NACE CP2 Exam 2023 / 153 Questions And
Answers/ Verified/ Graded A+
oxidation - -loss of electrons, positive charge atoms (anode)
-reduction - -gain of electrons, negative charged atoms (cathode)
-forms of corrosion - -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 - -Low hydrogen, alkaline, easy polarization
-Low PH - -high hydrogen, acidic, harder to polarize
-High oxygen/High Hydrogen concentration - -harder to polarize, work at the cathode
only, called cathodic depolarizers.
-factors affecting corrosion - -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 - -a. corrosion current reduces with polarization
b. polarization increases with CP current applied
c. Occurs at surface of both anode and cathode.
-shielding - -a. shorted casings
,b. proximity of other structures
c. reinforced concrete
-amphoteric materials - -corrode at low and high pH
-on potential - -native + polarization + IR drop
-polarized potential (off) - -native + polarization
-kirchoff's laws - -a. voltage (series circuits)
b. current (parallel circuits)
-faraday's law - -W=KIT
relates weight loss of metal in a corrosion cell with time and current flow.
-rate of corrosion - -directly proportional to current flow
-cathodic protection limitations - --shielding issues
-attenuation
-interference
-excessive current density
-contact with other metals (shorts)
-measurement methods - -true voltage reading
voltmeter reading
% error calculations
effect of voltmeter resistance
IR correction methods
-test stations - -allow electrical connection to structure for potential measurements and
bonds.
Spans allow current and direction (IR drop).
,inistall during construction
-pH - -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 - -- 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
-Voltmeter and Ammeter
-Surge Protection
-Filters
Esecondary = (Eprimary x Secondary turns) / primary turns
-Reference electrode location - -the reference electrode should be placed as close to the
structure as practical. (underground piping or tanks- over the center of the structure,
multiple readings along the structure as required)
internal surfaces of storage tanks, waterfront and offshore structures (as close to the
wall as possible)
-impressed current vs sacrificial - -impressed current- higher current, better control
sacrificial- no power required, less maintenance, easy to install, less land
-AC considerations - -capacitance, inductance, and resistance
, hazardous AC potential - 15 Vac
Safe method of connecting ground0 cable to ground then to pipe
arcing hazards
corrosion rates from AC (current density)
switching or pulse rectifiers
-Reference cells - -CuCuSO4- most common, (soil, fresh water)
AgAgCL - seawater
Calomel- lab
Hydrogen - standard (lab)
zinc- stationary
-Cathodic Protection - -protect the cathode
attempts to bring the cathode potential as negative as the anode potential
NACE criteria- what are the exceptions?
-high temperature
-bacteria
-sulfides
-acid environments
-dissimilar metals
Answers/ Verified/ Graded A+
oxidation - -loss of electrons, positive charge atoms (anode)
-reduction - -gain of electrons, negative charged atoms (cathode)
-forms of corrosion - -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 - -Low hydrogen, alkaline, easy polarization
-Low PH - -high hydrogen, acidic, harder to polarize
-High oxygen/High Hydrogen concentration - -harder to polarize, work at the cathode
only, called cathodic depolarizers.
-factors affecting corrosion - -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 - -a. corrosion current reduces with polarization
b. polarization increases with CP current applied
c. Occurs at surface of both anode and cathode.
-shielding - -a. shorted casings
,b. proximity of other structures
c. reinforced concrete
-amphoteric materials - -corrode at low and high pH
-on potential - -native + polarization + IR drop
-polarized potential (off) - -native + polarization
-kirchoff's laws - -a. voltage (series circuits)
b. current (parallel circuits)
-faraday's law - -W=KIT
relates weight loss of metal in a corrosion cell with time and current flow.
-rate of corrosion - -directly proportional to current flow
-cathodic protection limitations - --shielding issues
-attenuation
-interference
-excessive current density
-contact with other metals (shorts)
-measurement methods - -true voltage reading
voltmeter reading
% error calculations
effect of voltmeter resistance
IR correction methods
-test stations - -allow electrical connection to structure for potential measurements and
bonds.
Spans allow current and direction (IR drop).
,inistall during construction
-pH - -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 - -- 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
-Voltmeter and Ammeter
-Surge Protection
-Filters
Esecondary = (Eprimary x Secondary turns) / primary turns
-Reference electrode location - -the reference electrode should be placed as close to the
structure as practical. (underground piping or tanks- over the center of the structure,
multiple readings along the structure as required)
internal surfaces of storage tanks, waterfront and offshore structures (as close to the
wall as possible)
-impressed current vs sacrificial - -impressed current- higher current, better control
sacrificial- no power required, less maintenance, easy to install, less land
-AC considerations - -capacitance, inductance, and resistance
, hazardous AC potential - 15 Vac
Safe method of connecting ground0 cable to ground then to pipe
arcing hazards
corrosion rates from AC (current density)
switching or pulse rectifiers
-Reference cells - -CuCuSO4- most common, (soil, fresh water)
AgAgCL - seawater
Calomel- lab
Hydrogen - standard (lab)
zinc- stationary
-Cathodic Protection - -protect the cathode
attempts to bring the cathode potential as negative as the anode potential
NACE criteria- what are the exceptions?
-high temperature
-bacteria
-sulfides
-acid environments
-dissimilar metals
