Study On Process Of Zn-Ni Alloy Nanocomposite Planting Of Highanti-corrosion Property

Plating Zn-Ni alloy coating is one of the common methods of steel corrosion prevention, compared to zinc coating, corrosion resistance of Zn-Ni alloy coatings have been greatly improved.In order to further improve the corrosion resistance of the coating, by meas of add nanoparticles to bath, and plating nano-composite coating to improve its corrosion resistance, then discuss the experimental process. On this basis, the author combined the unique properties of rare earth elements, modified nanoparticles, and then add to the plating bath, first, the bath performance is determined, and then measure the coating adhesion, and by electrochemical measurements, SEM, EDS, XRD and other means to test the coating performance.First, the dispersibility, the coverage and the cathode current efficiency of the bath were measured. About zinc-nickel alloy plating process, the scope of each process of the experiment is substantially determined by orthogonal test method, and examine the substrate binding of each orthogonal coating, and then determined the optimum conditions by single variable method. And test different coatings,electrochemical impedance spectroscopy curve and polarization curves at different temperatures, current density, p H by electrochemical workstation. Founded that with the increase of various process conditions, the impedance of the coating increased at first and then a downward trend, and the corrosion current density decreased at first and then a upward trend. Confirmed the optimal process parameters of zinc-nickel alloy plating : temperature is 35℃, current density of 4 A·dm-2, p H value of 5.5, the stirring speed was 200 r·min-1.To prepare with the nano-composite coatings, we prepared nanoscale Si O2 by sol-gel, and then compared with the commercially available nano-Si O2. Founded that homemade nano particle size is large, but well dispersed, and commercially available nanoparticles has small particle size but easy to glomerate. At different stirring speeds, ultrasonic power, temperature and current density conditions,the dispersion of homemade nanoparticles in the coating is better than the commercially,and therefore we chose homemade nanoparticles. and then dispersed through different dispersants, dispersion effect of CTAB is best. Measured by electrochemical to test the plating AC impedance curve and polarization curves at different plating process, found that when the amount of nanoparticle composite is 6 wt%, the coating had highest impedance, reaching 10520Ω, corrosion current density as low as 3.302μA·dm-2. Observation of the coating microstructure by SEM founded that with the increase in the amount of nanoparticle composite coating by "rock-like" to "cauliflower-like " and then to " rod".To further improve the corrosion resistance of the coating, we first used rare earth oxide Ce O2 coated nanoparticles, made it contain the unique properties of nanoparticles of rare earth elements. by electrochemical test,we found that, under the same conditions, the corrosion resistance of this coating is higher than Zn- Ni-Si O2 composite coating. When the amount of nanoparticle composite is 6 wt%, the coating impedance reached 15460Ω, corrosion current density was 1.556μA·dm-2. In the plating solution, when added in an amount of nanoparticles of 10g/L, the current density was 6 A·dm-2, p H was 5.5, the nanoparticles in the coating dispersion best.