A cathode electrophoresis ternary phosphating solution

Abstract

The present invention belongs to the field of phosphating solutions, and specifically relates to a cathode electrophoretic ternary phosphating solution. The cathode electrophoretic ternary phosphating solution comprises the following components, calculated by mass: 20-50% phosphoric acid, 1-5% zinc oxide, 1-10% manganese carbonate, 1-5% nitric acid, 0.1-1% fluoride, 1-10% sodium carbonate, 5-20% nickel nitrate, and the balance being water. The cathode electrophoretic phosphating solution provided by the present invention offers excellent performance, convenient operation, and low cost. It overcomes the poor corrosion resistance of phosphate films, improves salt spray performance when used in conjunction with cathode electrophoresis, and is better compatible with electrophoresis.

Description

Technical Field

[0001] The invention belongs to the field of phosphating solutions, and in particular relates to a cathode electrophoresis ternary phosphating solution. Background Art

[0002] Phosphorization is a process in which chemical and electrochemical reactions form a phosphate conversion coating, known as a phosphate film. The primary purpose of phosphating is to protect the base metal, preventing corrosion to a certain extent. It is used as a primer before painting to improve the adhesion and corrosion resistance of the paint film. It also acts as a friction reducer and lubricant during metal cold working processes.

[0003] Traditional zinc-based phosphating solutions used with cathodes have many defects, including: too low P value, most of which are <80%; too thick film layer, which results in poor conductivity during electrophoresis; insufficient film density; and the phosphating film formed may produce holes and cracks after absorbing environmental moisture, oxygen and other factors, resulting in a decrease in the protective performance of the phosphating film, poor corrosion resistance of the film, and poor alkali resistance of the film.

[0004] Therefore, the development of phosphating solution that can meet the requirements of electrophoresis process has urgent significance and excellent development prospects. Summary of the Invention

[0005] In response to the above technical problems, the inventors have conducted extensive research and developed a cathode electrophoretic ternary phosphating solution, specifically including a cathode electrophoretic ternary phosphating solution with water as solvent, characterized in that, by mass fraction, it includes the following components: 20-50% phosphoric acid, 1-5% zinc oxide, 1-10% manganese carbonate, 1-5% nitric acid, 0.1-1% fluorine compound, 1-10% sodium carbonate, 5-20% nickel nitrate, and the balance is water.

[0006] Furthermore, it also includes 1-5% mercaptomalic acid.

[0007] Furthermore, 1-5% mercaptobenzoic acid is also included.

[0008] The specific steps of the preparation method of the cathode electrophoretic ternary phosphating solution provided by the present invention are as follows:

[0009] S1. Add the required water to the reactor and dissolve zinc oxide into a paste;

[0010] S2 phosphoric acid was slowly added to the reactor until the solution was clear, the remaining phosphoric acid and nitric acid were added to the reactor, stirred, and then manganese carbonate was added until the solution was clear;

[0011] S3. After complete dissolution, sodium carbonate, nickel nitrate, sodium fluoroborate were sequentially added to the reactor and stirred thoroughly;

[0012] S4. A mixture of sodium carbonate was added to the reactor, and the free acidity was adjusted to 0.7 to 1.6 points and the total acidity to 21 to 25 points;

[0013] S5. As needed, before phosphating, add mercaptomalic acid and / or mercaptobenzoic acid to the solution obtained in step S5.

[0014] The present invention provides a phosphating and electrophoresis method using a cathodic electrophoretic ternary phosphating solution, characterized by comprising the following steps: degreasing the workpiece, washing with water, conditioning the surface, phosphating, washing with water, and then washing with pure water, followed by electrophoresis; wherein the phosphating temperature is 35-45°C, the phosphating time is 3 minutes, and the electrophoresis process parameters are: voltage 200V, temperature 30±1°C, and time 3 minutes. The conditioning solution is a commercially available product and is not described in detail here.

[0015] The present invention has the following technical features:

[0016] (1) The cathode electrophoretic phosphating solution provided in the present invention has good use effect, is easy to operate, and has low cost. It overcomes the poor corrosion resistance of the phosphating film and improves the salt spray performance when matched with the cathode electrophoretic solution.

[0017] (2) The cathode electrophoretic ternary phosphating solution provided by the present invention has a phosphating film thickness of 1-3 μm, an alkaline weight loss of the phosphating film ≤ 5%, and a P ratio ≥ 95%, which can be better adapted to electrophoresis. DETAILED DESCRIPTION

[0018] Except as provided in the Examples, or where otherwise explicitly stated, all numerical values ​​used in the specification and claims representing quantities of components, reaction conditions, and the like should be construed as varying in all instances by the term "about." Therefore, unless otherwise indicated, the numerical parameters set forth in the following specification and claims are approximate and may vary depending on the desired properties of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in terms of significant figures and by applying ordinary rounding.

[0019] Although the numerical ranges and parameters setting forth the broad scope of the invention are approximate, the numerical values ​​set forth in the specific examples are reported as accurately as possible. However, any numerical value inherently contains certain errors. Such errors are the inevitable result of the standard deviation found in the respective measurements.

[0020] Furthermore, it should be understood that any numerical range recited herein is intended to include all subranges subsumed therein. For example, a range of "1 to 10" is intended to include all subranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, i.e., having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

[0021] In this application, unless otherwise expressly stated, the use of the singular includes the plural and the plural includes the singular. Furthermore, in this application, unless otherwise expressly stated, the use of "or" means "and / or," even though "and / or" could be explicitly used in certain circumstances. Furthermore, in this application, unless otherwise expressly stated, the use of "a" means "at least one." For example, "a" coating, etc., refers to any one or more of the items. And as will be appreciated by those skilled in the art, features of one embodiment can be used with other embodiments, even if not expressly stated herein.

[0022] The neutral salt spray test in the present invention is conducted on the paint film in accordance with GB10125-1997. A cross-sectioned sample after electrophoresis is placed in a salt spray test chamber at an angle of 15° to 30° from vertical. Spray is continuously applied at (35±2)°C, and the time required for the cross-section on the workpiece surface to diffuse unilaterally to 2 mm is observed.

[0023] Example 1

[0024] Phosphoric acid 20%, zinc oxide 1%, manganese carbonate 1%, nitric acid 1%, sodium fluoroborate 0.1%, sodium carbonate 1%, nickel nitrate 5%, the balance is water, adjust the free acidity to 0.7-1.6 points and the total acidity to 21-25 points.

[0025] Sodium fluoroborate can also be replaced by other fluorine compounds, such as fluosilicic acid, fluoboric acid, etc., which will not be described in detail in the subsequent examples.

[0026] The resulting phosphating solution is then used to phosphate the workpiece, followed by a neutral salt spray test. The phosphating process is as follows: workpiece degreasing → water washing → surface conditioning → phosphating process parameters: phosphating temperature: 45°C; phosphating time: 3 minutes; the electrophoresis process is as follows: phosphating → water washing → pure water washing → electrophoresis. The electrophoretic coating process parameters are: voltage 200V, temperature (30±1)°C, time 3 minutes.

[0027] The neutral salt spray test was performed on the test piece after phosphating and electrophoresis. Subsequent Examples 2-16 were all subjected to the neutral salt spray test in the same manner, which will not be described in detail in the subsequent examples.

[0028] Example 2

[0029] Phosphoric acid 30%, zinc oxide 2%, manganese carbonate 3%, nitric acid 2%, sodium fluoroborate 0.3%, sodium carbonate 3%, nickel nitrate 10%, and the balance is water. Adjust the free acidity to 0.7-1.6 points and the total acidity to 21-25 points.

[0030] Example 3

[0031] Phosphoric acid 35%, zinc oxide 3%, manganese carbonate 5%, nitric acid 3%, sodium fluoroborate 0.5%, sodium carbonate 5%, nickel nitrate 13%, the balance is water. Adjust the free acidity to 0.7-1.6 points and the total acidity to 21-25 points.

[0032] Example 4

[0033] Phosphoric acid 40%, zinc oxide 4%, manganese carbonate 7%, nitric acid 4%, sodium fluoroborate 0.7%, sodium carbonate 7%, nickel nitrate 15%, and the balance is water. Adjust the free acidity to 0.7-1.6 points and the total acidity to 21-25 points.

[0034] Example 5

[0035] Phosphoric acid 50%, zinc oxide 5%, manganese carbonate 10%, nitric acid 5%, sodium fluoroborate 1%, sodium carbonate 10%, nickel nitrate 20%, and the balance is water. Adjust the free acidity to 0.7-1.6 points and the total acidity to 21-25 points.

[0036] Table 1

[0037]

[0038] Example 6

[0039] Compared with Example 3, 1% of mercaptomalic acid was added, while the other components remained unchanged. The specific ingredients were: 35% phosphoric acid, 3% zinc oxide, 5% manganese carbonate, 3% nitric acid, 0.5% sodium fluoroborate, 5% sodium carbonate, 13% nickel nitrate, and 1% mercaptomalic acid, with the balance being water. The free acidity was adjusted to 0.7-1.6 points, and the total acidity to 21-25 points.

[0040] Example 7

[0041] Compared with Example 3, 2% of mercaptomalic acid was added, while the other components remained unchanged. The specific ingredients were: 35% phosphoric acid, 3% zinc oxide, 5% manganese carbonate, 3% nitric acid, 0.5% sodium fluoroborate, 5% sodium carbonate, 13% nickel nitrate, and 2% mercaptomalic acid, with the balance being water. The free acidity was adjusted to 0.7-1.6 points, and the total acidity to 21-25 points.

[0042] Example 8

[0043] Compared with Example 3, 3% mercaptomalic acid was added, while the other components remained unchanged. The specific ingredients were: 35% phosphoric acid, 3% zinc oxide, 5% manganese carbonate, 3% nitric acid, 0.5% sodium fluoroborate, 5% sodium carbonate, 13% nickel nitrate, and 3% mercaptomalic acid, with the balance being water. The free acidity was adjusted to 0.7-1.6 points, and the total acidity to 21-25 points.

[0044] Example 9

[0045] Compared with Example 3, 4% of mercaptomalic acid was added, while the other components remained unchanged. The specific ingredients were: 35% phosphoric acid, 3% zinc oxide, 5% manganese carbonate, 3% nitric acid, 0.5% sodium fluoroborate, 5% sodium carbonate, 13% nickel nitrate, and 4% mercaptomalic acid, with the balance being water. The free acidity was adjusted to 0.7-1.6 points, and the total acidity to 21-25 points.

[0046] Example 10

[0047] Compared with Example 3, 5% mercaptomalic acid was added, while the other components remained unchanged. The specific ingredients were: 35% phosphoric acid, 3% zinc oxide, 5% manganese carbonate, 3% nitric acid, 0.5% sodium fluoroborate, 5% sodium carbonate, 13% nickel nitrate, and 5% mercaptomalic acid, with the balance being water. The free acidity was adjusted to 0.7-1.6 points, and the total acidity to 21-25 points.

[0048] Table 2

[0049] Example Example 6 Example 7 Example 8 Example 9 Example 10 Neutral salt spray test (hours) 1050 1150 1000 950 920

[0050] Example 11

[0051] Compared with Example 3, 1% mercaptobenzoic acid was added, while the other components remained unchanged. The specific ingredients were: 35% phosphoric acid, 3% zinc oxide, 5% manganese carbonate, 3% nitric acid, 0.5% sodium fluoroborate, 5% sodium carbonate, 13% nickel nitrate, and 1% mercaptobenzoic acid, with the balance being water. The free acidity was adjusted to 0.7-1.6 points, and the total acidity to 21-25 points.

[0052] Example 12

[0053] Compared with Example 2, 2% mercaptobenzoic acid was added, while the other components remained unchanged. The specific ingredients were: 35% phosphoric acid, 3% zinc oxide, 5% manganese carbonate, 3% nitric acid, 0.5% sodium fluoroborate, 5% sodium carbonate, 13% nickel nitrate, and 2% mercaptobenzoic acid, with the balance being water. The free acidity was adjusted to 0.7-1.6 points, and the total acidity to 21-25 points.

[0054] Example 13

[0055] Compared with Example 2, 3% mercaptobenzoic acid was added, while the other components remained unchanged. The specific ingredients were: 35% phosphoric acid, 3% zinc oxide, 5% manganese carbonate, 3% nitric acid, 0.5% sodium fluoroborate, 5% sodium carbonate, 13% nickel nitrate, and 3% mercaptobenzoic acid, with the balance being water. The free acidity was adjusted to 0.7-1.6 points, and the total acidity to 21-25 points.

[0056] Example 14

[0057] Compared with Example 2, 4% mercaptobenzoic acid was added, while the other components remained unchanged. The specific ingredients were: 35% phosphoric acid, 3% zinc oxide, 5% manganese carbonate, 3% nitric acid, 0.5% sodium fluoroborate, 5% sodium carbonate, 13% nickel nitrate, and 4% mercaptobenzoic acid, with the balance being water. The free acidity was adjusted to 0.7-1.6 points, and the total acidity to 21-25 points.

[0058] Example 15

[0059] Compared with Example 2, 5% mercaptobenzoic acid was added, while the other components remained unchanged. The specific ingredients were: 35% phosphoric acid, 3% zinc oxide, 5% manganese carbonate, 3% nitric acid, 0.5% sodium fluoroborate, 5% sodium carbonate, 13% nickel nitrate, and 5% mercaptobenzoic acid, with the balance being water. The free acidity was adjusted to 0.7-1.6 points, and the total acidity to 21-25 points.

[0060] Table 3

[0061] Example Example 11 Example 12 Example 13 Example 14 Example 15 Neutral salt spray test (hours) 980 1130 1100 1030 1010

[0062] Example 16

[0063] Compared with Example 2, 2% mercaptomalic acid and 3% mercaptobenzoic acid are added, while the other components remain unchanged. The specific ingredients are: 35% phosphoric acid, 3% zinc oxide, 5% manganese carbonate, 3% nitric acid, 0.5% sodium fluoroborate, 5% sodium carbonate, 13% nickel nitrate, 2% mercaptomalic acid and 5% mercaptobenzoic acid, and the balance is water. The free acidity is adjusted to 0.7-1.6 points, and the total acidity is adjusted to 21-25 points.

[0064] Neutral salt spray test shows that the time required for the unilateral diffusion of the scratch on the surface of the workpiece to reach 2mm is 1250h.

[0065] Example 17

[0066] Since the temperature during the phosphating process of Examples 1-16 was all carried out at 45°C, in order to investigate whether good results were also achieved when the phosphating temperature was lowered, phosphating solutions of different components were used to phosphate the workpiece at different phosphating temperatures. The other phosphating and electrophoresis parameters remained unchanged, and then a neutral salt spray test was performed. The specific conditions and results are as follows.

[0067] Table 4

[0068]

[0069] The data in Table 4 show that the phosphating solution in Example 3 does not contain mercaptomalic acid or mercaptobenzoic acid, and the corrosion resistance decreases when the phosphating temperature is lowered. When mercaptomalic acid and / or mercaptobenzoic acid are added, good corrosion resistance can also be achieved at 35°C.

[0070] In addition, the cathode electrophoresis ternary phosphating solution provided by the present invention has a phosphating film thickness of 1-3 μm, an alkaline weight loss of the phosphating film of ≤5%, and a P ratio of ≥95%.

[0071] While particular aspects of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various other changes and modifications may be made without departing from the spirit and scope of the invention. It is therefore intended that the appended claims cover all such changes and modifications as fall within the scope of the invention.

Claims

1. A cathodic electrophoretic ternary phosphating solution using water as solvent, characterized in that: The composition comprises the following components by mass fraction: 20-50% phosphoric acid, 1-5% zinc oxide, 1-10% manganese carbonate, 1-5% nitric acid, 0.1-1% fluorine compound, 1-10% sodium carbonate, 5-20% nickel nitrate, and the balance being water; Also included is mercaptomalic acid 2% and / or mercaptobenzoic acid 2-3%.

2. The cathodic electrophoretic ternary phosphating solution according to claim 1, characterized in that: The invention comprises the following components: 30-40% phosphoric acid, 2-4% zinc oxide, 3-7% manganese carbonate, 2-4% nitric acid, 0.3-0.7% fluorine compound, 3-7% sodium carbonate, 10-15% nickel nitrate, and the balance is water.

3. The cathodic electrophoretic ternary phosphating solution according to claim 2, characterized in that: The invention comprises the following components: 40% phosphoric acid, 4% zinc oxide, 7% manganese carbonate, 4% nitric acid, 0.7% fluorine compound, 7% sodium carbonate, 15% nickel nitrate, and the balance is water.

4. The cathodic electrophoretic ternary phosphating solution according to claim 3, characterized in that: The fluorine compound is sodium fluoroborate.

5. The method for preparing a cathodic electrophoretic ternary phosphating solution according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Add the required water to the reactor and dissolve zinc oxide into a paste; S2 phosphoric acid was slowly added to the reactor until the solution was clear, the remaining phosphoric acid and nitric acid were added to the reactor, stirred, and then manganese carbonate was added until the solution was clear; S3. After complete dissolution, sodium carbonate, nickel nitrate, sodium fluoroborate were sequentially added to the reactor and stirred thoroughly; S4. A mixture of sodium carbonate was added to the reactor, and the free acidity was adjusted to 0.7 to 1.6 points and the total acidity to 21 to 25 points; S5. If necessary, before phosphating, add mercaptomalic acid and / or mercaptobenzoic acid to the solution obtained in step S5.

6. The phosphating electrophoresis method using a cathodic electrophoretic ternary phosphating solution according to any one of claims 1 to 4, characterized in that: The following steps are involved: The workpiece is degreased, washed, surface-conditioned, phosphated, washed, washed with pure water, and then electrophoresed; The phosphating temperature is 35~45℃; the phosphating time is 3min; the electrophoresis process parameters are: voltage 200V, temperature 30±1℃, time 3min.

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