Acid core flux is typically used for plumbing soldering. Which option lists the acid core?

• A. Rosin core
• B. Water core
• C. Lead core
• D. Acid core

Answer: (D)

Acid core flux is used for plumbing soldering because it contains acids that actively dissolve copper oxide and other surface oxides. This cleaning action lets the solder wet the copper surface more completely and flow into joints, forming a strong, reliable bond in plumbing work. Rosin core flux, by contrast, is resin-based and noncorrosive, which is why it’s favored for electronics where you don’t want corrosive residues. Water-soluble flux serves different applications and usually requires thorough cleanup, not the standard for copper plumbing. A lead core isn’t a flux type at all; lead relates to the solder material rather than the flux. So the option listing acid core matches the plumbing soldering context.