AMPP NACE Corrosion Technologist Exam Questions 1-
200 with Verified Answers and Rationales | Complete
Study Guide
QUESTION 1
What is the primary driving force for corrosion in an electrochemical cell?
A) Resistance in the electrolyte
B) Potential difference between anode and cathode
C) Temperature of the environment
D) pH of the solution
ANSWER: B) Potential difference between anode and cathode
Rationale: The potential difference (voltage) between the anode and cathode creates the
electromotive force that drives electron flow through the external circuit and ion flow
through the electrolyte, which is the fundamental driving force for corrosion. Without this
potential difference, no corrosion current would flow. Temperature and pH affect the rate
but do not provide the primary driving force.
,QUESTION 2
Which of the following is the anode reaction in the corrosion of iron in an acidic
solution?
A) Fe → Fe²⁺ + 2e⁻
B) 2H⁺ + 2e⁻ → H₂
C) Fe²⁺ + 2e⁻ → Fe
D) O₂ + 2H₂O + 4e⁻ → 4OH⁻
ANSWER: A) Fe → Fe²⁺ + 2e⁻
Rationale: In the corrosion of iron, the anodic reaction involves the oxidation of iron metal
to ferrous ions with the release of electrons. This is the half-cell reaction where metal
dissolves. Options B and D are cathodic reactions (reduction), and Option C is the reverse
of corrosion (electroplating).
QUESTION 3
The Nernst equation is used to calculate:
A) Corrosion rate
B) Electrode potential under non-standard conditions
C) Passivation potential
D) Polarization resistance
,ANSWER: B) Electrode potential under non-standard conditions
Rationale: The Nernst equation relates the electrode potential to the standard electrode
potential, temperature, and activities (or concentrations) of the species involved in the
electrochemical reaction. It is expressed as E = E° - (RT/nF)ln(Q), where Q is the reaction
quotient. It is not used directly for corrosion rate, passivation potential, or polarization
resistance calculations.
QUESTION 4
What type of corrosion is characterized by localized attack at grain boundaries?
A) Pitting corrosion
B) Crevice corrosion
C) Intergranular corrosion
D) Galvanic corrosion
ANSWER: C) Intergranular corrosion
Rationale: Intergranular corrosion occurs preferentially along grain boundaries due to the
presence of impurities, segregation of alloying elements, or precipitation of secondary
phases at grain boundaries, making them anodic relative to the grain interiors. This is
distinct from pitting (localized surface attack), crevice (attack in shielded areas), and
galvanic (dissimilar metal) corrosion.
, QUESTION 5
Which of the following metals is most susceptible to stress corrosion cracking (SCC) in
chloride environments?
A) Carbon steel
B) Aluminum alloys
C) Austenitic stainless steels
D) Copper alloys
ANSWER: C) Austenitic stainless steels
Rationale: Austenitic stainless steels (particularly 304 and 316) are highly susceptible to
chloride-induced stress corrosion cracking at temperatures above approximately 60°C
when tensile stresses are present. While other alloys can suffer SCC, the combination of
chlorides and tensile stress is particularly aggressive to austenitic stainless steels, leading
to transgranular cracking.
QUESTION 6
The term "passivation" refers to:
A) Complete prevention of corrosion
B) Formation of a protective oxide film on metal surface
C) Removal of corrosion products
D) Application of a protective coating
200 with Verified Answers and Rationales | Complete
Study Guide
QUESTION 1
What is the primary driving force for corrosion in an electrochemical cell?
A) Resistance in the electrolyte
B) Potential difference between anode and cathode
C) Temperature of the environment
D) pH of the solution
ANSWER: B) Potential difference between anode and cathode
Rationale: The potential difference (voltage) between the anode and cathode creates the
electromotive force that drives electron flow through the external circuit and ion flow
through the electrolyte, which is the fundamental driving force for corrosion. Without this
potential difference, no corrosion current would flow. Temperature and pH affect the rate
but do not provide the primary driving force.
,QUESTION 2
Which of the following is the anode reaction in the corrosion of iron in an acidic
solution?
A) Fe → Fe²⁺ + 2e⁻
B) 2H⁺ + 2e⁻ → H₂
C) Fe²⁺ + 2e⁻ → Fe
D) O₂ + 2H₂O + 4e⁻ → 4OH⁻
ANSWER: A) Fe → Fe²⁺ + 2e⁻
Rationale: In the corrosion of iron, the anodic reaction involves the oxidation of iron metal
to ferrous ions with the release of electrons. This is the half-cell reaction where metal
dissolves. Options B and D are cathodic reactions (reduction), and Option C is the reverse
of corrosion (electroplating).
QUESTION 3
The Nernst equation is used to calculate:
A) Corrosion rate
B) Electrode potential under non-standard conditions
C) Passivation potential
D) Polarization resistance
,ANSWER: B) Electrode potential under non-standard conditions
Rationale: The Nernst equation relates the electrode potential to the standard electrode
potential, temperature, and activities (or concentrations) of the species involved in the
electrochemical reaction. It is expressed as E = E° - (RT/nF)ln(Q), where Q is the reaction
quotient. It is not used directly for corrosion rate, passivation potential, or polarization
resistance calculations.
QUESTION 4
What type of corrosion is characterized by localized attack at grain boundaries?
A) Pitting corrosion
B) Crevice corrosion
C) Intergranular corrosion
D) Galvanic corrosion
ANSWER: C) Intergranular corrosion
Rationale: Intergranular corrosion occurs preferentially along grain boundaries due to the
presence of impurities, segregation of alloying elements, or precipitation of secondary
phases at grain boundaries, making them anodic relative to the grain interiors. This is
distinct from pitting (localized surface attack), crevice (attack in shielded areas), and
galvanic (dissimilar metal) corrosion.
, QUESTION 5
Which of the following metals is most susceptible to stress corrosion cracking (SCC) in
chloride environments?
A) Carbon steel
B) Aluminum alloys
C) Austenitic stainless steels
D) Copper alloys
ANSWER: C) Austenitic stainless steels
Rationale: Austenitic stainless steels (particularly 304 and 316) are highly susceptible to
chloride-induced stress corrosion cracking at temperatures above approximately 60°C
when tensile stresses are present. While other alloys can suffer SCC, the combination of
chlorides and tensile stress is particularly aggressive to austenitic stainless steels, leading
to transgranular cracking.
QUESTION 6
The term "passivation" refers to:
A) Complete prevention of corrosion
B) Formation of a protective oxide film on metal surface
C) Removal of corrosion products
D) Application of a protective coating
