CWB LEVEL 2 FINAL EXAM 2026 EXAM QUESTIONS AND
ANSWERS GRADED A+
✔✔What units/equipment does galvanic corrosion affect? - ✔✔*Galvanic Corrosion can
occur in any unit where there is a conductive fluid and alloys are coupled.
*Heat exchanges are susceptible if the tube material is different from the tube sheet
and/or baffles. Usually in salt water cooling systems
*Buried pipelines, electrical transmission support towers and ship hulls are typical
locations for galvanic corrosion
✔✔What is the appearance or Morphology of Damage with Galvanic Corrosion? -
✔✔*Damage occurs where 2 materials are joined at welded or bolted connections.
*The more active material can suffer generalized loss in thickness or may have the
appearance of a crevice, groove or pitting corrosion, depending on the driving force,
conductivity and relative anodic/cathodic areas ratio.
✔✔What is the best prevention for galvanic corrosion? - ✔✔Best method is through
design
*Differing alloys should be in intimate contact in conductive environments unless the
anode/cathode surface area ratio is favorable.
*Coatings can be helpful
*With piping specially designed electric insulating bolt sleeves and gaskets can
eliminate the electrical connection.
✔✔How can you inspect galvanic corrosion? - ✔✔Visual inspection UT thickness
gauging are very effective methods.
✔✔Describe Corrosion Under Insulation (CUI)? - ✔✔Corrosion in piping, pressure
vessels, and structual components resulting from water trapped under insulation or
fireproofing
✔✔What kind of material can be affected from Corrosion Under Insulation? - ✔✔Carbon
Steel, Low alloy steels, 300 Series SS, and duples stainless steels
✔✔What are some critical factors for Corrosion Under Insulation? - ✔✔It affects
externally insulated piping and equipment and those that are in intermittent service or
operate between:
10F(-12C) and 350F(175C) for carbon and low alloy
140F(60C) and 400F(205C) for austenitic stainless steels and duplex stainless steels.
Corrosion rates will increase with increasing metal temperature up to the point where
the water evaporates quickly (ex. Corrosion becomes more severe at metal
temperatures between boiling point 212F(100C) and 350F(121C), where water is less
likely to vaporize and insulation stays wet longer.
, Insulating material that hold moisture (wick) is a problem
Equipment that operates below water dew point creates condense water on metal
surfaces
Cyclic thermal operation or intermittent service can increase corrosion
Plants located in areas with high rain fall
Environments that provide airborne containments such as chlorides, stack emissions
(SO2), cooling tower drift
✔✔What kind of equipment is affected by corrosion under insulation? - ✔✔All
equipment is susceptible to CUI
✔✔What are some examples where corrosion under insulation can occur? - ✔✔Can be
found on equipment with damaged insulation, vapor barriers, weatherproofing or mastic,
or protrusions through the insulation or at insulation termination points such as flanges.
Piping or equipment with damaged/leaking steam tracing.
Localized damage to coating or paint systems
Where water/moisture will naturally collect.
Deadlegs (vents, drains, and other similar items)
Pipehangers
Caulking that has hardened, has separated, or is missing
✔✔What is the appearance of corrosion under insulation? - ✔✔Carbon and low alloy
steels are subject to localized pitting corrosion and loss of thickness
300 Series SS are subject to stress corrosion cracking is chloride is present
300 Series SS and Duplex SS are subject to pitting and localized corrosion
After insulation is removed from carbon and low alloy steels CUI often appears as loose
flaky scale covering corroded components.
✔✔What is some prevention for corrosion under insulation? - ✔✔Best achieved by
appropriate paints/coatings and maintaining insulation/sealing/vapor barriers to prevent
moisture ingress.
Flamed-Sprayed alluminum coatings have been used for carbon steels
ANSWERS GRADED A+
✔✔What units/equipment does galvanic corrosion affect? - ✔✔*Galvanic Corrosion can
occur in any unit where there is a conductive fluid and alloys are coupled.
*Heat exchanges are susceptible if the tube material is different from the tube sheet
and/or baffles. Usually in salt water cooling systems
*Buried pipelines, electrical transmission support towers and ship hulls are typical
locations for galvanic corrosion
✔✔What is the appearance or Morphology of Damage with Galvanic Corrosion? -
✔✔*Damage occurs where 2 materials are joined at welded or bolted connections.
*The more active material can suffer generalized loss in thickness or may have the
appearance of a crevice, groove or pitting corrosion, depending on the driving force,
conductivity and relative anodic/cathodic areas ratio.
✔✔What is the best prevention for galvanic corrosion? - ✔✔Best method is through
design
*Differing alloys should be in intimate contact in conductive environments unless the
anode/cathode surface area ratio is favorable.
*Coatings can be helpful
*With piping specially designed electric insulating bolt sleeves and gaskets can
eliminate the electrical connection.
✔✔How can you inspect galvanic corrosion? - ✔✔Visual inspection UT thickness
gauging are very effective methods.
✔✔Describe Corrosion Under Insulation (CUI)? - ✔✔Corrosion in piping, pressure
vessels, and structual components resulting from water trapped under insulation or
fireproofing
✔✔What kind of material can be affected from Corrosion Under Insulation? - ✔✔Carbon
Steel, Low alloy steels, 300 Series SS, and duples stainless steels
✔✔What are some critical factors for Corrosion Under Insulation? - ✔✔It affects
externally insulated piping and equipment and those that are in intermittent service or
operate between:
10F(-12C) and 350F(175C) for carbon and low alloy
140F(60C) and 400F(205C) for austenitic stainless steels and duplex stainless steels.
Corrosion rates will increase with increasing metal temperature up to the point where
the water evaporates quickly (ex. Corrosion becomes more severe at metal
temperatures between boiling point 212F(100C) and 350F(121C), where water is less
likely to vaporize and insulation stays wet longer.
, Insulating material that hold moisture (wick) is a problem
Equipment that operates below water dew point creates condense water on metal
surfaces
Cyclic thermal operation or intermittent service can increase corrosion
Plants located in areas with high rain fall
Environments that provide airborne containments such as chlorides, stack emissions
(SO2), cooling tower drift
✔✔What kind of equipment is affected by corrosion under insulation? - ✔✔All
equipment is susceptible to CUI
✔✔What are some examples where corrosion under insulation can occur? - ✔✔Can be
found on equipment with damaged insulation, vapor barriers, weatherproofing or mastic,
or protrusions through the insulation or at insulation termination points such as flanges.
Piping or equipment with damaged/leaking steam tracing.
Localized damage to coating or paint systems
Where water/moisture will naturally collect.
Deadlegs (vents, drains, and other similar items)
Pipehangers
Caulking that has hardened, has separated, or is missing
✔✔What is the appearance of corrosion under insulation? - ✔✔Carbon and low alloy
steels are subject to localized pitting corrosion and loss of thickness
300 Series SS are subject to stress corrosion cracking is chloride is present
300 Series SS and Duplex SS are subject to pitting and localized corrosion
After insulation is removed from carbon and low alloy steels CUI often appears as loose
flaky scale covering corroded components.
✔✔What is some prevention for corrosion under insulation? - ✔✔Best achieved by
appropriate paints/coatings and maintaining insulation/sealing/vapor barriers to prevent
moisture ingress.
Flamed-Sprayed alluminum coatings have been used for carbon steels
