Titanium And Magnesium Hot-dip Galvanized Layer Performance

Hot-dip zinc and its alloy are widely used all over the world. In order to improve theperformance of the hot-dip coating, many researches have been done on the addition of lots ofelements to the zinc bath. But the addition of elements to the pure zinc bath (to eliminate thedisturbance of impurity) is relatively less mentioned.In this paper, pure zinc (99.999%) was chosen as zinc bath, the disturbances of otherelements were basically eliminated. Zn-Ti alloy, Zn-Mg alloy and Zn-Ti-Mg alloy hot-dip coatingswere prepared. The coatings' corrosion behavior in the marine environment and the performanceof corrosion resistance was studied.The melting point of Ti(1668℃ ) is much higher than Zn(419.5℃ ), and the oxidation of Mgelement is difficult to avoid in high temperature condition. Therefore, middle alloys must beprepared and its contents were precisely analyzed. The middle alloys were added to zinc bathaccording to the dosage by calculation. This method is convenient and suitable. Since thecomponent of the outermost layer of the hot-dip coating is basically consistent with the bath alloy,the performance of bath alloy can reflect the performance of the coating. Zn-Ti electrodes andZn-Mg electrodes were prepared to perform electrochemical property test. The result showed thatthe addition of Ti, Mg can improve the corrosion resistance of the alloys in the marineenvironment.We adopted liquid flux method as pretreatment method of hot-dip galvanizing process,withproper technical conditions as follows: the mixture of ZnCl2 and NH4Cl solution as the flux ofgalvanizing, temperature 460℃, liquid zinc with different contents of Ti, Mg as bath. By checkingthe surface quality of the coatings we found that the quality are up to grade, the coating is brighterafter the addition of Ti. The coating's thickness is an important item to inspect the coating'sperformance. We found the coatings are uniform by measured, the coatings' thickness decreasewith the addition of Ti, increase a little with the addition of Mg and is intervenient with theaddition of Ti and Mg at the same time. After the addition of Ti, Mg element, the figure of EISdiagrams and polarization curves changed a little, the value of Rp that simulated by equivalentelectrical circuit increased. The results showed that the addition of Ti, Mg can improve thecorrosion resistance of hot-dip coatings in marine environment.The neutral salt spray test and immersion test had been done to check the coatings corrosionresistance. The results showed that after the addition of Ti, Mg the corrosion weight loss ratiodecreased.