Study on microstructure and properties of hot-dip zn-6ai-3mg alloy coatings and the required materials

Hot dip galvanizing is widely used in steel protection and has good economic benefit and development prospect. However, with the development of iron and steel materials and people's requirements on the performance of coatings are getting higher and higher. In hot-dip galvanization process, some alloy elements should be added into zinc bath to adjust the process parameters to produce high quality products that meet the market requirements. The hot plating of zn-ai-mg alloy on steel base surface is a hot topic in the international research on corrosion prevention of metal surface. Zn-ai alloy coating has the function of blocking and sacrificing anode protection. Adding a small amount of mg in zn-ai alloy can refine grain and strengthen grain boundary, which will greatly improve the corrosion resistance of the coating. In recent years, there have been more and more researches on zn-ai-mg alloy coatings at home and abroad, but the research is still at the initial stage, and the research on the structure and corrosion resistance mechanism of zn-ai-mg alloy coatings is very limited. And existing for coating solidification structure research also has different explanations, as most studies have shown that zinc - al - mg alloy coating is composed of three phase: with recent photograph, ai and zn2mg phase or zn11mg24 but in what way exists in the three phase coating upper without cutting study: some research shows that coating contains no binary for crystal, some studies have shown that the composition of binary zinc - mgzn2 binary crystal or zinc/ai for crystal but bulky groups; For uniphasic tissues, some studies have found that there are block ai phase and zn phase, while others have no single zn phase. Therefore, it is of great significance to study the structure of zn-6ai-3mg alloy coatings and explore the corrosion mechanism of zn-6ai-3mg alloy coatings.

Experimental materials and methods

1. The experiment to Q235 steel (6 cmx4cmx0. 4 cm) as the matrix material of hot zinc plating - 6 ai - 3 mg plate, adopt some traditional industrial process for the former treatment - help plating - drying - hot dip plating - cooling, the hot dip process parameters of 540 ℃, 60 s.

2. Use rigaku dmax-rc X-ray diffractometer to conduct physical phase analysis of zn-6ai-3mg coatings, determine the physical phase composition of the coatings, observe the structural appearance of the coatings with sl4800 scanning electron microscope, and record the tissue characteristics.

3. In order to compare, the preparation of substrate same with zinc or zinc plating, zinc plating - 6-5 ai ai - 3 mg plate specimen in salt spray test, salt fog box (35 and 5% naci, control the temperature in the cabinet 2 ℃), for naci neutral salt spray test to detect the coating corrosion resistance. The corrosion time is 120 hours.