308A Metal Types and Properties 2

Question 1

What is 'galvanic corrosion' and why must sheet metal workers be aware of it?

Accepted Answer

Accelerated corrosion that occurs when dissimilar metals are in contact in the presence of an electrolyte

Answer

Corrosion caused by water only

Answer

Corrosion caused by sunlight

Answer

Corrosion that only affects painted surfaces

Question 2

What is the thickness in inches of 24-gauge galvanized steel?

Accepted Answer

0.0239 inches

Answer

0.0598 inches

Answer

0.1000 inches

Answer

0.5000 inches

Question 3

What is copper sheet metal primarily used for in the sheet metal trade?

Accepted Answer

Roofing, flashing, gutters, and architectural features due to its durability and aesthetic patina

Answer

Structural framing

Answer

HVAC main trunk ductwork

Answer

Heavy industrial exhaust systems

Question 4

What is 'work hardening' and how does it affect sheet metal during fabrication?

Accepted Answer

The metal becomes harder, stronger, and more brittle with repeated bending or forming, eventually cracking if overworked

Answer

The metal gets softer with more bending

Answer

The metal changes colour

Answer

The metal becomes heavier

Question 5

What is the purpose of 'annealing' sheet metal?

Accepted Answer

To soften work-hardened metal by heating it to a specific temperature and cooling it slowly, restoring ductility

Answer

To make it harder

Answer

To add a protective coating

Answer

To increase its thickness

Question 6

What is the difference between 'ferrous' and 'non-ferrous' metals?

Accepted Answer

Ferrous metals contain iron as their primary element; non-ferrous metals do not contain significant iron

Answer

Ferrous metals are always stainless

Answer

Non-ferrous metals are always magnetic

Answer

There is no practical difference