Zinc ammonium chloride is commonly known as Flux

Flux (metallurgy)

In metallurgy, a flux , is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time...

, and is used for galvanizing steel. It is 60% ammonium chloride

Ammonium chloride

Ammonium chloride NH4Cl is an inorganic compound with the formula NH4Cl. It is a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. Sal ammoniac is a name of natural, mineralogical form of ammonium chloride...

 and 40% zinc chloride

Zinc chloride

Zinc chloride is the name of chemical compound with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. ZnCl2 itself is hygroscopic and even deliquescent. Samples should therefore be protected from...

 in it. The pH

PH

In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 of zinc ammonium chloride should be 4.2.

Zinc ammonium chloride is not to be confused with zinc ammonium carbonate.

Zinc ammonium chloride is not necessarily 60:40 ratio of Ammonium chloride and Zinc Chloride as stated by the writer above. The ratio is varied as per type of usage for the flux. However 60:40 is a more running grade of zinc ammonium chloride. Apart from ammonium chloride and zinc chloride, it also contains galvanizing additives like glycerol

Glycerol

Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...

, sodium dichromate

Sodium dichromate

Sodium dichromate is the chemical compound with the formula Na2Cr2O7. Usually, however, the salt is handled as its dihydrate Na2Cr2O7·2H2O. Virtually all chromium ore is processed via conversion to sodium dichromate. In this way, many millions of kilograms of sodium dichromate are produced...

, borax

Borax

Borax, also known as sodium borate, sodium tetraborate, or disodium tetraborate, is an important boron compound, a mineral, and a salt of boric acid. It is usually a white powder consisting of soft colorless crystals that dissolve easily in water.Borax has a wide variety of uses...

, etc. For a good write up of zinc ammonium chloride one may visit Zinc Ammonium Chloride Flux