JPS5818994B2 - How to manage electroless nickel plating film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the hardness of an electroless nickel plating film, and particularly to a method for controlling the phosphorus content in the plating film.

Generally, the plating method for parts that require hardness, such as sliding parts (pinion shafts, bottle idlers, etc.), involves immersing the parts to be plated in an electroless nickel plating bath using sodium hypophosphite as the reducing agent. The electroless nickel plating method that forms a nickel film on the surface is well known, and in this plating method, the phosphorus content of the nickel plating film is adjusted within the range of 3 to 15% depending on the pH of the plating bath and the concentration of the reducing agent. However, in order to increase the hardness (for example, Vickers hardness of 1000 or more), it is necessary to control the phosphorus content within a certain range (for example, 4% to 9%).

Conventionally, when controlling the phosphorus content in such electroless nickel plating films, the parts to be plated are used as samples, and the phosphorus components in the solution (sample solution) are dissolved in acid. However, in reality, it takes a very long time to dissolve all the parts to be plated, which is impractical, so measurements are performed only when the plating film has been properly dissolved.

In that case, the phosphorus component in the sample solution includes the phosphorus component in the base material of the part to be plated and the phosphorus component in the plating film, and it is difficult to distinguish between the two, so the estimation method is as follows: The phosphorus content P in the plating film is determined by a calculation formula.

P%=FeXP(.

Here, P': Total amount of phosphorus in the sample solution Ni: Amount of nickel in the sample solution H: Amount of phosphorus eluted from the base material of the part to be plated Fe: Amount of iron in the sample solution Po: Base material of the part to be plated In other words, in the above method, in addition to quantitatively measuring the amount of nickel and phosphorus in the sample solution, it is necessary to quantitatively measure the amount of iron, and from this amount of iron, the amount of phosphorus in the base material of the part to be plated can be determined. P/1
0.

Therefore, when measuring the phosphorus content in an electroless nickel plating film using the conventional method described above, the values vary widely, making it impossible to accurately and sufficiently control the hardness of the plating film, and also preventing iron content from being contained. Since it is necessary to measure the amount, there was a problem in that quantitative analysis measurements were time-consuming.

The present invention has been made in view of this point, and in controlling the hardness of the electroless nickel plating film, an iron-based steel material containing almost no nickel and phosphorus is used as a test piece, and is coated with the parts to be plated. By electrolytically nickel plating and dissolving only this test piece in acid and using it as a sample solution, since the test piece is small, it does not take much time to dissolve all of it in acid, and the shape and material are Since the amount of iron, phosphorus, and nickel contained in the test piece is known in advance by specifying The phosphorus content in the electroless nickel plating film can be calculated accurately and easily, and based on this, the hardness of the plating film on the parts to be plated can be accurately and easily controlled. The present invention will be described in detail below.First, the present invention will be explained in detail using an electroless nickel plating bath using sodium hypophosphite as a reducing agent (30 g/l of nickel chloride and 10 g of sodium hypophosphite).
In forming a nickel film on the surface of a part to be plated by immersing it in a bath having a bath composition of 50 g/l and 50 g/l of sodium hydroxyacetate, a test piece is prepared in advance separately from the part to be plated.

This test piece is made from ferrous steel materials that do not contain nickel and phosphorus as alloying elements, such as SPC material, SPH material, etc.
A rolled steel plate material such as SM material or SM material is used, and its size is approximately 20 mm x 50 mm9 with a thickness of Q and 7 mvt.
A thin plate of 100% is preferred.

Then, the test piece is immersed in the plating bath together with the parts to be plated (eg, pinion shaft, bottle idler, interlock sleeve, thrust washer, etc.) to form the same nickel coating on both surfaces.

Thereafter, the test piece on which the nickel film has been formed is taken out, and the test piece is dissolved in acid (for example, nitric acid solution) to prepare a sample solution.

Using this sample solution, the amount of Ni in the sample solution can be determined using citric acid addition spectrophotometry, atomic absorption spectrophotometry, or EDT.
Quantitative analysis is carried out using A titration method or the like, and the total phosphorus amount y in the sample solution is quantitatively measured using molybdenum blue absorptiometry or neutralization titration method.

Based on these measured amounts Ni and P', the phosphorus content P in the plating film of the test piece is calculated using the following formula.

Here, P〃: Amount of phosphorus eluted from the test piece base material out of the amount of phosphorus contained in the sample liquid S: Sampling amount Po: Phosphorus content of the test heath base material Furthermore, phosphorus content of the test piece base material Rate P.

is determined in advance by the quantitative analysis method for phosphorus in iron/steel (for example, molybdenum blue spectrophotometry).

Since the phosphorus content P calculated in this way is almost the same as the phosphorus content in the plating film of the part to be plated, the hardness of the plating film of the part to be plated can be almost accurately determined by the phosphorus content P. can be managed.

Next, to describe an example of the present invention, a 5P test piece with a thickness of 0.7 mm and a size of approximately 20 mm x 50 mm was used.
Using a C-1 plate, electroless nickel plating is applied to this 5PC-1 plate along with the 845C pinion shaft, which is the part to be plated.

The phosphorus content P in the plated film of this plated 5PC-1 plate was measured by the following analysis procedure.

That is, ■ Cut the above plated 5PC-1 board into small pieces, and weigh about 2 to 3 g (about 20 x 20 mm size) into 30 pieces.
Measure accurately into a 0rfLl beaker.

■ HNO3 (HNO3:H20=1:1 (volume ratio))
After adding 401 nl and heating and dissolving it, add H (J!0440-) and continue heating and evaporating to generate strong white smoke. Hold for a minute.

After cooling, add 100 yen of hontsuri to dissolve the salts and heat for 200 y.
Transfer to volumetric flask (d) and dilute to the marked line with water.

(2) Take 2.0 rILl of the solution (2) above into a 100 d volumetric flask, and add HCA041 mA' and water to make a liquid volume of about 10 m7.

Using this solution, the phosphorus content y is determined by molybdenum blue absorption photometry.

That is, 101 nl of a 10% hydrogen sulfite (IJ) solution was added to the above solution, stirred, and heated in a boiling water bath until the solution changed from reddish brown to almost colorless within 90°C.

Next, 251 rLl of coloring reagent solution is added, shaken and heated in a boiling water bath for 10 minutes to completely develop the color, and diluted to the marked line with drained water cooled to room temperature using running water.

A portion of this solution was taken into the absorption cell of a photometer, and a wavelength of 750
Absorbance around nm is measured and phosphorus is quantified using a calibration curve prepared in advance.

■ Also, add 1.07 rLl of the liquid from ■ above to 1001
Pour into an rLl volumetric flask and add water to bring the volume to about 10
−.

Using this solution, the nickel content Ni is determined by citric acid addition spectrophotometry.

That is, add 10 ml of 50% citric acid solution to the above solution and shake it, then add 10 ml of ammonia water and cool it to room temperature under running water while shaking, and then add 10 mA of iodine solution!
Add 3 ml of dimethylglyoxime solution and dilute to the marked line with water.

A portion of this solution was taken into the absorption cell of a photometer, and a wavelength of 530
Absorbance around nm is measured, and nickel is quantified using a calibration curve prepared in advance.

■ In addition, cut the unplated 5PC-1 plate into small pieces, accurately weigh out approximately 0.5 g into a 200 gobeaker, and use the method for quantitative analysis of phosphorus in iron and steel (molybdenum blue absorption spectrophotometry) described in (■) above. ) is the phosphorus content P of the 5PC-1 board base material.

Let's find out.

(2) Substitute the values F', Ni, and P□ obtained in the above (1) to (2) into the above-mentioned calculation formulas (1) and (2) to calculate the phosphorus content P in the plating film.

The measured values of phosphorus content P obtained in this manner (inventive examples, samples/16.8 to 14) were compared to the measured values of phosphorus content P obtained by the conventional method (conventional examples, samples/16.8 to 14). 1-7)
A comparison is shown in the table below.

From the above table, it can be seen that in the example of the present invention, the variation in the measured value of the phosphorus content P is smaller than in the conventional example, and an accurate value can be obtained.

As explained above, according to the present invention, in the method for controlling the hardness of an electroless nickel plating film, a test piece made of iron-based steel material that does not contain nickel and phosphorus as alloying elements is used together with the overcoat and the plated parts. After immersing the test piece in an electroless nickel plating bath using sodium phosphite as a reducing agent to form the same nickel film on both surfaces, only the test piece is dissolved in acid to reduce the phosphorus content in the plating film of the test piece. The method measures the amount of iron, controls the bath so that the phosphorus content is within a certain range, and controls the hardness of the parts to be plated within a certain range, so there is no need to measure the amount of iron as in the past. The phosphorus content in the electroless nickel plating film can be calculated accurately and easily, and therefore the hardness of the electroless nickel plating film of the part to be plated can be accurately and easily managed.

Claims (1)

[Claims] 1 An electroless nickel plating film in which a part to be plated is immersed in an electroless nickel plating bath using sodium hypophosphite as a reducing agent to form a nickel film on the surface, and the phosphorus content contained in the nickel film is controlled. In the hardness control method, a test piece made of iron-based steel that does not contain nickel and phosphorus as alloying elements is immersed together with the wave-plated parts in the plating bath to form the same nickel film on the surfaces of both parts, and then The phosphorus content in the plating film of the test piece is measured by dissolving only the test piece in acid, and the bath is controlled so that the phosphorus content is within a certain range, and the hardness of the part to be plated is within a certain range. A method for controlling the hardness of an electroless nickel plating film, characterized by controlling the hardness of an electroless nickel plating film.