Alkaline zinc trivalent chromium black passivation

1, characteristic in alkaline zinc surface passivation layer to form a black trivalent chromium-based non-hexavalent chromium black passivation generate a uniform and beautiful black appearance without blocking agents also have excellent corrosion resistance, does not affect 2 disposable wastewater conductivity, a bath operating parameters values ??SY-4900Ⅰ 30-80 ml / l (3-8% by volume) 50 ml / l (5% by volume) SY-4900Ⅱ 60-160 ml / l ( 6-16% by volume) 125 ml / l (12.5% ??by volume) Temperature 20-40 ℃ 30 ℃ pH 2.0-2.8 2.2 seconds to 60 seconds soaking time 20-70 PH adjusted with nitric acid or sodium hydroxide to adjust the mixture was stirred mechanically or air agitation filtration is recommended