Question 1

Susceptibility to sulfidation is determined by the _________ of the material.
A) Corrosion resistance
B) Tensile strength
C) Chemical composition
D) Yield strength

Accepted Answer

The susceptibility to sulfidation is determined by the chemical composition of the material, particularly the amount of sulfur present in the environment. Corrosion resistance, tensile strength, and yield strength may also be important factors in the overall performance of the material, but they are not the sole determinants of sulfidation susceptibility.

Question 2

With sour water corrosion, corrosion increases with __________ NH4HS concentration and __________ velocity.
A) Increasing, Decreasing
B) Increasing, Increasing
C) Decreasing, Decreasing
D) Decreasing, Increasing

Accepted Answer

Sour water corrosion occurs when NH4HS (ammonium hydrosulfide) is present in water and reacts with the metal surface to form hydrogen sulfide gas. As the concentration of NH4HS increases, so does the amount of hydrogen sulfide gas produced, leading to increasing corrosion. Additionally, as fluid velocity increases, the NH4HS is more likely to react with the metal surface, also leading to increasing corrosion. Therefore, the correct answer is B - increasing NH4HS concentration and increasing velocity both lead to increased sour water corrosion.

Question 3

_________ acid is most often used as a catalyst in polymerization units.
A) Polythionic
B) Naphthenic
C) Phosphoric
D) Sulfuric

Accepted Answer

The answer of _________ acid is most often used as...

Question 4

With sour water corrosion, streams with a pH below ________ indicate the presence of a strong acid.
A) 7.0
B) 5.5
C) 6.0
D) 4.5

Accepted Answer

A pH below 4.5 indicates the presence of a strong acid, which is a condition that can lead to sour water corrosion.

Question 5

________ injection downstream of the desalter is another common method used to reduce the amount of HCl going overhead.
A) Hydrogen
B) Nitrogen
C) Water
D) Caustic

Accepted Answer

Caustic injection (also known as alkaline injection) is the preferred method for neutralizing the HCl in the overhead stream because it reacts with the acid to form salt and water, which are easily separated from the hydrocarbon product. Hydrogen injection can also be used, but it requires careful control to avoid over-reduction and the formation of hazardous hydrogen sulfide (H2S) gas. Nitrogen and water injection do not have any neutralizing properties and can actually increase the volatility of the HCl, making the problem worse.

Question 6

Sour water corrosion in _________ containing environments may be accompanied by carbonate SCC.
A) H₂O
B) H₂S
C) CO₂
D) O₂

Accepted Answer

Sour water corrosion occurs in environments where carbon dioxide is present, such as in petroleum refining processes. This corrosion may also be accompanied by carbonate stress corrosion cracking.

Question 7

NAC may be found in hot hydrocarbon streams downstream of the crude and vacuum units, __________ any hydrogen mix point.
A) Upstream of
B) Downstream of
C) Adjacent to
D) Around

Accepted Answer

NAC (Naphthenic Acid Corrosion) is typically found upstream of any hydrogen mix point because hydrogen can neutralize naphthenic acids, reducing the risk of corrosion.

Question 8

Phosphoric acid corrosion is usually found in ________ areas.
A) High velocity
B) Low velocity
C) High temperature
D) Low temperature

Accepted Answer

Phosphoric acid corrosion is commonly encountered in low velocity areas such as heat exchangers and condenser tubes where stagnant acid can remain in contact with the metal surface. High velocity areas are less likely to experience phosphoric acid corrosion because the acid is flushed away. Temperature is not a determining factor in the occurrence of phosphoric acid corrosion.

Question 9

A minimum of ________ to ______ molybdenum is needed in an alloy to resist naphthenic acid corrosion.
A) 2%, 3%
B) 1 ½ %, 2 ½ %
C) 2%, 2 ½ %
D) 1%, 2%

Accepted Answer

A minimum of 2% to 2 ½ % molybdenum is needed in an alloy to resist naphthenic acid corrosion.

Question 10

Oxygen and iron in the wash water injected into reactor effluent can lead to __________ corrosion and fouling.
A) Increased
B) Decreased
C) Substantial
D) Minimal

Accepted Answer

The injection of oxygen and iron in the wash water can increase corrosion and fouling in the reactor effluent. Oxygen can act as an oxidizing agent, accelerating corrosion processes in the system, while iron can generate solid deposits due to its reactivity with other components present in the effluent. Therefore, the injection of these substances in the wash water should be carefully controlled to prevent undesirable effects on the equipment and the process performance.

Question 11

Type 304L SS is satisfactory for phosphoric acid concentration of 100% up to about _________. Type 321 is required from there to 225º F.
A) 140º F
B) 150º F
C) 100º F
D) 120º F

Accepted Answer

The answer of Type 304L SS is satisfactory for phosphoric...

Question 12

SCC tendency ________ towards the alkaline pH region
A) Decreases
B) Increases
C) Remains constant
D) Varies

Accepted Answer

SCC is the somatic cell count, which refers to the concentration of white blood cells in milk. The tendency of SCC towards the alkaline pH region decreases because at higher pH levels, the cell membranes of white blood cells are more likely to rupture, causing them to disintegrate and release DNA into the milk, increasing its SCC. Therefore, low pH levels in milk are preferred as they help maintain the integrity of the white blood cells and prevent an increase in SCC.

Question 13

300 Series SS can be used for sour water service at temperatures below ____________, where Chloride SCC is not likely.
A) 120º F
B) 140º F
C) 150º F
D) 175º F

Accepted Answer

The correct temperature limit for using 300 Series SS for sour water service without being susceptible to Chloride SCC is 140º F. Therefore, option B (140º F) is the correct choice. Options A (120º F), C (150º F), and D (175º F) are incorrect temperature limits.

Question 14

The regenerator reboiler and the regenerator are areas where the temperature and __________ of the amine stream are the highest and can cause significant corrosion problems.
A) Pressure
B) Stress
C) Turbulence
D) Concentration

Accepted Answer

The answer of The regenerator reboiler and the regenerator are...

Question 15

Cadmium and lead will cause LME on _____________.
A) Copper alloys
B) 300 Series SS
C) Aluminum alloys
D) High strength steel

Accepted Answer

The answer of Cadmium and lead will cause LME on...

Question 16

In HF service, carbon steel operating above ________ should be closely monitored for loss in thickness and may need to be upgraded to Alloy 400.
A) 150º F
B) 175º F
C) 160º F
D) 200º F

Accepted Answer

Carbon steel operating above 150º F should be closely monitored for loss in thickness and may need to be upgraded to Alloy 400.

Question 17

In HF service, carbon steel forms a protective _________ scale in dry concentrated acid. Loss of the protective scale through high velocities or turbulence will result in greatly accelerated corrosion rates.
A) Chloride
B) Fluoride
C) Iron sulfide
D) Iron oxide

Accepted Answer

In HF (hydrofluoric acid) service, carbon steel forms a protective fluoride scale in dry concentrated acid. This fluoride layer helps protect the steel from further corrosion.

Question 18

It is generally accepted that stresses approaching _________ are required for SCC to occur so that thermal stress relief is effective in preventing caustic SCC.
A) MAWP
B) Yield
C) Creep range
D) Critical

Accepted Answer

Stress corrosion cracking (SCC) typically occurs at stress levels approaching the yield strength of the material, making thermal stress relief effective in preventing caustic SCC.

Question 19

High temperature H₂ / H₂S corrosion damage is minimized by using alloys with high _________ content.
A) Carbon
B) Molybdenum
C) Chromium
D) Stainless

Accepted Answer

High chromium content is effective in reducing high temperature H₂/H₂S corrosion damage due to its ability to form a protective oxide layer on the surface of the alloy.

Question 20

The presence of _________ can destabilize the scale and turn it into a nonprotective scale.
A) H₂S
B) O₂
C) H₂
D) H₂O

Accepted Answer

The answer of The presence of _________ can destabilize the...

Exam 1: Corrosion and Materials

Susceptibility to sulfidation is determined by the _________ of the material.

With sour water corrosion, corrosion increases with NH4HS concentration and velocity.

_________ acid is most often used as a catalyst in polymerization units.

With sour water corrosion, streams with a pH below ________ indicate the presence of a strong acid.

________ injection downstream of the desalter is another common method used to reduce the amount of HCl going overhead.

Sour water corrosion in _________ containing environments may be accompanied by carbonate SCC.

NAC may be found in hot hydrocarbon streams downstream of the crude and vacuum units, __________ any hydrogen mix point.

Phosphoric acid corrosion is usually found in ________ areas.

A minimum of __ to molybdenum is needed in an alloy to resist naphthenic acid corrosion.

Oxygen and iron in the wash water injected into reactor effluent can lead to __________ corrosion and fouling.

Type 304L SS is satisfactory for phosphoric acid concentration of 100% up to about _________. Type 321 is required from there to 225º F.

SCC tendency ________ towards the alkaline pH region

300 Series SS can be used for sour water service at temperatures below ____________, where Chloride SCC is not likely.

The regenerator reboiler and the regenerator are areas where the temperature and __________ of the amine stream are the highest and can cause significant corrosion problems.

Cadmium and lead will cause LME on _____________.

In HF service, carbon steel operating above ________ should be closely monitored for loss in thickness and may need to be upgraded to Alloy 400.

In HF service, carbon steel forms a protective _________ scale in dry concentrated acid. Loss of the protective scale through high velocities or turbulence will result in greatly accelerated corrosion rates.

It is generally accepted that stresses approaching _________ are required for SCC to occur so that thermal stress relief is effective in preventing caustic SCC.

High temperature H₂ / H₂S corrosion damage is minimized by using alloys with high _________ content.

The presence of _________ can destabilize the scale and turn it into a nonprotective scale.