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


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


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


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


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

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

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

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

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

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

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

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

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

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

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