NACE CP2 - EXAM

NACE 2008 Student Manual!

START OF CHAPTER 1

Corrosion is an electrochemical process involving

A) flow of protons and electrons

B) flow of neutrons and ions

C) flow of protons and ions

D) flow of electrons and ions

E) flow of resistance and resistivity

d

Metal loss or corrosion occurs at the

A) cathode

B) anode

C) electronic path

D) metallic path

b

What are the four parts of the corrosion cell

A) anode, resistor, electrolyte, metallic path

B) anode, cathode, electron, electronic path

C) anode, cathode, electrolyte, metallic path

c

True or False (t or f):

Ions exist only in the electrolyte?

t

Electrons flow in a corrosion cell by which of the following paths?

A) anode to cathode via electrolyte

B) cathode to anode via electronic path

C) anode to cathode via electronic path

c

At the cathodic surface in a corrosion cell, the electrons from the ____ meet ____ ions from the solution.

A) cathode, hydrogen

B) cathode, OH-

C) anode, hydrogen

D) anode, OH-

c

Oxidation of the metal occurs at the ____

surfaces and reduction of ____ ions occurs at the ____.

A) anodic, hydrogen, cathodes

B) cathode, OH-, anodic

C) anodic, OH-, cathodes

D) cathode, anodic, electrolyte

E) cathode, hydrogen, electrolyte

a

True or false

Is oxidation necessarily associated with oxygen?

f

Current flow in a corrosion cell flows which path:

A) anode to metallic path to cathode

B) anode to electronic path to cathode

C) cathode to metallic to anode

D) cathode to electrolyte to anode

E) anode to electrolyte to cathode

Voltage is the measure of the electrochemical difference between two electrodes

in an electrolyte

e

_____ is the measure of the electrochemical difference between two electrodes

in an electrolyte

A) current

B) resistance

C) error

D) ohms

E) ohms-cm

F) voltage

f

The ________

represents the reversible work to move a unit charge from the electrode surface

through the solution to the reference electrode

A) current potential

B) electrode potential

C) resistance potential

D) ohms potential

E) Faraday potential

b

Metals occur in nature in the form of various chemical compounds referred to as

___

A) ores

B) anodic metals

C) cathodic metals

D) carbohydrates

a

The amount of energy required by a metal during the refining

process determines the ___ or _______ of the metal.

A) current, active state

B) voltage, active state

C) active resistance, voltage

D) resistance, active state

E) current, active resistance

b

During the refining stage of metal the ____ the energy, the more ____

the metal and the more tendency it has to corrode.

A) higher, inactive

B) lower, active

C) higher, active

D) lower, inactive

c

What is the most common iron ore?

A) hemophite

B) hematite

C) magnesium

D) calcium

E) aluminum

b

True or false

Iron is considered thermodynamically unstable?

t

True or false

Gold is more noble than zinc?

t

Which of the following metals is most active?

A) magnesium

B) copper

C) iron

D) nickel

E) platinum

a

Electromotive force (emf), is ____ in sign and magnitude to the electrode potential of the ___ less the electrode potential of the ____.

A) unequal, cathode, anode

B) unequal, anode, cathode

C) equal, cathode, anode

D) equal, anode, cathode

d

The driving force for electrochemical corrosion is ____

A) current

B) voltage

C) resistance

D) ohms

E) siemens-cm

b

In relation to a corrosion cell, ____ is the net transfer of electric charge per unit time

A) current

B) voltage

C) resistance

D) ohms

E) siemens-cm

a

If a metallic path connects two electrodes inside an electrolyte, the ____ difference will cause a

____ to flow between them

A) current, voltage

B) resistance, current

C) resistance, voltage

D) voltage, current

E) current, resistance

d

The more useful method of organizing metals in order of their tendency to corrode is _____

A) emf series

B) pgp series

C) nuclear series

D) electron series

E) galvanic series

e

The ____ expresses the exact electromotive force of a cell in terms of the activities of products and reactants of the cell

A) Ernest Equation

B) Faraday Equation

C) Ohm's Law Equation

D) Nernst Equation

E) Uniform Equation

d

Standard conditions for pure metals in the

emf series are based on one unit activity of metal ions in the electrolyte at ___ C

with no impurities in the metal or electrolyte and with reference to a standard

____ electrode.

A) 25, hydrogen

B) 35, hydrogen

C) 25, CSE

D) 35, CSE

E) 25, SSC

F) 35, SSC

a

The ____ the concentration of metal ions in the electrolyte, the ____ the metal.

A) lower, less active

B) higher, less active

C) lower, more active

D) higher, less active

b

In reference to the temperature in a corrosion cell, in most cases, electrode at the _____ temperature becomes the ____

A) lower, anode

B) higher, cathode

C) lower, cathode

D) higher, anode

d

During metal fabrication of structures, highly stressed areas of a metal will tend to be at ____ energy levels, thus more ____ than less stressed areas

A) higher, active

B) lower, active

C) higher, inactive

D) lower, inactive

a

True or False (t or f):

Corrosion cells may form because of differences in the electrolyte

t

____ cells are responsible for much of the corrosion that take place in soils, particularly in bare or poorly coated pipe

A) concentration

B) steady state

C) carbon

D) dynamic

E) telluric

a

In many cases in naturally occurring soils, a portion of pipe lying in the more _____ soil is the ____ and in the less ____soil is the ___.

A) inductive, anode / inductive, cathode

B) inductive, cathode / inductive, anode

C) conductive, anode / conductive, cathode

D) conductive, cathode /conductive, anode

c

The two most common types of concentration cells involved in promoting corrosion are ____ and ____.

A) oxygen, nonmettalic ion

B) oxygen, calcium

C) lack of oxygen, metal ion

D) oxygen, metal ion

d

What is the most common of the cathodic depolarizers, that can maintain and promote a cathodic reaction?

A) CO2

B) oxygen

C) carbon

D) OH-

E) Hydrogen

b

Most corrosion on pipelines is on the ____ portion of the pipe

A) sides

B) top

C) bottom

c

If a pipe is running through a section of pavement and through a section of non pavement:

A) anode is the metal outside the pavement, the cathode is the metal under the pavement

B) anode is the metal under the pavement, the cathode is the metal outside the pavement

C) cathode is the metal under the pavement, the anode is the metal outside the pavement

b

In a metal ion concentration cell, the surface in contact with ____ concentration of metal ions acts as the ____

A) lower, anode

B) lower, cathode

C) higher, anode

D) higher cathode

a

Theoretically, the potential of a structure changes by about ____mV for each pH unit

A) 40

B) 50

C) 20

D) 70

E) 60

e

The corrosion potential of a metal might be -500mV in an environment with a pH of 7, but the corrosion potential might be ____ at a pH of 8?

A) -440mV

B) -660mV

C) -300mV

D) -560mV

d

True or false (t or f)

an acidic pH can be harmful to concrete, such as reinforced concrete structures?

t

A pH of less than ____ is considered to be harmful to concrete?

A) 4

B) 6

C) 5

D) 2

E) 8

c

The rate of corrosion is directly ____ to ____ flow?

A) inproporinate, current

B) inproporinate, voltage

C) proportional, voltage

D) proportional, current

d

If a 1 Amp CP system must last 40 years and the electrochemical equivalent for silicon chromium cast iron anodes is 0.75 lb/A-yr, how many pounds of anodes are needed?

A) 50lbs

B) 35lbs

C) 25 lbs

D) 45lbs

E) 30lbs

e

All things being equal, the greater the magnitude of the difference between two voltages of metals, the ____ the current flow and rate of corrosion

A) higher

B) lower

a

True or False ( t or f)

Magnesium will corrode at a slower rate when connected to steel rather than zinc?

f

Which reference electrode is considered a primary reference electrode because it is used to determine the potential of other secondary reference electrodes that are better suited for field use?

A) CSE

B) Ag/AgCI

C) Calomel

D) Zinc

E) SHE

e

Most common used reference electrode for measuring potentials of underground structures?

A) CSE

B) Ag/AgCI

C) Calomel

D) Zinc

E) SHE

a

True or false (t or f)

The potential of a reference electrode in the sun can decrease from 10 to 50mV versus an electrode kept in the dark?

t

Which reference electrode is mostly commonly used in seawater?

A) CSE

B) Ag/AgCI

C) Calomel

D) Zinc

E) SHE

b

Which reference electrode is mostly commonly used in concrete structures?

A) CSE

B) Ag/AgCI

C) Calomel

D) Zinc

E) SHE

a

Which of the following is primarily a laboratory electrode?

A) CSE

B) Ag/AgCI

C) Calomel

D) Zinc

c

True or False (t or f)

The potential of a STATIONARY reference electrode should be checked from time to time

with a portable reference electrode that is known to be accurate under "no

current" conditions.

t

As current is impressed on a metal over time, where does polarization occur?

A) at the anode and the cathode

B) at the anode

C) at the cathode

a

Polarization _____ the potential difference between the anode and the cathode and by Ohm's Law, the current ___ and the corrosion rate ____ until an equilibrium is reached

A) lowers, drops, decreases

B) increases, increases, decreases

C) lowers, increases, decreases

D) lowers, drops, decreases

d

Depolarizers include:

I dissolved oxygen

II microbiological activity

III water flow

A) only I

B) only II

C) I and II

D) I, II , III

d

The name for the current that exists during the steady state of polarization is called the _____ of the system

A) telluric current

B) dynamic current

C) corrosion current

D) mixed potential current

E) closed current

c

The potential normally measured between the polarized cathode potential and the polarized anode potential

A) mixed potential

B) corrosion potential

C) corrosion current

D) open circuit potential

a

_____ are the potentials of the cathode and anode when the corrosion current is zero

A) mixed potentials

B) corrosion potentials

C) corrosion current potentials

D) open circuit potentials

d

______ is the result of the reaction steps at the structure/electrolyte interface including the actual transfer of charge

A) activation polarization

B) concentration polarization

C) mixed polarization

D) reactant polarization

a

In concentrated acids, _______ polarization predominates

A) activation polarization

B) concentration polarization

C) mixed polarization

D) reactant polarization

a

_______ is the result of reaction steps involving the diffusion of reactants up to the reaction products away from the reaction surface

A) activation polarization

B) concentration polarization

C) mixed polarization

D) reactant polarization

b

Anything that causes a depletion of available reactants or a buildup of reaction products results in a ____ in the reaction rate and an

_____ in concentration polarization.

A) decrease, increase

B) increase, decrease

a

If the slowest step in the overall process involves waiting for arrival of reactants or the removal of reaction products, the reaction is under __________ control.

A) activation polarization

B) concentration polarization

b

If the slowest step in the overall reaction process is is on the metal surface or in the charge transfer reaction the process is under _____

A) activation polarization

B) concentration polarization

a

__________ usually predominates in electrolytes where the

concentration of the reactants is low, as with dilute solutions, or there is a

buildup of reaction products from activation polarization or in stagnant

environments.

A) activation polarization

B) concentration polarization

b

As polarization ____ , current _____

A) increases, decreases

B) decreases, decreases

C) increases, increases

D) decreases, increases

c

An increase in ions will result in a ____ in resistivity

A) increase

B) decrease

b

The effect of current concentrated on a small area will be ____ than the effect of

the same amount of current on a ____ area. A coated structure will polarize more rapidly than a bare structure

A) larger, larger

B) less, larger

C) greater, smaller

D) smaller, smaller

E) greater, larger

e

True or False (t or f)

A small anode and a large cathode is desirable

f

A(n) ____ in temperature has a tendency to ____ chemical reactions, which _____ the electrodes and _____ current

A) increase, increase, depolarizes, increases

B) increase, increase, depolarizes, decrease

C) decrease, decrease, polarize, increase

D) decrease, increase, polarize, decrease

a

A(n) ____ in temperature results in a(n) ____ in polarization

A) increase, decrease

B) increase, increase

C) decrease, increase

D) decrease, decrease

c

____ movement results in a ____ in polarization and a(n) _____ in current

A) decreased, decrease, decrease

B) decreased, increase, decrease

C) increased, increase, decrease

D) increased, decrease, decrease

E) increased, increase, increase

d

A(n) _____ in the metal ion concentration of the anode metal results in a(n) ____ in polarization of the anode and a(n) ____ in current

A) increase, decrease, decrease

B) decrease, decrease, decrease

C) decrease, increase, decrease

D) increase, increase, decrease

E) decrease, decrease, increase

e

Polarization of the cathode can be affected by the concentration of cathodic

reactants, such as _____ or _____ ions

A) CO2, OH-

B) oxygen, OH-

C) carbon, OH-

D) oxygen, hydrogen

d

In regards to cathodic reactants, a(n) _____ in the concentration of either of the reactants of oxygen or hydrogen will _____ polarization of the cathode and _____ current and vice versa

A) increase, decrease, decrease

B) decrease, decrease, decrease

C) increase, decrease, increase

D) increase, increase, decrease

E) decrease, decrease, increase

c

Passivity can be defined as the

A) gain of chemical reactivity

B) polarization of chemical reactivity

C) loss of chemical reactivity

D) depolarization of molecular reactivity

E) polarization of molecular reactivity

c

The ____ region is when a slight increase in corrosion potential causes the corrosion current to increase

A) transpassive

B) passive

C) nonpassive

D) active

d

The ____ region is when the corrosion potential increases to a certain point, however, the corrosion current suddenly decreases and remain essentially constant

A) transpassive

B) passive

C) nonpassive

D) active

b

The ____ region occurs if the potential is increased sufficiently thus current again increases

A) transpassive

B) passive

C) nonpassive

D) active

a

For the active (or nonpassivating) metal, as corrosion potential _____,

corrosion current ____, more or less logarithmically (or linearly on a semi-

log graph).

A) increases, increases

B) decreases, decreases

C) increases, decreases

D) decreases, increases

a

This type of film which forms naturally on most metals when they are exposed to the air, can provide substantial protection against further attack by many environments

A) ore

B) oxide

C) reductant

D) selimum

b

Type of corrosion with an even loss of metal over the entire area or a large area of the structure

A) Galvanic attack

B) intergranular attack

C) selective leaching

D) velocity phenomena

E) pitting

F) crevice corrosion

G) uniform attack

g

This type of corrosion occurs where two tightly spaced

surfaces - either two metals or a metal and nonmetal - are exposed to a

corroding environment. Holes, gasket surfaces, lap joints, surface deposits, and

crevices are likely places for this type of corrosion.

A) Galvanic attack

B) intergranular attack

C) selective leaching

D) velocity phenomena

E) pitting

F) crevice corrosion

G) uniform attack

f

This corrosion occurs when two dissimilar metals are

connected. The potential of the two metals creates a voltage difference, the driving force for corrosion.

A) Galvanic attack

B) intergranular attack

C) selective leaching

D) velocity phenomena

E) pitting

F) crevice corrosion

G) uniform attack

a

Localized corrosion that occurs over a small area of the metal surface and leaves holes in the surface.

A) Galvanic attack

B) intergranular attack

C) selective leaching

D) velocity phenomena

E) pitting

F) crevice corrosion

G) uniform attack

e

This is a local corrosion attack at the grain boundaries

of an alloy. It is caused by a difference in element composition near the

boundaries, compared to the rest of the alloy.

A) Galvanic attack

B) intergranular attack

C) selective leaching

D) velocity phenomena

E) pitting

F) crevice corrosion

G) uniform attack

b

This type of corrosion involves the certain removal of

one of the elements from an alloy.

A) Galvanic attack

B) intergranular attack

C) selective leaching

D) velocity phenomena

E) pitting

F) crevice corrosion

G) uniform attack

c

This corrosion is associated with rapid movement of a

corrosive fluid over a metal, removing corrosion products.

A) Galvanic attack

B) intergranular attack

C) selective leaching

D) velocity phenomena

E) pitting

F) crevice corrosion

G) uniform attack

d

results from the reaction of

the metal with a corrosive environment and the presence of a stress

A) Galvanic attack

B) intergranular attack

C) selective leaching

D) velocity phenomena

E) environmental cracking

F) crevice corrosion

G) uniform attack

d

In general, hydrogen is generated in neutral environments at -

____ mV CSE

A) 1,000

B) 1,044

C) 1,500

D) 1,200

b

For aluminum, the polarized potential must be kept below -

_____ mV CSE to avoid alkali corrosion

A) 1,000

B) 1,044

C) 1,500

D) 1,200

d

For titanium, the maximum

potential is ____ mV ssc to prevent hydriding

A) 800

B) 700

C) 1,500

D) 1,200

b

For prestressed concrete, polarized potentials more negative than -____ mV should be avoided

A) 1,000

B) 1,044

C) 1,500

D) 1,200

a

The cracking of a metal under an applied tensile stress in the presence of a corrosive environment

A) stress corrosion cracking

B) intergranular attack

C) selective leaching

D) velocity phenomena

E) pitting

a

Stress Corrosion Cracking occurs in a narrow potential range of ______ at a pH between ______ , and is more likely at ____ temperatures

A) -525 to -725, 5 and 7, more

B) -625 to -825, 7 and 9.5, less

C) -525 to -725, 8 and 10.5, more

D) -625 to 700, 8 and 10.5, less

c

True or False (t or f)

MIC exist under non anaerobic conditions (presence of great oxygen)

f

In relation to MIC, consumption of _____ at the structure surface _____ the steel at cathodic areas and permits more rapid consumption of the metal by galvanic corrosion cells

A) hydrogen, polarizes

B) hydrogen, depolarizes

C) OH-, polarizes

D) OH-, depolarizes

END OF CHAPTER 1

b

START OF CHAPTER2:

Corrosion of the metal will cease once the applied cathodic protection current

_______ the corrosion current.

A) equals

B) equals or exceeds

C) falls below

b

As the potentials of the ___ sites polarize

toward the potentials of the ____ sites, corrosion current is ____.

A) anodic, cathodic, increase

B) cathodic, anodic, reduced

C) cathodic, anodic, increase

D) anodic, cathodic, decrease

b

Polarization occurs in a step-like manner with the more

____ or ____ sites polarizing first.

A) positive, anodic

B) positive, cathodic

C) negative, anodic

D) negative, cathodic

b

To mitigate corrosion, all existing cathode sites must be electronegatively

polarized to a potential ____ to the open circuit potential of the most ___

____ potential existing on the structure.

A) equal, inactive, cathode

B) unequal, active, anode

C) unequal, inactive, cathode

D) equal, active, anode

d