Device and method for measuring fluoride ion concentration in electrochromium plating solution

Abstract

The present invention discloses a device and method for determining the concentration of fluorine ions in an electrochromium plating solution, the method comprising the steps of: 1. taking an electrochromium plating solution sample and pouring it into a reaction cup (5); 2. pumping an ion strength adjusting agent and desalted water into the reaction cup; 3. mixing the solutions in the reaction cup to obtain a sample solution; 4. using an ion meter (2) to determine a potential value according to set determination parameters; 5. ending the measurement; 6. calculating the concentration of fluorine ions in the electrochromium plating solution sample. The present invention adopts an indicator electrode, based on a single sample standard addition method, by measuring and calculating the fluorine ion concentration, test solution volume and potential value before and after the sample is spiked, performing regression analysis to obtain the fluorine ion concentration in the sample, solving the influence of factors such as the pH value, temperature, stirring speed, matrix effect, and interfering ions of the determination solution, solving the influence of the drift hysteresis effect by controlling the potential, and automatically completing the rapid and accurate determination of the fluorine ion content in the chromium plating solution with only one sample solution.

Description

Technical Field

[0001] The invention relates to a detection device and method in a chromium electroplating production process, and in particular to a device and method for determining the fluoride ion concentration in a chromium electroplating solution. Background Art

[0002] During the production process of electroplating chromium, fluoride is usually added to the electroplating chromium solution to activate the surface of the chromium layer, thereby obtaining a bright chromium layer. However, the fluoride ions contained in the fluoride are highly corrosive to the workpiece, the plating tank, and the anode, and require high maintenance of the tank solution. Therefore, the fluoride ion concentration must be strictly controlled during the electroplating chromium production process. In the prior art, the fluoride ion concentration in the electroplating chromium solution is measured by the fluoride ion selective electrode potentiometer, which includes the standard curve method and the standard addition method.

[0003] The standard addition method usually prepares n test solutions of the same volume including the sample, measures their potentials to obtain the fluorine content in the sample, and makes a working curve to obtain the fluorine ion concentration of the sample. This method can eliminate the influence of complex matrix on fluorine determination. Since the fluorine ion potential is affected by factors such as matrix, temperature, stirring speed, hysteresis effect, matrix effect, interfering ions, etc., the actual measurement accuracy is poor and cannot meet the requirements of on-site detection and process control.

[0004] The document "Determination of Fluorosilicic Acid in Chromium Plating Solution by Fluoride Ion Selective Electrode" (Wang Xiaorong, "Electroplating and Finishing", Vol. 14, No. 3) discloses a method for determining the fluoride ion concentration in electroplated chromium by using a standard curve method. This method is based on the method of making a standard curve with the same matrix as the test sample. Since the preparation of the base solution of the standard curve is complicated, and the fluoride ion potential determination has a great influence on the temperature, stirring speed, and hysteresis effect, it is impossible to ensure that the sample and the standard curve are determined under exactly the same conditions, resulting in a large error in the determination result. The document "Determination of Fluoride Content in Chromium Plating Solution by Indicator Electrode" (Liu Chengliang et al., "Chemical Sensor", No. 02, 1982) discloses a method for determining the fluoride ion concentration in the chromium plating solution by using an analytical solution addition method. However, since the sample determination and the preparation of the standard curve are carried out separately, this method requires matrix matching and strict control of the sample pH value and temperature, which makes the determination difficult and costly. The document "Study on the Determination of Salt Fluoride by Single Standard Addition Method with Standard Curve and Measured Slope" (Cui Daolin, "Chinese Journal of Endemic Disease Prevention and Control", Vol. 6, No. 6, 1991) discloses a method for measuring the fluorine potential by adding a small volume of fluorine standard solution after the fluorine potential of the sample is measured. Since the small volume of standard solution added is negligible compared with the sample amount, the fluorine content in the sample can be obtained based on this. This method can solve the influence of factors such as temperature, stirring, and matrix effect on the measured potential, but the error of single addition is large and the accuracy of the measurement result is poor.

[0005] Chinese invention patent application CN201811069774.4 discloses a fluoride ion selective electrode-standard addition method for determining the fluoride ion concentration in zinc sulfate electroplating solution, and specifically discloses: using electrodes to respectively determine the potential value E0 of the zinc sulfate electroplating solution sample to be tested and the potential value Es of the sample after adding the fluorine standard solution, and then calculating the fluoride ion concentration C0 in the zinc sulfate electroplating solution sample to be tested according to the relationship. This method uses the change in fluoride ion potential before and after the addition of the standard to obtain the fluoride ion concentration in the sample by making and pre-making a working standard. Since the sample and the working curve are not measured under the same conditions, the measurement process is affected by temperature, stirring speed, hysteresis effect, etc., and the change in fluoride ion potential before and after the addition of the standard will deviate from the theoretical value and cause errors. Therefore, it can only meet the measurement of samples with a fluoride ion concentration not exceeding 0.1g / L, and is not suitable for high-concentration, high-precision sample measurement with a fluoride ion concentration of more than 0.1g / L in electroplating chromium solutions. Summary of the invention

[0006] One of the purposes of the present invention is to provide a device for determining the concentration of fluoride ions in an electrochromium plating solution, which realizes automated determination and calculation based on computer communication technology, thereby achieving rapid, simple and accurate determination of the fluoride ion content in the chromium plating solution.

[0007] The second object of the present invention is to provide a method for determining the fluoride ion concentration in an electrochromium plating solution, which adopts a standard addition method based on a single sample, solves the influence of factors such as the pH of the measuring solution, the influence of interfering ions on the temperature, the stirring speed, the matrix effect, the interfering ions, etc., and combines the fluoride ion potential analysis method to solve the influence of factors such as the hysteresis effect during the fluoride ion potential determination by the controlled potential method, thereby realizing a rapid and accurate determination of the fluoride ion content in the chromium plating solution.

[0008] The present invention is achieved in that:

[0009] A device for measuring fluoride ion concentration in chromium electroplating solution comprises an ion meter, a stirrer, a reaction cup, a reference electrode, an indicator electrode and a liquid adding component; the stirrer, the reference electrode, the indicator electrode and a plurality of liquid outlet pipes of the liquid adding component are all inserted into the reaction cup.

[0010] The reference electrode is a saturated calomel electrode, and the indicator electrode is a fluoride ion selective electrode.

[0011] A method for determining the concentration of fluorine ions in a chromium electroplating solution, the method being implemented based on a device for determining the concentration of fluorine ions in the chromium electroplating solution, the device comprising an ion meter, a stirrer, a reaction cup, a reference electrode, an indicator electrode and a liquid adding component;

[0012] The method for determining the fluoride ion concentration in the chromium electroplating solution comprises the following steps:

[0013] Step 1: Take a sample of the electroplating chromium solution and pour it into a reaction cup;

[0014] Step 2: The liquid adding component pumps the ion strength adjusting agent into the reaction cup, and pumps the desalted water into the reaction cup;

[0015] Step 3: The solution in the reaction cup is uniformly mixed by a stirring bar to obtain a sample test solution;

[0016] Step 4: Set the measurement parameters and start the ion meter, which measures the potential value through the indicator electrode and the reference electrode according to the set measurement parameters;

[0017] Step 5: Measurement ends;

[0018] Step 6: Calculate the concentration of fluoride ions in the sample solution, that is, the concentration of fluoride ions in the electroplating chromium solution sample C x .

[0019] The volume V0 of the chromium electroplating solution sample is 0.1-10 mL.

[0020] The ion strength adjusting agent pumped into the reaction cup is a buffer solution composed of acetic acid-sodium acetate, sodium citrate, and sodium chloride. The volume of the ion strength adjusting agent is V 10 5-100mL, the pH value of the ion strength adjuster is 5-6; the volume of desalted water pumped into the reaction cup is V 11 50-300mL.

[0021] The step 4 comprises the following sub-steps:

[0022] Step 4.1: Set the drift threshold. The drift is the ratio of the potential change △E to the time increment △t, that is, △E / △t, in units of mv / min;

[0023] Step 4.2: Set the acquisition frequency to T, in seconds, and the acquisition time range [t min , t max ], unit is s;

[0024] Among them, the minimum acquisition time t min The value range is: 0≤t min <t max ;

[0025] The maximum acquisition time is determined by the drift amount, and the formula is:

[0026]

[0027] Step 4.3: Collect at a sampling frequency T in the sampling time range [t min , t max] collect the fluoride ion potential value in the sample solution, and calculate the potential drift △E / △t, and judge whether the fluoride ion potential drift △E / △t in the sample solution meets the drift threshold. If so, the potential value at this point is recorded as the measured value. If not, the potential value at this point is recorded as the measured value. max The potential value at the moment is recorded as the measured value; the measured value recorded in step 4.3 is the sample test solution potential value E0, in mV;

[0028] Step 4.4: Set the concentration of fluoride ion standard solution to C in g / L, and add n times of fluoride ion standard solution. The volumes of the fluoride ion standard solution added in n times are V1, ..., V n , unit is mL;

[0029] Step 4.5: The liquid adding component pumps the fluoride ion standard solution into the sample test solution for the first time to obtain the first test solution. The volume of the fluoride ion standard solution pumped into the reaction cup is V1;

[0030] Step 4.6: Collect at a sampling frequency T in the sampling time range [t min , t max ] collect the potential value of fluoride ions in the first test solution, and calculate the potential drift △E / △t, and determine whether the potential drift △E / △t of fluoride ions in the first test solution meets the drift threshold range. If so, the potential value at this point is recorded as the measured value. If not, t max The potential value at the moment is recorded as the measured value; the measured value recorded in step 4.6 is the measuring liquid potential value E1 of the first measuring liquid, in mV;

[0031] Step 4.7: Repeat steps 4.5-4.6 until the required n fluoride ion standard solutions are pumped into the reaction cup in sequence, and the measured values ​​are recorded in sequence to obtain the potential values ​​E1-E of the n test solutions. n .

[0032] The drift threshold value ranges from 0.1 to 50 mv / min, and the acquisition frequency T ranges from 0.1 to 3 s.

[0033] The fluoride ion standard solution is added for a number of times n≥3.

[0034] The concentration of the fluoride ion standard solution is 0.1-10g / L

[0035] The step 6 comprises the following sub-steps:

[0036] Step 6.1: When the measurement starts, the calculation formula for the fluoride ion concentration C0 in the sample solution is:

[0037] C0=C x *V0 / (V0+V 10 +V 11 ) Formula (2)

[0038] The unit of fluoride ion concentration C0 in the sample solution is g / L;

[0039] Among them, C x is the concentration of fluoride ions in the chromium electroplating solution sample, in g / L;

[0040] V0 is the sampling volume, in mL;

[0041] V 10 is the volume of the added ion strength adjuster, in mL;

[0042] V 11 is the volume of desalted water added, in mL;

[0043] Step 6.2: After the first pumping of the fluoride ion standard solution with a volume of V1 and a concentration of C, the calculation formula for the fluoride ion concentration C1 in the first test solution is:

[0044] C1=(C x *V0+C*V1) / (V0+V 10 +V 11 +V1) Formula (3);

[0045] The unit of the fluoride ion concentration C1 in the first test solution and the concentration C of the fluoride ion standard solution is g / L, and the unit of the volume V1 of the fluoride ion standard solution added for the first time is mL;

[0046] Step 6.3: The volume of the nth pump is V n , the concentration of fluoride ions in the nth test solution is C n The calculation formula is:

[0047] C n =(C x *V0+∑ i＝1 n C*V i ) / (V0+V 10 +V 11 +∑ i＝1 n V i ) formula (4);

[0048] The units of the fluoride ion concentration C1 in the first test solution and the concentration C of the fluoride ion standard solution are g / L, and the volume V of the fluoride ion standard solution added for the nth time is n The unit is mL;

[0049] Step 6.4: According to the Nernst equation, E and logC are linearly related and the linear regression equation is obtained:

[0050] E=a+K*logC Formula (5)

[0051] Among them, a is the intercept of the linear regression equation, and K is the slope of the linear regression equation;

[0052] According to the linear regression equation and the potential value E0 of the sample solution, in mv, the fluoride ion concentration C0 in the sample solution is calculated, in g / L.

[0053] Step 6.5: Substitute the fluoride ion concentration C0 in the sample solution calculated in step 6.4 into formula (2) to calculate the fluoride ion concentration C0 in the chromium electroplating solution sample. x , unit is g / L.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] 1. The present invention adopts a fluoride ion potential analysis method, introduces a physical quantity of potential drift, that is, the ratio of the potential change △E to the time increment △t, and sets a potential drift threshold. When performing sample and each spike measurement, only the potential that meets the potential drift threshold is recorded as the measured value, thereby ensuring that the potential of each measurement is at the same stable level, solving the influence of the hysteresis effect of the fluoride ion potential, and effectively solving the disadvantage of poor potential stability and inability to obtain the same stable level of potential when measuring high-concentration fluoride ions above 0.1 g / L and complex matrix samples, resulting in poor measurement accuracy. At the same time, computer data transmission and calculation are used to realize rapid and accurate calculation of the fluoride ion content in the electroplating chromium solution.

[0056] 2. The method of the present invention adopts a single sample standard addition method, that is, n certain volumes of fluoride ion standard solutions are added in sequence in a sample test, and then the fluoride ion concentration in the sample is obtained through mathematical processing of the fluoride ion concentration, volume and measured potential before and after the addition; since the measurement is carried out under the same conditions such as the same sample, the same acidity, the same stirring speed, the same interfering ion concentration, and a working curve is prepared to obtain the fluoride ion concentration, the shortcomings of the equal volume working curve method and the equal volume standard addition method, which are affected by factors such as temperature, pH value, stirring speed, matrix effect, interfering ions, etc., resulting in poor measurement accuracy, etc., are effectively solved, and the method has good measurement accuracy and is particularly suitable for the determination of fluoride ion concentration in electrochromium plating solutions.

[0057] 3. The measuring device of the present invention combines detection technology with automation technology, realizes the automation of the measurement process, improves work efficiency, reduces problems such as large human errors, and can be extended to the production line to realize online automatic detection.

[0058] The present invention adopts a standard addition method based on a single sample, solves the influence of factors such as pH value, temperature, matrix effect, interfering ions, stirring speed and the like of the measuring solution, and combines the fluoride ion potential analysis method to solve the influence of factors such as the hysteresis effect during the fluoride ion potential measurement by controlling the potential method, thereby realizing rapid and accurate measurement of the fluoride ion content in the chrome plating solution. Only one sample solution needs to be prepared to automatically complete the entire measurement process. At the same time, automatic measurement and calculation are realized based on computer communication technology, thereby realizing rapid and accurate measurement of the fluoride ion content in the chrome plating solution, and the operation is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is a flow chart of the method for determining the fluoride ion concentration in the chromium electroplating solution of the present invention;

[0060] Figure 2 The present invention is a schematic diagram of the structure of a device for measuring the fluoride ion concentration in a chromium electroplating solution.

[0061] In the figure, 1 is a computer, 2 is an ion meter, 3 is a stirrer, 4 is a stirring bar, 5 is a reaction cup, 6 is a support, 7 is a reference electrode, 8 is an indicator electrode, 9 is a syringe, 9 is a first medicine box, 10 is a first liquid adding pump, 101 is a second medicine box, 11 is a second liquid adding pump, and 111 is a third medicine box. DETAILED DESCRIPTION

[0062] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0063] Please see attached Figure 2 , a device for determining the concentration of fluoride ions in a chromium electroplating solution, comprising a computer 1, an ion meter 2, a stirrer 3, a reaction cup 5, a reference electrode 7, an indicator electrode 8, and a liquid adding component consisting of a syringe 9, a first liquid adding pump 10 and a second liquid adding pump 11; the reaction cup 5 is placed on the stirrer 3, and the stirrer 4 of the stirrer 3, the reference electrode 7, the indicator electrode 8, the liquid outlet pipe of the syringe 9, the liquid outlet pipe of the first liquid adding pump 10 and the liquid outlet pipe of the second liquid adding pump 11 are all inserted into the reaction cup 5 through a bracket 6; the input end of the ion meter 2 is connected to the reference electrode 7 and the indicator electrode 8, and the output end of the ion meter 2 is connected to the computer 1; the liquid inlet pipe of the syringe 9 is connected to the first medicine box 91, the liquid inlet pipe of the first liquid adding pump 10 is connected to the second medicine box 101, the liquid inlet pipe of the second liquid adding pump 11 is connected to the third medicine box 111, and the control ends of the syringe 9, the first liquid adding pump 10 and the second liquid adding pump 11 are all connected to the computer 1.

[0064] Preferably, the reference electrode 7 can be a saturated calomel electrode, and the indicator electrode 8 can be a fluoride ion selective electrode. With the reference electrode 7 as a benchmark, the potential difference between the indicator electrode 8 and the reference electrode 7 can be measured by the ion meter 2, and the potential difference is the fluoride ion potential in the test solution.

[0065] Preferably, the stirrer 3 can be a magnetic stirrer, and the stirrer 4 can be a polytetrafluoroethylene stirrer, so that each solution can be fully stirred and mixed in the reaction cup 5.

[0066] Preferably, the first liquid adding pump 10 and the second liquid adding pump 11 can both be peristaltic pumps, and quantitative addition of the solution can be achieved by setting parameters such as the rotation speed and time of the peristaltic pumps.

[0067] Preferably, the ion meter 2 has RS232 communication function, establishes communication and control with the computer 1 through the communication port COMX, bit rate, data bit number, validation bit, etc., and outputs the measured value. The ion meter 2 transmits the potential value obtained by each calculation to the computer 1, which facilitates the computer to process and calculate the data.

[0068] Preferably, the injector 9 has RS232 communication function, and establishes communication and control with the computer 1 through the communication port COMX, bit rate, data bit number, validation bit, etc. The computer 1 can control the injector 9 to pump the fluoride ion standard solution into the reaction cup 5 in a timely and quantitative manner, so as to facilitate obtaining the spiked test solution and measuring the potential of the test solution.

[0069] Please see attached Figure 1 A method for determining the concentration of fluorine ions in a chromium electroplating solution is provided. The method is implemented based on a device for determining the concentration of fluorine ions in a chromium electroplating solution. The method for determining the concentration of fluorine ions in a chromium electroplating solution comprises the following steps:

[0070] Step 1: Take a sample of the electroplating chromium solution and pour it into the reaction cup 5. Subsequent operations are all based on the electroplating chromium solution sample. The electroplating chromium solution sample only needs to be prepared once in the entire measurement process, thereby ensuring the accuracy of the measurement results.

[0071] Preferably, the volume V0 of the chromium electroplating solution sample is 0.1-10 mL.

[0072] Step 2: The first liquid adding pump 10 of the liquid adding component pumps the ion strength adjusting agent in the second reagent box 101 into the reaction cup 5. The ion strength adjusting agent is usually a buffer solution composed of acetic acid-sodium acetate, sodium citrate, and sodium chloride. At the same time, the second liquid adding pump 11 of the liquid adding component pumps the desalted water in the third reagent box 111 into the reaction cup 5.

[0073] Preferably, the pH value of the ion strength adjusting agent pumped into the reaction cup 5 is 5-6, and the volume V of the ion strength adjusting agent is 10 The volume V of desalted water pumped into the reaction cup 5 is 5-100 mL. 11 50-300mL.

[0074] Step 3: Start the stirrer 3, and the solution in the reaction cup 5 is uniformly mixed by the stirrer 4 to obtain a sample test solution. Preferably, the rotation speed of the stirrer 4 is 100-3000 rpm.

[0075] Step 4: Set the measurement parameters and start the ion meter 2. The ion meter 2 measures the potential value through the indicator electrode 8 and the reference electrode 7 according to the set measurement parameters.

[0076] The step 4 comprises the following sub-steps:

[0077] Step 4.1: Set the drift threshold. The drift is the ratio of the potential change △E to the time increment △t, that is, △E / △t, in units of mv / min. The potential difference between the indicator electrode 8 and the reference electrode 7 in the sample solution is measured by the ion meter 2 to obtain the fluoride ion potential E (in units of mv) in the sample solution. The fluoride ion potential E in the sample solution at a certain moment depends on the set potential drift threshold.

[0078] Preferably, the drift threshold has a value range of 0.1-50 mv / min. The setting of the drift threshold can solve the influence of the drift hysteresis effect, and effectively solve the problems of poor potential stability of the test solution and changes over time caused by factors such as matrix effect, interfering ions, test solution acidity, measurement temperature, stirring speed and fluoride ion concentration in the test solution, so that the fluoride ion potential E in the sample test solution measured during the measurement process is always at the same stable level.

[0079] Step 4.2: Since the measurement process is affected by factors such as temperature, stirring speed, coexisting ions, and matrix, the fluoride ion potential is unstable. Set the acquisition frequency T (in seconds) and the acquisition time range [t min , t max ] (unit: s). In the acquisition time range [t min , t max ] Collect fluoride ion potential values.

[0080] Among them, the minimum acquisition time t min The value range is: 0≤t min <t max , unit is s.

[0081] Set the maximum acquisition time t according to the drift amount max , the unit is s, and the calculation formula is:

[0082]

[0083] The acquisition frequency T ranges from 0.1 to 3 seconds.

[0084] Step 4.3: Collect at a sampling frequency T in the sampling time range [t min , tmax ] collect the fluoride ion potential value in the sample solution, and calculate the potential drift △E / △t, and judge whether the fluoride ion potential drift △E / △t in the sample solution meets the drift threshold. If so, the potential value at this point is recorded as the measured value. If not, the potential value at this point is recorded as the measured value. max The potential value at the moment is recorded as the measured value; the measured value recorded in step 4.3 is the sample test solution potential value E0, in mV.

[0085] Step 4.4: Set the number of times the fluoride ion standard solution with a concentration of C is added n times, the concentration of the fluoride ion standard solution is 0.1-10g / L, and the volumes of the fluoride ion standard solution added n times are V1, ..., V n (Unit is mL).

[0086] Preferably, the number of times n of adding the fluoride ion standard solution is usually ≥ 3, and the volumes of the fluoride ion standard solution added n times may be different or the same.

[0087] Step 4.5: The syringe 9 of the liquid adding assembly pumps the fluoride ion standard solution in the first reagent box 91 into the reaction cup 5 for the first time to obtain a first measurement solution. The volume of the fluoride ion standard solution pumped into the reaction cup 5 is V1 (in mL).

[0088] Step 4.6: Collect at a sampling frequency T in the sampling time range [t min , t max ] collect the fluorine ion potential value in the first measuring liquid, and calculate the potential drift △E / △t, and determine whether the fluorine ion potential drift △E / △t in the first measuring liquid meets the drift threshold range. If so, the potential value at this point is recorded as the measured value. If not, t max The potential value at the moment is recorded as the measured value; the measured value recorded in step 4.6 is the measuring liquid potential value E1 (in mV) of the first measuring liquid.

[0089] Step 4.7: Repeat steps 4.5-4.6 until the n fluoride ion standard solutions to be added are pumped into the reaction cup 5 in sequence, and the measured values ​​are recorded in sequence to obtain the potential values ​​E1-E of the n test solutions. n (Unit: mv).

[0090] Step 5: lift the bracket 6, rinse the indicator electrode 8, the reference electrode 7, and the filling pipes of the first filling pump 10 and the second filling pump 11 with deionized water, remove the reaction cup 5, and place the indicator electrode 8 in the air to maintain the activity of the fluoride ion selective electrode and the head exchange membrane of the indicator electrode 8. The reference electrode 7 is immersed in a 3M KCl solution (i.e., a KCl solution with a concentration of 3 mol / l) to protect the reference electrode 7, and the measurement is completed.

[0091] Step 6: Calculate the concentration of fluoride ions in the sample solution, that is, the concentration of fluoride ions in the electroplating chromium solution sample C x (Unit: g / L).

[0092] The step 6 comprises the following sub-steps:

[0093] Step 6.1: When the measurement starts, the calculation formula for the fluoride ion concentration C0 in the sample solution is:

[0094] C0=C x *V0 / (V0+V 10 +V 11 ) Formula (2)

[0095] Among them, C x It is the concentration of fluoride ions in the chromium electroplating solution sample, in g / L.

[0096] V0 is the sampling volume in mL.

[0097] V 10 is the volume of the added ion strength adjuster, in mL.

[0098] V 11 is the volume of desalted water added, in mL.

[0099] Step 6.2: After the fluoride ion standard solution with a volume of V1 (in mL) and a concentration of C (in g / L) is pumped in for the first time, the calculation formula for the fluoride ion concentration C1 (in g / L) in the first test solution is:

[0100] C1=(C x *V0+C*V1) / (V0+V 10 +V 11 ) formula (3).

[0101] Step 6.3: The volume of the nth pump is V n (unit: mL) and a fluoride ion standard solution with a concentration of C (unit: g / L), the concentration of fluoride ions in the nth test solution is C n (Unit: g / L) is calculated as:

[0102] C n =(C x *V0+∑ i＝1 n C*V i ) / (V0+V 10 +V 11 +∑ i＝1 n V i ) formula (4).

[0103] Step 6.4: According to the Nernst equation, the potential is linearly related to the ion concentration, so E is linearly related to logC, and the linear regression equation is obtained:

[0104] E=a+K*logC Formula (5)

[0105] Among them, a is the intercept of the linear regression equation, and K is the slope of the linear regression equation.

[0106] According to the linear regression equation and the potential value E0 (in mv) of the sample solution, the concentration C0 (in g / L) of fluoride ions in the sample solution is calculated.

[0107] Step 6.5: Substitute the fluoride ion concentration C0 (in g / L) in the sample solution calculated in step 6.4 into formula (2) to calculate the fluoride ion concentration C0 in the chromium electroplating solution sample. x (Unit: g / L).

[0108] Embodiment 1:

[0109] This embodiment 1 is implemented based on a device for measuring the fluoride ion concentration in a chromium electroplating solution, and the measuring steps are as follows:

[0110] Step 1: Take a sample of the electroplating chromium solution and pour it into the reaction cup 5, the volume of the electroplating chromium solution sample V0=2mL.

[0111] Step 2: The first liquid adding pump 10 pumps the ion strength adjusting agent in the second reagent box 101 into the reaction cup 5. In this embodiment, the ion strength adjusting agent is a buffer solution composed of acetic acid-sodium acetate, sodium citrate, and sodium chloride, with a pH of 5.2. The volume of the ion strength adjusting agent is V 10 = 20 mL, at the same time, the second liquid adding pump 11 pumps the desalted water in the third reagent box 111 into the reaction cup 5, and the volume of the desalted water V 11 =100mL.

[0112] Step 3: Start the stirrer 3, and mix the solution in the reaction cup 5 evenly with the stirring bar 4 at a rotation speed of 1000 rpm to obtain a sample solution.

[0113] Step 4: Set the measurement parameters and start the ion meter 2. The ion meter 2 measures the potential value through the indicator electrode 8 and the reference electrode 7 according to the set measurement parameters.

[0114] Step 4.1: Set the drift threshold to 1.0mv / min.

[0115] Step 4.2: Set the acquisition frequency T = 2s, the minimum acquisition time t min = 10s, according to formula (1), set the maximum acquisition time t max=154s, then the acquisition time range is [10, 154] (in seconds).

[0116] Step 4.3: Within the acquisition time [10, 154], the fluoride ion potential value of the sample solution is collected at an acquisition frequency of T = 2s, and the potential drift is calculated, and the potential value that meets the drift threshold of 1.0mv / min is recorded as the sample solution potential value E0 = 157.5mv.

[0117] Step 4.4: Set the number of additions of the fluoride ion standard solution with a concentration of C = 2 g / L to n = 3, and take 3 fluoride ion standard solutions with volumes of V1 = 2 mL, V2 = 4 mL, and V3 = 6 mL respectively.

[0118] Step 4.5: The syringe 9 pumps 2 mL of the fluoride ion standard solution from the first reagent box 91 into the reaction cup 5 for the first time to obtain the first measurement solution.

[0119] Step 4.6: Within the acquisition time range [10, 154], the fluoride ion potential value of the first test liquid is acquired at an acquisition frequency of T = 2s, and the potential drift is calculated, and the potential value that meets the drift threshold of 1.0mv / min is recorded as the test solution potential value E1 = 139.2mv of the first test liquid.

[0120] Step 4.7: The syringe 9 pumps 4 mL of fluoride ion standard solution from the first reagent box 91 into the reaction cup 5 for the second time to obtain a second test solution; within the collection time range [10, 154], the fluoride ion potential value of the second test solution is collected at a collection frequency of T = 2s, and the potential drift is calculated, and the potential value that meets the drift threshold of 1.0 mv / min is recorded as the test solution potential value E2 = 122.0 mv of the second test solution.

[0121] The syringe 9 pumps 6 mL of fluoride ion standard solution from the first reagent box 91 into the reaction cup 5 for the third time to obtain the third test solution; within the collection time range [10, 154], the fluoride ion potential value of the third test solution is collected at a collection frequency of T = 2s, and the potential drift is calculated, and the potential value that meets the drift threshold of 1.0 mv / min is recorded as the test solution potential value E3 = 108.8 mv of the third test solution.

[0122] Step 5: lift the bracket 6, rinse the indicator electrode 8, the reference electrode 7, and the filling pipes of the first filling pump 10 and the second filling pump 11 with deionized water, remove the reaction cup 5, and suspend the indicator electrode 8 in the air to maintain the activity of the exchange membrane at the head of the fluoride ion selective electrode. Immerse the reference electrode 7 in 3M KCl solution to protect the reference electrode 7, and the measurement is completed.

[0123] Step 6: Calculate the concentration of fluoride ions in the sample solution, that is, the concentration of fluoride ions in the electroplating chromium solution sample C x(Unit: g / L).

[0124] Step 6.1: According to formula (2), the fluoride ion concentration in the test solution at the beginning of the measurement is concentration C0 (in g / L): C0 = C x *2 / (2+20+100).

[0125] Step 6.2: After pumping in 2 mL of fluoride ion standard solution for the first time, the concentration of fluoride ions in the first test solution, C1 (in g / L), is: C1 = (C x *2+2*2) / (2+20+100+2).

[0126] Step 6.3: After pumping in 4 mL of fluoride ion standard solution for the second time, the concentration of fluoride ions in the second test solution, C2 (in g / L), is: C2 = (C x *2+2*2+2*4) / (2+20+100+2+4).

[0127] After 6 mL of fluoride ion standard solution is pumped in for the third time, the concentration of fluoride ions in the third test solution, C3 (in g / L), is: C3 = (C x *2+2*2+2*4+2*6) / (2+20+100+2+4+6).

[0128] Step 6.4: According to the Nernst equation, E and logC are linearly related, and the linear regression equation is E = 69.1-57.9*logC.

[0129] From E0=157.5mv, we get C0=0.02973g / L.

[0130] Step 6.4: Substitute the fluoride ion concentration C0 in the sample solution into formula (2) to calculate the fluoride ion concentration C in the chromium electroplating solution sample. x =1.81g / L.

[0131] Embodiment 2:

[0132] This embodiment 2 is implemented based on a device for measuring the fluoride ion concentration in a chromium electroplating solution, and the measuring steps are as follows:

[0133] Step 1: Take a sample of the electroplating chromium solution and pour it into the reaction cup 5, the volume of the electroplating chromium solution sample V0=5mL.

[0134] Step 2: The first liquid adding pump 10 pumps the ion strength adjusting agent in the second reagent box 101 into the reaction cup 5. In this embodiment, the ion strength adjusting agent is a buffer solution composed of acetic acid-sodium acetate, sodium citrate, and sodium chloride, with a pH of 5.2. The volume of the ion strength adjusting agent is V 10= 20 mL, at the same time, the second liquid adding pump 11 pumps the pure saline in the third reagent box 111 into the reaction cup 5, and the volume of the desalted water V 11 =100mL.

[0135] Step 3: Start the stirrer 3, and mix the solution in the reaction cup 5 evenly with the stirring bar 4 at a rotation speed of 1000 rpm to obtain a sample solution.

[0136] Step 4: Set the measurement parameters and start the ion meter 2. The ion meter 2 measures the potential value through the indicator electrode 8 and the reference electrode 7 according to the set measurement parameters.

[0137] Step 4.1: Set the drift threshold to 10mv / min.

[0138] Step 4.2: Set the acquisition frequency T = 2s, the minimum acquisition time t min = 10s, according to formula (1), set the maximum acquisition time t max =52s, then the acquisition time range is [10, 52] (in seconds).

[0139] Step 4.3: Within the acquisition time [10, 52], the fluoride ion potential value of the sample solution is collected at an acquisition frequency of T = 2s, and the potential drift is calculated, and the potential value that meets the drift threshold of 10mv / min is recorded as the sample solution potential value E0 = 186.1mv.

[0140] Step 4.4: Set the number of additions of the fluoride ion standard solution with a concentration of C = 5 g / L to n = 3, and take 3 fluoride ion standard solutions with volumes of V1 = 2 mL, V2 = 4 mL, and V3 = 6 mL respectively.

[0141] Step 4.5: The syringe 9 pumps 2 mL of the fluoride ion standard solution from the first reagent box 91 into the reaction cup 5 for the first time to obtain the first measurement solution.

[0142] Step 4.6: Within the acquisition time range [10, 52], the fluoride ion potential value of the first test liquid is acquired at an acquisition frequency of T = 2s, and the potential drift is calculated. The potential value that meets the drift threshold of 10mv / min is recorded as the test liquid potential value E1 = 153.2mv of the first test liquid.

[0143] Step 4.7: The syringe 9 pumps 4 mL of fluoride ion standard solution from the first reagent box 91 into the reaction cup 5 for the second time to obtain a second test solution; within the collection time range [10, 52], the fluoride ion potential value of the second test solution is collected at a collection frequency of T = 2s, and the potential drift is calculated, and the potential value that meets the drift threshold of 10 mv / min is recorded as the test solution potential value E2 = 131.2 mv of the second test solution.

[0144] The syringe 9 pumps 6 mL of fluoride ion standard solution from the first reagent box 91 into the reaction cup 5 for the third time to obtain the third test solution; within the collection time range [10, 52], the fluoride ion potential value of the third test solution is collected at a collection frequency of T = 2s, and the potential drift is calculated, and the potential value that meets the drift threshold of 10 mv / min is recorded as the test solution potential value E3 = 116.2 mv of the third test solution.

[0145] Step 5: lift the bracket 6, rinse the indicator electrode 8, the reference electrode 7, and the filling pipes of the first filling pump 10 and the second filling pump 11 with deionized water, remove the reaction cup 5, and suspend the indicator electrode 8 in the air to maintain the activity of the exchange membrane at the head of the fluoride ion selective electrode. Immerse the reference electrode 7 in 3M KCl solution to protect the reference electrode 7, and the measurement is completed.

[0146] Step 6: Calculate the concentration of fluoride ions in the sample solution, that is, the concentration of fluoride ions in the electroplating chromium solution sample C x (Unit: g / L).

[0147] Step 6.1: According to formula (2), the concentration of fluoride ions in the test solution at the beginning of measurement is C0 (in g / L): C0 = C x *5 / (5+20+100).

[0148] Step 6.2: After the first pumping of 2 mL of fluoride ion standard solution, the concentration of fluoride ions in the first test solution, C1 (in g / L), is: C1 = (C x *5+5*2) / (5+20+100+2).

[0149] Step 6.3: After pumping in 4 mL of fluoride ion standard solution for the second time, the concentration of fluoride ions in the second test solution, C2 (in g / L), is: C2 = (C x *5+5*2+5*4) / (5+20+100+2+4).

[0150] After pumping in 6 mL of fluoride ion standard solution for the third time, the fluoride ion concentration C3 (in g / L) in the second test solution is: C3 = (Cx*5+5*2+5*4+5*6) / (5+20+100+2+4+6).

[0151] Step 6.4: According to the Nernst equation, E and logC are linearly related, and the linear regression equation E = 97.3-58.5*logC is obtained. According to the linear regression equation, from E0 = 186.1 mV, C0 = 0.03034 / L is obtained.

[0152] Step 6.5: Substitute the fluoride ion concentration C0 in the sample solution into formula (2) to calculate the fluoride ion concentration C in the chromium electroplating solution sample. x =0.76g / L.

[0153] Embodiment 3:

[0154] This embodiment 3 is implemented based on a device for measuring the fluoride ion concentration in a chromium electroplating solution, and the measuring steps are as follows:

[0155] Step 1: Take a sample of the electroplating chromium solution and pour it into the reaction cup 5, the volume of the electroplating chromium solution sample V0=2mL.

[0156] Step 2: The first liquid adding pump 10 pumps the ion strength adjusting agent in the second reagent box 101 into the reaction cup 5. In this embodiment, the ion strength adjusting agent is a buffer solution composed of acetic acid-sodium acetate, sodium citrate, and sodium chloride, with a pH of 5.2. The volume of the ion strength adjusting agent is V 10 = 20 mL, at the same time, the second liquid adding pump 11 pumps the desalted water in the third reagent box 111 into the reaction cup 5, and the volume of the desalted water V 11 =100mL.

[0157] Step 3: Start the stirrer 3, and mix the solution in the reaction cup 5 evenly with the stirring bar 4 at a rotation speed of 1000 rpm to obtain a sample solution.

[0158] Step 4: Set the measurement parameters and start the ion meter 2. The ion meter 2 measures the potential value through the indicator electrode 8 and the reference electrode 7 according to the set measurement parameters.

[0159] Step 4.1: Set the drift threshold to 5.0mv / min.

[0160] Step 4.2: Set the acquisition frequency T = 2s, the minimum acquisition time t min = 10s, according to formula (1), set the maximum acquisition time t max =72s, then the acquisition time range is [10, 72] (in seconds).

[0161] Step 4.3: Within the acquisition time [10, 72], the fluoride ion potential value of the sample solution is collected at an acquisition frequency of T = 2s, and the potential drift is calculated, and the potential value that meets the drift threshold of 5.0mv / min is recorded as the sample solution potential value E0 = 172.4mv.

[0162] Step 4.4: Set the number of additions of the fluoride ion standard solution with a concentration of C = 2 g / L to n = 3, and take 3 fluoride ion standard solutions with volumes of V1 = 5 mL, V2 = 5 mL, and V3 = 5 mL respectively.

[0163] Step 4.5: The syringe 9 pumps 5 mL of the fluoride ion standard solution from the first reagent box 91 into the reaction cup 5 for the first time to obtain the first measurement solution.

[0164] Step 4.6: Within the acquisition time range [10, 72], the fluoride ion potential value of the first test liquid is acquired at an acquisition frequency of T = 2s, and the potential drift is calculated. The potential value that meets the drift threshold of 5.0mv / min is recorded as the test liquid potential value E1 = 140.0mv of the first test liquid.

[0165] Step 4.7: The syringe 9 pumps 5 mL of fluoride ion standard solution from the first reagent box 91 into the reaction cup 5 for the second time to obtain a second test solution; within the collection time range [10, 72], the fluoride ion potential value of the second test solution is collected at a collection frequency of T = 2s, and the potential drift is calculated, and the potential value that meets the drift threshold of 5.0 mv / min is recorded as the test solution potential value E2 = 127.1 mv of the second test solution.

[0166] The syringe 9 pumps 5 mL of fluoride ion standard solution from the first reagent box 91 into the reaction cup 5 for the third time to obtain the third test solution; within the collection time range [10, 72], the fluoride ion potential value of the third test solution is collected at a collection frequency of T = 2s, and the potential drift is calculated, and the potential value that meets the drift threshold of 5.0 mv / min is recorded as the test solution potential value E3 = 119.1 mv of the third test solution.

[0167] Step 5: lift the bracket 6, rinse the indicator electrode 8, the reference electrode 7, and the filling pipes of the first filling pump 10 and the second filling pump 11 with deionized water, remove the reaction cup 5, and suspend the indicator electrode 8 in the air to maintain the activity of the exchange membrane at the head of the fluoride ion selective electrode. Immerse the reference electrode 7 in 3M KCl solution to protect the reference electrode 7, and the measurement is completed.

[0168] Step 6: Calculate the concentration of fluoride ions in the sample solution, that is, the concentration of fluoride ions in the electroplating chromium solution sample C x (Unit: g / L).

[0169] Step 6.1: According to formula (2), the fluoride ion concentration in the test solution at the beginning of the measurement is concentration C0 (in g / L): C0 = C x *2 / (2+20+100).

[0170] Step 6.2: After pumping in 5 mL of fluoride ion standard solution for the first time, the concentration of fluoride ions in the first test solution, C1 (in g / L), is: C1 = (C x *2+2*5) / (2+20+100+5).

[0171] Step 6.3: After pumping in 5 mL of fluoride ion standard solution for the second time, the concentration of fluoride ions in the second test solution, C2 (in g / L), is: C2 = (C x *2+2*5+2*5) / (2+20+100+5+5).

[0172] After the third pumping of 5 mL of fluoride ion standard solution, the concentration of fluoride ions in the third test solution, C3 (in g / L), is: C3 = (C x *2+2*5+2*5+2*5) / (2+20+100+5+5+5).

[0173] Step 6.4: According to the Nernst equation, E and logC are linearly related, and the linear regression equation is E = 83.8-58.2*logC.

[0174] From E0=172.4mv, we get C0=0.03004g / L.

[0175] Step 6.4: Substitute the fluoride ion concentration C0 in the sample solution into formula (2) to calculate the fluoride ion concentration C in the chromium electroplating solution sample. x =1.83g / L.

[0176] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining the fluoride ion concentration in a chromium electroplating solution, characterized in that: The determination method is implemented based on a device for determining the concentration of fluorine ions in an electroplating chromium solution. The device for determining the concentration of fluorine ions in an electroplating chromium solution comprises an ion meter (2), a stirrer (4), a reaction cup (5), a reference electrode (7), an indicator electrode (8) and a liquid adding component. The method for determining the fluoride ion concentration in the chromium electroplating solution comprises the following steps: Step 1: Take a sample of the electroplating chromium solution and pour it into a reaction cup (5); Step 2: The liquid adding component pumps the ion strength adjusting agent into the reaction cup (5), and pumps the desalted water into the reaction cup (5); Step 3: The solution in the reaction cup (5) is uniformly mixed by a stirring bar (4) to obtain a sample test solution; Step 4: setting measurement parameters, starting the ion meter (2), and the ion meter (2) measures the potential value according to the set measurement parameters through the indicator electrode (8) and the reference electrode (7); Step 5: Measurement ends; Step 6: Calculate the concentration of fluoride ions in the sample solution, that is, the concentration of fluoride ions in the electroplating chromium solution sample C x , unit is g / L; The step 4 comprises the following sub-steps: Step 4.1: Set the drift threshold. The drift is the ratio of the potential change △E to the time increment △t, that is, △E / △t, in units of mv / min; Step 4.2: Set the acquisition frequency to T, in seconds, and the acquisition time range [t min , t max ], unit is s; Among them, the minimum acquisition time t min The value range is: 0≤t min <t max ; The maximum acquisition time is determined by the drift amount and is calculated as: Step 4.3: Collect at a sampling frequency T in the sampling time range [t min , t max ] collect the fluoride ion potential value in the sample solution, and calculate the potential drift △E / △t, and judge whether the fluoride ion potential drift △E / △t in the sample solution meets the drift threshold. If so, the potential value at this point is recorded as the measured value. If not, the potential value at this point is recorded as the measured value. max The potential value at the moment is recorded as the measured value; the recorded measured value is the sample test solution potential value E0, in mV; Step 4.4: Set the concentration of fluoride ion standard solution to C in g / L, and add n times of fluoride ion standard solution. The volumes of the fluoride ion standard solution added in n times are V1, ..., V n , unit is mL; Step 4.5: The liquid adding component pumps the fluoride ion standard solution into the sample test solution for the first time to obtain a first test solution. The volume of the fluoride ion standard solution pumped into the reaction cup (5) is V1; Step 4.6: Collect at a sampling frequency T in the sampling time range [t min , t max ] collect the potential value of the fluoride ion in the first measuring liquid, and calculate the potential drift △E / △t, and determine whether the potential drift △E / △t of the fluoride ion in the first measuring liquid meets the drift threshold range. If so, the potential value at this point is recorded as the measured value. If not, t max The potential value at the time is recorded as the measured value; the recorded measured value is the measuring liquid potential value E1 of the first measuring liquid, in mV; Step 4.7: Repeat steps 4.5 to 4.6 until the required n fluoride ion standard solutions are pumped into the reaction cup (5) in sequence, and the measured values ​​are recorded in sequence to obtain the potential values ​​E1-E of the n test solutions. n ; The step 6 comprises the following sub-steps: Step 6.1: When the measurement starts, the calculation formula for the fluoride ion concentration C0 in the sample solution is: C0=C x *V0 / (V0+V 10 +V 11 ) Formula (2) The unit of fluoride ion concentration C0 in the test solution is g / L; Among them, C x is the concentration of fluoride ions in the chromium electroplating solution sample, in g / L; V0 is the sampling volume, in mL; V 10 is the volume of the added ion strength adjuster, in mL; V 11 is the volume of desalted water added, in mL; Step 6.2: After the first pumping of the fluoride ion standard solution with a volume of V1 and a concentration of C, the calculation formula for the fluoride ion concentration C1 in the first test solution is: C1=(C x *V0+C*V1) / (V0+V 10 +V 11 +V1) Formula (3); The unit of the fluoride ion concentration C1 in the first test solution and the concentration C of the fluoride ion standard solution is g / L, and the unit of the volume V1 of the fluoride ion standard solution added for the first time is mL; Step 6.3: The volume of the nth pump is V n , the concentration of fluoride ions in the nth test solution is C n The calculation formula is: C n =(C x *V0+∑ i＝1 n C*V i ) / (V0+V 10 +V 11 +∑ i＝1 n V i ) formula (4); The concentration of fluoride ions in the nth test solution C n The concentration C of the fluoride ion standard solution is in g / L, and the volume V of the fluoride ion standard solution added for the nth time is n The unit is mL; Step 6.4: According to the Nernst equation, E and logC are linearly related, and the linear regression equation is obtained: E=a+K*logC Formula (5) Among them, a is the intercept of the linear regression equation, and K is the slope of the linear regression equation; According to the linear regression equation and the potential value E0 of the sample solution, in mv, the fluoride ion concentration C0 in the sample solution is calculated, in g / L. Step 6.5: Substitute the fluoride ion concentration C0 in the sample solution calculated in step 6.4 into formula (2) to calculate the fluoride ion concentration C0 in the chromium electroplating solution sample. x , unit is g / L.

2. The method for determining the fluoride ion concentration in the chromium electroplating solution according to claim 1, wherein: The volume V0 of the chromium electroplating solution sample is 0.1-10 mL.

3. The method for determining the fluoride ion concentration in the chromium electroplating solution according to claim 1, wherein: The ion strength adjusting agent pumped into the reaction cup (5) is a buffer solution composed of acetic acid-sodium acetate, sodium citrate, and sodium chloride. The volume of the ion strength adjusting agent is V 10 The volume of desalted water pumped into the reaction cup (5) is V 11 50-300mL.

4. The method for determining the fluoride ion concentration in the chromium electroplating solution according to claim 1, wherein: The drift threshold value ranges from 0.1 to 50 mv / min, and the acquisition frequency T ranges from 0.1 to 3 s.

5. The method for determining the fluoride ion concentration in the chromium electroplating solution according to claim 1, wherein: The fluoride ion standard solution is added for a number of times n≥3.

6. The method for determining the fluoride ion concentration in the chromium electroplating solution according to claim 1 or 5, characterized in that: The concentration of the fluoride ion standard solution is 0.1-10 g / L.

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