Which is the best flux to use when soldering galvanized steel?

When soldering galvanized steel, the use of the appropriate flux is crucial for achieving a strong and effective joint. In this case, the correct flux is zinc chloride.

Zinc chloride is particularly effective with galvanized surfaces because it helps to remove oxidation from the surface, allowing for better solder penetration and adhesion. Galvanized steel has a layer of zinc coating, which provides corrosion resistance but can also inhibit soldering if not properly treated. Zinc chloride aids in breaking down this layer and improving the bonding between the solder and the metal.

While muriatic acid, which is a strong mineral acid, is often used in various cleaning applications and can act as a flux, it is too aggressive for most soldering applications on galvanized surfaces. It can damage the base metal and the coating if not used carefully.

Rosin is typically used for soldering with electronic components or in plumbing applications but may not be suited specifically for galvanized steel as it does not clean the surface as effectively as zinc chloride.

Killed acid is a term more commonly associated with acid pickling methods used in metal cleaning and rust removal rather than a flux for soldering processes.

Ultimately, zinc chloride emerges as the best choice for soldering galvanized steel due to its effectiveness in removing protective oxid