Definition - What does Flux mean?
Flux is a chemical purifying agent, flowing agent or cleaning agent. Most commonly, it is used in metal joining and metallurgy. Some examples of flux include:
- Ammonium chloride
- Zinc chloride
- Hydrochloric acid
Corrosionpedia explains Flux
The main function of flux is to prevent filler materials' and base oxidation. It is a substance that is almost inert at average room temperature, but can be intensely reducing when exposed to higher temperatures, which prevents metal oxide formation.
In metal joining, flux dissolves the metal surface oxides that facilitate the molten metal wetting, which acts as a barrier to oxygen, mitigating oxidation. The idea behind fluxes is that they are used to generate a surface for wetting the solder.
However, they can contain bromine and chlorine that could remain corrosive after the soldering process, causing corrosion to the surface throughout production or operation. Due to this, testing and cleaning techniques have been developed to test and clean the surfaces. This is to make sure that the surface remains noncorrosive after the processes.
The most common tests involved are designed to identify the flux residues' corrosive properties under extreme conditions in the environment. With the tests, a solder pellet is melted as it comes in contact with the flux under testing over a metal sheet. Afterward, the solder is exposed to variables of humidity. The corrosion generated is then evaluated visually.