KR20190053323A - High-efficiency aluminum treatment method in electro-galvanizing - Google Patents

Abstract

The present invention relates to a galvanization method for an aluminum product, which comprises a pretreatment process, a nickel plating process, and a galvanization process. According to the present invention, nickel is primarily plated on a surface of an aluminum product as a base, thereby providing effects of increasing corrosion resistance of the aluminum product which is base metal, and preventing discoloration even after a long time use. When zinc is directly plated on the aluminum product, plating properties of zinc is bad due to numerous pinholes existing on a surface of the aluminum product and, in particular, in the case of a casting product, tendency of an uneven surface of an object to be plated is big due to bubbles generated during a casting process. Therefore, nickel plating fills the bubbles to increase adhesion of zinc plating, thereby providing an advantage of increasing durability of a plating layer. A surface gloss of an aluminum product, which is an object to be plated, is increased more than that of a direct zinc plated surface of the aluminum product, thereby providing an effect of providing a beautiful appearance. Moreover, due to high hardness and strength of nickel, the overall lifespan of the zinc plated product can be increased, corrosion can be prevented by a nickel plating layer even if the zinc plating layer is scratched, and a product can be protected.

Description

TECHNICAL FIELD [0001] The present invention relates to a high-efficiency aluminum treatment method for electro-galvanizing,

The present invention relates to a method of electro-galvanizing an aluminum material, comprising a pretreatment step of removing impurities on the surface of an aluminum product to be plated and enhancing the adhesion of the plating, and a pretreatment step of filling the surface of the aluminum product with a pre- The present invention also relates to a zinc plating method for an aluminum product including a nickel undercoating process for flattening a plating process and a galvanizing process for electroplating a plated material subjected to a nickel undercoating process.

The zinc plating method of the aluminum product having such a constitution can improve the corrosion resistance of the aluminum product as the base metal by plating the surface of the aluminum product with nickel firstly and prevent discoloration even when used for a long period of time, There is a pinhole on the surface of the body to be plated and its surface is not uniform. By flattening it by nickel plating, the durability of the plating layer can be improved by increasing the adhesion of the zinc plating.

The present invention relates to a method of electro-galvanizing an aluminum (Al) material, and more particularly to an electro-galvanized aluminum product having improved properties by primary plating of nickel (Ni) 0001] The present invention relates to an electro-galvanizing method of an aluminum product.

Typical platings are divided into electroplating, chemical plating, and hot dip galvanizing. The chemical plating is a plating process in which a non-conductive product is plated in a chemical plating solution. The plated coating is a solution in which a metal such as zinc, tin or aluminum is dissolved Steel plates are plated with zinc and aluminum. Typical examples are steel plates for relatively large structures, building materials, street lamps, and the like.

In addition, electroplating is carried out for various purposes such as decorating, rust-proofing, and the like, by applying a plating metal to the surface of the electrolytic solution as a negative electrode by conducting an object as a negative electrode. Sound, aircraft, telecommunication, computer parts, jewelry, construction materials, and so on.

Such electroplating is advantageous in that it can process various kinds of small quantities, can give a texture of various metals, and can obtain a film having excellent characteristics and good adhesion to expensive metals.

On the other hand, zinc plating is an anti-corrosion plating method, which is the most common method for coping with structures such as structures due to excellent corrosion efficiency and economical efficiency. Especially, when a scratch occurs on a zinc plated film, Zinc has a sacrificial way of protecting the base metal electrochemically by becoming a cation and there is little change in the mechanical strength of the base metal itself so that it can be used as it is originally designed and various coating processes are possible It has a wide range of applications, and is economically advantageous in long-term maintenance cost.

The pretreatment step S1 includes degreasing S2 for removing the residues, pickling S3 for removing rust, washing S4 for removing iron salts and plating, drying , S5), galvanizing (S6), testing (S7), mapping and finishing (S8).

The degreasing step S2 is a step of removing the base metal product by a degreasing agent or a separate cleaning method when oil or the like is present on the article to be plated.

An alkaline aqueous solution or an acidic degreasing agent is mainly used. After degreasing, the iron structure is washed in the flushing tank to prevent the degreasing solvent from flowing into the next process.

The pickling step S3 is a step of removing rust and debris commonly present on the surface of the steel. It is usually treated with dilute hydrochloric acid or sulfuric acid and is intended to chemically clean the surface before plating. This pickling time depends on the degree of rust development and the concentration of the acid solution.

Washing (S4) is a step of washing with a flushing tank in order to minimize the inflow of the acid solution in the process after chemically cleaning by pickling (S3).

The base metal product having undergone the above process is subjected to an electro-galvanizing process (S6), and the product is made through a final inspection (S7).

However, the galvanized product produced according to such a process has a problem that the uniform surface of the zinc plated layer is not formed due to the fine pinholes formed on the surface of the base metal product, thereby causing a problem of inferior corrosion resistance and durability, There has been a problem in that it is easily discolored when the wet season is particularly wet.

Further, in the state of only the zinc plated layer, there is a problem that the color is easily discolored and fingerprints are deposited to deteriorate the corrosion resistance. In particular, in a severe atmosphere, the thickness of the zinc plated layer must be increased in order to secure corrosion resistance, The workability is lowered. Therefore, there is a demand for a new zinc plating method which can solve the above problems.

The present invention has been made in view of the above-mentioned need, and it is an object of the present invention to provide a zinc plating product which can improve the corrosion resistance of an aluminum product as a base metal and prevent discoloration even when used for a long period of time, And an object of the present invention is to provide a method for producing an aluminum product.

Another object of the present invention is to provide a zinc plating method of an aluminum product which can improve the durability of the plating layer by increasing the adhesion of the zinc plating by filling uneven surfaces such as pin holes existing on the surface of the aluminum product by nickel plating I have to. It is still another object of the present invention to provide a method of galvanizing an aluminum product in which the surface of an aluminum product to be plated is improved in gloss and appearance as compared with the case where the surface is directly galvanized. It is a further object of the present invention to provide a method for preventing corrosion of a galvanized product by the nickel plating layer even when a scratch is generated in the zinc plated layer, And to provide a method of galvanizing an aluminum product which can be manufactured by a conventional method.

According to an aspect of the present invention, there is provided a method of manufacturing an aluminum product, comprising: a pretreatment step of removing impurities on a surface of an aluminum product to be plated to improve adhesion of the plating; And a galvanizing step of electro-galvanizing the material to be plated which has undergone the nickel undercoating process. The present invention also relates to a method of galvanizing an aluminum product.

According to an aspect of the present invention, there is provided a method of manufacturing an aluminum product, the method comprising: a pretreatment step of removing impurities on a surface of an aluminum product to be plated to increase adhesion of the aluminum product; And a galvanizing step of electro-galvanizing the material to be plated which has undergone the nickel undercoating process. The present invention also relates to a method of galvanizing an aluminum product.

At this time, it is preferable that the pretreatment step is carried out in the order of acid treatment, water washing, alkali degreasing, washing, zincate, and washing.

In the acid treatment step, it is preferable to mix acetic acid and hydrofluoric acid in a volume ratio of 8: 2 to 9: 1, and the jingate step is carried out using a METEX 6881 in a zincate bath for 10 to 30 seconds . The nickel undercoating process is preferably carried out in a plating solution containing 240 to 300 g / L of nickel sulfate, 40 to 60 g / L of nickel chloride, 40 to 60 g / L of boric acid and a slight polishing agent.

The zinc plating process is also carried out in a plating solution comprising 25 to 32 g / L of metal zinc, 65 to 98 g / L of blue soda (NaCN), 80 to 90 g / L of caustic soda (NaOH) .

In addition, the zinc plating method may further include a chromate step as a post-treatment step.

A nickel plating layer is formed on an aluminum (Al) material as a base metal product, and a zinc plating layer is formed thereon.

In this case, the electroplated nickel has three kinds of hardness, durability, stress and tensile strength depending on the plating solution. Typical nickel plating baths include sulfamate, fluoroborate, and pyrophosphorus. Typical thicknesses of the nickel- 8 mu m.

The reason why such nickel undercoating is performed is that nickel can prevent the base metal from diffusing into the plating layer, and the plating layer can be thinned by performing the nickel plating treatment. In addition, since the surface of the base metal is reduced in pores to prevent surface corrosion, nickel is harder than zinc and a hard base layer is formed, so that the wear resistance of zinc can be improved.

The improvement in durability and corrosion resistance by the nickel undercoating can be confirmed by a chlorine spray test in which a 5% sodium chloride (NaCl) solution is sprayed.

Zinc plating methods are roughly classified into a pretreatment process, a nickel undercoating process, and a zinc plating process.

The pretreatment process will be described below. First, when a base metal material made of aluminum is received, it is treated with acid in a PVC bottle to remove foreign matter on the surface of the product, and then the adhesion of the plating film is improved during the nickel base plating process.

In the acid treatment step, sulfuric acid is mostly used in steel materials, but hydrofluoric acid and acetic acid are widely used in aluminum materials.

In the present invention, acetic acid and hydrofluoric acid are preferably mixed in a ratio of 8: 2 to 9: 1 based on the volume ratio. By this ratio, it is possible to more effectively remove foreign matter.

The base metal material subjected to the acid treatment is washed and inspected and then degreased to remove organic matter. The degreasing step is performed by removing degreasing agent or a separate washing method . In the present invention, the degreasing solution, sodium cyanide (NaCN), caustic soda (Na2CO3), sodium hydroxide (Na2CO3), and the like are used in order to prevent the degreasing solvent from flowing into the next process. Sodium hydroxide (NaOH)) is used to degrade the alkali.

The aluminum product subjected to the degreasing process is subjected to a zincate process by hanging on a rack hanging table, which is treated for 10 to 30 seconds using METEX 6811, which is an alkaline agent.

At this time, the METEX 6811 preferably has a concentration of 240 ml / L and the temperature is in the range of 13 to 30 ° C.

The aluminum product passed through the zincate process is subjected to washing and inspection steps to check whether the nickel plating layer is adhered in a predetermined shape.

The aluminum product that has undergone the washing and inspection steps undergoes a preheating drying step to remove moisture and impurities on its surface, and then enters a nickel undercoating step.

At this time, a nickel plating solution is used which is composed of 240 to 300 g / L of nickel sulfate (NiSO4), 40 to 60 g / L of nickel chloride (NiCl2), 40 to 60 g / L of boric acid and a little polishing agent.

Such a nickel plating plating solution has a pH of about 4.5 to 5.5, a temperature of 45 to 55 ° C, and a voltage of 1 to 10 V to be used.

On the surface of an aluminum product processed by a metal mold, rolling, or casting, bubbles are formed in the above-described processing, and a large number of fine pinholes are generally formed.

If zinc is directly plated on the surface of the fine pinholes formed thereon, the surface condition of the plated layer is not homogeneous, and since some pinholes tend not to be filled up, nickel plating is performed primarily on the aluminum surface, It is made of zinc and plated with zinc.

Next, the nickel-plated aluminum product subjected to the nickel undercoating step is washed and inspected and then subjected to a zinc plating step, which includes 25 to 32 g / L of metal zinc (Zn) and 65 to 98 an aqueous solution consisting of a mixture of g / L sodium cyanide (NaCN) and 80 to 90 g / L sodium hydroxide (NaOH) is used as a plating solution.

At this time, the temperature of the plating solution is 18 to 24 ° C, the applied voltage is 3 to 15 V, and the ratio of the amount of germanium sulfate (g / L) to the amount of zinc (g / , Which should be maintained in the range of 2.5 to 3.0.

As the electro-galvanizing progresses, the amount of zinc in the plating solution increases and the M ratio becomes low. If the amount falls outside the above range, plating may not be performed smoothly. Therefore, water should be diluted regularly.

Particularly in the case of aluminum, the M ratio is more sensitive to the M ratio than the steel material, so more careful management is required.

In addition, the product that has undergone the above-described electro-galvanizing step may be further subjected to a water-washing treatment and, if necessary, a chromate step as a post-treatment step, which is a process for coloring black, natural color, olive color or national color.

Particularly, the chromate step for coloration of the above-mentioned green color is carried out by mixing 225g / L of chromic acid anhydride (CrO3), 40cc / L of acetic acid (CH3COOH), 40cc / L of lactic acid (C3H6O3) Of phosphoric acid (H 3 PO 4) and 20 cc / L of glacial acetic acid (CH 3 COOH).

Also, the above-mentioned coloring chromate step is performed by immersing at a temperature of 27 to 34 ° C for 50 to 60 seconds. Through this chromate process, various colors can be obtained and an effect of protecting the zinc plating layer can be obtained .

After the above-mentioned process, the zinc plated aluminum product is finally inspected and the process is completed.

Claims (1)

A pretreatment step of removing impurities on the surface of the aluminum product to increase the adhesion of the plating; A nickel undercoating process for making the surface uniform by filling a pinhole of the aluminum product after the pretreatment; And a galvanizing step of subjecting the plated body that has been subjected to the nickel bottom plating step to electro-galvanizing.