NACE CP2 EXAM QUESTIONS AND ANSWERS
1. oxidation
ANS loss of electrons, positive charge atoms (anode)
2. reduction
ANS gain of electrons, negative charged atoms (cathode)
3. forms of corrosion
ANS uniform, crevice, galvanic (dissimilar metals) if two metals have to be couple then best to
couple metals close together in the galvanic series, pitting, intergranular, selective leaching
(dezincification, graphitization), velocity phenomena, environmental cracking (corrosion fatigue, hydrogen
embrittlement,
SCC (Carbonates/bicarbonates)
4. High PH
ANS Low hydrogen, alkaline, easy polarization
5. Low PH
ANS high hydrogen, acidic, harder to polarize
6. High oxygen/High Hydrogen concentration
ANS harder to polarize, work at the cathode only, called cathodic depolarizers.
,7. factors affecting corrosion
ANS A. anything that affects polarization. (temp. etc...)
B. concentration cells (oxygen, temp, etc.) In an oxygen concentration cell, what is the anode? (i.e. the
area with more or less oxygen?) In a metal ion cell, which area is the anode (i.e. the area with the
greater of lower concentration)?
C. Anaerobic bacteria (MIC) Absence of oxygen, depolarizer
8. polarization
ANS a. corrosion current reduces with polarization
b. polarization increases with CP current applied
c. Occurs at surface of both anode and cathode.
9. shielding
ANS a. shorted casings
b. proximity of other structures
c. reinforced concrete
10. amphoteric materials
ANS corrode at low and high Ph
11. on potential
ANS native + polarization + IR drop
,12. polarized potential (off)
ANS native + polarization
13. kirchoff's laws
ANS a. voltage (series circuits)
b. current (parallel circuits)
14. faraday's law
ANS W=KIT
relates weight loss of metal in a corrosion cell with time and current flow.
15. rate of corrosion
ANS directly proportional to current flow
16. cathodic protection limitations
ANS -shielding issues
-attenuation
-interference
-excessive current density
-contact with other metals (shorts)
17. measurement methods
ANS true voltage reading voltmeter reading
, % error calculations
effect of voltmeter
resistance IR correction
methods
18. test stations
ANS allow electrical connection to structure for potential measurements and bonds.
Spans allow current and direction (IR drop).
inistall during construction
19. pH
ANS measure of acidity(hydrogen ion
concentration) high pH is alkaline
low pH is acid
pH is a log function therefore each increase in pH is a factor of 10.
20. RECTIFIER
ANS - positive to anode
-negative to structure
- AC suppy
-AC circuit breaker
-Transformer (increase or decrease voltage)
-AC fuse
-rectifier bridge - diodes change AC to DC
1. oxidation
ANS loss of electrons, positive charge atoms (anode)
2. reduction
ANS gain of electrons, negative charged atoms (cathode)
3. forms of corrosion
ANS uniform, crevice, galvanic (dissimilar metals) if two metals have to be couple then best to
couple metals close together in the galvanic series, pitting, intergranular, selective leaching
(dezincification, graphitization), velocity phenomena, environmental cracking (corrosion fatigue, hydrogen
embrittlement,
SCC (Carbonates/bicarbonates)
4. High PH
ANS Low hydrogen, alkaline, easy polarization
5. Low PH
ANS high hydrogen, acidic, harder to polarize
6. High oxygen/High Hydrogen concentration
ANS harder to polarize, work at the cathode only, called cathodic depolarizers.
,7. factors affecting corrosion
ANS A. anything that affects polarization. (temp. etc...)
B. concentration cells (oxygen, temp, etc.) In an oxygen concentration cell, what is the anode? (i.e. the
area with more or less oxygen?) In a metal ion cell, which area is the anode (i.e. the area with the
greater of lower concentration)?
C. Anaerobic bacteria (MIC) Absence of oxygen, depolarizer
8. polarization
ANS a. corrosion current reduces with polarization
b. polarization increases with CP current applied
c. Occurs at surface of both anode and cathode.
9. shielding
ANS a. shorted casings
b. proximity of other structures
c. reinforced concrete
10. amphoteric materials
ANS corrode at low and high Ph
11. on potential
ANS native + polarization + IR drop
,12. polarized potential (off)
ANS native + polarization
13. kirchoff's laws
ANS a. voltage (series circuits)
b. current (parallel circuits)
14. faraday's law
ANS W=KIT
relates weight loss of metal in a corrosion cell with time and current flow.
15. rate of corrosion
ANS directly proportional to current flow
16. cathodic protection limitations
ANS -shielding issues
-attenuation
-interference
-excessive current density
-contact with other metals (shorts)
17. measurement methods
ANS true voltage reading voltmeter reading
, % error calculations
effect of voltmeter
resistance IR correction
methods
18. test stations
ANS allow electrical connection to structure for potential measurements and bonds.
Spans allow current and direction (IR drop).
inistall during construction
19. pH
ANS measure of acidity(hydrogen ion
concentration) high pH is alkaline
low pH is acid
pH is a log function therefore each increase in pH is a factor of 10.
20. RECTIFIER
ANS - positive to anode
-negative to structure
- AC suppy
-AC circuit breaker
-Transformer (increase or decrease voltage)
-AC fuse
-rectifier bridge - diodes change AC to DC
