Introduction to Potassium Fluoroaluminate

Potassium Fluoraluminate (also known as potassium fluoralinate), whose chemical formula is usually represented as $KAlF_4$ or $K_3AlF_6$, is commonly referred to as fluorine-aluminum acid potassium flux or non-corrosive flux in the industrial field. It is a white powdery inorganic salt.

1. Physical and chemical properties:

   It appears as a white or light gray powder.

   • Main components: It is usually a eutectic mixture composed of tetra-fluoroaluminate ($KAlF_4$) and hexa-fluoroaluminate ($K_3AlF_6$).
   • Melting point: It has a relatively low melting point, typically ranging from 557°C to 580°C, which is just below the melting points of pure aluminum and most aluminum alloys.
   • Solubility: Slightly soluble in water.
2. The primary function of potassium fluoroaluminate in the core industrial applications is as a flux (welding agent) in the aluminum brazing process.
   • Removing oxide film: The surface of aluminum is prone to forming a dense layer of aluminum oxide ($Al_2O_3$), which hinders the welding process. Potassium fluoroaluminate can quickly dissolve this oxide film in the molten state.
   • Non-corrosive: Unlike traditional chloride fluxes, the residue left after welding with potassium fluoroaluminate does not absorb moisture, does not dissolve in water, and is non-corrosive to the aluminum substrate. This means that no special complex cleaning procedures are required after welding.
   • Application fields: Widely used in the welding of aluminum materials in automotive condensers, radiators, air conditioning aluminum piping, and household appliances.
3. Other application scenarios:

   Besides being used as a flux, it also holds significant importance in the following industries:

   • Abrasive industry: As a filler for grinding wheels and abrasive discs, it can effectively reduce heat generation during grinding and enhance wear resistance.
   • Glass and ceramics: Used as a milky agent to increase the light-blocking property and whiteness of the products.
   • Pesticides: In certain specific formulations, it is used as an insecticide.
4. Safety and Storage

   Although it is called "non-corrosive", this refers only to metals. For humans, it still has certain toxicity and irritation:

   • Protection: During operation, a dust mask and gloves must be worn to avoid inhaling dust or prolonged skin contact.
   • Environment: It contains fluorine. The disposal of waste must comply with environmental protection requirements to prevent water pollution.

One more point to add: This material has played a "behind-the-scenes" role in the process of automotive lightweighting. Without it, the efficient welding of aluminum radiators would be much more difficult.