Question 1

High strength, low allow steels such as A193-B7 bolts and compressor parts are susceptible to hydrogen stress cracking. A193-B7M bolts are susceptible if __________.

Accepted Answer

A193-B7M bolts are susceptible to hydrogen stress cracking if overtightened.

Question 2

Corrosion due to acidic sour water containing H₂S at a pH between 4.5 and 7.0 is called sour water corrosion. Carbon dioxide (CO₂) may also be present. Which of the following materials is susceptible to sour water corrosion?

Accepted Answer

Carbon steel is susceptible to sour water corrosion due to the acidic and corrosive nature of the environment. Stainless steel, including both 300 and 400 series, is more resistant to sour water corrosion but may still corrode in certain conditions. However, carbon steel is the most vulnerable.

Question 3

Which of the following materials is not susceptible to Cl SCC?

Accepted Answer

The answer of Which of the following materials is not...

Question 4

With decarburization, the decarburized layer will be free of carbide phases. Carbon steel will be ______.

Accepted Answer

Decarburization is the process of removing carbon from the surface of a steel. This can be done by heating the steel in an oxygen-rich atmosphere, which causes the carbon to react with the oxygen to form carbon dioxide gas. The decarburized layer will be free of carbide phases, which are hard and brittle compounds that can make the steel more difficult to work with. Annealing is a process of heating and cooling steel to soften it, quenching is a process of rapidly cooling steel to harden it, and pure iron is a type of steel that does not contain any carbon.

Question 5

___________ is the result of cyclic stresses caused by variations in temperature.

Accepted Answer

Thermal fatigue is the result of cyclic stresses caused by variations in temperature. This can occur in materials that experience frequent heating and cooling, such as metal components in engines or machinery. Over time, the repeated expansion and contraction can cause cracks and damage to the material, leading to failure.

Question 6

________ of a component is the most important factor in determining a components resistance to mechanical fatigue.

Accepted Answer

The answer of ________ of a component is the most...

Question 7

Caustic embrittlement is a form of stress corrosion cracking characterized by surface-initiated cracks that occur in piping and equipment exposed to caustic, primarily adjacent to non-PWHT welds. Which of the following materials is the most resistant to embrittlement?

Accepted Answer

Nickel based alloys are the most resistant to caustic embrittlement due to their high nickel content, which increases their resistance to corrosion and cracking. Carbon steel, low alloy steels, and 400 series stainless steel are more susceptible to caustic embrittlement.

Question 8

The best method to inspect for SCC is ____.

Accepted Answer

The answer of The best method to inspect for SCC...

Question 9

Naphthenic acid corrosion is a form of high temperature corrosion that occurs primarily in crude and vacuum units and downstream units that process certain fractions that contain naphthenic acid. Which of the following materials is susceptible to naphthenic acid corrosion?

Accepted Answer

All of the listed materials, including carbon steel, 300 Series stainless steel, and 400 Series stainless steel, can be susceptible to naphthenic acid corrosion under certain conditions, particularly at high temperatures and in the presence of naphthenic acids.

Question 10

Stress levels and __________ are the critical factors causing carbonate stress corrosion cracking.

Accepted Answer

Carbonate stress corrosion cracking is caused by the combined effect of stress levels and water chemistry, particularly high levels of carbonate ions. Temperature and velocity can contribute to the corrosion process but are not the critical factors in this specific type of corrosion.

Question 11

Increasing the chromium in steels offers no major improvement in resistance to CO₂ corrosion until a minimum of __________ is reached.

Accepted Answer

According to industry standards and research, a minimum of 12% chromium is required to provide significant improvement in resistance to CO₂ corrosion in steels. Therefore, option B is the correct answer.

Question 12

Annealed steels are more resistant to Spheroidization than normalized steels. _________ grained steels are more resistant than ______ grained steels.

Accepted Answer

Coarse-grained steels are more resistant to spheroidization than fine-grained steels because the larger grain size reduces the boundary area where spheroidization can initiate.

Question 13

What is the chemical symbol for ethane or ethylene?

Accepted Answer

Ethane is represented by the chemical formula C₂H₆, and ethylene is represented by C₂H₄. The correct choice for the chemical symbol representing the carbon atoms in both ethane and ethylene is C₂.

Question 14

A condition where steel loses strength due to the removal of carbon and carbides leaving only an iron matrix is called decarburization. This occurs during high temperatures, during PWHT and from exposure to fires. Which of the following materials is not affected by this?

Accepted Answer

Duplex SS is not affected by decarburization as it contains both austenite and ferrite phases, which maintain their strength even when decarburization occurs. Both low alloy steel and carbon steel are affected by decarburization.

Question 15

_________ significantly increases the probability and severity of blistering, HIC and SOHIC.

Accepted Answer

The answer of _________ significantly increases the probability and severity...

Question 16

A form of corrosion caused by living organisms such as bacteria, algae or fungi is _______ .

Accepted Answer

MIC stands for Microbial Induced Corrosion, which is caused by living organisms such as bacteria, algae or fungi. Choice A (HIC) stands for Hydrogen Induced Cracking, and choice B (SOHIC) stands for Sulfide Stress Induced Cracking, both of which are not related to living organisms.

Question 17

Dissimilar metal welds with a 300 Series stainless steel weld metal on a ferritic steel may also result in narrow region of _________ at the toe of the weld, near the fusion line on the ferritic side.

Accepted Answer

The answer of Dissimilar metal welds with a 300 Series...

Question 18

____________ are characterized by a localized loss in thickness in the form of pits, grooves, gullies, waves, rounded holes and valleys. These losses often exhibit a directional pattern.

Accepted Answer

Erosion and corrosion/erosion both involve localized loss in thickness with patterns like pits and grooves, often showing a directional pattern due to the movement of fluids or particles.

Question 19

Stainless steels with sigma can normally withstand normal operating stresses but upon cooling to temperatures below _______ may show a complete lack of fracture toughness as measured by a Charpy impact test.

Accepted Answer

Sigma phase embrittlement in stainless steels typically becomes a concern at temperatures below 500º F, where the material may lose fracture toughness.

Question 20

Regular and controlled carbon grades of stainless steels such as types 304/304H and 316/316H are particularly susceptible to sensitization in the weld HAZ. Low carbon "L" grades are less susceptible and usually can be welded without sensitizing. The "L" grades will not sensitize provided long term operating temperatures do not exceed about __________.

Accepted Answer

The "L" grades will not sensitize provided long term operating temperatures do not exceed about 750º F.

Exam 1: Corrosion and Materials