Influence of rare earth yttrium on the structure and corrosion resistance of hot-dip aluminum coating

The work aims to study the influence of rare earth Y on the hot-dip aluminum coating and improve its corrosion resistance. By adding different contents of aluminum-yttrium alloy to the hot-dip aluminum coating solution, hot-dip aluminum-coated parts containing different rare earth yttrium content were obtained. In the experiment, the corrosion solution was 3.5% NaCl solution. SEM and EDS were used to observe morphology and composition and electrochemical tests and full immersion tests were used to study the effect of rare earth Y on corrosion resistance of coatings. When the content of Y was 0.2%, the surface of the hot-dip aluminized layer was smooth without holes, the needle-like phase was fine, the aluminized layer was thinner, and the shape of transition layer changed from the sawtooth to the continuous band. The rare earth Y made the corrosion potential shift positively and decreased the self-corrosion current, which the most positive self-corrosion potential was ‒0.7857 V and the minimum self-corrosion current was 1.3505×10‒8 A/cm2. Compared with other rare earth elements, the breakthrough potential Eb of the coating, when 0.2% Y was added was, the most positive potential is ‒0.6957 V. The impedance spectroscopies of hot-dip aluminized parts with different rare earth contents were all single capacitive reactance arcs. The radius of the capacitive reactance arc was the largest when the rare earth content was 0.2% Y and the corrosion rate of coated parts was the lowest when 0.2% Y was added in the full immersion test The addition of rare earth yttrium can make the surface of the hot-dip aluminum coating smooth and continuous, and the corrosion resistance can be improved. Furthermore, the corrosion resistance of aluminum-coated parts is the best when the addition amount is 0.2% Y. © 2021, Chongqing Wujiu Periodicals Press. All rights reserved.