Section 4 - Corrosion of Above Ground Steel Storage Tanks
Section 4 - Corrosion of Above Ground Steel Storage Tanks
1.According to API Recommended Practice - 651, there are four
components in each corrosion cell. Theses components are an anode
and all but which of the following?
a) DC current supplied by batteries
b) A cathode
c) A metallic path connecting the anode and cathode
d) An electrolyte
Reference: API-651 Paragraph 4.1.1
2.The base metal goes into solution (corrodes) by releasing
electrons and forming positive metal ions. This statement describes
what takes place at what component of a corrosion cell?
a) The cathode
b) The electrolyte
c) The metallic connection between the cathode and the anode
d) The anode
Reference: API-651 Paragraph 4.1.1(a)
3.Which of the following is the most correct statement regarding
the cathode?
a) Moderate corrosion takes place at the cathode
b) No corrosion takes place at the cathode
c) All corrosion takes place at the cathode
d) A chemical reaction takes place using electrons released at
the electrolyte
Reference: API-651 Paragraph 4.1.1(b)
4.The electrolyte contains ions and conducts positive current
from the anode to the cathode. The most common electrolyte for
external tank bottom surfaces is _______, while the most common for
internal surfaces is _________.
a) Water, sludge and moist soil
b) Moist soil, water and sludge
c) Acidic soil, water and sludge
d) Moist soil, product and sludge
Reference: API-651 Paragraph 4.1.1(d)
5.The two most common types of corrosion to tank bottoms are
______ and ______.
a) Stress corrosion and galvanic
b) Erosion and erosion/corrosion
c) General and pitting
d) Stray current and bimetallic
Reference: API-651 Paragraph 4.1.2
6.Which type of corrosion results in relatively uniform metal
loss?
a) Erosion and erosion/corrosion
b) Stray current
c) General
d) Pitting
Reference: API-651 Paragraph 4.1.2
7.Which type of corrosion may only affect relatively small
areas, while substantial areas of the surface are unaffected by
corrosion?
a) Galvanic
b) General
c) Brittle
d) Pitting
Reference: API-651 Paragraph 4.1.2
8.Composition of the metal is a factor in determining which
areas become anodes and which become cathodes. What else can cause
corrosion?
a) Differences between weld metal, heat affected zone, and
parent metal
b) Differences in thickness between adjacent plates
c) Improper fit-up of the welded joint
d) Slag inclusion in the weld metal
Reference: API-651 Paragraph 4.1.3
9.Which of the following is a correct statement regarding oxygen
concentration of the electrolyte.
a) Oxygen concentration in the electrolyte has no impact on the
corrosion cell
b) Areas of lower oxygen concentrations become anodic and areas
of higher concentrations become cathodic.
c) Areas of lower oxygen concentrations become cathodic and
areas of higher concentrations become anodic
d) Areas of lower oxygen concentrations become acidic and areas
of higher concentrations become alkaline
Reference: API-651 Paragraph 4.1.4
10.Soil characteristics substantially affect what?
a) What type of product may be stored in the tank
b) What the maximum fill height of the tank is
c) The type and rate of corrosion on a structure in contact with
soil
d) Perk rate for dissipation of small leaks from the tank
bottom
Reference: API-651 Paragraph 4.1.5
11.What is another term used for "stray currents"?
a) Short circuits
b) Positive currents
c) Impressed currents
d) Interference currents
Reference: API-651 Paragraph 4.2.1
12.The most common and potentially the most damaging stray
currents are:
a) Direct currents
b) Alternating currents
c) Intermittent currents
d) Close proximity alternating currents
Reference: API-651 Paragraph 4.2.1
13.Which of the following is not likely to be a source of stray
currents?
a) Static electricity
b) Welding machines
c) Impressed current cathodic protection systems
d) Railroads
Reference: API-651 Paragraph 4.2.1
14.Two metals with different compositions connected in an
electrolyte is a general description of:
a) A battery
b) A current suppressor
c) A short circuit
d) Galvanic corrosion
Reference: API-651 Paragraph 4.2.2
15.All but one of the following is listed as major factors which
influence the severity of internal corrosion. Which is not a
factor?
a) The pH level of the fluid in contact with the steel
bottom
b) The amount of nitrogen in the fluid in contact with the steel
bottom
c) Suspended solids in the fluid in contact with the steel
bottom
d) Conductivity of the fluid in contact with the steel
bottom
Reference: API-651 Paragraph 4.2.3
16.Three major types of internal corrosion to be considered are
general corrosion, pitting corrosion, and to a lesser extent in
tanks, environmental cracking.
a) True
b) False
Reference: API-651 Paragraph 4.2.3
Answers to API-651 Section 4, corrosion of Aboveground Steel
Storage Tanks
Question NumberAnswer
1A
2D
3B
4B
5C
6C
7D
8A
9B
10C
11D
12A
13A
14D
15B
16A
Should you find a mistake or disagree with any answer listed,
please bring it to our attention for correction or
clarification.
BAY Technical Associates, Inc. has attempted to provide answers
developed from paragraphs of the respective Code, Standard, or
Recommended Practice.
You can reach BAY Tech by phone at (610) 594-9036, by fax at
(610) 594-2612, or by
e-mail at [email protected].
Section 5 - Determination of Need for Cathodic Protection
1.API Recommended Practice 651 states that the need for cathodic
protection must be determined for all storage facilities. Decisions
governing the need for cathodic protection should be based on all
but which of the following?
a) Data from corrosion surveys and operating records
b) National Board and ASME recommendations
c) Prior test results with similar systems in similar
environments
d) National, state, and local code requirements and the
recommendations in API-651
Reference: API RP 651, Paragraph 5.1
2.When should corrosion control by cathodic protection for new
ASTs be provided?
a) After final welding and before hydrostatic testing
b) After all stress relief has been carried out
c) In the initial design
d) After the tank is in service for 6 months
Reference: API RP 651, Paragraph 5.1.1
3.Generally tanks in petroleum service use ______ on the
internal surfaces to control internal corrosion.
a) AC Current instead of DC current cathodic protection
systems
b) Coatings
c) Cathodic protection in conjunction with coatings
d) Since pure hydrocarbon fluids are usually not corrosive
experience shows that internal corrosion will never occur
therefore, corrosion control is not necessary
Reference: API RP 651, Paragraph 5.1.3
4.Cathodic protection is an effective means of corrosion control
only if it is possible to pass electrical current between what two
components?
a) Anode and cathode
b) Tank shell and roof support system
c) Roof to bottom through roof support structures
d) Tank shell and tank bottom
Reference: API RP 651, Paragraph 5.1.4
5.A full evaluation of tank history should be performed prior to
_______.
a) Filling the tank for the 25th time
b) Painting the exterior surface of the tank
c) Temporarily removing the tank from service
d) Determining the need for cathodic protection
Reference: API RP 651, Paragraph 5.2.1
6.Such items as site plan, soil properties, previous repairs,
existing cathodic protection of nearby structures, maintenance
history, and expected life should be investigated and determined
when conducting the ____________.
a) Evaluation of the location of a refinery
b) Probability study of tank settlement
c) Evaluation of tank design/construction history
d) Evaluation of tank repairs and alterations
Reference: API RP 651, Paragraph 5.2.1.1
7.Of the following items which is not an item that should be
investigated and determined in the evaluation of types of
service?
a) Type of product stored
b) Product temperature
c) Ambient temperature
d) Presence and depth f water bottoms
Reference: API RP 651, Paragraph 5.2.1.2
8.Such items as tank inspections per API Standard 653, corrosion
rate records, stray current problems, design and performance of
previous protection systems, and structure-to-soil potential
surveys should be investigated and determined when conducting the
______.
a) Evaluation of tank repair/alteration/construction history
b) Evaluation of tank design/construction history
c) Evaluation of types of service
d) Evaluation of inspection/corrosion history
Reference: API RP 651, Paragraph 5.2.1.3
9.The cushion material under the tank has a significant effect
on external corrosion of the tank bottom. The material can also
influence:
a) The effectiveness and applicability of external cathodic
protection
b) The effectiveness and applicability of internal cathodic
protection
c) The decision to use or not use a rectifier or DC generator
set to supply current
d) The type of product that may be stored in the tank
Reference: API RP 651, Paragraph 5.3.1.1
10.What is an advantage of using fine particles for the cushion
material?
a) The fine particles should be uniform which makes it easier to
transport
b) Fine particles provide a more dense cushion to help reduce
the influx and outflow of oxygen
c) Fine particles will not permit the passage of product should
a leak occur in the tank bottom
d) Fine particles will hold moisture longer permitting it to
stabilize and prevent acid from forming in the electrolyte
Reference: API RP 651, Paragraph 5.3.1.1
11.What is the main disadvantage in using large size particles
in the soil cushion material?
a) The large particles may puncture the tank bottom
b) The large particles may trap moisture and allow general
corrosion to form
c) If large particles are used, differential aeration corrosion
may result where the particles contact the tank bottom
d) The large particles are more difficult to transport
Reference: API RP 651, Paragraph 5.3.1.1
12.A soil resistivity of about 1250 OHM-CM would indicate the
soil is probably ____.
a) Mildly corrosive
b) Very corrosive
c) Corrosive
d) Moderately corrosive
Reference: API RP 651, Paragraph 5.3.1.2
13.The results of soil resistivity surveys can be used to
determine ________.
a) When it is time to replace the cushion material under the
tank bottom
b) The need for cathodic protection
c) The amount of compression of the cushion material under the
tank
d) The best place to install a corrosion test bed
Reference: API RP 651, Paragraph 5.3.1.2
14.A properly designed concrete tank cushion constructed on
stable, properly prepared subsoil may be effective in all but which
of the following?
a) Cracks in the tank bottom weld seams
b) Intrusion of groundwater
c) Soil-side corrosion
d) The need for cathodic protection
Reference: API RP 651, Paragraph 5.3.2.1
15.Cracks through the concrete cushion may permit water and
contaminants to permeate to the steel tank bottom and provide a
path for proper electrical current flow.
a) True
b) False
Reference: API RP 651, Paragraph 5.3.2.1
16.Corrosion of the steel tank bottom installed on a concrete
cushion may result from moisture accumulation caused by all but
which of the following?
a) Condensation
b) Blowing snow or rain
c) Humidity in the air surrounding the tank
d) Flooding
Reference: API RP 651, Paragraph 5.3.2.2
17.Why would it be more important to provide proper support
under cushions of new asphalt than for concrete?
a) Asphalt is inherently alkaline and therefore does not have
the potential of preventing corrosion
b) Asphalt is not inherently alkaline and therefore does not
have the potential of preventing corrosion
c) Asphalt may degrade and become a corrosive substance
d) Asphalt may crack allowing moisture to reach the tank bottom
where it will react violently with the asphalt and the steel tank
bottom
Reference: API RP 651, Paragraph 5.3.3.1
18.How can the condition of the external surface of tank bottom
and the asphalt cushion be determined?
a) Raise the entire tank and inspect the tank bottom and the
asphalt
b) Take a core sample from the asphalt for testing. This test
will reveal the amount of steel that has gone into solution and
been trapped in the asphalt
c) Conduct a soil resistivity survey around the periphery of the
tank containment
d) By cutting coupons from the tank bottom
Reference: API RP 651, Paragraph 5.3.3.2
19.A soil analysis reveals the pH of a native soil cushion to be
6.25. This soil is considered to be:
a) Moderately corrosive
b) Mildly corrosive
c) Corrosive
d) Very corrosive
Reference: API RP 651, Paragraph 5.3.4.1 and Table 2
20.A soil analysis reveals the sulfates level of a native soil
cushion to be 5525ppm. This soil is considered to be
a) Moderately corrosive
b) Mildly corrosive
c) Corrosive
d) Very corrosive
Reference: API RP 651, Paragraph 5.3.4.1 and Table 2
21.What is the most common material used as a cushion beneath
storage tank bottoms?
a) Clean concrete
b) Clean sand
c) Clean Asphalt
d) Clean modified aggregate
Reference: API RP 651, Paragraph 5.3.5
22.The use of oiled sand beneath tank bottoms does not eliminate
the need for cathodic protection and in fact may cause cathodic
protection to be less effective because:
a) The oiled sand has higher resistivity
b) The sand is unable to conduct electrical current
c) The oil acts as an insulator and blocks all current flow
d) The oil creates a vapor bearer entrapping water and
contaminants next to the tank bottom
Reference: API RP 651, Paragraph 5.3.5
23.There are several ways the tank cushion can become
contaminated. Three of the following are methods of cushion
contamination, which one is not?
a) In coastal areas salt spay may be washed down the side of the
tank
b) Fertilizer from spraying operations in rural areas
c) Airborne chemicals from industrial operations
d) Residual build-up of electrons in the sand cushion
Reference: API RP 651, Paragraph 5.3.6.1
24.Leakage of product from the tank bottom can cause accelerated
corrosion by creating ____.
a) Stray current corrosion
b) Corrosion cells where none existed before
c) More positively charged electrons
d) A film that would block electrical current flow
Reference: API RP 651, Paragraph 5.3.6.2
25.When a layer of crushed-limestone or clam-shell is used for
the tank cushion, why is it important to ensure the particles are
fine and uniform?
a) Large particles could puncture the tank bottom
b) Differential aeration corrosion cells will cause pitting at
contact areas between the large particles and the metal
c) Large particles may allow the formation of dissolved gas
pockets which could become a hazard if hot tap work is performed on
the tank bottom
d) Large particle will eventually fracture and create voids in
the tank cushion
Reference: API RP 651, Paragraph 5.3.7
26.What is an advantage of using crushed-limestone or clam-shell
under tank bottoms?
a) This material is plentiful and relatively inexpensive
b) Contamination is easier to detect because of
discoloration
c) Water from rain or groundwater makes the environment under
the tank alkaline, which may reduce corrosion
d) The use of this material eliminates the need for cathodic
protection
Reference: API RP 651, Paragraph 5.3.7
27. Heated tanks or tanks storing hot product can cause:
a) Increased water intrusion due to causing snow to melt and run
down the tank sides
b) Excessive drying out of concrete foundations resulting in
premature deterioration and failure
c) Accelerated corrosion on the internal surface especially in
tanks with water bottoms
d) Accelerated corrosion on the external surface due to elevated
temperature is the area is wet
Reference: API RP 651, Paragraph 5.4.1
28.There are a variety of methods for secondary containment,
which of the following is not an accepted method of secondary
containment.
a) Dual bottom tank design
b) Sand bags
c) Use of impervious clay pad in tank dike
d) Impervious nonmetallic membrane
Reference: API RP 651, Paragraph 5.4.3.1
29.During the installation of a new steel bottom over an
existing steel bottom, which has been repaired, if water or other
electrolyte intrudes into the annulus, what can happen?
a) A galvanic cell may form which will cause the new steel tank
bottom to corrode at an accelerated rate
b) An electrochemical reaction may take place creating hazardous
gasses
c) A galvanic cell may form which will cause the old tank bottom
to corrode at an accelerated rate
d) A galvanic cell may form which will turn the old tank bottom
into an anode
Reference: API RP 651, Paragraph 5.4.3.2
30.With the installation of _____ in a diked area prior to new
tank construction, most cathodic protection systems are rendered
ineffective.
a) A secondary containment system utilizing a perforated
impervious membrane
b) A secondary containment system utilizing an impervious
membrane
c) A secondary containment system utilizing a metallic
impregnated screen membrane
d) A secondary containment system utilizing a non-impervious
membrane
Reference: API RP 651, Paragraph 5.4.3.3
Answers to API-651 Section 5, Determination of Need for Cathodic
Protection
Question NumberAnswer
1B
2C
3B
4A
5D
6C
7C
8D
9A
10B
11C
12D
13B
14A
15B
16C
17B
18D
19C
20D
21B
22A
23D
24B
25B
26C
27D
28B
29A
30B
Should you find a mistake or disagree with any answer listed,
please bring it to our attention for correction or
clarification.
BAY Technical Associates, Inc. has attempted to provide answers
developed from paragraphs of the respective Code, Standard, or
Recommended Practice.
You can reach BAY Tech by phone at (610) 594-9036, by fax at
(610) 594-2612, or by
e-mail at [email protected].
Section 6- Methods of Cathodic Protection for Corrosion
Control
1.What is the basic principle that makes cathodic protection
effective.
a) Cathodic protection is a technique for preventing corrosion
by making the entire surface of the metal to be protected act as
the rectifier
b) Cathodic protection is a technique for preventing corrosion
by making the entire surface of the metal to be protected act as
the corrosion cell
c) Cathodic protection is a technique for preventing corrosion
by making the entire surface of the metal to be protected act as
the cathode
d) Cathodic protection is a technique for preventing corrosion
by making the entire surface of the metal to be protected act as
the anode
Reference: API-651, Paragraph 6.1
2.What are the two systems of cathodic protection?
a) Galvanic and repressed current
b) Galvanic and impressed current
c) Galvanic and reversed current
d) Galvanic and induced current
Reference: API-651, Paragraph 6.1
3.Galvanic cathodic protection systems use a metal, that is more
active than the structure to be protected, to supply the current
required to stop corrosion. What is another term(s) used to
describe this material?
a) Anode, commonly referred to as a galvanic or sacrificial
anode
b) Cathode, commonly referred to as a galvanic or sacrificial
cathode
c) Ribbon cathode, commonly referred to as a sacrificial ribbon
cathode
d) Impressed current anode, commonly referred to as the
impressed anode
Reference: API-651, Paragraph 6.2.1
4.Where on the galvanic series is clean and shiny mild
steel?
a) Clean and shiny mild steel has a value of 1.1 volts
b) Clean and shiny mild steel has a value of 1.0 volts
c) Clean and shiny mild steel has a value of 0.8 volts
d) Clean and shiny mild steel has a value of 0.5 to -0.8
volts
Reference: API-651, Paragraph 6.2.1 and Table 3
5.The most common metals used as galvanic anodes in soil
are:
a) Lead and copper
b) Aluminum alloy (5% zinc) and Mild steel (clean and shiny)
c) Magnesium and zinc
d) Mild steel in concrete and cast iron
Reference: API-651, Paragraph 6.2.1
6.Of the following, which is not an advantage of galvanic
cathodic protection systems?
a) No external power is needed
b) Capital investment is low for small-diameter tanks
c) Method is limited to use in low-resistivity soils
d) Interference problems (stray currents) are rare
Reference: API-651, Paragraph 6.2.2
7.Impressed current cathodic protection systems use:
a) Alternating current
b) Direct current usually provided by a rectifier
c) Direct current usually provided by a dry cell battery
d) Either direct current or alternating current depending upon
which is available
Reference: API-651, Paragraph 6.3.1
8.Of the following, which is not a disadvantage of impressed
current cathodic protection systems?
a) High current output
b) High maintenance costs
c) High operating costs
d) High capital cost for small installations
Reference: API-651, Paragraph 6.3.3
9.A cathodic protection rectifier has two major components; what
are they?
a) A step-down transformer to reduce the AC supply voltage and
rectifying elements to convert DC to AC output
b) A step-down transformer to reduce the AC supply voltage and
rectifying elements to convert AC to DC output
c) A step-down transformer to reduce the DC supply voltage and
rectifying elements to convert DC to AC output
d) A step-down transformer to reduce the AC supply voltage and
rectifying elements to regulate the AC output
Reference: API-651, Paragraph 6.3.3
10.Impressed current anodes used in soil are not made of:
a) Graphite
b) High silicon cast iron
c) Zinc
d) Mixed metal oxides on titanium
Reference: API-651, Paragraph 6.3.5
11.Impressed current anodes may be installed underneath the
tank.
a) True
b) False
Reference: API-651, Paragraph 6.3.5
Answers to API-651 Section 6, Methods of Cathodic Protection for
Corrosion Control
Question NumberAnswer
1C
2B
3A
4D
5C
6C
7B
8A
9B
10C
11A
Should you find a mistake or disagree with any answer listed,
please bring it to our attention for correction or
clarification.
BAY Technical Associates, Inc. has attempted to provide answers
developed from paragraphs of the respective Code, Standard, or
Recommended Practice.
You can reach BAY Tech by phone at (610) 594-9036, by fax at
(610) 594-2612, or by
e-mail at [email protected].
Section 7 Design of Cathodic Protection Systems
1.It has been decided to install an impervious membrane under a
new storage tank being installed in a diked area. Cathodic
protection of the tank bottom is required. Where must the anodes be
placed?
a) Anodes shall be placed outside the diked area
b) Directly under the membrane beneath the tank
c) As close as possible to the rectifier
d) Between the membrane and the tank bottom
Reference: API 651, Paragraph 7.2.3.1
2.Inspection experience has disclosed the need for cathodic
protection for an existing tank in a diked area. There is a
membrane installed under the tank. What would be an option for
installing anodes under this tank?
a) Jack the tank up on the side opposite the fill and discharge
lines and slide the ribbon anodes under
b) Bore under the tank at a very shallow angle and install the
anodes
c) Bore under the membrane at a very shallow angle and install
the anodes
d) Install deep ground bed anodes in coke breeze backfill
outside the diked area
Reference: API 651, Paragraph 7.2.3.2
3.If an existing tank bottom is protected by cathodic protection
and/or if cathodic protection is planned for the new bottom (by
deep or shallow groundbeds), what should be done with the old
bottom?
a) The old tank bottom should be electrically connected to the
cathodic protection system to now act as an anode
b) The old tank bottom should be painted with a corrosion
resistant coating and left in place
c) The old tank bottom should be completely removed
d) Nothing needs to be done with the old tank bottom
Reference: API 651, Paragraph 7.2.4.3
4.It has been decided to install a new tank bottom in a tank
with cathodic protection. What would be the result of leaving the
old bottom in place and not properly prepared?
a) The old bottom forms a shield that collects the cathodic
current flowing through the ground and prevents cathodic protection
of the new tank bottom
b) The old bottom forms a shield that collects the anodic
current flowing through the ground and prevents cathodic protection
of the new tank bottom
c) The old bottom forms a shield that collects the galvanic
current flowing through the ground and prevents cathodic protection
of the new tank bottom
d) The old bottom forms a shield that collects the stray current
flowing through the ground and prevents cathodic protection of the
new tank bottom
Reference: API 651, Paragraph 7.2.4.3
5.Industry experience has shown that if a conductive electrolyte
exists between an old and a new tank bottom:
a) The current flow and metal loss will be from the old
bottom
b) The current flow and metal loss will be from the new
bottom
c) The current flow will be from the old bottom and metal loss
will be from the new bottom
d) The current flow will be from the new bottom and metal loss
will be from the old bottom
Reference: API 651, Paragraph 7.2.4.3
6.There are several advantages to installing a secondary
containment. Of the following, which would not be considered an
advantage?
a) Provides a means of detecting and containing leaks and
preventing ground contamination
b) Prevents the natural current flow between the old bottom and
the new bottom
c) Permits the addition of cathodic protection at a later
date
d) May reduce the entry of groundwater into the space between
the bottoms
Reference: API 651, Paragraph 7.2.5.1.1
7.There are several disadvantages to installing a secondary
containment. Of the following, which would not be considered a
disadvantage
a) The membrane may act as a basin to contain water or any other
electrolyte that might wet the sand between the bottoms
b) The membrane could entrap hydrocarbon products, which would
require extra care for hot work
c) Makes the future addition of cathodic protection virtually
impossible
d) Acts as a barrier to groundwater
Reference: API 651, Paragraph 7.2.5.1.2
8.When an external cathodic protection system is being designed,
there are several items to be considered. Of the following four
items, which one would not be a consideration?
a) Selection and design of the cathodic protection system for
optimum economy of installation, maintenance, and operation
b) Specification of materials and installation practices that
meet applicable codes, such as National Electrical Manufacturers
Association standards, NACE recommended practices, and federal,
state, and local regulations
c) Provisions for monitoring the cathodic protection system
d) Specification of materials and installation practices that
meet applicable codes, such as American Society of Mechanical
Engineers standards, NACE recommended practices, and federal,
state, and local regulations
Reference: API 651, Paragraph 7.3.2
9.Information that is useful for design of an external cathodic
protection system can be divided into three categories:
a) Specifications, site conditions, and jurisdictional
requirements
b) Specifications and practices, site conditions, and U.S.
Geological survey reports
c) Specifications and practices, site conditions, and field
survey, corrosion test data, and operating experience
d) Specifications and practices, tank shell conditions, and
field surveys
Reference: API 651, Paragraph 7.3.3
10.What are the two types of cathodic protection systems most
commonly used?
a) Galvanic cathode system and impressed voltage system
b) Galvanic anode system and impressed current system
c) Galvanic anode system and interference current system
d) Galvanic anode system and interference voltage system
Reference: API 651, Paragraph 7.3.5.1 and 7.3.5.2
11.Galvanic cathodic protection systems are more economical
on:
a) Small-diameter tanks
b) Large-diameter tanks
c) Bare, poorly coated structures
d) Multiple large tanks in a diked area
Reference: API 651, Paragraph 7.3.5.1.1
12.The three most common galvanic anode materials used for soil
installations are:
a) High potential magnesium alloys, zinc, and pure aluminum
b) High potential magnesium alloys, Standard magnesium, and
Copper
c) High potential magnesium alloys, standard magnesium, and
zinc
d) High potential magnesium alloys, standard magnesium, and
stainless steel
Reference: API 651, Paragraph 7.3.5.1.2
13.What are the advantages of using a special backfill with
anodes for installation in soil environments?
a) Reduces the possibility of contaminating the environment and
promotes anode efficiency
b) Promotes anode efficiency, lengthens the life of the anode,
dissipates stray currents
c) Promotes anode efficiency, lengthens anode life, and keeps
anode environment moist
d) Promotes anode efficiency, keeps anode environment moist, and
prevents total deterioration of the anode
Reference: API 651, Paragraph 7.3.5.1.3
14.The number of anodes required to provide cathodic protection
depends upon what two factors?
a) The distance from the galvanic anode to the tank bottom and
soil discharge rate
b) Total current requirements and the expected individual anode
discharge rate in the soil
c) Total stray currents expected and the total current
requirements
d) Total current requirements and the expected individual
cathode discharge rate in the soil
Reference: API 651, Paragraph 7.3.5.1.4
15.In placing the anodes, how is better current distribution and
more uniform polarization obtained?
a) By distributing anodes uniformly around the tank or under the
membrane for new construction
b) By distributing anodes uniformly around the diked area or
under the tank for new construction
c) By distributing the cathodes uniformly around the tank or
under the tank for new construction
d) By distributing the anodes uniformly around the tank or under
the tank for new construction
Reference: API 651, Paragraph 7.3.5.1.4
16.How are impressed current anodes installed?
a) These anodes are installed either fully coated or in special
backfill material
b) These anodes are installed either bare or in special backfill
material
c) These anodes are installed either directly on the tank bottom
or in special backfill material
d) These anodes are installed either bare or in special liquid
filled cylinders
Reference: API 651, Paragraph 7.3.5.2.1.1
17.Impressed current anodes are connected with an insulated
conductor:
a) Singly to the positive terminal of a DC source
b) In groups to the positive terminal of a DC source
c) Either singly or in groups to the negative terminal of an DC
source
d) Either singly or in groups to the positive terminal of an DC
source
Reference: API 651, Paragraph 7.3.5.2.1.1
18.Of the following, which is not the preferred material for
impressed current anodes used in soil installations?
a) Graphite
b) Zinc
c) High silicon cast iron
d) Mixed metal oxide
Reference: API 651, Paragraph 7.3.5.2.1.2
19.Of the following, which is not the best material for
impressed current anodes used in water installations
a) Titanium
b) Tantalum
c) Copper
d) Platinized niobium
Reference: API 651, Paragraph 7.3.5.2.1.2
20.In an impressed current cathodic protection system, proper
groundbed design should do which of the following?
a) Avoid physical interference with existing facilities, provide
uniform current distribution, and avoid stray current interference
with off-site structures
b) Provide for direct connection with existing facilities,
provide uniform current distribution, and avoid stray current
interference with off-site structures
c) Avoid physical interference with existing facilities, provide
random current distribution, and avoid stray current interference
with off-site structures
d) Avoid physical interference with existing facilities, provide
uniform current distribution, and intercept stray current
interference with off-site structures
Reference: API 651, Paragraph 7.3.5.2.1.3
21.In an impressed current system why would additional anodes be
considered in the distributed anode design?
a) To provide uniform current distribution and provide back-up
anodes for replacement
b) To provide uniform current distribution and provide allowance
in case of isolated cathode connection failure or partial cathode
depletion
c) To provide uniform current distribution and provide allowance
in case of isolated anode connection failure or partial anode
depletion
d) To provide random current distribution and provide allowance
in case of isolated anode connection failure or partial anode
depletion
Reference: API 651, Paragraph 7.3.5.2.1.4
22.The current required for cathodic protection should be
calculated using the results of current requirement tests. In lieu
of this test, what is the generally accepted protective current
density?
a) Between 0.5 and +0.5 milliamps per square foot at ambient
conditions
b) Between 0.01 and 0.1 milliamps per square foot at ambient
conditions
c) Between 0.1 and 0.2 milliamps per square foot at ambient
conditions
d) Between 1 and 2 milliamps per square foot at ambient
conditions
Reference: API 651, Paragraph 7.3.5.2.2.1
23.The current requirement test can only be performed on
existing tanks using a temporary groundbed and an appropriate
source of direct current. Depending on the current required, the
power source can vary by how much?
a) From a 24 volt storage battery to a 300-amp welding unit
b) From a 12 volt storage battery to a 300-amp welding unit
c) From a 6 volt storage battery to a 300-amp welding unit
d) From a 1.2 volt solar panel to a 300-amp welding unit
Reference: API 651, Paragraph 7.3.5.2.2.1
24.During the current requirement test, how is maximum contact
of the tank bottom with the cushion material ensured?
a) The tank is filled to an adequate liquid level to ensure
maximum bottom contact
b) The tank is pressurized with an inert gas to ensure maximum
bottom contact
c) The tank is completely filled and subjected to a hydrostatic
pressure
d) The tank is emptied and concrete weights are installed and
the tank filled to half design liquid level
Reference: API 651, Paragraph 7.3.5.2.2.2
25.The voltage necessary to drive the required amount of current
depends largely on what two factors?
a) The type of power source available and the resistivity of the
soil
b) The number and location of anodes and the resistivity of the
soil
c) The number and location of cathodes and the resistivity of
the soil
d) The number and location of the anodes and the resistivity of
the special backfill
Reference: API 651, Paragraph 7.3.5.2.2.3
26.In an impressed current system, rectifiers with a moderated
excess capacity should be selected to allow for adjustments during
the life of the cathodic protection system and to prevent damage
due to overloads. What is the typical excess capacity of such
rectifiers?
a) 40% to 50%
b) 30% to 50%
c) 20% to 50%
d) 10% to 50%
Reference: API 651, Paragraph 7.3.5.2.3
27.Electrical grounding of electrical equipment is an essential
element in personnel safety.
a) True
b) False
Reference: API 651, Paragraph 7.3.6.2
28.Condition and type of coating (if any), minimum and maximum
water level in tank, compatibility of stored liquid with anodes and
cables, and internal inspection interval of tank which affects
design life are all factors that:
a) Influence the design of an external cathodic protection
system
b) Influence the design of a depressed current cathodic
protection system
c) Influence the design of an internal cathodic protection
system
d) Influence the design of the rectifier used in a cathodic
protection system
Reference: API 651, Paragraph 7.4.1
Answers to API-651 Section 7, Design of Cathodic Protection
Systems
Question NumberAnswer
1D
2B
3C
4A
5B
6C
7D
8D
9C
10B
11A
12C
13C
14B
15D
16B
17D
18B
19C
20A
21C
22D
23B
24A
25B
26D
27A
28C
Should you find a mistake or disagree with any answer listed,
please bring it to our attention for correction or clarification.
You can reach BAY Tech by phone at (610) 594-9036, by fax at (610)
594-2612, or by e-mail at [email protected].
Section 8 Criteria for Cathodic Protection
1.API-651 provides criteria for determining the adequacy of
cathodic protection of aboveground storage tanks. What document is
referenced for a more detailed description?
a) ASME Section V, Nondestructive Examination
b) API-Standard 650, Welded Steel Tanks for Oil Storage
c) API-Standard 653, Tank Inspection, Repair, Alteration, and
Reconstruction
d) NACE RP-01-69
Reference: API-651, Paragraph 8.2.1
2.In determining if adequate cathodic protection is being
achieved, which of the following would be correct?
a) A negative (cathodic) potential of at least 850 mV with
cathodic current applied
b) A positive (cathodic) potential of at least 850 mV with
cathodic current applied
c) A negative (cathodic) potential of at least 85.0 mV with
cathodic current applied
d) A positive (cathodic) potential of at least 85.0 mV with
cathodic current applied
Reference: API-651, Paragraph 8.2.2.1
3.How must the required negative potential be measured?
a) This potential shall be measured with respect to a saturated
copper/copper sulfate reference electrode (CSE) contacting the
metal tank bottom
b) This potential shall be measured with respect to a saturated
copper/copper sulfate reference electrode (CSE) contacting the
electrolyte
c) This potential shall be measured with respect to a saturated
copper/copper sulfate reference electrode (CSE) contacting the
metal casing of the rectifier
d) This potential shall be measured with respect to a saturated
copper/copper sulfate reference electrode (CSE) contacting the
positive terminal of the power source
Reference: API-651, Paragraph 8.2.2.1
4.In determining if adequate cathodic protection is being
achieved, which of the following would be correct?
a) Negative polarized potential of at least 8.50 mV relative to
a CSE
b) Negative polarized potential of at least 85.0 mV relative to
a CSE
c) Negative polarized potential of at least 850 mV relative to a
CSE
d) Negative polarized potential of at least .850 mV relative to
a CSE
Reference: API-651, Paragraph 8.2.2.2
5.Name a common method of measuring polarized potential.
a) Measuring the distance between the tank bottom and the
anode
b) Measuring the AC current relative to the DC current
c) Using the instant on method
d) Using the instant off method
Reference: API-651, Paragraph 8.2.2.2
6.In determining if adequate cathodic protection is being
achieved, which of the following would be correct?
a) A minimum of 1000 mV of cathodic polarization measured
between the tank bottom metallic surface and a standard reference
electrode contacting the electrolyte
b) A minimum of 850 mV of cathodic polarization measured between
the tank bottom metallic surface and a standard reference electrode
contacting the electrolyte
c) A minimum of 100 mV of cathodic polarization measured between
the tank bottom metallic surface and a standard reference electrode
contacting the electrolyte
d) A minimum of -0.85 mV of cathodic polarization measured
between the tank bottom metallic surface and a standard reference
electrode contacting the electrolyte
Reference: API-651, Paragraph 8.2.2.3
7.The standard method of determining the effectiveness of
cathodic protection on a tank bottom is the __________
measurement
a) Resistivity
b) DC current
c) Tank-to-soil
d) Interference current
Reference: API-651, Paragraph 8.3.1
8.How is the tank-to-soil potential measurement performed?
a) This measurement is performed using a low-impedance voltmeter
and a stable, reproducible reference electrode contacting the
electrolyte
b) This measurement is performed using a high-impedance
voltmeter and a stable, regenerative reference electrode contacting
the electrolyte
c) This measurement is performed using a high-impedance
voltmeter and a stable, reproducible reference electrode contacting
the electrolyte
d) This measurement is performed using a high-impedance
voltmeter and an unstable, non-reproducible reference electrode
contacting the electrolyte
Reference: API-651, Paragraph 8.3.1
9.Tank-to-soil potential measurements are typically taken with
current applied; however, corrections for ______ in the soil must
be made.
a) IW drop(s)
b) IR drop(s)
c) ER drop(s)
d) IE drop(s)
Reference: API-651, Paragraph 8.3.2
10.Correction for IR drop in the soil is often necessary for
measurements made at the tank perimeter even if the reference
electrode is placed immediately adjacent to the tank. This is
especially true if ______ is/are close to the tank.
a) Distributed anodes
b) The cathodic protection power supply rectifier
c) The sacrificial anode
d) The DC power supply (battery)
Reference: API-651, Paragraph 8.3.2
11.Monitoring the actual structure-to-soil potential under the
tank should be considered. How can this be accomplished?
a) Permanently installed reference electrode or by burying
reference electrode every 20 feet around the perimeter of the
tank
b) Inserting a reference electrode under the tank through a
perforated tube or attaching a reference electrode to the tank
shell
c) Permanently installed reference electrode or by inserting a
reference electrode under the tank through a perforated tube
d) Permanently installed bare copper wire connected to the tank
bottom or by inserting a reference electrode under the tank through
a perforated tube
Reference: API-651, Paragraph 8.3.4
12.Other standard reference electrodes may be substituted for
the saturated copper/copper sulfate reference electrode. Which of
the following is not a common substitute?
a) Reference electrode ( Zinc, Voltage ( +0.25
b) Reference electrode ( Saturated KCI calomel Voltage (
-0.78
c) Reference electrode ( Silver/silver chloride Voltage (
-0.80
d) Reference electrode ( Aluminum alloy (5% zinc) Voltage (
+0.08
Reference: API-651, Paragraph 8.4 and Table 4
Answers to API-651 Section 8, Criteria for Cathodic
Protection
Question NumberAnswer
1D
2A
3B
4C
5D
6C
7C
8C
9B
10A
11C
12D
Should you find a mistake or disagree with any answer listed,
please bring it to our attention for correction or
clarification.
BAY Technical Associates, Inc. has attempted to provide answers
developed from paragraphs of the respective Code, Standard, or
Recommended Practice.
You can reach BAY Tech by phone at (610) 594-9036, by fax at
(610) 594-2612, or by
e-mail at [email protected].
Section 9 - Installation of Cathodic Protection Systems
1.Installation of cathodic protection systems shall be in strict
accordance with the drawings and specifications. Exceptions may be
made only with the approval of which of the following?
a) The API-653 Inspector or personnel qualified and trained by
the Inspector
b) The National Board Inspector or personnel qualified and
trained by the Inspector
c) The owner, operator, or personnel qualified by the owner or
operator
d) The manufacturer of the tank or the authorized representative
of the tank manufacturer
Reference: API-651, Paragraph 9.1.2
2.Packaged galvanic anodes should be back-filled with
______.
a) Compacted special backfill material such as coke breeze
b) Compacted sand
c) Compacted limestone or clam shell backfill material
d) Compacted native soil
Reference: API-651, Paragraph 9.2.1
3.How may galvanic anodes, used to protect the internal surfaces
of tank bottoms, be installed?
a) Bolted or welded to the tank bottom
b) Laid on the tank bottom at specific intervals around the
perimeter and in the center
c) Held in place with a special adhesive or welded
d) Held in place by epoxy coating that will adhere to the tank
bottom
Reference: API-651, Paragraph 9.2.3
4.When installing galvanic anodes, care must be taken during the
backfilling operation to
a) Ensure the limestone or clamshell backfill is not
disturbed
b) Prevent damage to the lead wires and connections
c) Ensure the proper impervious membrane has been installed
under the anode
d) Prevent damage to the AC/DC rectifier
Reference: API-651, Paragraph 9.2.5
5.Which if the following is a true statement with regards to
installing galvanic anodes?
a) It is customary to carry the anode to the site by the lead
wire to ensure its tightness
b) The lead wire should only be long enough to reach the tank
bottom with no slack
c) Anodes should not be carried or lowered into the excavation
by the lead wires
d) The anode should be stored in a container of water until it
is placed in the excavation
Reference: API-651, Paragraph 9.2.5
6.In an impressed current cathodic protection system, care must
be taken not to crack or damage the anode during handling and
installation. Of the following, which would be a true
statement?
a) Anodes with very small cracks near the bottom of the anode
may be used without repair
b) Cracked anodes should be inspected to ensure the insulation
on the lead wires is not damaged before installing the anode
c) Anodes with cracks greater than 0.0625" in width shall not be
used
d) Cracked anodes should not be used
Reference: API-651, Paragraph 9.3.1.1
7.How can the life of an impressed current anode be
increased?
a) By installing a timing device that activates the current at
thirty-second intervals
b) Properly installing the backfill material
c) Use a substitute anode material
d) Using AC current instead of DC current
Reference: API-651, Paragraph 9.3.1.2
8.Of the following, which is not a principal point that needs to
be observed in the installation of impressed current anodes?
a) The anode should be installed so that at least one side is in
contact with the soil
b) Buried connections must be protected against the entrance of
moisture
c) Anodes and cable should be installed at a sufficient depth to
protect against accidental damage
d) Care should be taken to protect the cable connection to the
anode
Reference: API-651, Paragraph 9.3.1.3
9.For a typical vertical anode installation, the hole is
excavated ____ inches in diameter by approximately ______ feet
deep.
a) Six to ten,five to ten
b) Eight to twelve, ten to twenty
c) Twelve to eighteen, twelve to twenty-four
d) Eighteen to twenty-four, eighteen to thirty
Reference: API-651, Paragraph 9.3.2.1
10.When it is necessary to install an impressed current anode in
the horizontal position, a layer of crushed coke breeze is laid in
the trench and the anode is laid on top of the coke breeze.
Compacted native soil is then filled in on top of the anode.
a) True
b) False
Reference: API-651, Paragraph 9.3.2.2
11.For impressed current cathodic protection systems, when would
installation of the anode in the horizontal position be acceptable
or practical?
a) Where rock is encountered at a shallow depth or where soil
resistivity decreases markedly with depth
b) Where sand is encountered at a shallow depth or where soil
resistivity decreases markedly with depth
c) Where rock is encountered at a shallow depth or where soil
resistivity increases markedly with depth
d) Where sand is encountered at a shallow depth or where soil
resistivity increases markedly with depth
Reference: API-651, Paragraph 9.3.2.2
12.To improve current distribution to the center of the tank in
an impressed current cathodic protection system, it may be
desirable to do which of the following?
a) Install fifty percent more anodes
b) Extend the shallow groundbed an additional twenty-five
percent greater diameter around the tank
c) Use AC current instead of DC current
d) Install anodes in holes drilled at an angle under the
perimeter of the tank bottom
Reference: API-651, Paragraph 9.3.2.3
13.In situations where a deep groundbed installation is
required, why is it important to consider the environmental aspects
of this type of installation?
a) The groundbed may be located in contaminated soil, which
could allow contamination of the atmosphere
b) The groundbed installation may fracture bedrock and permit
the release of radon contamination
c) The groundbed installation may be located through underground
aquifers
d) The groundbed installation may cause cracking of foundations
of nearby structures during the drilling process
Reference: API-651, Paragraph 9.3.3
14.An impressed current cathodic protection system is installed;
the installing contractor connected the positive connection of the
rectifier to the tank. Is this a satisfactory installation?
a) Yes it does not matter how the leads are connected
b) No the positive lead should have been connected to anode so
the tank bottom would be the anode
c) Yes the connection is correct the tank bottom will act as the
anode as intended
d) No the connection is incorrect, the tank bottom will now act
as the anode resulting in rapid corrosion of the tank bottom
Reference: API-651, Paragraph 9.3.4.3
15.What is the preferred means of connecting the negative
rectifier lead wire to the structure to be protected?
a) A powder weld connection (Cadweld, Thermite, or
equivalent)
b) Brazed
c) Soldered
d) Any arc welding process
Reference: API-651, Paragraph 9.3.4.4
16.All positive cable connections and wire splices should be
waterproofed and covered with electrical insulating material. What
should be done if mechanical connections are used?
a) Mechanical connections should be buried to protect them from
vandalism
b) Mechanical connections should not be buried
c) Mechanical connections should be buried to protect them from
accidental damage
d) Mechanical connections should not be used for rectifier
installation
Reference: API-651, Paragraph 9.3.4.4
17.Underground splices of the positive lead wire to the
groundbed should be ______.
a) Braided and soldered
b) Made up with mechanical splices
c) Avoided
d) Close to the surface for ease of maintenance
Reference: API-651, Paragraph 9.3.5.2
18.One of the problems with monitoring cathodic protection
systems on the tank bottom is the inability to place a portable
reference electrode in close proximity to the underside. How can
this situation be remedied during new construction of a tank?
a) Permanently installed reference electrodes and lead wires to
the roof support structure where provided
b) Installing polyvinyl chloride or fiber reinforced plastic
pipe for use in profiling the tank-to-soil potential from the
perimeter to the center
c) Installing polyvinyl chloride or terracotta pipe for use in
profiling the tank-to-soil potential from the perimeter to the
center
d) Installing perforated polyvinyl chloride or fiber reinforced
plastic pipe for use in profiling the tank-to-soil potential from
the perimeter to the center
Reference: API-651, Paragraph 9.9.4.4
19.For existing tanks, not scheduled for bottom repair or
replacement, how can installation of permanent reference electrodes
be accomplished?
a) Air lance or mechanical procedures
b) Water jetting or mechanical procedures
c) Steam blast or mechanical procedures
d) Controlled explosives or mechanical procedures
Reference: API-651, Paragraph 9.4.6
20.Why is it a good practice to install permanent test leads,
grounding lugs, or short pieces of cable for measuring tank-to-soil
potential?
a) Repeated contact with the tank by a knife or ice pick will
eventually puncture the tank
b) Repeated contact with the tank by a knife or ice pick can
cause short circuiting of the cathodic protection system
c) Repeated contact with the tank by a knife or ice pick can
cause early failure of the tank's paint system.
d) Repeated contact with the tank by a knife or ice pick can
cause stress risers due to cutting the tank surface
Reference: API-651, Paragraph 9.4.7
Answers to API-651 Section 9, Installation of Cathodic
Protection Systems
Question NumberAnswer
1C
2D
3A
4B
5C
6D
7B
8A
9B
10B
11C
12D
13C
14D
15A
16B
17C
18D
19B
20C
Should you find a mistake or disagree with any answer listed,
please bring it to our attention for correction or
clarification.
BAY Technical Associates, Inc. has attempted to provide answers
developed from paragraphs of the respective Code, Standard, or
Recommended Practice.
You can reach BAY Tech by phone at (610) 594-9036, by fax at
(610) 594-2612, or by
e-mail at [email protected].
Section 10 - Interference Currents
1.What can be a problem caused by the installation of a new
impressed current cathodic protection system?
a) A new impressed cathodic protection system may cause an
unacceptable drain on the electrical substation for the
refinery
b) A new impressed cathodic protection system may cause
interference with neighboring structures
c) A new impressed cathodic protection system may cause
interference with certain radio signals
d) A new impressed cathodic protection system may cause
interference with operating controls of nearby process units
Reference: API-651, Paragraph 10.1.1
2.What is the most common source of "constant current"
interference currents?
a) Rectifiers energizing nearby cathodic protection systems
b) Electromagnetic fields set up by the operation of very large
motors close to the cathodic protection system
c) Electromagnetic fields caused by transformers in nearby
substations
d) Electromagnetic fields caused by overhead high tension
wire
Reference: API-651, Paragraph 10.2.1
3.With regard to "fluctuating current", which of the following
is not a normal source for this type of stray current?
a) Underground mining electrical systems
b) Electric railways
c) Rapid transit systems
d) AC to DC rectifiers
Reference: API-651, Paragraph 10.2.2
4.During a corrosion control survey, the inspector noticed a
positive shift of the structure-to-soil potential on the affected
structure at a point where current may be discharged from the
affected structure. What would this indicate?
a) Interference from the cathodic protection system
rectifier
b) Interference from a nearby lighting circuit
c) Interference from a neighboring source
d) Interference from a galvanic anode system
Reference: API-651, Paragraph 10.3
5.Interference currents have been detected. How could this
problem be resolved?
a) Design, proper bonding, and use of sacrificial anodes
b) Design, relocation of the tank, use of sacrificial anodes
c) Design, proper bonding, removal of cathodic protection
system
d) Design, proper bonding, different choice of coating on the
structure
Reference: API-651, Paragraph 10.4.1
Answers to API-651 Section 10, Interference Currents
Question NumberAnswer
1B
2A
3D
4C
5A
Should you find a mistake or disagree with any answer listed,
please bring it to our attention for correction or
clarification.
BAY Technical Associates, Inc. has attempted to provide answers
developed from paragraphs of the respective Code, Standard, or
Recommended Practice.
You can reach BAY Tech by phone at (610) 594-9036, by fax at
(610) 594-2612, or by
e-mail at [email protected].
Section 11 - Operation and Maintenance of Cathodic Protection
Systems
1.Why is it important to conduct potential surveys when there is
an adequate liquid level in a tank?
a) Bottom-to-electrolyte potential readings may indicate
adequate protection for the portion of the tank in contact with the
soil but when the tank is full and all of the bottom is in contact,
protection may not be sufficient
b) Bottom-to-anode potential readings may indicate adequate
protection for the portion of the tank in contact with the soil but
when the tank is full and all of the bottom is in contact,
protection may not be sufficient
c) Bottom-to-cathode potential readings may indicate adequate
protection for the portion of the tank in contact with the soil but
when the tank is full and all of the bottom is in contact,
protection may not be sufficient
d) Bottom-to-electrolyte potential readings may indicate
adequate protection for the portion of the tank in contact with the
soil but when the tank is full and all of the bottom is in contact,
protection may be far more than necessary
Reference: API-651, Paragraph 11.1.3
2.Measurements of the native structure-to-soil potential should
be made ________.
a) Immediately after any cathodic protection system is
energized
b) Within two days after any cathodic protection system is
energized
c) Within 6 months after any cathodic protection system is
energized
d) Prior to energizing a new cathodic protection system
Reference: API-651, Paragraph 11.3.1
3.After a system has been energized, it may take _____ for
polarization to a steady state to take place.
a) Two and a half years
b) One year
c) Several months
d) Fifteen minutes
Reference: API-651, Paragraph 11.3.1
4.To ensure the effectiveness of cathodic protection, how often
should cathodic protection surveys be taken?
a) Every two years
b) Annually
c) Bi-annually
d) Quarterly
Reference: API-651, Paragraph 11.3.2
5.How often should all sources of impressed current be
checked?
a) At intervals not exceeding two years
b) At intervals not exceeding one year
c) At intervals not exceeding two months
d) At intervals not exceeding two weeks
Reference: API-651, Paragraph 11.3.3.1
6.Tank bottoms shall be examined for evidence of corrosion at
least once each year by conducting an internal inspection and
taking coupon cutouts.
a) True
b) False
Reference: API-651, Paragraph 11.3.3.4
7.Records to demonstrate the need for corrosion control measures
should be retained for
a) 5 years
b) 10 years
c) 15 years
d) As long as the facility remains in service
Reference: API-651, Paragraph 11.4.7
8.Records related to the effectiveness of cathodic protection
should be retained for a ______ period unless a shorter period is
specifically permitted by regulation
a) 5 years
b) 10 years
c) 15 years
d) As long as the facility remains in service
Reference: API-651, Paragraph 11.4.7
Answers to API-651 Section 11, Operation and Maintenance of
Cathodic Protection Systems
Question NumberAnswer
1A
2D
3C
4B
5C
6B
7D
8A
Should you find a mistake or disagree with any answer listed,
please bring it to our attention for correction or clarification.
You can reach BAY Tech by phone at (610) 594-9036, by fax at (610)
594-2612, or by e-mail at [email protected].
API-653 Exam Prep CourseBAY Technical Associates, Inc.(610)
594-9036