Research Of The Formation Mechanism And Corrosion Resistance Of Zn-Ti-Al Coating By Hot-dip Galvanizing

With the unceasing enhancement for the development of modern industry on steel structure corrosion resistance,exterior quality and formability, coating alloying technology has become an important process of hot-dip. Based on the current study status, this paper attempt to study Zn-Ti-Al ternary alloy coating organization structure and corrosion resistantce characteristics.Based on the preliminary research, the corrosion resistance and the formation mechanism of the three Zn-Ti-Al alloy coating was further explored in this paper.Comprehensive utilization of metallographic microscope,SEM and EDS.electrochemical workstation,Neutral salt spray test chamber,X-ray diffractometer etc on the comparison and analysis of the different corrosion resistance between the various coatings by altering dipping time and temperature,obtain the following conclusions:Along with the increases of dipping time.coating thickness of various scheme are increases.But compared with the pure zinc plating,Zn-Ti alloy coating thickness increased relatively stable,the phenomenon about super thick growth ofζphase won't appear;Zn-Ti-Al alloy coating thickness increased relatively stable too,meanwhile it can obtain more thin coating than Zn-Ti alloy coatings, the main reason is the Ti, Al elements onζphase growth all have certain inhibition,while Al elements has significantly improved alloy bath flow property,so coating the outer mostηpure zinc phaseas as to thin relatively.At the same dipping time,pure zinc and Zn-Ti alloy coatings basically expression is as hot-dip temperature rises,the coating corrosion rate decre-ase.But Zn-Ti-Al coating corrosion rate as hot-dip temperature change influence of law is not obvious, thereinto, in hot-dip time for 60 seconds or 240 seconds,the corrosion resistant of A3 alloy coatings resistance hardly with hot-dip temperature changing.Experiment also shows that,the influence of hot-dip time and temper-ature on the coating apparent performance and salt spray corrosion rate is relatively laarge,and on the coating electrochemical polarization influence on the performance of the lesser.Alloy composition is the main factors of influence on coating electrochemical polarization characteristic.Based on the diffusion theory,this paper explains diffusion response rate was changed by hot-dip time and hot-dip temperature,and the coating the phase composition and structure of coating appears certain changes.At the same time,because of Si element diffuse into zinc bath,leading to the coating dispersion delta phase (Diffuse-Δ) appear in coating,while joining Ti,Al elements inhibit the growth ofζphase,which indirectly accelerated the dispersion delta facies to appear.