The Study Of PPS-PTFE Low Surface Energy Organic Coating Upon Hot Dip Aluminum Coating

Under the influence of air and water, exposed steel will lose effectiveness arising from electrochemical corrosion. To prolong lifetime of the sample and endow it with the self-cleaning capability, the low surface energy organic coating was coated on hot dip aluminized steel. Such two protection layers can make full use of the advantages of their own. Having lower corrosion potential than steel, the hot-dip aluminum coating that even has pores could protect the steel for several decades. On the polyphenylenesulfide (PPS)-polytetrafluoroethene(PTFE) coating with low surface energy, water has bigger contact angle and smaller rolling angle than hot-dip aluminum coating, which makes it easy to be cleaned. The problem that hot-dip aluminum coating becomes aging and dirty after years’service could be solved with such low surface energy organic coating.On the basis of hot dip aluminizing and chemical oxidation, the formula of paint and the sintering process of PPS-PTFE coating were studied systematically in this work. The smooth and homogeneous hot-dip aluminum layer can be obtained during the rise of temperature from720℃to725℃. The uneven feature appears in the chemical oxidation solution at35℃for6minutes with dissolved CrO3(25g·L-1) and H3PO4(60ml·L-1) and (NH4)2HPO4(2.5g·L-1) and NH4HF (3.5g-L-1) and H3BO3(1.2g-L-1). The best suspension contains PPS of60g and TiO2of3g and Cr2O3of3g and PVA of lOg and SDS of4g and H2O of300mL. The best volume ratio of PPS and PTFE is12to1. The roller coating was firstly sintered at the temperature of80℃for5minutes, then200℃for15minutes,360℃for15minutes at last, in this way, can we get the best coatings. The best cooling method is in the air.None of the25grids by portraying cross is damaged, which shows that the adhesion of coating is very good. The largest contact angle is126°, which provide good self-cleaning capacity. Through the analysis of polarization curves and impedance, samples with organic coatings have10times corrosion current less than those without organic coatings in3.5%NaCl solution, while the impedance is orders of magnitude larger than those without coatings (105Ωcm2vs400Ωcm2), which significantly improve the corrosion resistance of hot dip aluminum coating.