JP4832854B2 - Black chrome plating solution and black chrome plating method using the same - Google Patents

Description

  The present invention relates to a black chrome plating solution and a black chrome plating method using the same, and more particularly, a black chrome plating solution containing trivalent chromium instead of conventional hexavalent chromium, and such black chromium plating. The present invention relates to a hexavalent chromium-free black chromium plating method using a liquid.

  Hexavalent chromium has been widely used for metal surface treatment. For example, in addition to being used as a corrosion inhibitor in the form of chromate, metal rust prevention such as zinc, aluminum, magnesium, etc. by utilizing excellent properties such as self-repair even if physically damaged It is also used as a treatment agent.

  In addition, in the black film obtained by using such hexavalent chromium, in addition to the above-mentioned rust prevention effect, low reflectance of light due to matte black color tone, ease of thin film formation, high adhesion, etc. Is also used for the processing of parts surfaces that require high precision, such as optical parts and measuring equipment parts.

  By the way, hexavalent chromium is a harmful substance that affects the human body in the same way as lead, mercury, cadmium and the like, and therefore, an environmental standard value is determined by the Basic Environment Law. In particular, when hexavalent chromium contained in the coating of chrome-treated parts contacts the skin for a long time, it not only causes chromium allergies and ulcers, but also has a suspected carcinogenicity. Movements to eliminate such chrome-treated parts are taking place mainly in the European Union (EU), and the response is also being urged in Japan.

  Under such circumstances, research and development of alternative technologies that do not use hexavalent chromium (hexavalent chromium-free) are being actively conducted. Various methods have been proposed for forming a (black) film using a metal surface treatment agent using +3 chromium (trivalent chromium) instead of +6 or a metal surface treatment agent containing such trivalent chromium. ing.

  Specifically, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-213446), an acidic aqueous solution containing a sulfite ion source, an oxidizing substance source and a trivalent chromium source and having a pH of 6 or less is used. Metal surface treatment agents have been proposed.

  Patent Document 2 (Japanese Patent Laid-Open No. 2003-171778) includes a step of coating a metal surface with a layer formed from an aqueous acidic liquid composition and a step of drying the aqueous acidic liquid composition without rinsing. A method for forming a protective film of a metal, wherein the aqueous acidic liquid composition is at least selected from the group consisting of (A) trivalent chromium, (B) an organic acid and / or an inorganic acid and / or a salt thereof. One type, (C) at least one selected from the group consisting of Li, Na, K, etc., (D) a method for forming a protective film of a metal that contains fluorine as an optional component is shown.

Furthermore, in patent document 3 (Unexamined-Japanese-Patent No. 2004-263237), the electroplating bath which contains a trivalent chromium ion and contains boric acid at the density | concentration of 0.1-1.0 mol / dm < ³ > is used. , A method for producing a black chromium plating film characterized by electroplating at a current density of 10 to 80 A / dm ² has been proposed. Furthermore, in Patent Document 4 (Japanese Patent Laid-Open No. 2005-126769), In the method for forming a black film in which a black film is deposited on the surface of a member to be treated with an electrolyte containing trivalent chromium, the electrolyte contains a high concentration complexing agent and a trivalent chromate. A method for forming a black film has been proposed.

  However, in the conventional metal surface treatment agent and the method for forming a film as described above, although it is possible to form a black film, it is not yet sufficient from an industrial viewpoint. The development of a black chromium plating solution containing trivalent chromium having a novel composition that has not been heretofore and a black chromium plating method using the same is still desired.

JP 2003-213446 A JP 2003-171778 A JP 2004-263237 A JP 2005-126769 A

  Here, the present invention has been made in the background of such circumstances, and the problem to be solved is a black chromium plating solution containing trivalent chromium, which is uniform and dense. Another object is to provide a method for easily forming a black chrome plating film using such a black chrome plating solution. There is also to do.

  In order to solve the problem related to the black chrome plating solution as described above, the present invention is to dissolve chromium chloride together with sodium sulfite and / or potassium sulfite in water and further contain potassium iodide. The black chrome plating solution characterized by the above is the gist thereof.

  Moreover, in order to solve the subject concerning the above-mentioned black chromium plating method, the present invention dissolves chromium chloride in water together with sodium sulfite and / or potassium sulfite, and further contains potassium iodide. The gist of the present invention is also a black chrome plating method characterized by carrying out an electroplating operation using a plating solution.

  Thus, in the black chromium plating solution according to the present invention, sodium sulfite and / or potassium sulfite and potassium iodide are contained together with chromium chloride as a source of trivalent chromium. Therefore, by carrying out a general electroplating operation using such a black chrome plating solution, a uniform and dense thin-film matte black chrome plating film having excellent adhesion can be formed advantageously. It could be done.

By the way, chromium chloride, which is one of the essential components constituting the black chromium plating solution according to the present invention, is used as a source of trivalent chromium for performing chromium plating, and is dissolved in water. The main component of the plating solution according to the present invention. As “chromium chloride”, chromium (II) [CrCl ₂ ], chromium (III) [CrCl ₃ ], and chromium (IV) [CrCl ₄ ] are generally known. “Chromium chloride” in the description and claims means chromium (III) chloride [CrCl ₃ ].

  The amount of chromium chloride used is appropriately adjusted according to the intended black chromium plating film, but is generally 100 g / L or more (up to saturation), preferably about 100 to 400 g / L. Will be. A plating solution with a small amount of chromium chloride causes problems such as insufficient uniform electrodeposition of the plating film and insufficient blackening of the plating film, while too much chromium chloride. The use of this causes problems such as exceeding its solubility limit and forming precipitates at the bottom of the plating bath.

  Further, in the present invention, sodium sulfite and / or potassium sulfite (hereinafter also referred to as sulfite as appropriate) needs to be contained in the plating solution. By carrying out an electroplating operation (cathodic electrolysis) using a plating solution containing such sulfite and chromium chloride and potassium iodide described later, metallic chromium is applied to the surface of the material to be treated as the cathode. A black chrome plating film made of chromium sulfide, oxide, and the like, which has a uniform appearance, is dense, and has excellent adhesion, can be advantageously obtained. In the present invention, it is possible to use sodium sulfite or potassium sulfite alone, but it is also possible to use them together. In particular, sodium sulfite and potassium sulfite are used in combination, or potassium sulfite. By using singly, the object of the present invention can be achieved more advantageously.

  Here, the amount of sulfite used is appropriately selected according to the amount of chromium chloride used and the intended black chrome plating film. Generally, the concentration of sulfite in the plating solution (sodium sulfite) And the amount of the total amount in the case where potassium sulfite is used in combination, the amount is such that the ratio is about 50 to 200 g / L, preferably about 50 to 100 g / L. Used in. If the amount of sulfite used is too small, the target black chrome plating film may not be obtained. On the other hand, if the amount of sulfite used is too large, no significant improvement is observed in the effect of addition. Because.

  The black chromium plating solution according to the present invention further contains potassium iodide (KI). Although the exact behavior of potassium iodide (KI) during electroplating has not been clarified, potassium iodide (KI) functions as a catalyst during film formation during electroplating, Therefore, it is presumed that a thin, matte black chrome plating film that is uniform and dense and has excellent adhesion can be obtained.

  Thus, potassium iodide, which is considered to contribute greatly to the formation of black chrome plating films with excellent characteristics, may result in the target black chrome plating film not being formed effectively if the amount used is too small. On the other hand, even if the amount used is too large, no significant improvement is observed in the addition effect, so potassium iodide is contained in the black chromium plating solution according to the present invention at a rate of about 1 to 50 g / L. In such an amount, it is preferably used in such an amount that the ratio is about 10 to 30 g / L.

  As described above, the essential components constituting the black chrome plating solution according to the present invention have been described. However, the black chrome plating solution of the present invention adversely affects the realization of the object of the present invention in addition to the above-described essential components. It goes without saying that various blending components used in conventionally known chromium plating solutions (baths) can be appropriately added and incorporated to the extent that they are not.

  The preparation of the black chrome plating solution according to the present invention as described above is performed according to the same method as that for preparing a conventional, general hexavalent chromium-containing black chrome plating solution. Specifically, chromium water, sodium sulfite and / or potassium sulfite, and potassium iodide are added, dissolved, or stirred simultaneously or in any order in water maintained at a predetermined temperature. Prepared.

  By the way, when black chrome plating is performed on an object to be plated (a material to be processed) such as an optical component or a measuring instrument component using the black chrome plating solution thus obtained, for example, the following general description is given. According to an electroplating process.

  First, in order to prevent dirt such as fats and oils existing on the surface of the object to be plated (processed material) from dissolving or diffusing in the plating solution, a predetermined value corresponding to the composition of the object to be plated (processed material) is used. Using a solvent, the surface of the object to be plated (processed material) is cleaned (preliminary cleaning).

  Next, the surface of the object to be plated (material to be treated) is degreased by the saponification action using a predetermined alkaline solution (alkali cleaning).

  Further, if the object to be plated (material to be treated) has fine irregularities, and dirt (oils and fats) cannot be sufficiently removed even by washing by the above two steps, electrolytic washing is performed. Such a cleaning mechanism for electrolytic cleaning is a combination of a degreasing action with an alkaline solution and an action of mechanically removing dirt (such as oils and fats) by hydrogen or oxygen bubbles generated by the electrolytic reaction. .

  Next, the object to be plated (material to be treated) is removed in order to remove the thin oxide film formed on the surface by washing with water after each of the above-described cleaning steps or leaving the object to be plated (material to be treated) in the air. Is immersed in a weak acid for a predetermined time (weak acid immersion).

  And as mentioned above, while preparing the to-be-plated thing (material to be processed) by which the surface was wash | cleaned, the black chrome plating liquid which concerns on this invention is accommodated in the plating tank in a predetermined electroplating apparatus. An anode made of a material insoluble in the plating solution (insoluble anode) while a plating bath is immersed in a plating bath (material to be processed) and the material to be plated (processing material) is used as a cathode. ) To conduct the electroplating operation by energizing the two electrodes. After such an operation, the object to be plated (material to be treated) is washed with water and dried to obtain an object to be plated (material to be treated) having a target black chrome plating film formed on the surface thereof. .

Here, iron, copper, zinc, nickel, chromium, and alloys thereof can be used as the objects to be plated (materials to be treated) capable of forming a black chromium plating film using the black chromium plating solution according to the present invention. As long as they are made of the above, it is possible to plate them. In addition, the current density, processing time (energization time), and plating solution (bath) temperature during the electroplating operation are appropriately set according to the composition of the black chrome plating solution used, the intended black chrome plating film, and the like. In general, the current density is set to 1 A / dm ² or more, the processing time is set to about 1 to 10 minutes, and the plating solution (bath) temperature is set to 60 ° C. or less. In the electroplating operation using the black chrome plating solution of the present invention, any conventionally known electroplating apparatus can be used.

  In addition to the examples described later, the inventors of the present application performed the following electroplating operation on the brass plate as the object to be plated (material to be processed) using the plating solution of the present application. I knew. 1) When sodium sulfite was used as a sulfite, a black chrome plating film was obtained at a lower current density as the amount used was larger. On the other hand, between the film and the object to be plated (processed material) Adhesion was slightly reduced. 2) When potassium sulfite is used, the greater the amount used, the better the adhesion between the film and the object to be plated (material to be treated), but the black chrome plating film is formed. In order to do this, it was necessary to carry out the electroplating operation at a high current density. 3) When the amount of potassium iodide used was large, a black chrome plating film was obtained at a lower current density when the plating solution (bath) temperature was lower. As is clear from this, it is necessary to appropriately set the conditions such as the current density during the electroplating operation in consideration of the composition of the plating solution and the intended black chrome plating film. It is.

  Some examples of the present invention will be shown below to clarify the present invention more specifically. However, the present invention is not limited by the description of such examples. Needless to say. In addition to the following examples, the present invention includes various modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention, in addition to the above specific description. It should be understood that modifications, improvements, etc. can be made.

  First, using chromium chloride, sodium sulfite and / or potassium sulfite, and potassium iodide, they are added to a predetermined amount of water at each ratio listed in Table 1 below, and stirred. Thus, four types of plating solutions according to the present invention (plating solutions 1 to 4) were prepared.

Next, a separately prepared electrolytic bath is accommodated in a separately prepared electrolytic bath and used as a plating bath. The anode is an insoluble anode, and the cathode is an iron plate to be plated (material to be treated). The electroplating operation was carried out according to the bath temperature (° C.), current density (A / dm ² ) and treatment time (min) listed in Table 1 below. After performing the electroplating operation using each plating solution, the iron plate was taken out from the plating bath, washed with water and dried, and then the appearance of the film formed on the surface of the iron plate was visually observed. The observation results are also shown in Table 1 below.

  On the other hand, by using only chromium chloride and sodium sulfite and / or potassium sulfite, and adding them to a predetermined amount of water in the respective proportions listed in Table 1 below, and stirring them, two types are obtained. The plating solutions (plating solutions 5 and 6) were prepared. For the plating solutions 5 and 6, the electroplating operation is performed according to the conditions listed in the following Table 1 according to the same method as the plating solutions 1 to 4. After the operation, the iron plate as the object to be plated is washed with water and dried. The appearance of the film formed on the surface was visually observed. The observation results are also shown in Table 1 below.

  As is clear from the results in Table 1, the plating solutions (plating solutions 1 to 4) according to the present invention can be used to perform the electroplating operation to thereby surface the object to be plated (iron plate). Further, it was confirmed that a matte black film can be formed advantageously. It was also recognized that the black film formed was uniform and dense.

On the other hand, even if the electroplating operation is performed using a plating solution that does not contain potassium iodide (plating solutions 5 and 6), a film is formed on the surface of the object to be plated (iron plate). The appearance was confirmed to remain gray instead of black.

Claims (2)

  A black chromium plating solution, wherein chromium chloride is dissolved in water together with sodium sulfite and / or potassium sulfite and further contains potassium iodide. A black chrome plating method comprising performing electroplating using a black chrome plating solution in which chromium chloride is dissolved in water together with sodium sulfite and / or potassium sulfite and further containing potassium iodide. .