CN111197150A

CN111197150A - Rare earth yttrium zinc aluminum magnesium alloy coating and preparation method thereof

Info

Publication number: CN111197150A
Application number: CN202010114778.0A
Authority: CN
Inventors: 董瑶加; 张舒婷; 吕玉光; 朱颐申
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-02-25
Filing date: 2020-02-25
Publication date: 2020-05-26

Abstract

The invention discloses a rare earth yttrium zinc aluminum magnesium alloy coating and a preparation method thereof, wherein the coating is prepared from Zn, Al, Mg and Y, and the coating comprises the following components in parts by weight: the doping amount of Al is 2 wt.% of the coating, the doping amount of Mg is 1 wt.% of Zn, and the doping amount of Y is 0.03-0.10 wt.% of Zn, preferably 0.08 wt.%. The invention selects to add rare earth Y element into Zn-Al-Mg plating solution on the basis of Zn-Al-Mg plating layer. With the addition of the rare earth element Y, the generated corrosion product continuously covers the surface of the coating, and the form of the corrosion product is compact. It is these dense corrosion products that prevent the intrusion of corrosive media and protect the substrate. The multi-element alloy coating prepared by the invention has better corrosion resistance, does not change the existing hot galvanizing production line, and is beneficial to popularization and application.

Description

Rare earth yttrium zinc aluminum magnesium alloy coating and preparation method thereof

Technical Field

The invention relates to a zinc-based alloy coating and a preparation method thereof, in particular to a rare earth yttrium zinc aluminum magnesium alloy coating and a preparation method thereof.

Background

The research on improving the corrosion resistance of production equipment is not only a simple technical problem, but also the first economic and social problems of energy conservation, environmental protection, safe production and ensuring smooth production and daily life. Steel is directly or indirectly applied to various industries of industrial production due to its large production, relatively low price and excellent performance, and the loss of steel caused by corrosion is extremely serious, and 1/3 of steel production is lost due to corrosion every year all over the world. According to relevant statistics, steel that is not continuously used due to corrosion accounts for one tenth of the total production volume each year. At present, the economic loss caused by corrosion all over the world is as high as 7000 billion dollars, which accounts for about 2% -4% of the total value of national production, so that the corrosion protection technology of steel needs to be researched.

Hot dip plating is a technique in which a plated article is immersed in a molten metal for a certain period of time and then taken out, and a uniform plating layer having excellent bonding force is obtained after cooling. When the plated part is immersed in the plating metal liquid, the surface of the plated part can generate complex chemical reaction with the plating liquid, and the metal plating liquid can be dissolved and diffused on the surface of the plated part to finally form an alloy plating layer with tight combination. After the plated piece is taken out from the molten plating solution, the molten metal plating solution can be rapidly solidified on the surface of the plated piece, and a plating layer is formed after cooling. It can be seen that the bonding force between the plated layer obtained by hot dip plating and the plated article is very strong. In addition, hot dip plating is thicker than plating obtained by electroplating and electroless plating, which is one of the reasons why hot dip plating has good corrosion resistance.

Rare earth elements refer to scandium, yttrium and all lanthanides. Because of their rare content in the earth crust, their oxides are similar in nature to the earth elements such as calcium oxide, and thus they are named. Yttrium and the other rare earth element cerium are two elements of the rare earth elements with a larger content in the earth crust, so that they are firstly found in the rare earth elements and are cheaper than other rare earth oxides. The zinc-based alloy plating layer with higher corrosion resistance and the plating layer with special performance are also more and more emphasized. Although the corrosion resistance of the coatings is greatly improved compared with the traditional hot galvanizing, the production process is complex, the production cost is high, and the coatings are not widely applied in China. The research on a new coating with the production cost equivalent to that of the traditional hot galvanizing and greatly improved corrosion resistance is still one of the research trends in the field.

Disclosure of Invention

The invention aims to provide a rare earth yttrium zinc aluminum magnesium alloy coating and a preparation method thereof, and the method adds a proper amount of rare earth yttrium element into Zn-Al-Mg plating solution, so that the prepared multi-element alloy coating has better corrosion resistance, does not change the existing hot galvanizing production line, and is beneficial to popularization and application.

The purpose of the invention is realized by the following technical scheme:

a rare earth yttrium zinc aluminum magnesium alloy coating is prepared from Zn, Al, Mg and Y, wherein: the doping amount of Al is 2 wt.% of the coating, the doping amount of Mg is 1 wt.% of Zn, and the doping amount of Y is 0.03-0.10 wt.% of Zn, preferably 0.08 wt.%.

A preparation method of the rare earth yttrium zinc aluminum magnesium alloy coating adopts an electrolytic activation plating assistant method to carry out hot-dip plating on the Zn-Al-Mg-Y alloy coating, and comprises the following steps:

step 1: adding rare earth element Y into a molten alloy furnace filled with Zn-Al-Mg plating solution, wherein the rare earth element Y is added in a manner of intermediate alloy, in order to reduce burning loss of the alloy element, the surface of the molten alloy is protected by a flux, and the main component of the flux is MgCl₂、KCl、CaF₂，MgCl₂、KCl、CaF₂The mass ratio of (A) to (B) is 3:2: 1;

step 2: immersing the pretreated and dried base material into a 400-500 ℃ molten alloy furnace for hot plating for 1-5 min;

and step 3: extracting the base material, and naturally cooling to room temperature under the air atmosphere condition to obtain the rare earth yttrium zinc aluminum magnesium alloy coating on the surface of the base material, wherein: the extraction speed is in the range of 0.1-0.3 m/s.

Compared with the prior art, the invention has the following advantages:

the invention selects to add rare earth Y element into Zn-Al-Mg plating solution on the basis of Zn-Al-Mg plating layer. With the addition of the rare earth element Y, the generated corrosion product continuously covers the surface of the coating, and the form of the corrosion product is compact. It is these dense corrosion products that prevent the intrusion of corrosive media and protect the substrate.

Drawings

FIG. 1 is a polarization curve of a plating layer added with different amounts of rare earth Y in a 3% NaCl solution, 1-0.03% Y, 2-0.05% Y, 3-0.08% Y, 4-0.10% Y;

FIG. 2 is a surface analysis of a Zn-Al-Mg-Y plated test piece;

FIG. 3 is a surface analysis of a Zn-Al-Mg-Y plated test piece;

FIG. 4 shows the surface micro-morphology of the plating after 3000h salt spray test, (a) x 5003000h Zn-2% Al-1% Mg-0.08% Y, and (b) x 20003000h Zn-2% Al-1% Mg-0.08% Y.

Detailed Description

The technical solution of the present invention is further described below with reference to the accompanying drawings, but not limited thereto, and any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be covered by the protection scope of the present invention.

The invention discloses a preparation method of a rare earth yttrium zinc aluminum magnesium alloy coating, which adopts the theory of the existing hot galvanizing production equipment and process, and adds rare earth Y elements with different doping amounts on the basis of an electrolytic activation plating assistant method to prepare a hot-dip Zn-Al-Mg-Y alloy coating. The method comprises the following specific steps:

step 1: 2% of Al and 1% of Mg are added into zinc liquid (99.8%), rare earth elements are added in a mode of intermediate alloy, and the adding amount of each element is calculated according to the chemical composition of the pre-plating layer. In order to reduce the burning loss of alloy elements, the surface of the alloy after melting is protected by a flux, and the main component of the flux is MgCl₂、KCl、CaF₂，MgCl₂、KCl、CaF₂The mass ratio of (A) to (B) is 3:2: 1.

Step 2: and immersing the pretreated and dried base material into a molten alloy furnace with the temperature of about 450 ℃ for hot plating for 2 min.

And step 3: controlling the speed within the range of 0.1-0.3 m/s, extracting from the crucible resistance furnace, and naturally cooling to room temperature under the air atmosphere condition.

The rare earth yttrium can improve the corrosion resistance of the zinc-based coating, wherein the corrosion resistance of the Zn-2% Al-1% Mg-0.08% Y alloy coating is the best. The invention utilizes the existing hot galvanizing production equipment and process, and adds a small amount of Al (2%), Mg (1%) and trace rare earth elements on the basis of hot-dip Al-Mg-Zn alloy coating by an electrolytic activation plating assistant method to obtain a multi-element alloy coating with higher corrosion resistance.

From the results of the salt spray test in fig. 1, it can be concluded that the salt spray corrosion resistance of the plating layer is improved to various degrees after the alloy elements are added to the plating layer, the corrosion rate of the plating layer is continuously reduced after the Al and Mg are added, and the corrosion resistance of the plating layer is also continuously improved, wherein the corrosion resistance of the Zn-2% Al-1% Mg alloy plating layer is optimal. Rare earth elements are added into the Zn-Al-Mg alloy, so that the corrosion resistance of the plating layer is greatly improved compared with a pure zinc plating layer. In the range that the doping amount of the rare earth Y is less than 0.1 percent, the corrosion resistance of the plating layer is continuously improved along with the increase of the addition amount of the rare earth Y. When the doping amount reaches 0.08%, the corrosion resistance is optimal, and when the doping amount of the rare earth Y is continuously increased to reach 0.10%, the corrosion resistance is reduced.

FIG. 2 shows the surface topography of the test piece. As seen from the SEM image, the surface of the plating layer was intact, no significant defects were observed, and a small amount of particulate matter was occasionally attached to the surface.

As can be seen from fig. 3: the surface also contains a small amount of elements such as Fe, O, C1 and the like, mainly comes from surface oxidation and plating assistant agents, the continuous phase in the plating layer is Zn, the dark-color inlay is Zn-Al alloy, and the white attachment is mainly Mg and Y.

As can be seen from fig. 4: the addition of Al, Mg and Y elements to the zinc liquid can improve the corrosion resistance of the hot-dip galvanized layer. Al can form a compact oxide film on the surface of the coating; mg can refine grains to form eutectic structures; y has higher chemical activity, can improve the corrosion resistance of the zinc-based coating, plays a role in purifying alloy liquid and the surface of the coating, and is cheaper than other rare earth oxides, economical and practical. In the alloy coatings, the addition of Al, Mg and Y is less, and the process parameters such as hot-dipping temperature, hot-dipping time and the like are not changed greatly compared with the traditional hot-dipping zinc, so that the alloy coatings can be produced under the condition of not changing a hot-dipping zinc production line, and are convenient to popularize and apply.

In addition, after the rare earth element is added into the alloy liquid, the surface tension of the alloy liquid can be reduced, so that the plating liquid and the substrate are fully wetted. The addition of trace rare earth can refine grains, and the surface tension of the alloy liquid is reduced, so that the specific surface energy of a solid-liquid interface is reduced, the surface energy change of a nucleation system is reduced, the critical nucleus radius is reduced, the nucleation rate is improved, and the grains are refined.

Claims

1. The rare earth yttrium zinc aluminum magnesium alloy coating is characterized by being prepared from Zn, Al, Mg and Y, wherein: the doping amount of Al is 2 wt% of the coating, the doping amount of Mg is 1 wt% of Zn, and the doping amount of Y is 0.03-0.10 wt% of Zn.

2. A rare earth yttrium zinc aluminum magnesium alloy coating according to claim 1, wherein Y is added in an amount of 0.08 wt.% Zn.

3. A method of producing a rare earth yttrium zinc aluminium magnesium alloy coating according to any one of claims 1 to 2, comprising the steps of:

step 1: adding a rare earth element Y into a molten alloy furnace filled with Zn-Al-Mg plating solution, wherein the rare earth element Y is added in a manner of intermediate alloy, and the surface of the molten alloy is protected by adopting a flux;

and step 3: and extracting the base material, and naturally cooling to room temperature under the air atmosphere condition to obtain the rare earth yttrium zinc aluminum magnesium alloy coating on the surface of the base material.

4. The method of claim 3, wherein the flux component is MgCl₂、KCl、CaF₂，MgCl₂、KCl、CaF₂The mass ratio of (A) to (B) is 3:2: 1.

5. The method for preparing a rare earth yttrium zinc aluminum magnesium alloy coating according to claim 3, wherein the extraction rate is in the range of 0.1-0.3 m/s.