Microstructures and Key Properties of Mechanically Deposited Zn-Al Coatings

摘要

Zn-Al coatings can provide protection to exposed steel parts in most environments. For this reason,the investigation of Zn-Al coatings become very popular in recent years. In order to study the microstructures and properties of mechanically deposited Zn-Al coating,zinc powders and aluminum powders were used to deposit Zn-Al coating by mechanical plating. The microstructures,phase constitutes and compositions of the coating were observed and analyzed with optical microscopy （OM）,scanning electron microscopy（SEM）,X-ray diffraction（XRD） and X-ray energy-dispersive spectroscopy（EDS）. The results of observation show that the coating consists of almost spherically shaped zinc particles point contacting with each other; the coatings are composed of zinc particles,aluminum particles,interstice,and tin; extra fine zinc powders and some smaller interspersed inclusions are positioned in the interstices. Porosity and thickness of the coating were tested by ferroxyl test and magnetic method. The corrosion resistance of coatings was studied by neutral salt spraying test（NSS） ,immersion test and electrochemical polarization. It is found that the thickness of the coating dose lacks uniformity,with an uneven thickness distribution and an average variation of approximately 2-5μm; the coating can afford cathodic protection to the steel substrate; the corrosion resistance of Zn-Al coatings is better than that of the mechanically plated zinc coatings with same thickness. These conclusions can be applied to improve anti-corrosion performance by mechanically deposit Zn-Al coatings.