Question 1

Hydrogen blisters may form at many different depths from the surface of the steel, in the middle of the plate or near a weld. In some cases, neighboring or adjacent blisters that are at slightly different depths (planes) may develop cracks that link them together. Interconnecting cracks between the blisters often have a __________ appearance.

Accepted Answer

The interconnecting cracks between hydrogen blisters often have a step-like appearance due to the different depths at which the blisters form, creating a layered effect.

Question 2

With creep, increased stress due to loss in thickness from corrosion will ________ time to failure.

Accepted Answer

Creep is the plastic deformation of material under a constant load or stress. When a material corrodes, the loss in thickness reduces its ability to withstand stress, which increases the likelihood of creep. This increased creep will accelerate the rate of deformation and ultimately lead to failure. Therefore, the increased stress due to loss in thickness from corrosion will reduce time to failure.

Question 3

A hard, brittle surface layer will develop on some alloys due to exposure to high temperature process streams containing high levels of nitrogen compounds such as ammonia or cyanides, particularly under reducing conditions, is called _______.

Accepted Answer

The process described in the question is called nitriding, which occurs when high-temperature process streams containing nitrogen compounds are exposed to certain alloys. This can create a hard and brittle surface layer on the alloy. Carburization is a similar phenomenon but involves the absorption of carbon instead of nitrogen. Spheroidization is a completely different process, involving the transformation of certain types of carbides into spherical shapes. Therefore, the correct answer is C, nitriding.

Question 4

In general, the resistance of carbon steel and other alloys to High temperature corrosion is determined by the ________ content of the material.

Accepted Answer

The resistance to high temperature corrosion is determined primarily by the chromium content of the material. Molybdenum can also contribute to this resistance, but carbon content is not a significant factor. Therefore, choice B (chromium) is the best answer.

Question 5

What is the chemical symbol for propane or propylene?

Accepted Answer

Propane and propylene both have three carbon atoms, so their chemical symbols start with C3. Propane is C3H8 and propylene is C3H6.

Question 6

Thermal fatigue cracks usually propagate _______ to the stress and they are usually dagger-shaped.

Accepted Answer

Thermal fatigue cracks typically propagate transverse to the direction of the stress, meaning they form perpendicular to the stress direction.

Question 7

There is currently no known metal alloy that is immune to _________ under all conditions.

Accepted Answer

While carburization and decarburization can be mitigated through material selection and process control, metal dusting is still a relatively poorly understood phenomenon with no universally effective preventative measures. Therefore, option B is the best choice.

Question 8

Corrosion in boiler feedwater and condensate return systems is usually the result of dissolved gases, oxygen and ________.

Accepted Answer

Corrosion in boiler feedwater and condensate return systems is usually the result of dissolved gases, oxygen, and carbon dioxide. Carbon dioxide in water forms carbonic acid, which can be aggressive to metal piping and equipment, causing corrosion.

Question 9

Surface initiated cracks caused by environmental cracking of 300 Series SS and some nickel based alloys under the combined action of tensile stress, temperature and an aqueous chloride environmental is called ________. The presence of dissolved oxygen ___________ the propensity for cracking.

Accepted Answer

The description matches that of Chloride Stress Corrosion Cracking (Cl SCC). The presence of dissolved oxygen increases the propensity for cracking.

Question 10

The signature mark of a fatigue failure is a _______ type fingerprint that has concentric rings.

Accepted Answer

The signature mark of a fatigue failure is a "Clam Shell" type fingerprint that has concentric rings, indicating the progressive nature of the crack growth.

Question 11

Metallic components form a surface __________ when exposed to sulfur compounds. This may react with air (oxygen) and moisture to form sulfur acids (polythionic acid).

Accepted Answer

Metallic components form a surface sulfide scale when exposed to sulfur compounds. This scale may react with air (oxygen) and moisture to form sulfur acids (polythionic acid).

Question 12

SSC is a form of hydrogen stress cracking resulting from the absorption of ________ that is produced by the sulfide corrosion process on the metal surface.

Accepted Answer

SSC (Sulfide Stress Cracking) is caused by the absorption of atomic hydrogen, which is produced during the sulfide corrosion process on the metal surface.

Question 13

Susceptibility of an alloy to sulfidation is determined by its ability to form protective _________.

Accepted Answer

The answer of Susceptibility of an alloy to sulfidation is...

Question 14

Sulfide stress cracking (SSC) is defined as cracking of metal under the combined action of tensile stress and corrosion in the presence of _________ and _________.

Accepted Answer

Sulfide stress cracking (SSC) occurs in the presence of water and H₂S. The other choices (A, B, and C) involve other types of corrosion or chemicals that are not directly related to SSC.

Question 15

In general, the resistance of iron and nickel based alloys to sulfidation is determined by the ________ content of the material.

Accepted Answer

Chromium content in iron and nickel-based alloys enhances their resistance to sulfidation by forming a protective chromium sulfide layer.

Question 16

Low creep ductility is _____ prevalent at the lower temperatures in the creep range. Or low stresses in the upper creep range.

Accepted Answer

Low creep ductility is more prevalent at the lower temperatures in the creep range or low stresses in the upper creep range. This means that the material is more likely to experience low creep ductility under these conditions compared to other temperatures and stresses in the creep range. Therefore, option A is the correct choice.

Question 17

300 Series SS, 400 Series SS and duplex SS are subject to pitting and localized corrosion under insulation. In addition, __________ are also subject to SCC if chlorides are present, while _________ are less susceptible.

Accepted Answer

300 Series Stainless Steels are more susceptible to Stress Corrosion Cracking (SCC) in the presence of chlorides, while Duplex Stainless Steels are less susceptible due to their microstructure and higher resistance to chloride-induced SCC.

Question 18

Formation of a metallurgical phase known as sigma phase results in a loss of _________ in some stainless steels as a result of high temperature exposure.

Accepted Answer

The answer of Formation of a metallurgical phase known as...

Question 19

For galvanic corrosion to take place, three conditions must be met, presence of an electrolyte, two different materials or alloys and ___________.

Accepted Answer

An electrical connection is necessary for galvanic corrosion to occur, allowing electron flow between the two different materials or alloys.

Question 20

With high temperature sulfide corrosion (Sulfidation), noticeable increases may be found downstream of _________ injection points.

Accepted Answer

High temperature sulfide corrosion, or sulfidation, is often exacerbated by the presence of hydrogen, which can increase the rate of corrosion downstream of hydrogen injection points.

Exam 1: Corrosion and Materials