🔍 Key Concepts

• soldering flux purpose in metal joining • role of oxides on metal surfaces during heating • difference between changing metal properties vs. cleaning the surface

💭 Think About

• When two metals are soldered, what typically prevents the molten solder from sticking well to the metal surface? • Does flux primarily change the metal’s hardness/softness, or does it mainly affect the condition of the surface? • Think about what forms on hot metal surfaces when exposed to air and how that affects bonding.

✅ Before You Answer

• Check which option describes surface preparation rather than changing the metal’s internal structure. • Eliminate any option that suggests a permanent change in mechanical properties (hardening or softening) of the base metal. • Focus on the choice that deals with contamination or films on the metal surface just before soldering.