JP2007016280A - METHOD OF FORMING Ni-P ELECTROPLATING COATING FILM AND THE COATING FILM - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Ni-P electroplating coating film having high hardness even in a plated state, and excellent sliding performance. <P>SOLUTION: The electroplating is carried out in a plating bath containing Ni ion, phosphite ion, a complexing agent and 0.15-0.25 wt.% saccharin, wherein the complexing agent is a mixture complexing agent comprising lactic acid, glycine and acetic acid in a ratio (lactic acid):(glycine):(acetic acid) of (0.5-1.0):(1.0-2.8):(0.5-1.0). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for forming an electric Ni-P plating film. More specifically, the present invention provides a Ni-P plating film having high hardness suitable for a sliding member by electroplating in a plated state. The present invention relates to a film forming method.

Ni-P plating is broadly divided into electroless plating (sometimes referred to as “chemical plating”) and electroplating (sometimes referred to as “electrolytic deposition”).
It is well known that electroless Ni-P plating has a coating hardness that is increased by heat treatment at 300 to 400 ° C. after plating (Non-Patent Document 1: “Electroless plating”). “Basics and Applications, edited by the Electroplating Society, April 27, 2001, page 37 (see Figure 2.9)). In FIG. 2.9, it is explained that the phenomenon that the electroless Ni—P plating film is hardened by heat treatment is related to the change of the structure from amorphous to crystalline.

Regarding the deposition mechanism of electroless Ni-P plating, several theories have been introduced in Non-Patent Document 2: Electroless Plating, pages 27-28. According to the deposition mechanism theory by atomic hydrogen, 1 The two electrons generated by the oxidation of the molecular phosphinate ion reduce the Ni ion. Electroless plating that occurs in such a reaction mechanism has a slower reaction rate than electroplating.
In electroless Ni-P plating, various complexing agents are used to form a stable soluble complex with Ni ions and prevent Ni from precipitating as a phosphate (Non-patent Document 2: Id. Plating "Fundamentals and Applications, page 26, Table 2.6).

  Patent Document 1: According to Japanese Patent Laid-Open No. 6-240437, an electroless Ni-P plating film having a hardness of about Hv400 is applied on an Al alloy base material while being plated, and then cured by heat treatment. Are listed. Further, since there is a description that electroplating may be used instead of electroless plating, it is considered in this patent document that a Ni-P electroplating film having the above degree of hardness can be formed. .

  In electro Ni-P plating, amorphous Ni-P plating films containing 9.5 wt%, 11.5 wt% and 14.4 wt% P electrodeposited from a watt bath containing phosphorous acid are about Hv650 at 300K. It has a hardness of ˜750, and it can be cured at a temperature of 600˜700 K to reach a hardness of Hv1100 or higher. Non-Patent Document 3, Metal Surface Technology Vol31 (1980), No. 12, pp. 667-672 It is described in.

Patent Document 2: According to Japanese Patent Publication No. 2003-511563, a Co alloy containing at least one of Ni, Fe, Sn, In, Pd, Au and Bi, with the balance exceeding 35%, A method of forming a film by electroplating using an electroplating bath to which butyl diol to which mito (saccharin) is added is added as a brightener is described. By drawing and ironing the cold-rolled material subjected to the electroplating, the plating layer is cracked to increase the contact area of the battery with the electroplating bath.
Japanese Patent Laid-Open No. 6-240437 Special table 2003-511563 gazette “Electroless Plating” Fundamentals and Applications, edited by Electroplating Study Group, published on April 27, 2001, page 37 (Figure 2.9)) "Electroless plating" basics and application, edited by Electroplating Research Group, published on April 27, 2001, pages 26-28 (see Figure 2.9) Metal Surface Technology Vol31 (1980), No. 12, pp. 667-672

    The electroless Ni-P plating film has a hardness just after deposition as low as about HV500, and when used as an abrasion resistant material, it is essential to increase the hardness to about Hv720 by heat treatment. However, since the heat treatment temperature is 300 to 400 ° C., it is difficult to apply to a substrate such as aluminum from the viewpoint of heat resistance. In addition, there is a drawback that the reaction rate is slower than electroplating.

  On the other hand, the electric Ni-P plating film has been conventionally used for decoration, etc. utilizing corrosion resistance and luster, and has a low hardness immediately after plating, so it was unsuitable for wear resistance applications. Therefore, electric Ni plating in which hard particles such as ceramics are dispersed has been used as a film for wear resistance. However, the hard particles are likely to wear away the mating material or, on the contrary, fall off the plating surface during sliding. On the other hand, non-patent literature relating to amorphous electric Ni-P plating only mentions corrosion resistance and gloss as properties in the non-heated state.

    The Ni-P plating method of the present invention is characterized in that electroplating is performed in an electroplating bath containing Ni ions, phosphite ions, a specific mixed complexing agent, and 0.15-0.25 wt% saccharin. To do. The complexing agent used in the present invention is a mixed complexing agent composed of lactic acid: glycine: acetic acid = 0.5 to 1.0: 1.0 to 2.8: 0.5 to 1.0 by weight ratio.

In the electroplating according to the present invention, as in the conventional plating bath composition, Ni ions and phosphite ions are kept so as not to precipitate and can be electrodeposited, and the basic components are Ni ions and phosphite ions. This is performed in a plating bath. Preferably, it can be performed in a phosphorous acid bath containing Ni ²⁺ ions. Ni ²⁺ ion concentration is preferably 25~45wt%, and most preferably 35.0 wt%. The concentration of phosphorous acid is preferably 4.3 to 4.9 wt%, and most preferably 4.6 wt%. The balance is water except for the complexing agent, saccharin and sodium dodecyl sulfate described below. However, an anion constituting the Ni salt, for example, SO ₄ ²⁻ , Cl ^{2 −} , pH adjusting agent, for example, NaOH can be used. In Ni electroplating, a stress relaxation agent may be added as an auxiliary agent. As described later, in Ni-P electroplating, saccharin has the effect of a stress relaxation agent, and other stress relaxation agents are used in combination. However, the same effect is not achieved. Further, although smoothing agents are also known, in the present invention, saccharin and sodium dodecyl sulfate have the effect, and even if other smoothing agents are used in combination, the same effect is not achieved.

The temperature of the plating bath is preferably 80 to 90 ° C, and most preferably 85 ° C. The current density is preferably ^{1.8~10A / dm 2, 2A / dm} 2 and most preferably. The pH is preferably 2.2 to 2.8, and most preferably 2.5. Moreover, although electroplating is performed by a normal method, diaphragm electrolysis may be performed.

Surprisingly, the Ni-P plating film deposited from a Ni-P electroplating bath containing a specific mixed complexing agent and saccharin has a markedly developed crystal structure, which causes a significant change in hardness, resulting in a plating state. Thus, a Ni-P electroplating film having a crystallite size of 90 angstroms or more and a film hardness of Hv750 or more, which can be used as a wear-resistant film, was obtained.
Hereinafter, the present invention will be described with reference to an electroplating experiment conducted at a plating bath temperature of 80 ° C. using Ni wire as an anode and a buffed Al plate as a cathode.

Fig. 1 shows the experimental results of electroplating using a plating bath of 10.0 wt% complexing agent, 4.6 wt% phosphorous acid, 35.3 wt% nickel sulfate, and a pH of about 2.5 and varying the saccharin concentration. Uniform strain was measured by X-ray analysis. From this figure, it can be said that saccharin has a remarkable effect as a stress relaxation agent.
FIG. 2 shows the change in crystallite size in the experiment under the same conditions as FIG. The size of the crystal grains was obtained by the calculation formula of ε = λ / Bcosθ, which is Scherrer's formula. Here, λ is an X-ray diffraction wavelength (angstrom), B is an integral width (rad), and θ is a diffraction angle (°).

Fig. 3 shows the relationship between the current density of electroplating and the film hardness after plating when the saccharin concentration is constant at 0.2 wt%. When the current density is 0.01 A / cm ² (1 A / dm ² ) or more, Although higher hardness than the conventional one can be obtained, the hardness equivalent to that of Ni-P-based electroless plating after heat treatment is obtained especially at 0.02 A / cm ² (2 A / dm ² ) or more. The current efficiency at this current density is about 90%, and a maximum plating rate of 110 μm / h can be obtained. This corresponds to several times the plating speed of electroless plating. Of course, the higher the current density, the higher the growth rate of the plating film. However, if the current density exceeds 0.10 A / cm ² (10 A / dm ² ), the denseness of the film decreases and the attack on the mating material increases. Adverse effects such as seizure are likely to occur, hydrogen gas is generated to reduce film growth, and film thickness uniformity is poor.

  FIG. 4 shows the X-ray diffraction result of the film formed under the electroplating conditions of FIG. 1, and it can be seen that the (111) plane strength of Ni increases with the amount of saccharin added. From FIGS. 1, 2 and 4, it can be seen that 0.2 wt% or more of saccharin contributes to the crystallization of the film structure.

FIG. 5 shows an experiment in which the amount of saccharin added was changed in a plating bath of 10.0 wt% complexing agent, 4.6 wt% phosphorous acid, 35.3 wt% nickel sulfate, pH of about 2.5, and current density of 0.02 A / cm ² . The film hardness of the obtained plating film is shown. From this graph, it can be seen that when the saccharin addition amount is 0.15 to 0.25 wt%, a high film hardness suitable for the sliding film can be obtained.

  If a specific mixed complexing agent is not added in an electroplating bath to which saccharin has been added, the film form will be poor and peeling will occur, and the current efficiency will be extremely deteriorated. -Both current efficiency can be improved. As the complexing agent, 20 to 30 g / L lactic acid, 50 to 65 g / L glycine, and 20 to 30 g / L acetic acid can be used. These three complexing agents are mixed at a mixing ratio of lactic acid: It is necessary to add a mixed complexing agent mixed so that glycine: acetic acid = 0.5 to 1.0: 1.0 to 2.8: 0.5 to 1.0. Here, the preferable addition amount of the mixed complexing agent to the plating bath is 1.0 to 30.0 wt%, and the most preferable addition amount is 10.0 wt%. In addition, when the addition of the complexing agent is only one or two of the three types, or the complexing agent concentration or / and the mixing ratio is out of the above ranges, other than the above range, Good film properties and current efficiency cannot be obtained. The most preferred concentrations of the three complexing agents are lactic acid: 25 g / L, glycine: 58 g / L, and acetic acid: 25 g / L. The most preferred mixing ratio is lactic acid: glycine: acetic acid = 25: 58: 25 It is.

  FIG. 6 is a graph showing the relationship between the concentration of sodium dodecyl sulfate further added to the 0.2 wt% saccharin addition bath and the film hardness. It shows that the added sodium dodecyl sulfate has almost no influence on the film hardness at 0.2 wt% or less. However, sodium dodecyl sulfate was recognized as a smoothing agent that smoothes the surface of the film.

  According to the present invention, a high-hardness film can be obtained at high speed and without heat treatment, so that an abrasion-resistant film can be formed on a base material that is softened by heat treatment such as an Al alloy. Moreover, since the film deposition rate is higher than that of electroless plating, the productivity is improved, which is advantageous in terms of cost.

It is a graph which shows the relationship between the saccharin density | concentration in an electroplating bath, and nonuniform distortion. It is a graph which shows the relationship between the saccharin density | concentration in an electroplating bath, and the magnitude | size of a crystallite. It is a graph which shows the relationship between the current density of an electroplating bath, and film hardness. 2 is an X-ray diffraction image of a film obtained from a saccharin electroplating bath. It is a graph which shows the relationship between the saccharin density | concentration in an electroplating bath, and film hardness. It is a graph which shows the relationship between sodium dodecyl sulfate density | concentration of an electroplating bath, and film | membrane hardness.

Claims (4)

In the film forming method of the Ni-P-based plating film, Ni ion, phosphite ion, complexing agent and 0.15-0.25 wt% saccharin are contained, and the complexing agent is lactic acid: glycine: acetic acid = weight ratio. 0.5-1.0: 1.0-2.8: A method for forming a Ni-P plating film, wherein electroplating is performed in a plating bath which is a mixed complexing agent comprising 0.5-1.0. The method for forming a Ni-P-based plating film according to claim 1, wherein phosphate ions are contained in place of some or all of the phosphite ions. The Ni-P plating film forming method according to claim 1 or 2, wherein the electroplating bath further contains sodium dodecyl sulfate. Crystals of 90 angstroms or more electrolytically deposited by a plating bath containing a mixed complexing agent consisting of lactic acid: glycine: acetic acid = 0.5 to 1.0: 1.0 to 2.8: 0.5 to 1.0 and 0.15 to 0.25 wt% saccharin by weight ratio Ni-P-based electroplated film that consists of a child and has a film hardness of Hv750 or higher.