Question 1

Time to failure by thermal fatigue is primarily affected by:

Accepted Answer

A)  Magnitude of stress and operating temperature. 
B)  Magnitude of stress and number of cycles. 
C)  Carbon content in material and operating temperature. 
D)  Carbon content in material and number of cycles.

Question 2

__________ is a change in the microstructure of steels after exposure in the 850º F to 1400º F range, where the carbide phases in carbon steels are unstable and may agglomerate from their normal plate-like appearance.

Accepted Answer

A)  Carburization 
B)  Spheroidization 
C)  Graphiding 
D)  885º Embrittlement

Question 3

Oxidation of carbon steel begins to become significant above _________.

Accepted Answer

A)  800º F 
B)  900º F 
C)  1000º F 
D)  1100º F

Question 4

Sulfidation usually creates:

Accepted Answer

A)  Uniform corrosion. 
B)  Isolated pitting. 
C)  Intergranular cracking. 
D)  Transgranular cracking. 
E)  Hard and brittle zones.
F) Inspection nightmares.

Question 5

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

Accepted Answer

A)  Carbon steel 
B)  Low alloy steel 
C)  Stainless steel 
D)  None of the above

Question 6

The extent and depth of decarburization is a function of temperature and ______.

Accepted Answer

A)  Pressure 
B)  Material properties 
C)  Exposure time 
D)  Velocity

Question 7

If the BHN is 400-500 it may indicate __________.

Accepted Answer

A)  Carburization 
B)  Hydriding 
C)  Temper embrittlement 
D)  Caustic embrittlement

Question 8

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

Accepted Answer

A)  Temperature 
B)  Velocity 
C)  Water chemistry 
D)  None of the above

Question 9

Nitriding begins above ________ and becomes severe above _______.

Accepted Answer

A)  500º F, 800º F 
B)  600º F, 900º F 
C)  800º F, 1000º F 
D)  700º F, 1100º F

Question 10

Dissimilar weld metal cracking forms at the toe of the weld in the heat affected zone of the ________ material.

Accepted Answer

A)  Ferritic 
B)  Austenitic 
C)  Martensitic 
D)  Both B and C

Question 11

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

Accepted Answer

A)  Carburization 
B)  Metal dusting 
C)  Decarburization 
D)  None of the above

Question 12

In design and fabrication, it is advisable to avoid sharp changes in cross section, such as short radius fillets or undercut that can give rise to _________. Long-seam welds are particularly susceptible to reheat cracking due to mismatch caused by fit up problems.

Accepted Answer

A)  Stress concentrations 
B)  Cracking 
C)  Circumferential stress 
D)  All of the above

Question 13

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

Accepted Answer

A)  Hydrogen 
B)  Caustic 
C)  Ammonia 
D)  Water

Question 14

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

Accepted Answer

A)  9% 
B)  12% 
C)  5% 
D)  7%

Question 15

________ is a loss in toughness due to a metallurgical change that can occur in alloys containing a ferrite phase, as a result of exposure in the temperature range 600º F to 1000º F.

Accepted Answer

A)  Caustic embrittlement 
B)  Notch toughness 
C)  885º F embrittlement 
D)  Ductile embrittlement

Question 16

Mechanical fatigue is caused by:

Accepted Answer

A)  Cyclic stresses occurring over a long period of time. 
B)  Higher than average stresses at high temperatures. 
C)  Constant stresses occurring at low temperatures. 
D)  Cyclic operating conditions of bird poop then rain, bird poop then rain, etc.

Question 17

With sulfuric acid corrosion, alloys such as Alloy 20 resist dilute acid corrosion and form a protective ________ film on the surface.

Accepted Answer

A)  Sulfide 
B)  Chloride 
C)  Iron sulfate 
D)  Iron oxide

Question 18

Convert these temperatures - 156º C and 450º F

Accepted Answer

A)  304º F, 151º C 
B)  284º F, 218º C 
C)  312º F, 232º C 
D)  296º F, 246º C

Question 19

In piping and equipment, creep cracking can occur where high metal temperatures and _________ occur together. Creep cracking, once initiated, can progress rapidly.

Accepted Answer

A)  Pressures 
B)  Stress risers 
C)  Velocities 
D)  None of the above

Question 20

Many thermal fatigue cracks are filled with:

Accepted Answer

A)  chlorides. 
B)  hydroslime. 
C)  oxides. 
D)  sulfides.

Exam 1: Corrosion and Materials