| In order to reduce the environmental pollution caused by the electroplating industry in use of chromate salt, this paper studies a novel chromium-free passivating liquid technological formulation used for bright blue passivation of alkaline galvanized layer. This passivating liquid takes silicate as main raw materials and contains substances such as hydrogen peroxide, fluorin ion and others. Using the method of combining orthogonal optimization and single factor optimization, the impact of all the components of Silicate type passivation liquid upon galvanized layer passivation membrane is discussed. Besides, the systematic research on galvanized silicate passivation technology is carried on, and the impact of passivation solution composition, passivation temperature, passivation time, passivation solution pH value, time of pause, Activation time, glaring time upon the passivation membrane and membrane layer noncorrodibility. Passivation solution composition and process conditions is as the followed:Na2SiO3·9H2O 18g/LHNO3 15ml/LZnSO4·7H2O 28 g/LNaF 2.4 g/LH2O2 10ml/LPassivation Time 20 spH Value 2-3Passivation temperature 25℃Time of pause 0-1 sActivation time 25 sGlaring time 5 sDry conditions Blowing drywith Hot airExperimental material is an alkaline electricity galvanized steel plate. After the above mentioned solution is passivated,the noncorrodibility of this silicate passivation samples has been researched by way of neutral salt spray test(NSS test), acid copper dropping test, salt water immersion test and electrochemical test, etc. and the passivation membrane is characterized by scanning electron microscope and XPS.The research shows that by this silicate passivation technology bright blue passivation membrane with good gloss and high noncorrodibility can be acquired in the surface of galvanized layer, which can replace traditional chrome salt passivation technology so as to solve the problem of environmental pollution, and has good application prospect. |
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