Which statement is true when comparing 4043 and 5356 filler metals used in GTAW of aluminum?

Which statement is true when comparing 4043 and 5356 filler metals used in GTAW of aluminum?

• A. 4043 contains magnesium
• B. 5356 contains silicon
• C. 4043 contains silicon
• D. 5356 contains boron

Answer: (C)

Filler-metal designation for aluminum shows the main alloying element. The 4xxx family is silicon-based, so a filler labeled 4043 contains silicon. That makes the statement true. The 4xxx fillers are not defined by magnesium as the primary element, so 4043 does not predominantly contain magnesium. The 5xxx family, which includes the 5356 filler, is defined by magnesium as the major alloying element, not silicon, so it does not primarily contain silicon. Boron is not a standard major constituent in these common aluminum fillers. This distinction helps explain why silicon is the identifying component of 4043, and guides selection: 4043 provides good flow and crack resistance due to its silicon content, while 5356 offers magnesium-based properties for different strength and corrosion considerations.

Filler-metal designation for aluminum shows the main alloying element. The 4xxx family is silicon-based, so a filler labeled 4043 contains silicon. That makes the statement true. The 4xxx fillers are not defined by magnesium as the primary element, so 4043 does not predominantly contain magnesium. The 5xxx family, which includes the 5356 filler, is defined by magnesium as the major alloying element, not silicon, so it does not primarily contain silicon. Boron is not a standard major constituent in these common aluminum fillers. This distinction helps explain why silicon is the identifying component of 4043, and guides selection: 4043 provides good flow and crack resistance due to its silicon content, while 5356 offers magnesium-based properties for different strength and corrosion considerations.