API 651 - 5 ( Determination of Need for Cathodic Protection)

Question 1

the decisions governing the need for cathodic protection should be based

Answer 1

on data from corrosion surveys , operating records; prior test results on similar tank systems; jurisdictional requirements and recommendations of API 651

Question 2

corrosion control by cathodic protection for the new aboveground storage tanks should be evaluated

Answer 2

in the initial design of the tank

Question 3

corrosion control by cathodic protection for new aboveground storage tanks should be maintained

Answer 3

during the service life of the tank

Question 4

studies should be made within a suitable time frame in accordance with API Standard 653 concerning the possible need for cathodic protection. when these studies indicate that corrosion will affect the safe or economic operation of the system

Answer 4

adequate corrosion control measure should be used

Question 5

studies should be made within a suitable time frame in accordance with API Standard 653 concerning the possible need for cathodic protection.When these studies indicate that corrosion will affect the________ or economic operation of the system, adequate corrosion control measure should be used

Answer 5

safe

Question 6

pure hydrocarbon fluids are usually

Answer 6

not corrosive

Question 7

what is generally used to reduce or eliminate corrosion on the internal surfaces of underground storage tanks

Answer 7

coatings

Question 8

internal cathodic protection in conjunction with coatings has:

Answer 8

not gained wide spread use

Question 9

cathodic protection is an effective means of corrosion control only if it is possible to pass electric current between the

Answer 9

anode and the cathode (tank bottom)

Question 10

prior to determining the need for cathodic protection of an aboveground storage tank:

Answer 10

a full evaluation of tank history is advised

Question 11

information about an aboveground storage tank such as foundation design,site plan, construction date, soil properties, location of water table, presence and types (s) of linings, previous repairs,whether it has a secondary bottom, maintenance history,etc. all make up:

Answer 11

the tank design and construction history

Question 12

information about an aboveground storage tank such as the type of product stored, the producttemperature , the presence and depth of water bottoms, and the frequency of fill and discharge, all make up:

Answer 12

the type of service the tank is in

Question 13

in certain cases, internal cathodic protection in conjunction with a ________may be applicable.

Answer 13

lining

Question 14

if internal corrosion is known to be a problem with an aboveground storage tank:

Answer 14

use of an internal lining should be considered.

Question 15

the _______ under the tank bottom has a significant effect on external corrosion of the tank bottom

Answer 15

cushion material

Question 16

if large particle sizes are used in the cushion beneath a tank bottom,differentinal aeration _______ may result at points where the large particles or debris contact the bottom .

Answer 16

corrosion

Question 17

Soil __________provides valuable information about the corrosivity of the material used under and around a tank bottom.

Answer 17

resistivity

Question 18

Soils with a resistivity range,OHM-CM, of less than 500 indicates it is probably:

Answer 18

very corrosive

Question 19

corrosive soil beneath a high resistivity foundation material may contaminate the foundation fill by:

Answer 19

capillary action

Question 20

a properly designed concrete tank cushion constructed on a stable , properly prepared subsoil may be effective in eliminating:

Answer 20

intrusion of groundwater, soil- soil corrosion, and the need for cathodic protection

Question 21

Unstable soil beneath a concrete tank cushion constructed on a stable, properly prepared subsoil may be effective in eliminating :

Answer 21

intrusion of ground water ,soil-side corrosion , and the need for cathodic protection

Question 22

Unstable soil beneath a concrete tank cushion may induce cracks in the slab through which water and contaminants can permeate to steel tank bottom and provide a ____ environment

Answer 22

corrosive

Question 23

corrosion from soil may be prevented by a:

Answer 23

concrete pad

Question 24

if a tank is constructed on a concrete pad or foundation (or cushion) ,corrosion of the external tank bottom may occur from:

Answer 24

moisture accumulation because of condensation,flooding,blowing rain.etc.

Question 25

where a non -continuous concrete pad is utilized oxygen entry is not restricted.In situations where water may condense on the tank bottom or water is retained above the concrete pad,_____ may occur

Answer 25

accelerated atmospheric corrosion

Question 26

a cushion of new ____ may provide many of the same advantages as a concrete cushion for reducing corrosion and eliminating the need for cathodic protection

Answer 26

asphalt

Question 27

Asphalt degrades with the time and can provide a path for water and dissolved chemicals to come into contact with the steel tank bottom,allowing _______ to occur

Answer 27

corrosion

Question 28

a deteriorated asphalt cushion may allow corrosion of the tank bottom to occur . cathodic protection, if applied

Answer 28

may or may not stop corrosion occurring

Question 29

a useful test of sand pad material for helping to determine whether potential corrosion activity will be high enough to make cathodic protection necessary is

Answer 29

an electrical resistivity test

Question 30

measuring pH and soil resistivity are tests that are helpful in further corrosion analysis of the native soil cushion if a pH measured to be less than 5.0 this indicates that the soil cushion is

Answer 30

very corrosive

Question 31

the presence of aggressive ions such as chlorides and sulfates in the native soil cushion are very helpful in corrosion analysis. if the chlorides are measured to be greater then 10 ppm, this indicates that the soil cushion could cause ________type corrosion to a carbon steel bottom .

Answer 31

pitting

Question 32

the presence of aggressive ions such as chlorides and sulfates in the native soil cushion are very helpful in corrosion analysis. if the sulfates are measured to be greater than 200 ppm, this indicates that the soil cushion contains__________.

Answer 32

a high concentration of organic matter

Question 33

when soil analysis data ( by resisivity testing) indicates that a sand pad cushion for a tank is corrosive , what measures should be considered ?

Answer 33

install cathodic protection or take other corrosion control measures

Question 34

what is the most common material used as a cushion beneath storage tank bottoms ?

Answer 34

clean sand

Question 35

if oil alone is added to the clean sand beneath a tank bottom, industry experience show that it:

Answer 35

does not eliminate the need for cathodic protection

Question 36

Salt sprays ( especially in coastal areas) fertilizers or chemicals from spraying may:

Answer 36

get into the tank cushion and contaminate it where corrosion may take place.

Question 37

if a tank with water bottoms leaks into the tank’ s cushion, the environment under the tank may become :

Answer 37

more corrosive

Question 38

if product leaks from a tank into the tank’ s cushion, it could create corrosion cells that did not exist before or adversely affect the effectiveness of the :

Answer 38

cathodic protection

Question 39

cathodic protection is. ___________in areas beneath a tank bottom where a leak has washed away part of the foundation material

Answer 39

not effective

Question 40

the use of crushed limestone or calm shells as tank cushion makes the environment under tanks alkaline. this does what ?

Answer 40

it may reduce corrosion

Question 41

Accelerated corrosion can occur on the external surface of the bottom of heated tanks due to elevated temperatures if the areas is :

Answer 41

wet

Question 42

an impervious clay pad beneath the tank levees,a dual bottom tank bottom design, or an impervious non metallic membrane beneath the primary bottom of a tank are all examples of:

Answer 42

secondary containment

Question 43

To reduce the environmental impact of a tank bottom leak

Answer 43

secondary containment may be used

Question 44

most cathodic protection systems are rendered ineffective when:

Answer 44

an impervious membrane lining is a diked area prior to tank construction.

Question 45

Thick -film,laminated,corrosion & chemical resistant linings are installed in tanks primarily to prevent:

Answer 45

internal corrosion

Question 46

The use of a thick-film laminate or other type of internal lining can:

Answer 46

not be considered as sufficient justification to eliminate external cathodic protection

Question 47

A thick - film,laminated ,internal tank bottom lining:

Answer 47

is not designed for structural strength.