JPH0456115B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a product made of aluminum and having a mirror-finished surface provided by plating. [Prior art] Aluminum and its alloys have traditionally been used in various machinery and appliances because they are lightweight and have excellent workability, but when used as a material for mirrors, they are soft and deform. Mirrors made of aluminum were only used in special cases because they were easily scratched, easily scratched, and an oxide film easily formed on the surface, impairing plating properties. The product is obtained by first processing aluminum material to form an alumite layer, and then applying bright plating to the pear surface, so the image is unclear compared to ordinary mirrors made of glass or stainless steel. In particular, it was completely unusable for full-length mirrors, back mirrors, etc. As a result of various studies to eliminate these drawbacks, the inventor of the present invention used aluminum or its alloy as a material, added a specific treatment to remove scratches on the material itself such as pits, and further applied multiple nickel electroplated layers. By making use of the bright aluminum material, we succeeded in giving the surface a mirror surface that is extremely clear, lightweight, and unbreakable compared to conventional mirrors made of glass or other materials. Aluminum products that have been given a mirror-like reflective function by this type of plating are manufactured by sequentially coating the aluminum surface with a chemical conversion coating layer of zinc and nickel, a semi-bright nickel electroplated layer and a bright nickel electroplated layer. An electroplated layer and a chrome electroplated layer are provided, and the thickness ratio of the semi-bright nickel electroplated layer to the bright nickel electroplated layer is 1:1.5 to 2.5 (Tokuko Showa).
57-22998). As a result of further research, the present inventor found that by reducing the thickness ratio of the semi-bright nickel electroplated layer to the bright nickel electroplated layer below the above value, the corrosion resistance of the plated product could be further improved without impairing the specular reflection function. The present invention was completed based on the discovery that improvements could be made. [Structure of the Invention] The present invention is made of aluminum, and the surface thereof is sequentially coated with a plurality of nickel electroplated layers including a zinc-containing chemical conversion coating layer, a semi-bright nickel electroplated layer and a bright nickel electroplated layer, and chrome. an electroplated layer is provided, and the ratio of the thickness (a) of the semi-bright nickel electroplated layer to the thickness (b) of the bright nickel electroplated layer is 0.25≦b/
This is an aluminum product with specular reflection function given by plating, where a<1.5. Furthermore, the present invention degreases the surface of aluminum,
After wiping off impurities remaining on the surface and activating the surface, a plating base film is formed by chemical conversion treatment using an aqueous solution containing a zinc compound and sodium hydroxide, and a semi-gloss base film is formed on this film. Multiple nickel electroplating from nickel electroplating layer and bright nickel electroplating, 45
Applied at a temperature of ~65° C., a current density of 2.5 to 5.5 A/dm ² and a pH value of 3.2 to 5.7, thickness a of the semi-bright nickel electroplated layer versus thickness of the bright nickel electroplated layer (b) The ratio is 0.25≦b/a<1.5
on the thus formed nickel electroplated layer at a temperature of 45-55°C and 10-20A/
This is a method of manufacturing a product made of aluminum and given a mirror surface by plating, by applying chrome electroplating at a current density of dm ² . Aluminum used as a raw material in the present invention includes not only pure aluminum but also aluminum alloys, and can be in various shapes such as plates, rods, wires, tubes, and spheres. When producing the aluminum product with the light reflecting function of the present invention, first, the surface of the aluminum material is made shiny by special rolling, special polishing, etc., and then treated with an organic solvent such as trichlorethylene and sodium hydroxide. After degreasing by sequentially immersing in an aqueous solution, the surface is wiped with a soft cloth to remove impurities. In this case, ordinary electrolytic degreasing will not completely remove the impurities, and the remaining impurities will cause peeling of the plating layer in the future and unevenness of the plating layered on top of it, so it is not recommended to use the above-mentioned wiping process. Advantageous due to complete removal of impurities. Next, the surface treated in this way is treated by a conventional method.
For example, after immersing in nitric acid to activate the
A plating base film is formed by immersing it in an aqueous solution containing 300 to 700 g/preferably 400 to 600 g of sodium hydroxide for chemical conversion treatment. This aqueous solution for chemical conversion treatment contains other common ingredients,
For example, it can contain potassium hydrogen tartrate, potassium sodium hydrogen tartrate, sodium cyanide, potassium cyanide, sodium nitrate, and the like. In addition to zinc oxide, zinc sulfate can also be used as the zinc compound. Furthermore, it is also preferable to add nickel chloride, nickel sulfate, ferric chloride and/or copper sulfate as other metal compounds. On the plating base film thus formed, a plurality of nickel plating layers are applied by a conventional method. For this purpose, a semi-bright nickel electroplating process is carried out in a conventional manner, followed by a bright nickel electroplating layer. For performing nickel electroplating, for example, nickel sulfate 280-350g/preferably 300-320g
g/, nickel chloride 35-60 g/preferably 40
In a plating bath of PH 3.2 to 5.7 preferably PH 4 to 4.6 containing ~50 g/brightener and a current density of 2.5
~5.5A/ ^dm2 preferably 3~4.5A/ ^dm2 , temperature
45-60℃, preferably 50-55℃, 0.3-0.6Kg/ ^cm2
It is preferably operated under an air pressure of 0.4 to 0.5 Kg/cm ² for stirring. In this case, for the first semi-bright nickel electroplating, brighteners are usually used, such as butyne diol, lauryl alcohol sulfate, coumarin or homarin, and for the subsequent bright nickel electroplating, brighteners are used. For example, butyl alcohol, propargyl alcohol or a mixture thereof is used. By performing these two types of nickel plating, the ratio of the thickness (a) of the semi-bright nickel electroplated layer and the thickness (b) of the bright nickel electroplated layer is 0.25≦b/a<
When the value is 1.5, the surface is given an extremely high brightness and reflection function, and a product with excellent properties as a mirror and excellent corrosion resistance can be obtained. The value of b/a is about 0.5 to 0.8, especially about 0.6 to
0.7 is desirable. In order to achieve the ratio of the thicknesses of the semi-bright and bright nickel plating layers within the range mentioned above, conventional means are used, for example, the plating conditions (plating bath composition, current density, plating time, etc.) and/or Alternatively, the number of times of plating processing can be changed. The greater the number of nickel plating treatments, the better the properties of the product, but for operational and economic reasons, a total of 2 to 3 treatments is desirable. Non-conductive fine particles of about 0.02 μm are uniformly suspended in the above-mentioned nickel electroplating bath by air agitation, and eutectoid with nickel. So-called microporous nickel electroplating can diffuse local corrosion currents and further improve the corrosion resistance. This microporous nickel electroplating is particularly preferably carried out in the last nickel electroplating. Finally, apply 200 to 300 g of chromic anhydride/preferably 250 to 260 g of chromic anhydride onto this nickel plating layer.
g/, trivalent chromium 1 to 5 g/preferably 2 to
3g/and sulfuric acid 1-3g/preferably 1.5
In a plating bath containing ~2 g/
~20A/ ^dm2 preferably 12-15A/ ^dm2 , temperature 45
Chrome plating is carried out at ~55°C, preferably 45-48°C, for 2-8 minutes, preferably 3-5 minutes. This chrome plating layer prevents discoloration in the atmosphere, maintains a beautiful glossy surface, and provides excellent wear resistance and corrosion resistance. This protects the mirror surface from scratches, corrosion, etc. Instead of this conventional chrome electroplating, it is also possible to carry out so-called micro-crack chrome electroplating, which forms minute cracks in the plating layer, or to carry out the former plating followed by the latter. In these cases, as in the case of micropolar nickel electroplating, the corrosion resistance can be further improved because minute cracks diffuse the corrosion current. Note that a water washing step is naturally inserted between each treatment. According to the method of the present invention, it is possible to give the surface of aluminum or aluminum alloy material a uniform and excellent mirror-like reflection function without any scratches or distortions. Unlike mirrors made from aluminum, there is no double reflection, and the image quality is excellent. Another advantage of the present invention is that it is possible to take advantage of the lightness and brightness of the aluminum material, and to reinforce its softness and flexibility to prevent subsequent deformation and generation of scars. The product of the present invention does not break like glass and is lightweight, has excellent post-processability, and has good thermal conductivity, so there is little clouding phenomenon caused by water vapor, and it can withstand rapid changes in temperature. It has many advantages such as good adhesion, no peeling of the coating, and excellent corrosion resistance. Therefore, this product can be subjected to post-processing such as bending, punching, cutting, and pressing, as well as processing into irregular shapes and parts, such as unevenness. This product is suitable for use in areas that are easily breakable or dangerous to break, and areas where the reflective surface is easily damaged.It is also suitable for use in areas that require weight reduction, areas where glass mirrors cannot be used due to legal regulations, and areas where glass mirrors cannot be used due to the It can be widely used in fields that undergo rapid changes, fields that require surface reflection, and various other fields that utilize reflective functions. The applied products are as follows. Indoor and outdoor building materials that utilize mirror surfaces, such as decorative mirror surfaces and ceilings, mirrors such as bathroom mirrors, lighting mirrors, railroad and vehicle mirrors, automobile back mirrors and side mirrors, outdoor signs, and other jars, pots, etc. Daily necessities such as microwaves. [Example 1] An aluminum plate made bright by special polishing was immersed in trichlorethylene in a conventional manner, washed with water, further immersed in an aqueous sodium hydroxide solution, washed with water, and finally wiped the surface with a soft cloth. to completely remove fats and oils and other impurities. For the specially polished aluminum plate, we used a forged steel quenched rolling roll whose surface had been polished to a mirror-like finish using a No. 800 whetstone using a conventional method, and while pouring light oil into the roll, we rolled the raw aluminum plate at a processing rate of 10%. An aluminum plate was used which had been given luster by repeating rolling five times under these conditions. The aluminum plate thus degreased is immersed in a 15% nitric acid aqueous solution at 30°C for 1 minute, and then washed with water. Next, zinc sulfate 40g/, nickel sulfate 30g/, sodium hydroxide 100g/, potassium cyanide 10
The sample was immersed in an aqueous solution containing 40 g of potassium hydrogen tartrate and 40 g of potassium hydrogen tartrate for 1.5 minutes at room temperature with stirring, and then washed with water. After forming the chemical conversion coating layer in this way, the current density was
Nickel plating is performed at 4.5 A/dm ² and 55°C for 18 minutes, and then washed with water. Next, nickel sulfate 300g/
, 50 g of nickel chloride, 40 g of boric acid, and 1 to 2 mg of a mixture of butyl alcohol and propargyl alcohol as brighteners at a current density of 4.5 A/dm ² , 55° C., and stirring air pressure of 0.4 Kg/cm ^{2 .} Perform nickelmetuki for 12 minutes. After washing with water, in order to maintain the strength of the nickel plating layer and increase the function of the mirror surface, nickel plating is performed again under the same conditions as for the glossy nickel plating described above, and the product is washed with water. Nickel sulfate is added to further improve corrosion resistance.
300g/, nickel chloride 50g/, boric acid 40g/
and 30g/30g of non-conductive fine particles with a particle size of approximately 0.02μm.
in a plating bath consisting of a current density of 4.5 a/dm ² ,
Microporous nickel plating is carried out at 55°C and stirring air pressure of 0.4 kg/cm ² for 2 minutes, followed by washing with water. Finally, on this nickel plating layer, apply 260 g of chromic anhydride, 3 g of trivalent chromium, and 2 sulfuric acid.
A current density of 15 A/d in a plating bath consisting of
m ² , chrome plated at 45°C for 3 minutes, and then washed with water. The surface of the aluminum plate thus obtained is rich in brightness and has a uniform and excellent reflective function. Aluminum alloys such as Al-Mg-Si 6063
When using a molded material, it is possible to impart an excellent reflective function to its surface by treating it in the same manner as described above. [Example 2] Products were manufactured in the same manner as in Example 1, except that the times of semi-bright nickel plating and bright nickel plating were varied to produce products with different thickness ratios of the two nickel plating layers. These products were tested for corrosion resistance (JIS H8617, 16 hours x 2 times) and reflectance (JIS
D5705) and strain rate (JIS D5705) are shown in the table below.

[Table] Ratio = Thickness of bright nickel plating layer (b) / Thickness of semi-bright nickel plating layer (a) As is clear from the results, the products of the present invention (Nos. 2 to 4) are superior to the comparative products (No. It has better corrosion resistance than .1) and also has good specular properties.

Claims (1)

[Claims] 1 Degrease the surface of aluminum, wipe off any impurities remaining on the surface, then activate the surface, and then perform a compound treatment using an aqueous solution containing a zinc compound and sodium hydroxide to form a plating base film. Then, on this coating, multiple nickel electroplatings from semi-bright nickel electroplating and bright nickel electroplating were applied at a temperature of 45 to 65°C.
It is applied at a current density of 2.5 to 5.5 A/dm ² in a nickel plating bath consisting of nickel sulfate, nickel chloride, boric acid, brighteners, etc., with a pH number of 3.2 to 5.7, and the thickness of the semi-bright nickel electroplated layer is (a) Thickness of glossy nickel electroplated layer (b)
The ratio of b/a is 0.25≦b/a<1.5, and 45 to 55
Current density 10~ in plating bath at temperature of ℃
A method of manufacturing a product made of aluminum and given a mirror surface by plating with chrome electroplating at 20A/dm ² .