Methods and compositions that serve to both darken a zinc or other active! metal surface and impart corrosion-resistant properties thereto, are disclosed. The compositions include an aqueous solution containing about 0.1 percent to about 5 percent ammonium chloride and about 0.1 percent to about 5 percent ammonium molybdate. The compositions utilize particular ratios of concentrations of ammonium chloride and ammonium molybdate.