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NACE CP2 exam questions and answers
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NACE CP2 exam questions and answers
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NACE CP2 exam questions and answersoxidation - 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)?
,NACE CP2 exam questions and answers
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)
,NACE CP2 exam questions and answers
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.
, NACE CP2 exam questions and answers
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
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