NACE CP2 Study Guide
1. oxidation: loss of electrons, positive charge atoms (anode)
2. reduction: gain of electrons, negative charged atoms (cathode)
3. 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)
4. High PH: Low hydrogen, alkaline, easy polarization
5. Low PH: high hydrogen, acidic, harder to polarize
6. High oxygen/High Hydrogen concentration: harder to polarize, work
at the cathode only, called cathodic depolarizers.
7. factors affecting corrosion: A. anything that affects polarization.
1/
, (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
8. polarization: a. corrosion current reduces with polarization
b. polarization increases with CP current applied
c. Occurs at surface of both anode and cathode.
9. shielding: a. shorted casings
b. proximity of other structures
c. reinforced concrete
10.amphoteric materials: corrode at low and high pH
11.on potential: native + polarization + IR drop
12.polarized potential (off): native + polarization
13.kirchoff's laws: a. voltage (series circuits)
b. current (parallel circuits)
14.faraday's law: W=KIT
2/
,relates weight loss of metal in a corrosion cell with time and current
flow.
15.rate of corrosion: directly proportional to current flow
16.cathodic protection limitations: -shielding issues
-attenuation
-interference
3/
, -excessive current density
-contact with other metals (shorts)
17.measurement methods: true voltage
reading voltmeter reading
% error calculations
effect of voltmeter
resistance IR correction
methods
18.test stations: allow electrical connection to structure for potential
measure- ments and bonds.
Spans allow current and direction (IR
drop). inistall during construction
19.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.
20.RECTIFIER: - positive to anode
-negative to structure
4/
1. oxidation: loss of electrons, positive charge atoms (anode)
2. reduction: gain of electrons, negative charged atoms (cathode)
3. 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)
4. High PH: Low hydrogen, alkaline, easy polarization
5. Low PH: high hydrogen, acidic, harder to polarize
6. High oxygen/High Hydrogen concentration: harder to polarize, work
at the cathode only, called cathodic depolarizers.
7. factors affecting corrosion: A. anything that affects polarization.
1/
, (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
8. polarization: a. corrosion current reduces with polarization
b. polarization increases with CP current applied
c. Occurs at surface of both anode and cathode.
9. shielding: a. shorted casings
b. proximity of other structures
c. reinforced concrete
10.amphoteric materials: corrode at low and high pH
11.on potential: native + polarization + IR drop
12.polarized potential (off): native + polarization
13.kirchoff's laws: a. voltage (series circuits)
b. current (parallel circuits)
14.faraday's law: W=KIT
2/
,relates weight loss of metal in a corrosion cell with time and current
flow.
15.rate of corrosion: directly proportional to current flow
16.cathodic protection limitations: -shielding issues
-attenuation
-interference
3/
, -excessive current density
-contact with other metals (shorts)
17.measurement methods: true voltage
reading voltmeter reading
% error calculations
effect of voltmeter
resistance IR correction
methods
18.test stations: allow electrical connection to structure for potential
measure- ments and bonds.
Spans allow current and direction (IR
drop). inistall during construction
19.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.
20.RECTIFIER: - positive to anode
-negative to structure
4/
