NACE CP2 Key Concepts And Accurate
Answers 2025\2026 A+ Grade
oxidation
- accurate answers-loss of electrons, positive charge atoms (anode)
reduction
- accurate answers-gain of electrons, negative charged atoms (cathode)
forms of corrosion
- accurate answers-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
- accurate answers-Low hydrogen, alkaline, easy polarization
Low PH
- accurate answers-high hydrogen, acidic, harder to polarize
High oxygen/High Hydrogen concentration
- accurate answers-harder to polarize, work at the cathode only, called
cathodic depolarizers.
factors affecting corrosion
- accurate answers-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
- accurate answers-a. corrosion current reduces with polarization
b. polarization increases with CP current applied
c. Occurs at surface of both anode and cathode.
,shielding
- accurate answers-a. shorted casings
b. proximity of other structures
c. reinforced concrete
amphoteric materials
- accurate answers-corrode at low and high pH
on potential
- accurate answers-native + polarization + IR drop
polarized potential (off)
- accurate answers-native + polarization
kirchoff's laws
- accurate answers-a. voltage (series circuits)
b. current (parallel circuits)
faraday's law
- accurate answers-W=KIT
relates weight loss of metal in a corrosion cell with time and current flow.
rate of corrosion
- accurate answers-directly proportional to current flow
cathodic protection limitations
- accurate answers--shielding issues
-attenuation
-interference
-excessive current density
-contact with other metals (shorts)
measurement methods
- accurate answers-true voltage reading
voltmeter reading
% error calculations
effect of voltmeter resistance
IR correction methods
, test stations
- accurate answers-allow electrical connection to structure for potential
measurements and bonds.
Spans allow current and direction (IR drop).
inistall during construction
pH
- accurate answers-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
- accurate answers-- 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
- accurate answers-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
- accurate answers-impressed current- higher current, better control
sacrificial- no power required, less maintenance, easy to install, less land
Answers 2025\2026 A+ Grade
oxidation
- accurate answers-loss of electrons, positive charge atoms (anode)
reduction
- accurate answers-gain of electrons, negative charged atoms (cathode)
forms of corrosion
- accurate answers-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
- accurate answers-Low hydrogen, alkaline, easy polarization
Low PH
- accurate answers-high hydrogen, acidic, harder to polarize
High oxygen/High Hydrogen concentration
- accurate answers-harder to polarize, work at the cathode only, called
cathodic depolarizers.
factors affecting corrosion
- accurate answers-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
- accurate answers-a. corrosion current reduces with polarization
b. polarization increases with CP current applied
c. Occurs at surface of both anode and cathode.
,shielding
- accurate answers-a. shorted casings
b. proximity of other structures
c. reinforced concrete
amphoteric materials
- accurate answers-corrode at low and high pH
on potential
- accurate answers-native + polarization + IR drop
polarized potential (off)
- accurate answers-native + polarization
kirchoff's laws
- accurate answers-a. voltage (series circuits)
b. current (parallel circuits)
faraday's law
- accurate answers-W=KIT
relates weight loss of metal in a corrosion cell with time and current flow.
rate of corrosion
- accurate answers-directly proportional to current flow
cathodic protection limitations
- accurate answers--shielding issues
-attenuation
-interference
-excessive current density
-contact with other metals (shorts)
measurement methods
- accurate answers-true voltage reading
voltmeter reading
% error calculations
effect of voltmeter resistance
IR correction methods
, test stations
- accurate answers-allow electrical connection to structure for potential
measurements and bonds.
Spans allow current and direction (IR drop).
inistall during construction
pH
- accurate answers-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
- accurate answers-- 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
- accurate answers-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
- accurate answers-impressed current- higher current, better control
sacrificial- no power required, less maintenance, easy to install, less land
