Research On New Hot-dipped Zn-based Coatings And Processes

The study of metal corrosion and protection is significant, and Hot-Dipping technology is one of effective means to improve the corrosion resistance of steel and iron. Zn-Al alloy coatings as a new anticorrosive material owing to good viscidity, wear-resistance, corrosion resistance, simple process and low cost, have been applied far and wide and become a hot-spot of research. In this thesis, the optimum components of RE, Mg and Ti based on Zn-4.5%Al alloy and effects of CeCl₃ addition in infusion of assistant plating, as well as Ultrasonic assistant plating technics on the thickness, surface quality and corrosion resistance of the coatings have been investigated.Effects of RE, Mg and Ti additions on the microstructure and corrosion resistance of Zn-4.5%Al alloy were investigated. The results of morphology and electrochemistry test to the single addition alloy indicated that the effect was comparatively obvious when the single addition content of RE, Mg and Ti has been 0.10%, 0.10% and 0.03% respectively. Orthogonal experiments were carried out on the base of upper results. Results of SEM, neuter salt spray corrosion and electrochemistry test implied that excellent eutectic microstructure and corrosion resistance property were obtained in the Zn-4.5%Al-0.10%RE-0.05%Mg-0.05%Ti alloy. Finally, the mechanism of corrosion resistance was discussed, trace adiditions of the alloy elements have obvious effects on the refinements of intergranular corrosion and grains.The technics of assistant plating on self-made alloy coatings through orthogonal experiments were investigated in this work. The optimum process was that the content of CeCl₃ has been about 0.5wt%, the time of assistant plating has been 3 minutes and the temperature has been 40℃. We founded that the Ultrasonic technics could certainly enhance the corrosion resistance of the samples. The samples were characterized by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), and the results indicated that the utility of infusion of assistant...