| As zinc, aluminum and their alloys are widely used in industry, the traditionalphosphating craftwork has not been able to satisfy the demand for hull painting in industry, sophosphating carbon steel, zinc, aluminum and another kinds of metal in one phosphatingtrough is a very important studuing direction of modem phosphating technique, which has agood market foreground.Under this background, this text studies phosphating carbon steel, galvanized steel andaluminum in one phosphating trough primarily. Through studying the effect of the chiefcomponents in phosphating fluid such as F-, Zn2+, Mn2+, Ni2+ and accelerator on weight andcorrosion resistance of phosphate coatings on carbon steel, galvanized steel and aluminum,this experiment assure the fit content of each component while phosphating carbon steel,galvanized steel and aluminum in one trough, and a optimized process is gotten by orthogonalexperiment. Then through studying the effect of pH, time and temperature on phosphatecoatings, the craftwork parameters of this process is taken. At last the microstructure,elements and compositions are analyzed through SEM, energy spectrum and XRD, and theperformances of phosphate coatings are studied by the method of canceling films and coppersulphate spot test.The result shows: the optimized process by is Zn2+. 2.0g/L, Mn2+: 1.5g/L, Ni2+: 3.0g/L,F-: 2.0g/L, accelerator: 17.5g/L. When the pH of this phosphating process is between 2.8 and3.4, the time is 15 min, and the temperature is 40℃, the coatings formed are even. The colorof phosphate coatings formed on carbon steel appears black gray, the weight is between 5 and12g/m2, the time tested by copper sulphate spot test is over 130 seconds, and themicrostructure is cosh-shaped by means of SEM. The color of phosphate coatings formed ongalvanized steel appears deep gray, the weight is between 4 and 8g/m2, the time tested bycopper sulphate spot test is over 30 seconds, and the microstructure is cosh-shaped by meansof SEM. The color of phosphate coatings formed on aluminum appears light gray, the weightis between 5 and 12 /m2, the time tested by copper sulphate spot test is over 30 seconds, andthe microstructure is gad-shaped by means of SEM... |
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