Which of the following is NOT usually used as a flux for soldering?

Explanation:

Soldering is the process by which metallic materials are joined with the help of another liquified metal (solder).

All metal rust to some extent, when exposed to the atmosphere because of oxidation. The layer of the rust must be removed before soldering. For this, a chemical compound applied to the joint is called flux.

Different types of fluxes are given below:

Inorganic fluxes:

• Hydrochloric acid: Concentrated hydrochloric acid is a liquid that fumes when it comes into contact with air. It is used as a flux for sheet metals of zinc-iron or galvanized sheets. This is also known as muriatic acid.
• Zinc chlorides: Zinc chlorides are known as killed spirits. It is mainly used for soldering copper, brass and tin sheets.
• Ammonium chloride or Sal-Ammoniac: It is a solid white crystalline substance used when soldering copper, brass, iron, and steel (cast iron sheets).
• Phosphoric acid: It is mainly used as a flux for stainless steel.
• Borax: It is used in various household laundry and cleaning products. A mixture of borax and ammonium chloride is used as a flux when welding iron and steel. Borax is also used mixed with water as a flux when soldering jewelry metals such as gold or silver.

Organic fluxes:

• Resin: It is used for soldering copper, brass, bronze, tin plate, cadmium, nickel, silver and some alloys of these metals.
• Tallow: It is a form of animal fat. It is used when soldering lead, brass, and electrical joints.