CWB LEVEL 1 INSPECTOR METALLURGY AND
MATERIAL SPECIFICATION CERTIFICATION
EVALUATION 2026 QUESTIONS WITH
PRACTICE SOLUTION GRADED A+
◉ What are the properties of Al ? Answer: 1. low density
2. Corrosion resistance
3. High electrical resistance
4. High thermal conductivity
5. good appearance
6. toughness at low temps
◉ True / False ?
Al is covered with a coherent oxide. Answer: True
◉ Thermal conductivity of Al is _______ times that of Steel Answer: 4
◉ Melting point of Al is about _______ of Steel Answer: half
◉ Coefficient of thermal expansion for Al is about _______ that of Steel
Answer: twice
,◉ Modulus of elasticity (stiffness) for Al is about _______ that of Steel
Answer: one-third
◉ True / False
"Nitrogen is not inert to Al and is not used for sheilding" Answer:
True
◉ What is responsible for Al's excellent corrosion resistance?
Answer: Al oxide but it changes to Magnesium oxide (MgO) or
Magnesium spinel ( Mg Al2O4) when the Mg % exceeds 0.05%.
◉ What is the thickness of Al oxide on the surface of Al ? Answer:
50-150 angstroms
◉ True/ False ?
The form of magnesium oxide is a function of the magnesium
concentration and the thermal history of the alloy Answer: True
◉ True / False ?
The oxide transformation from aluminum oxide to magnesium oxide
or magnesium spinel ,has a profound effect on the solid -state
bonding b/w any clad and the Al base Answer: True
,◉ The solid -state bonding b/w Al and another metal or another
Aluminum alloy generally requires a control of the magnesium level
to ____ % Answer: Less than 0.05%
◉ Why does Mg has the profound influence on the oxide found on
Al? Answer: 1. Mg has a greater affinity than Al for O2.
2. Mg behaves as a surface-active element in Al, that is, it tends to
diffuse readily to the surface of the metal.
◉ The oxidation rate of Mg containing alloys is _____________ than for
Mg free alloys. Answer: greater
◉ Why is oxide thickness on an Mg- Al alloy surface thicker than one
on a Mg free alloy for the same thermal / mechanical history?
Answer: The oxidation rate of Mg containing alloys is greater than
for Mg free alloys.
◉ Which is the element which reacts with Mg oxide to form its
oxides on the Al surface? Answer: Lithium
◉ Which is the surface oxide for lithium bearing Al alloys? Answer:
Lithium oxide / spinel
◉ True / False ?
, When the Al oxide is transformed to lithium oxide or spinal, then the
coherency between the oxide and the metal substrate may change.
Instead of the oxide being tenacious it may be a porous scale layer
that does not protect the parent metal or that can readily trap
moisture or any other air borne contaminant. Answer: True
◉ True / False ?
Oxide is scrapped off the metal prior to welding Al-Li alloys to
minimize the weld porosity Answer: True
◉ True / False?
After mechanical milling or chemical treatment for oxide removal
prior to welding, the surface will almost instantly re-oxidize in dry
air. Answer: True
◉ True / False
Oxide removal prior to welding, the surface will form local
electrolytic cells between dry and wet sections and the wet part will
corrode preferentially, forming a stain. Answer: True
MATERIAL SPECIFICATION CERTIFICATION
EVALUATION 2026 QUESTIONS WITH
PRACTICE SOLUTION GRADED A+
◉ What are the properties of Al ? Answer: 1. low density
2. Corrosion resistance
3. High electrical resistance
4. High thermal conductivity
5. good appearance
6. toughness at low temps
◉ True / False ?
Al is covered with a coherent oxide. Answer: True
◉ Thermal conductivity of Al is _______ times that of Steel Answer: 4
◉ Melting point of Al is about _______ of Steel Answer: half
◉ Coefficient of thermal expansion for Al is about _______ that of Steel
Answer: twice
,◉ Modulus of elasticity (stiffness) for Al is about _______ that of Steel
Answer: one-third
◉ True / False
"Nitrogen is not inert to Al and is not used for sheilding" Answer:
True
◉ What is responsible for Al's excellent corrosion resistance?
Answer: Al oxide but it changes to Magnesium oxide (MgO) or
Magnesium spinel ( Mg Al2O4) when the Mg % exceeds 0.05%.
◉ What is the thickness of Al oxide on the surface of Al ? Answer:
50-150 angstroms
◉ True/ False ?
The form of magnesium oxide is a function of the magnesium
concentration and the thermal history of the alloy Answer: True
◉ True / False ?
The oxide transformation from aluminum oxide to magnesium oxide
or magnesium spinel ,has a profound effect on the solid -state
bonding b/w any clad and the Al base Answer: True
,◉ The solid -state bonding b/w Al and another metal or another
Aluminum alloy generally requires a control of the magnesium level
to ____ % Answer: Less than 0.05%
◉ Why does Mg has the profound influence on the oxide found on
Al? Answer: 1. Mg has a greater affinity than Al for O2.
2. Mg behaves as a surface-active element in Al, that is, it tends to
diffuse readily to the surface of the metal.
◉ The oxidation rate of Mg containing alloys is _____________ than for
Mg free alloys. Answer: greater
◉ Why is oxide thickness on an Mg- Al alloy surface thicker than one
on a Mg free alloy for the same thermal / mechanical history?
Answer: The oxidation rate of Mg containing alloys is greater than
for Mg free alloys.
◉ Which is the element which reacts with Mg oxide to form its
oxides on the Al surface? Answer: Lithium
◉ Which is the surface oxide for lithium bearing Al alloys? Answer:
Lithium oxide / spinel
◉ True / False ?
, When the Al oxide is transformed to lithium oxide or spinal, then the
coherency between the oxide and the metal substrate may change.
Instead of the oxide being tenacious it may be a porous scale layer
that does not protect the parent metal or that can readily trap
moisture or any other air borne contaminant. Answer: True
◉ True / False ?
Oxide is scrapped off the metal prior to welding Al-Li alloys to
minimize the weld porosity Answer: True
◉ True / False?
After mechanical milling or chemical treatment for oxide removal
prior to welding, the surface will almost instantly re-oxidize in dry
air. Answer: True
◉ True / False
Oxide removal prior to welding, the surface will form local
electrolytic cells between dry and wet sections and the wet part will
corrode preferentially, forming a stain. Answer: True
