NACE CP2 ALL EVALUATION TEST ANSWERS AND
QUESTIONS SURE A+
✔✔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
✔✔Isolation Requirement - ✔✔confine protection to protected structure thus limiting the
current required for protection.
use for stray current with care
✔✔continuity requirement - ✔✔bonds are necessary for continuity: mechanical fittings
(compression, bell & spigot, rebar etc.)
✔✔Impressed Current Anodes - ✔✔graphite
cast iron (high silicon chromium)
, mixed metal oxides
scrap iron
conductive polymer
cylindrical, tubular
soil..... backfilled in coke breeze
✔✔current span - ✔✔current in a pipe can be measured by taking a voltage drop across
a known length and either calibrating the section in question or using resistance from
tables.
unknown pipe size must be calibrated by using I/ deltamV or R= V/I using 4 wires
✔✔Sacrificial anode types - ✔✔magnesium
zinc
cylindrical, bullet, ribbon, bracelet
soil backfilled in gypsum, bentonite mixture to reduce contact resistance to soil and to
retain moisture
make sure to remove plastic shipping bag
✔✔small anode to large cathode ratio - ✔✔higher corrosion penetration rate
✔✔large anode to small cathode ratio - ✔✔lower corrosion penetration rate
✔✔4 elements of a corrosion cell - ✔✔Anode
Cathode
Metallic Patch
Electrolyte
✔✔Faraday's law calculates - ✔✔metal lost due to current over time
✔✔the stability of a copper-copper sulfate reference electrode does not vary with - ✔✔a
saturated solution of the copper ions.
✔✔if a digital meter displays a negative value while measure a voltage across a
resistor, it indicates - ✔✔
✔✔Which of the following are depolarizers?
QUESTIONS SURE A+
✔✔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
✔✔Isolation Requirement - ✔✔confine protection to protected structure thus limiting the
current required for protection.
use for stray current with care
✔✔continuity requirement - ✔✔bonds are necessary for continuity: mechanical fittings
(compression, bell & spigot, rebar etc.)
✔✔Impressed Current Anodes - ✔✔graphite
cast iron (high silicon chromium)
, mixed metal oxides
scrap iron
conductive polymer
cylindrical, tubular
soil..... backfilled in coke breeze
✔✔current span - ✔✔current in a pipe can be measured by taking a voltage drop across
a known length and either calibrating the section in question or using resistance from
tables.
unknown pipe size must be calibrated by using I/ deltamV or R= V/I using 4 wires
✔✔Sacrificial anode types - ✔✔magnesium
zinc
cylindrical, bullet, ribbon, bracelet
soil backfilled in gypsum, bentonite mixture to reduce contact resistance to soil and to
retain moisture
make sure to remove plastic shipping bag
✔✔small anode to large cathode ratio - ✔✔higher corrosion penetration rate
✔✔large anode to small cathode ratio - ✔✔lower corrosion penetration rate
✔✔4 elements of a corrosion cell - ✔✔Anode
Cathode
Metallic Patch
Electrolyte
✔✔Faraday's law calculates - ✔✔metal lost due to current over time
✔✔the stability of a copper-copper sulfate reference electrode does not vary with - ✔✔a
saturated solution of the copper ions.
✔✔if a digital meter displays a negative value while measure a voltage across a
resistor, it indicates - ✔✔
✔✔Which of the following are depolarizers?
