1. A corrosion inhibitor is a substance which, when added to an environment, decreases the rate of attack by the environment.
a. True
b. False
2. Corrosion always results in the deposition of metal at the
a. Cathode
b. Anode
c. Both a and b d. Neither a nor b
3. Sea water is more corrosive than fresh water?
a. True
b. False
4. A chemical substance which, when added to an environment, decreases the rate of attack by that environment.
a. Galvanic cathode b. Galvanic anode c. Corrosion inhibitor d. Electrolyte
5. An ion is a neutral atom.
a. True
b. False
6. In seawater, which of the following metals is anodic with respect to steel?
a. Copper
b. Titanium
c. Zinc
d. Type 304 Stainless Steel
7. Corrosion rates generally increase when temperature increases.
a. True
b. False
8. Electrode potentials are sensitive to a. Temperature
b. Presence of depolarizers c. Both a and b
d. Neither a nor b
9. Nearly all metals exhibit crystalline structures.
a. True
b. False
10. In a galvanic couple, which of the following is likely to promote the most rapid corrosion reaction?
a. Large cathode area, small anode area b. Small cathode area, large anode area c. Polarized cathode
d. Cathodic protection
11. Metals conduct electricity through the flow of ions.
a. True
b. False
12. Which of the following is not an electrochemical cell?
a. A galvanic corrosion cell b. An active/passive cell c. A thermogalvanic cell d. None of the above
13. Water used to make concrete should be free of chemical contaminants.
a. True
b. False
14. Crevice corrosion
a. Occurs most commonly on film-protected metals b. Occurs where free access to environment is restricted c. Both a and b
d. Neither a nor b
15. Hydrogen induced cracking may occur at cathodes.
a. True
b. False
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16. Sacrificial coatings
a. Corrode instead of a steel substrate
b. Act as a barrier between the substrate and the corrosive medium c. Both a and b
d. Neither a nor b
17. Passivating inhibitors cause a shift in cathode potential, causing the cathode to become more positive.
a. True
b. False
18. Corrosion detection is used for
a. Safety
b. Cost effectiveness c. Both a and b d. Neither a nor b
19. Oxidizing anodic inhibitors require the presence of oxygen.
a. True
b. False
20. Silicates and phosphates are common oxygen scavengers.
a. True
b. False
Sample Questions - Senior Corrosion Technologist Open-book Examination Exercise II –excerpts from Corrosion Science/Cathodic Protection
1. According to the classic definition of cathodic protection, the object is to polarize a. anodic areas
b. cathodic areas c. both a and b d. neither a or b
2. In a basic corrosion cell, the electrode having the greatest tendency to give up electrons is the cathode.
a. True
b. False
3. Half cell potentials measured at the structure-to-electrolyte boundary are influenced by:
a. Surface chemistry
b. Concentration of metal ions
c. Flow of electric current to or from the structure d. All of the above
4. Polyphase powered cathodic protection rectifiers are more efficient than single phase units.
a. True
b. False
5. Which material is not a common impressed current anode:
a. graphite b. high silicon iron c. platinum clad titanium
d. aluminum
6. All cathodic protection systems require an external power source to drive the required current.
a. True
b. False
7. Usually the best choice of cathodic protection design for an un-isolated, bare piping system is
a. distributed galvanic anodes b. point-type impressed current c. point-type galvanic anodes d. distributed impressed current
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8. Attenuation along the anode header cable may be a significant factor in the design of an impressed current distributed anode system.
a. True
b. False
9. Calculate the service life of a galvanic anode system which is supplying 540 milliamperes of current and consists of six (6) 14.5 kg (32 lb.) anodes at 6 meter (20 feet) spacings.
Assume an output capacity of 1100 ampere-hours/kg.
a. 7.2 years
b. Less than one year c. 20.2 years
d. 23.5 years
10. The first step in designing an impressed current cathodic protection system is to size the D.C. output of the rectifier to be used.
a. True
b. False
11. The Wenner four pin method is the test method commonly used to calculate:
a. Cathodic polarization b. Soil resistivity c. Current attenuation d. None of the above
12. An advantage of an impressed current cathodic protection system is the availability of larger driving voltages, thereby providing flexibility of current output.
a. True
b. False
13. Estimate the resistance to earth of an anode bed 48.8 meters (160 feet) long in 6,000 ohm-cm soil consisting of 9 prepackaged impressed current anodes installed vertically on 6 meter (20 feet) centers. Each anode is 0.203 m (8 inch) diameter by 2.13 meters (7 feet) long. The bottom of each anode will be installed to a depth of 4.6 meters (15 feet) below grade.
a. 4.68 ohms b. 2.34 ohms c. 1.27 ohms d. 3.43 ohms
14. If a piping system is not isolated from other underground metallic structures, the amount of current required to protect that piping will be less than if it were isolated.
a. True
b. False
15. Which of the following is true of a galvanic anode cathodic protection system?
a. Structure is protected where current leaves the structure
b. Relies upon the natural difference in potential between two dissimilar metals to cause protection current to flow
c. Protective currents flow from the cathode through the soil to the pipe
d. Are used on large bare structures because of the galvanic anode system high current output
16. Cathodic protection system design life should be equal to structure design life.
a. True
b. False
17. Calculate the total current needed to protect:
6,363.6 square meters (68,500 sq. ft.) of pipeline surface area Coating efficiency of 70%
Soil resistivity of 10,000 ohm-cm
Design current density of 21.5 mA/square meter a. 0.75 amps
b. 41.0 amps c. 20.6 amps d. 68.5 amps
18. Knowledge of the presence of high strength steels in the structure to be protected is of importance to the cathodic protection design engineer.
a. True
b. False
19. The Wenner "four pin method" can be used to measure the resistivity of the environment for a deep well anode.
a. True
b. False
20. An impressed current cathodic protection system is operating at 10 volts and 15 amperes.
The total circuit resistance
a. cannot be identified with the data available b. is 0.66 ohms
c. is 0.06 ohms
d. can be changed by turning the rectifier up