Question 1

Which of these materials are not susceptible to PASCC?

Accepted Answer

Carbon steel and 400 Series Stainless Steel are not susceptible to Polythionic Acid Stress Corrosion Cracking (PASCC), which typically affects austenitic stainless steels like the 300 Series.

Question 2

With steam blanketing, failure occurs as a result of _________ in the tube from the internal steam pressure at the elevated temperature.

Accepted Answer

With steam blanketing, the internal steam pressure at the elevated temperature leads to the accumulation of steam in the tube, creating a hoop stress. This, in turn, causes the metal to weaken and eventually rupture, leading to failure. Stress risers and velocity are not directly related to steam blanketing, and tensile strength does not explain the mechanism of failure in this case.

Question 3

Vibration-induced fatigue can be eliminated or reduced through _________ and the use of supports and vibration dampening equipment. Material upgrades are not usually a solution.

Accepted Answer

Vibration-induced fatigue can be addressed through proper design and the use of supports and vibration dampening equipment. Material upgrades may not be effective in reducing vibration-induced fatigue. Hangers and dummy legs may also be helpful in reducing vibration, but design and equipment choices are more important factors.

Question 4

In pressure containing equipment, SOHIC and SCC damage is most often associated with __________.

Accepted Answer

SOHIC (stress-oriented hydrogen-induced cracking) and SCC (stress corrosion cracking) damage in pressure containing equipment is most often associated with weldments. This is because welding can introduce residual stress and hydrogen, which can contribute to the development of these types of damage. Internals and branches may also be susceptible to these types of damage, but it is less common.

Question 5

Cracking of a metal due to stress relaxation during PWHT or in service at elevated temperatures is called ______. It is most often found in heavy wall sections.

Accepted Answer

Reheat cracking, also known as delayed cracking or stress relief cracking, is a type of cracking that occurs due to stress relaxation during post-weld heat treatment or service at elevated temperatures. It is commonly seen in heavy wall sections of steel structures, especially those that have been welded. Thermal cracking, on the other hand, refers to cracking that occurs due to rapid cooling or heating of metals, and step-like cracking is not a commonly recognized term in metallurgy.

Question 6

MIC is often found in _________, bottom water of storage tanks, piping with stagnant or low flow and piping in contact with some soils.

Accepted Answer

The answer of MIC is often found in _________, bottom...

Question 7

Hardness is primarily an issue with SSC. Typical low strength carbon steels should be controlled to produce weld hardness less than ________.

Accepted Answer

According to industry standards, the maximum acceptable hardness for low strength carbon steels to prevent SSC is 200 BHN. Therefore, option C is the best choice.

Question 8

Cavitation is a form of erosion caused by the formation and instantaneous collapse of innumerable tiny vapor bubbles. Temperatures approaching the boiling point of the liquid are _________ to result in bubble formation.

Accepted Answer

Temperatures approaching the boiling point of the liquid are more likely to result in bubble formation because the liquid is closer to turning into a gas and forming vapor bubbles.

Question 9

Carbon dioxide corrosion results when CO₂ dissolves in water to form _________ acid.

Accepted Answer

Carbon dioxide dissolves in water to form carbonic acid, which can cause corrosion in certain materials.

Question 10

Localized corrosion due to the concentration of caustic or alkaline salts that usually occurs under evaporative conditions is _________.

Accepted Answer

The question describes the process of caustic corrosion, which occurs when concentrated alkaline solutions come into contact with a metal surface. Therefore, the best choice is B, caustic corrosion.

Question 11

Naphthenic acid is _____ by catalytic reactions in downstream hydro processing and FCC units.

Accepted Answer

Naphthenic acid is destroyed by catalytic reactions in downstream hydro processing and FCC units.

Question 12

Once cracking from LME has occurred, grinding out the affected area ______ an acceptable fix.

Accepted Answer

Grinding out the affected area is not an acceptable fix for cracking from LME because it can weaken the structure and potentially introduce further stress concentration points, leading to further cracking. The best solution is to prevent LME from occurring in the first place, by controlling the cooling rate and using appropriate heat treatment processes.

Question 13

Amine corrosion refers to the general and/or localized corrosion that occurs principally on _________ in amine treating processes. Corrosion is not caused by the amine itself, but results from dissolved acid gases (CO₂ and H₂S), amine degradation products, heat stable amine salts and other contaminants.

Accepted Answer

Carbon steel is the most commonly used material for equipment in amine treating processes and is therefore the most susceptible to amine corrosion. Duplex SS and the 300/400 series SS are more resistant to corrosion than carbon steel, but they are not immune to it.

Question 14

Characteristic stress corrosion cracks have many branches and may be visually detectable by a __________ appearance on the surface.

Accepted Answer

The answer of Characteristic stress corrosion cracks have many branches...

Question 15

Refractory lined equipment should be designed for erosion, thermal shock and __________.

Accepted Answer

The answer of Refractory lined equipment should be designed for...

Question 16

Which if the following materials are not susceptible to hydrogen stress cracking?

Accepted Answer

Stainless steel is not susceptible to hydrogen stress cracking due to its high corrosion resistance and low susceptibility to hydrogen embrittlement. Carbon steel and low alloy steel, on the other hand, are susceptible to hydrogen stress cracking as they are not as resistant to corrosion and can become embrittled by hydrogen atoms entering the metal lattice.

Question 17

___________ cooling water outlet temperatures and/or process side outlet temperatures tend to __________ corrosion rates as well as fouling tendency.

Accepted Answer

Increasing cooling water outlet temperatures and/or process side outlet temperatures tend to increase corrosion rates as well as fouling tendency due to higher rates of chemical reactions and deposition.

Question 18

___________ is when oxygen reacts with carbon steel and other alloys at high temperatures converting the metal to oxide scale.

Accepted Answer

The answer of ___________ is when oxygen reacts with carbon...

Question 19

Lean amine is generally not corrosive because they have either low conductivity and/or high pH. Corrosion rates increase with increasing temperatures, particularly in rich amine service. Temperatures above _________ can result in acid gas flashing and severe localized corrosion.

Accepted Answer

Temperatures above 220º F can result in acid gas flashing and severe localized corrosion.

Question 20

____________ is the reduction in toughness due to a metallurgical change that can occur in some low alloy steels as a result of long-term exposure in the temperature range of about 650º F to 1100º F.

Accepted Answer

Temper embrittlement is a phenomenon where certain low alloy steels lose their toughness due to a change in their microstructure from long-term exposure in the temperature range of 650º F to 1100º F. This change can make the steel brittle and susceptible to cracking or failure under stress, even at lower temperatures. This effect is reversible by heating the metal to a higher temperature and cooling it slowly.

Exam 1: Corrosion and Materials