NACE CP2 COMPREHENSIVE
EXAMINATION TEST VERIFIED QUESTIONS
AND ACCURATE ANSWERS
●● reduction
Answer: gain of electrons, negative charged atoms (cathode)
●● forms of corrosion
Answer: 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)
●● High PH
Answer: Low hydrogen, alkaline, easy polarization
●● Low PH
Answer: high hydrogen, acidic, harder to polarize
●● High oxygen/High Hydrogen concentration
Answer: harder to polarize, work at the cathode only, called cathodic
depolarizers.
,●● factors affecting corrosion
Answer: 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
●● polarization
Answer: a. corrosion current reduces with polarization
b. polarization increases with CP current applied
c. Occurs at surface of both anode and cathode.
●● shielding
Answer: a. shorted casings
b. proximity of other structures
c. reinforced concrete
●● amphoteric materials
Answer: corrode at low and high pH
●● on potential
,Answer: native + polarization + IR drop
●● polarized potential (off)
Answer: native + polarization
●● kirchoff's laws
Answer: a. voltage (series circuits)
b. current (parallel circuits)
●● faraday's law
Answer: W=KIT
relates weight loss of metal in a corrosion cell with time and current
flow.
●● rate of corrosion
Answer: directly proportional to current flow
●● cathodic protection limitations
Answer: -shielding issues
-attenuation
-interference
-excessive current density
, -contact with other metals (shorts)
●● measurement methods
Answer: true voltage reading
voltmeter reading
% error calculations
effect of voltmeter resistance
IR correction methods
●● test stations
Answer: allow electrical connection to structure for potential
measurements and bonds.
Spans allow current and direction (IR drop).
inistall during construction
●● pH
Answer: 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.
●● RECTIFIER
EXAMINATION TEST VERIFIED QUESTIONS
AND ACCURATE ANSWERS
●● reduction
Answer: gain of electrons, negative charged atoms (cathode)
●● forms of corrosion
Answer: 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)
●● High PH
Answer: Low hydrogen, alkaline, easy polarization
●● Low PH
Answer: high hydrogen, acidic, harder to polarize
●● High oxygen/High Hydrogen concentration
Answer: harder to polarize, work at the cathode only, called cathodic
depolarizers.
,●● factors affecting corrosion
Answer: 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
●● polarization
Answer: a. corrosion current reduces with polarization
b. polarization increases with CP current applied
c. Occurs at surface of both anode and cathode.
●● shielding
Answer: a. shorted casings
b. proximity of other structures
c. reinforced concrete
●● amphoteric materials
Answer: corrode at low and high pH
●● on potential
,Answer: native + polarization + IR drop
●● polarized potential (off)
Answer: native + polarization
●● kirchoff's laws
Answer: a. voltage (series circuits)
b. current (parallel circuits)
●● faraday's law
Answer: W=KIT
relates weight loss of metal in a corrosion cell with time and current
flow.
●● rate of corrosion
Answer: directly proportional to current flow
●● cathodic protection limitations
Answer: -shielding issues
-attenuation
-interference
-excessive current density
, -contact with other metals (shorts)
●● measurement methods
Answer: true voltage reading
voltmeter reading
% error calculations
effect of voltmeter resistance
IR correction methods
●● test stations
Answer: allow electrical connection to structure for potential
measurements and bonds.
Spans allow current and direction (IR drop).
inistall during construction
●● pH
Answer: 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.
●● RECTIFIER
