to ___ of the maximum dry density

Answer 8

95%

Question 9

The corrosion rate of steel may double with every _____ increase in temperature above 77°F (25°C).

Answer 9

18°F (10°C)

Question 10

Metals commonly used as galvanic anodes in soil are __________ in either cast or ribbon form.

Answer 10

magnesium and zinc

Question 11

Galvanic systems are normally applied only to small diameter tanks (e.g., _________) or for tanks with externally coated bottoms.

Answer 11

less than 60 ft [18 m]

Question 12

The rectifier converts _______ current to ______ current

Answer 12

alternating, direct

Question 13

A typical cathodic protection rectifier has two major components: (a) a _______ to reduce the AC supply voltage, and (b) _______ to convert AC input to DC output.

Answer 13

step-down transformer, rectifying elements

Question 14

However, in lieu of a current requirement test, the generally accepted protective current density is between ________ at ambient temperatures, and current density between ________for elevated temperature
tanks.

Answer 14

1 mA/ft2 and 2 mA/ft2 , 2 mA/ft2 and 8 mA/ft2

Question 15

Rectifiers with a moderate excess capacity (typically _______) should be selected to allow for adjustments during the life of the cathodic protection system and to prevent damage due to voltage overloads.

Answer 15

10% – 50%

Question 16

NACE ______ should be consulted for design information for impressed current systems.

Answer 16

RP0388

Question 17

It is recommended that Sections 4 and 5 of

NACE _____ be consulted when designing similar systems for aboveground hydrocarbon storage tank bottoms

Answer 17

RP0575

Question 18

Refer to the latest revision of NACE ______ for electrical isolation requirement.

Answer 18

RP0177

Question 19

To ensure adequate cathodic protection has been achieved on aboveground storage tanks, refer to the latest edition of NACE ______

Answer 19

RP0193

Question 20

A negative (cathodic) potential of at least _____ mV with the cathodic protection current applied

Answer 20

850

Question 21

A minimum of ___ mV of cathodic polarization measured between the tank bottom metallic surface and a stable reference electrode contacting the electrolyte.

Answer 21

100

Question 22

Tank bottom surface area contacting the tank pad may vary with the tank content level, causing variations to _______ reading.

Answer 22

tank-to-soil potential

Question 23

For a typical shallow vertical anode installation, the hole is excavated __________ in diameter by approximately _________ deep.

Answer 23

8 in. – 12 in. (20 cm – 30 cm) , 10 ft – 20 ft (304 cm – 366 cm)

Question 24

The greatest sources of ______ are the electric railway, rapid transit system, underground mining electrical systems, and welding machines

Answer 24

stray current

Question 25

______cathodic protection surveys are recommended to ensure the effectiveness of cathodic protection

Answer 25

Annual

Question 26

All sources of impressed current should be checked at intervals not exceeding ___ months unless specified otherwise by regulation.

Answer 26

two