Senior Internal Corrosion Technologist
Certification Exam
1.
The dominant corrosion mechanism in wet gas pipelines with
CO₂ present is:
A. Uniform oxidation
B. CO₂ (sweet) corrosion producing carbonic acid
C. Caustic SCC
D. Sulfidation at high temperature
Answer: B
Explanation: CO₂ dissolves into water to form carbonic acid
(H₂CO₃), increasing corrosion on carbon steel.
2.
The main cathodic reaction in CO₂ corrosion at neutral pH is:
A. 2H⁺ + 2e⁻ → H₂
B. O₂ + 2H₂O + 4e⁻ → 4OH⁻
C. H₂CO₃ + e⁻ → HCO₃⁻ + H•
D. Fe²⁺ + 2e⁻ → Fe
Answer: B
Explanation: Oxygen reduction dominates when oxygen is
present; in deoxygenated systems, hydrogen evolution
becomes important.
,3.
The de Waard–Milliams model is used to predict:
A. Erosion rate in elbows
B. CO₂ corrosion rate on carbon steel
C. H₂S cracking threshold stress
D. Paint delamination risk
Answer: B
Explanation: Empirical model for sweet corrosion as a
function of temperature, pCO₂, and pH.
4.
Which factor most reduces CO₂ corrosion by promoting
FeCO₃ scale formation?
A. Low temperature
B. High shear
C. High Fe²⁺ and high temperature
D. Low pH and high Cl⁻
Answer: C
Explanation: Supersaturation of FeCO₃ (high Fe²⁺, higher T)
supports protective scale precipitation.
5.
In sour systems, the presence of H₂S can:
A. Always increase corrosion rate
B. Always decrease corrosion rate
C. Form FeS scales that may inhibit or under certain
conditions promote localized attack
,D. Have no effect
Answer: C
Explanation: FeS films can be protective or unstable (leading
to pitting/MIC synergy).
6.
A key indicator of MIC by SRB in production lines is:
A. White powdery deposits
B. Black, slimy tubercles and FeS
C. Blue-green copper salts
D. Yellow zinc salts
Answer: B
Explanation: SRB form iron sulfide and black biofilms.
7.
Internal corrosion in multiphase flow is most severe at:
A. Top of line in dry gas
B. Bottom of line where water and solids accumulate
C. Midline center
D. All locations equally
Answer: B
Explanation: Water phase settles at the invert carrying
corrosives and solids.
, 8.
Top-of-the-line corrosion (TLC) in wet gas condensate systems
is mainly driven by:
A. Chloride scaling
B. Water condensation of acid gases on a cool pipe wall
C. Graphitic corrosion
D. Oxygen ingress only
Answer: B
Explanation: Water condenses with CO₂/organic acids
forming acidic films on the upper wall.
9.
A critical water cut in oil pipelines indicates:
A. The minimum water fraction needed to transport sand
B. The water fraction below which water is entrained and not
separated (less internal corrosion)
C. The water fraction at which oxygen pick-up occurs
D. The maximum inhibitor dosage
Answer: B
Explanation: Below critical water cut, no continuous water
phase → corrosion risks drop.
10.
Localized corrosion risk increases substantially with:
A. Homogeneous flow regime
B. Stable FeCO₃ film
C. Under-deposit conditions (solids, biofilm)
Certification Exam
1.
The dominant corrosion mechanism in wet gas pipelines with
CO₂ present is:
A. Uniform oxidation
B. CO₂ (sweet) corrosion producing carbonic acid
C. Caustic SCC
D. Sulfidation at high temperature
Answer: B
Explanation: CO₂ dissolves into water to form carbonic acid
(H₂CO₃), increasing corrosion on carbon steel.
2.
The main cathodic reaction in CO₂ corrosion at neutral pH is:
A. 2H⁺ + 2e⁻ → H₂
B. O₂ + 2H₂O + 4e⁻ → 4OH⁻
C. H₂CO₃ + e⁻ → HCO₃⁻ + H•
D. Fe²⁺ + 2e⁻ → Fe
Answer: B
Explanation: Oxygen reduction dominates when oxygen is
present; in deoxygenated systems, hydrogen evolution
becomes important.
,3.
The de Waard–Milliams model is used to predict:
A. Erosion rate in elbows
B. CO₂ corrosion rate on carbon steel
C. H₂S cracking threshold stress
D. Paint delamination risk
Answer: B
Explanation: Empirical model for sweet corrosion as a
function of temperature, pCO₂, and pH.
4.
Which factor most reduces CO₂ corrosion by promoting
FeCO₃ scale formation?
A. Low temperature
B. High shear
C. High Fe²⁺ and high temperature
D. Low pH and high Cl⁻
Answer: C
Explanation: Supersaturation of FeCO₃ (high Fe²⁺, higher T)
supports protective scale precipitation.
5.
In sour systems, the presence of H₂S can:
A. Always increase corrosion rate
B. Always decrease corrosion rate
C. Form FeS scales that may inhibit or under certain
conditions promote localized attack
,D. Have no effect
Answer: C
Explanation: FeS films can be protective or unstable (leading
to pitting/MIC synergy).
6.
A key indicator of MIC by SRB in production lines is:
A. White powdery deposits
B. Black, slimy tubercles and FeS
C. Blue-green copper salts
D. Yellow zinc salts
Answer: B
Explanation: SRB form iron sulfide and black biofilms.
7.
Internal corrosion in multiphase flow is most severe at:
A. Top of line in dry gas
B. Bottom of line where water and solids accumulate
C. Midline center
D. All locations equally
Answer: B
Explanation: Water phase settles at the invert carrying
corrosives and solids.
, 8.
Top-of-the-line corrosion (TLC) in wet gas condensate systems
is mainly driven by:
A. Chloride scaling
B. Water condensation of acid gases on a cool pipe wall
C. Graphitic corrosion
D. Oxygen ingress only
Answer: B
Explanation: Water condenses with CO₂/organic acids
forming acidic films on the upper wall.
9.
A critical water cut in oil pipelines indicates:
A. The minimum water fraction needed to transport sand
B. The water fraction below which water is entrained and not
separated (less internal corrosion)
C. The water fraction at which oxygen pick-up occurs
D. The maximum inhibitor dosage
Answer: B
Explanation: Below critical water cut, no continuous water
phase → corrosion risks drop.
10.
Localized corrosion risk increases substantially with:
A. Homogeneous flow regime
B. Stable FeCO₃ film
C. Under-deposit conditions (solids, biofilm)
