Correct option is D
In brazing, flux is used to prevent oxidation and promote wetting of the filler metal by cleaning and protecting the joint area from contaminants. The most commonly used flux in brazing is borax (sodium tetraborate, Na₂B₄O₇). It dissolves oxides on the metal surfaces and ensures a strong and clean joint.
· Borax-based fluxes are commonly used in silver brazing, copper brazing, and brass brazing.
· Flux is applied before heating to ensure proper joint formation.
· Available in powder, paste, or liquid form.
· Used in HVAC, plumbing, automotive, and aerospace industries.
