王志斌 1刘柯 2王胜民 2侯德宝 1彭斯 1牛犇 1章平1
作者信息
- 1. 太行城乡建设集团有限公司,石家庄 050222
- 2. 昆明理工大学材料科学与工程学院,昆明 650093
- 折叠
摘要
Abstract
Hot-dip galvanized aluminum-magnesium coatings have experienced rapid development over the past few decades and are now widely used in various industries.Current researches on hot-dip galvanized aluminum-magnesium mainly focus on continuous galvanizing,with limited research on batch galvanizing.Batch galvanizing processes in production often suffer from issues such as poor coating adhesion,numerous defects,and difficulties in controlling aluminum and magnesium content.Therefore,the work aims to employ a batch galvanizing process through a self-developed ammonium-free flux and flux treatment process to investigate the effect of Al and Mg element content in the zinc bath on the microstructure and properties of batch hot-dip galvanized aluminum-magnesium coatings.Zinc-aluminum-magnesium alloy coatings with different aluminum and magnesium contents were prepared with an intermittent plating method.The microstructure and chemical composition of the coatings were systematically characterized through scanning electron microscopy(SEM)combined with energy-dispersive spectroscopy(EDS).The corrosion resistance of the coatings was comprehensively evaluated through electrochemical polarization curve testing,neutral salt spray(NSS)corrosion testing,and full immersion corrosion experiments.X-ray diffraction(XRD)was used to analyze the corrosion products of the coatings.After aluminum and magnesium were added to the zinc bath,the coatings consisted of a zinc-rich phase,a Zn/Al/MgZn2 ternary eutectic phase,a Zn/MgZn2 binary eutectic phase,and a Fe2Al5Zn0.8 alloy phase.The distribution of aluminum in the coatings was obvious,located at the interface between the coating and the substrate,exhibiting a band-like overlapping feature with iron,indicating the presence of a Fe-Al alloy phase.Magnesium did not show aggregation,was widely distributed,and mainly existed in the dendrite structure,while zinc was significantly enriched in the free solidified layer.As the magnesium content increased,the Zn/Al/MgZn2 ternary eutectic phase and Zn/MgZn2 binary eutectic phase in the coatings increased.With the increase of aluminum content,the Fe2Al5Zn0.8 phase layer at the coating-substrate interface thickened,and a blocky structure similar to the Fe2Al5Zn0 8 phase formed in the coatings.This process involved iron atoms in the substrate,breaking through the inhibition of the Fe2Al5Zn0.8 alloy phase layer and diffusing outward,leading to the gradual thinning of the Fe2Al5Zn0.8 alloy phase layer at the coating-substrate interface and its evolution into a dispersed blocky distribution within the coatings.Simultaneously,the coating thickness gradually increased.As the magnesium and aluminum content increased,the self-corrosion potential of the coatings gradually shifted positively,the corrosion current density showed a decreasing trend,the polarization resistance gradually increased,and the full immersion corrosion rate of the coatings gradually decreased.Neutral salt spray corrosion results showed that the corrosion resistance of zinc-aluminum-magnesium coatings was significantly better than that of pure zinc coatings.Corrosion product analysis showed that,compared to pure zinc coatings,the white corrosion products of the Zn-2Al-2Mg coatings did not contain ZnO but included compounds containing Mg2CO3,and the diffraction peak of Zn5(OH)8Cl2H2O increased.Therefore,by adding aluminum(0.5wt.％-2wt.％)and magnesium(0.5wt.％-2wt.％)to the zinc bath,batch plating can achieve zinc-aluminum-magnesium coatings with distinct characteristics of Zn/MgZn2 binary eutectic and Zn/Al/MgZn2 ternary eutectic phases.The corrosion products also show significant differences from those of pure zinc coatings,and the corrosion resistance of the coatings is gradually improved with the increasing amounts of aluminum and magnesium.关键词
批量热浸镀锌/锌铝镁镀层/Al、Mg元素含量/锌浴/微观组织/耐蚀性能Key words
batch hot-dip galvanizing/zinc-aluminum-magnesium coating/Al and Mg element content/zinc bath/microstructure/corrosion resistance分类
金属材料
