Zinc chloride fluxes are used for? brazing to bind two metals together due to the hydrochloric acid formed during hydrolysis which occurs when the flux is heated.? The HCl reacts with the metal oxide layer of the metal.? Here's a series of reactions with iron sulfate:
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ZnCl2 + 2H2O > Zn(OH)2 + 2HCl
FeS + 2HCl > FeCl2 + H2S
ZnCl2 + H2S > ZnS + HCl
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Now most of the HCl is a gaseous product, but you can see that the presence of zinc chloride continues to reduce the by-products of the initial reaction with the metal oxide layer.? It doesn't matter that the ZnCl2 is neutral under ambient conditions.? Because the process of heating it will create acidic byproducts like HCl.??
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Frank Mashockie