A plating process for automotive trim

Abstract

The application relates to the technical field of electroplating, in particular to an electroplating process for automobile decoration parts. The electroplating process for automobile decoration parts comprises an electroplating pretreatment and an electroplating procedure, the electroplating pretreatment procedure comprises pretreatment and roughening, the roughening step comprises immersing the pretreated decoration part into a roughening solution; the roughening solution contains the following components: 15-30 g / L of potassium permanganate, 3-8 g / L of potassium nitrate, 1-3 g / L of a complexing agent, and the rest is supplemented with water. The electroplating process for automobile decoration parts can solve the problem of poor corrosion resistance of automobile decorative electroplated parts.

Description

Technical Field

[0001] This application relates to the field of electroplating technology, and more specifically, to an electroplating process for automotive trim parts. Background Technology

[0002] In recent years, with the booming development of the automotive industry, domestic and joint venture manufacturers and brand-new models have emerged like mushrooms after rain. Manufacturers are paying more and more attention to the personalization of vehicle appearance. ABS plastic electroplated parts are an important component of automotive trim.

[0003] Because automotive decorative electroplated parts are typically exposed to the outdoors, they must withstand various environmental challenges such as extreme cold, intense sunlight, corrosion, mud, stone impacts, and scratches, resulting in high requirements for appearance and corrosion resistance. However, due to its chemical inertness and hydrophobicity, ABS plastic is difficult to completely wet with aqueous solutions, making it difficult to induce metal deposition. This leads to poor adhesion between the metal plating and the ABS plastic, resulting in peeling, blistering, and even incomplete plating, ultimately causing poor corrosion resistance in automotive decorative electroplated parts. Summary of the Invention

[0004] To address the problem of poor corrosion resistance in automotive decorative electroplated parts, this application provides an electroplating process for automotive decorative parts.

[0005] In a first aspect, this application provides an electroplating process for automotive decorative parts, employing the following technical solution: An electroplating process for automotive decorative parts includes a pre-plating treatment and an electroplating process. The pre-plating treatment process includes pre-treatment and roughening. The roughening step includes immersing the pre-treated decorative parts in a roughening solution. The roughening solution contains the following components: potassium permanganate 15-30 g / L, potassium nitrate 3-8 g / L, complexing agent 1-3 g / L, with the remainder made up with water.

[0006] By employing the above technical solution, potassium permanganate and potassium nitrate, as oxidants, can perform micro-etching treatment on ABS, resulting in numerous micropores on the surface of the ABS decorative parts and the generation of hydrophilic groups. This facilitates metal deposition on the surface and improves the bonding strength between the metal coating and the ABS plastic. Potassium permanganate is a strong oxidant, while potassium nitrate has a slightly weaker oxidizing power. The synergistic effect of the two creates alternating, fine, and dense micropores on the surface of the ABS decorative parts, resulting in a stronger anchoring effect between the metal coating and the ABS plastic. The complexing agent can complex with the reduced manganese ions, improving the oxidation performance of the roughening solution and further enhancing the bonding strength between the metal coating and the ABS plastic.

[0007] In summary, the combined action of potassium permanganate, potassium nitrate, and complexing agents improved the bonding strength between the metal coating and ABS plastic, thereby solving the problem of poor corrosion resistance in automotive decorative electroplated parts.

[0008] Preferably, the mass ratio of potassium permanganate to potassium nitrate is (3-6):1.

[0009] By adopting the above technical solution, when the mass ratio of potassium permanganate to potassium nitrate is within the above range, the mass ratio of potassium permanganate to potassium nitrate is moderate, the bonding strength between the metal coating and ABS plastic is high, and the corrosion resistance of automotive decorative electroplated parts is better.

[0010] Preferably, the complexing agent is one or more of phytic acid, citric acid, ethylenediaminetetraacetic acid, and iminodisuccinic acid.

[0011] Preferably, the complexing agent is citric acid and / or ethylenediaminetetraacetic acid.

[0012] By adopting the above technical solution, citric acid and ethylenediaminetetraacetic acid have a synergistic effect in improving the bonding strength between the metal coating and ABS plastic.

[0013] Preferably, the complexing agent is phytic acid.

[0014] By adopting the above technical solution, phytic acid can not only complex with manganese ions, but also act as a stabilizer for potassium permanganate, reducing the possibility of potassium permanganate hydrolysis failure, extending its service life, further improving its oxidation performance, further improving the bonding strength between the metal coating and ABS plastic, and improving the corrosion resistance of automotive decorative electroplated parts.

[0015] Preferably, the roughening solution further contains 0.6-1.2 g / L sodium dodecylbenzenesulfonate.

[0016] By adopting the above technical solution, sodium dodecylbenzenesulfonate reduces the surface tension of the roughening liquid on the substrate, thereby improving the roughening effect. On the other hand, the inventors unexpectedly discovered that sodium dodecylbenzenesulfonate can also slow down the oxidation rate to a certain extent, improve the stability of the oxidation reaction, make the micropores on the ABS plastic surface uniformly distributed, further improve the bonding strength between the metal coating and the ABS plastic, and improve the corrosion resistance of automotive decorative electroplated parts.

[0017] Preferably, the electroplating process includes semi-bright nickel plating, bright nickel plating, and microporous nickel plating, wherein the electroplating solution used in the semi-bright nickel plating step contains 30-80 mg / L of potential difference stabilizer.

[0018] By adopting the above technical solution, the potential difference stabilizer in the electroplating solution can enable a large and stable potential difference between the semi-bright nickel layer, the bright nickel layer and the microporous nickel layer, thereby further improving the corrosion resistance of automotive decorative electroplated parts.

[0019] Preferably, the potential difference stabilizer is one or more of acetic acid, aminoacetic acid, glycolic acid, triacetic acid, and malonic acid.

[0020] Preferably, the potential difference stabilizer is nitrilotriacetic acid and / or malonic acid.

[0021] By adopting the above technical solution, the large molecular weight of nitric acid and malonic acid can further increase the potential difference between the semi-bright nickel layer, the bright nickel layer and the microporous nickel layer, thereby further improving the corrosion resistance of automotive decorative electroplated parts.

[0022] In summary, this application has the following beneficial effects: 1. This application uses potassium permanganate, potassium nitrate, and a complexing agent as the main components of the roughening solution. Potassium permanganate is a strong oxidizing agent, while potassium nitrate has a slightly weaker oxidizing power. The synergistic effect of these two components creates alternating, fine, and dense micropores on the surface of the ABS decorative parts, resulting in a stronger anchoring effect between the metal plating and the ABS plastic. The complexing agent can complex with the reduced manganese ions, improving the oxidation performance of the roughening solution. Under the combined action of potassium permanganate, potassium nitrate, and the complexing agent, the bonding strength between the metal plating and the ABS plastic is improved, thereby solving the problem of poor corrosion resistance in automotive decorative electroplated parts.

[0023] 2. The roughening solution of this application also contains sodium dodecylbenzenesulfonate. Sodium dodecylbenzenesulfonate reduces the surface tension of the roughening solution on the substrate and improves the roughening effect. On the other hand, the inventors unexpectedly discovered that sodium dodecylbenzenesulfonate can also slow down the oxidation rate to a certain extent, improve the stability of the oxidation reaction, make the micropores on the ABS plastic surface uniformly distributed, further improve the bonding strength between the metal coating and the ABS plastic, and improve the corrosion resistance of automotive decorative electroplated parts.

[0024] 3. The electroplating solution used in the semi-bright nickel electroplating step of this application contains a potential difference stabilizer. The potential difference stabilizer enables a large and stable potential difference between the semi-bright nickel layer, the bright nickel layer and the microporous nickel layer, thereby further improving the corrosion resistance of automotive decorative electroplated parts. Detailed Implementation

[0025] The present application will be further described in detail below with reference to the embodiments.

[0026] Unless otherwise specified, the specifications of the raw materials used in the following examples and comparative examples are detailed in Table 1.

[0027] Table 1. Raw material specifications information ABS resin Brand: PA-727 Nickel plating brightener Model: CY-G75 dispersant Grade: Ni-351C Nickel sealing powder Grade: Ni-351D The automotive trim samples used in the examples and comparative examples were self-made, and the raw material was the aforementioned ABS resin.

[0028] Example of roughening solution preparation Preparation Example 1 The roughening solution has the following formula: 150g potassium permanganate, 30g potassium nitrate, 10g phytic acid (a complexing agent), and purified water.

[0029] A method for preparing a roughening solution includes the following steps: Dissolve potassium permanganate in 5L of purified water to prepare solution A; dissolve potassium nitrate and phytic acid in 2L of purified water to prepare solution B; slowly add solution B to solution A, and then add purified water to bring the volume to 10L.

[0030] Preparation Examples 2-5 The roughening solution differs from that in Preparation Example 1 in that its raw material composition is different, as shown in Table 2 below: Table 2. Raw material composition of the roughening solution Preparation Example 6 The roughening solution differs from that in Preparation Example 1 in that the complexing agent is different; in this preparation example, phytic acid is replaced by citric acid.

[0031] Preparation Example 7 The roughening solution differs from that in Preparation Example 1 in that the complexing agent is different; in this preparation example, phytic acid is replaced by ethylenediaminetetraacetic acid.

[0032] Preparation Example 8 The roughening solution differs from that in Preparation Example 1 in that the complexing agent is different. In this preparation example, the complexing agent is 5g of citric acid and 5g of ethylenediaminetetraacetic acid.

[0033] Preparation Example 9 The roughening solution differs from that in Preparation Example 1 in that the complexing agent is different; in this preparation example, phytic acid is replaced by iminodisuccinic acid.

[0034] Preparation Example 10 The difference between the roughening solution and the preparation example 1 is that 6g of sodium dodecylbenzenesulfonate is added to solution B in the roughening solution preparation step.

[0035] Preparation Example 11 The difference between the roughening solution and the preparation example 1 is that 12g of sodium dodecylbenzenesulfonate is added to solution B in the roughening solution preparation step.

[0036] Preparation of roughening solution (comparative example) Preparation of Comparative Example 1 The roughening solution differs from that in Preparation Example 1 in that its raw material composition is different, as shown in Table 3 below: Table 3. Raw material composition of the roughening solution Example

[0037] Example 1 An electroplating process for automotive decorative parts, comprising the following steps: Pretreatment: The automotive trim sample was cleaned with a sodium carbonate aqueous solution at 60℃ and pH=7.5 for 4 minutes; then cleaned with an acetic acid aqueous solution at pH=6 for 2 minutes; and finally cleaned with deionized water at 40℃ for 3 minutes to obtain the pretreated automotive trim sample.

[0038] Roughening: The pretreated automotive trim sample was immersed in the roughening solution prepared in Preparation Example 1 and ultrasonically treated for 25 minutes with an ultrasonic power of 150W and an ultrasonic frequency of 20kHz to obtain the roughened automotive trim sample.

[0039] Pickling: Immerse the roughened automotive trim sample in the pickling solution and treat it at 55°C for 60 seconds. The pickling solution is a mixed aqueous solution of sulfuric acid and oxalic acid, in which sulfuric acid is 25 wt%, oxalic acid is 2 wt%, and the remainder is water. Then rinse it three times with deionized water.

[0040] Activation: Immerse the acid-washed automotive trim sample in the activation solution and activate it at 35°C for 5 minutes. The activation solution consists of 10 g / L stannous chloride, 0.4 g / L palladium chloride, 10 ml / L hydrochloric acid (37%), 180 g / L sodium chloride, and the remainder is water.

[0041] De-colloidalization: First, rinse the activated automotive trim sample with deionized water, then immerse the automotive trim sample in a 30% (volume fraction) hydrochloric acid solution at 50°C for 2 minutes to remove the tin colloid and thus activate the palladium.

[0042] Chemical nickel plating: The degummed automotive trim sample was immersed in a plating solution consisting of 28 g / L NiSO4·6H2O, 30 g / L NaH2PO2·H2O, 20 g / L C6H8O7·H2O, 15 g / L CH3COONa·3H2O, with the remainder being water. The pH was 5. The sample was treated at 70°C for 60 min, then removed and rinsed three times with deionized water.

[0043] Copper plating: A sample of an automotive trim part with a surface deposited with electroless nickel was immersed in a copper electroplating solution. At 25°C, using the automotive trim part sample as the cathode and pure copper as the anode, a direct current was applied for 50 minutes at a current density of 3 A / dm³.2 The electroplating solution consists of 200 g / L copper sulfate, 70 g / L sulfuric acid, 65 mg / L chloride ions, and the remainder is water.

[0044] Semi-bright nickel plating: A copper-plated automotive trim sample was immersed in a semi-bright nickel plating solution at 55°C and pH 4, using the automotive trim sample as the cathode and metallic nickel as the anode. A direct current was applied for 30 minutes at a current density of 3 A / dm³. 2 The electroplating solution consists of 280 g / L nickel sulfate, 45 g / L nickel chloride, 45 g / L boric acid, 30 mg / L glycolic acid (potential stabilizer), 25 mg / L sodium dihexyl succinate (wetting agent), and the balance is water.

[0045] Bright nickel plating: Immerse a sample of automotive trim with a semi-bright nickel plating layer in a bright nickel electroplating solution at 55°C and pH 4, using the automotive trim sample as the cathode and metallic nickel as the anode, and apply direct current for 14 minutes at a current density of 3 A / dm³. 2 The electroplating solution includes 300 g / L nickel sulfate, 45 g / L nickel chloride, 45 g / L boric acid, 100 mg / L nickel plating brightener, 25 mg / L wetting agent sodium dihexyl succinate sulfonate, and the balance is water. After electroplating, the sample of the automotive trim part with bright nickel plating is taken out and rinsed with deionized water at 25°C for 2 minutes.

[0046] Microporous nickel plating: A sample of an automotive trim part with a bright nickel-plated surface was immersed in a microporous nickel electroplating solution at 30°C and pH 3.5. The automotive trim part sample was used as the cathode, and metallic nickel as the anode. Direct current was applied for 4 minutes at a current density of 3 A / dm³. 2 The electroplating solution consists of 300 g / L nickel sulfate, 45 g / L nickel chloride, 45 g / L boric acid, 6 ml / L dispersant, and 12 g / L nickel sealing powder. After electroplating, the sample automotive trim piece with microporous nickel plating is removed and rinsed with deionized water at 25°C for 2 minutes.

[0047] Chromium plating: A sample of an automotive trim part with a microporous nickel-plated surface was immersed in a chromium electroplating solution at 40°C and pH 4. Using the automotive trim part sample as the cathode and a lead-tin plate as the anode, a direct current was applied for 5 minutes at a current density of 9.5 A / dm². 2 The electroplating solution consisted of 250 g / L chromic anhydride, 1.5 g / L sulfuric acid, and 4 g / L trivalent chromium. After electroplating, the sample was removed and rinsed with deionized water at 25°C for 2 minutes.

[0048] Finished product: Place the chrome-plated automotive trim sample into an oven and treat it at 65°C for 35 minutes to obtain the electroplated finished product.

[0049] Example 2-11 The electroplating process for automotive decorative parts differs from that in Example 1 in that the source of the roughening solution is different, as shown in Table 4 below: Table 4. Sources of roughening solution Example 12 An electroplating process for automotive decorative parts differs from Example 1 in that the concentration of the potential difference stabilizer is different; in this example, the concentration of the potential difference stabilizer is 80 mg / L.

[0050] Example 13 The difference between this electroplating process for automotive decorative parts and Example 1 lies in the choice of potential difference stabilizer. In this example, glycolic acid is replaced with aminotriacetic acid.

[0051] Example 14 The difference between this electroplating process for automotive decorative parts and Example 1 lies in the choice of potential difference stabilizer. In this example, glycolic acid is replaced with malonic acid.

[0052] Example 15 The electroplating process for automotive decorative parts differs from that in Example 1 in that the potential difference stabilizer is different. In this example, the potential difference stabilizer is 15 mg / L nitric acid and 15 mg / L malonic acid.

[0053] Example 16 An electroplating process for automotive decorative parts differs from Example 1 in that no potential difference stabilizer is added in this example.

[0054] Comparative Example Comparative Examples 1-3 The electroplating process for automotive decorative parts differs from that in Example 1 in that the source of the roughening solution is different, as shown in Table 5 below: Table 5. Sources of roughening solution Example 1 Preparation Example 1 Comparative Example 2 Preparation of Comparative Example 2 Comparative Example 1 Preparation of Comparative Example 1 Comparative Example 3 Preparation of Comparative Example 3 Detection methods According to GB / T 10125, the electroplated automotive trim samples prepared in Examples 1-16 and Comparative Examples 1-3 were subjected to CASS (Copper Salt Accelerated Acetic Acid Mist Test), and the time to the appearance of corrosion spots was recorded. The longer the time, the better the corrosion resistance. The specific test results are shown in Table 6 below: use The CMS STEP potential difference meter was used to measure the potential difference between semi-bright nickel plating and bright nickel plating, as well as the potential difference between microporous nickel plating and bright nickel plating. The bright nickel plating had the lowest potential. The specific test results are shown in Table 6 below. Referring to GB / T 9797-1997, the thickness of multiple electroplated layers and the micropore density of the microporous nickel plating layer in the electroplated automotive trim sample pieces prepared in Examples 1-16 and Comparative Examples 1-3 were tested. The total thickness of the nickel layer was 25±2.5 μm, the ratio of the semi-bright nickel layer thickness to the total nickel layer thickness was greater than 60%, the ratio of the bright nickel layer thickness to the total nickel layer thickness was greater than 30%, and the chromium layer thickness was 0.3±0.03 μm. The micropore density of the microporous nickel layer was 20,000-30,000 pores / cm³. 2 .

[0055] Table 6. Performance Testing of Electroplated Finished Products for Automotive Interior Parts Samples As shown in Table 6, the electroplated automotive trim parts prepared in Examples 1-16 all showed corrosion points after CASS testing at times exceeding 48 hours. This indicates that the pass rate of the 48-hour CASS test for the electroplated automotive trim parts prepared in this application is 100%. In contrast, the electroplated automotive trim parts prepared in Comparative Examples 1-3 corroded within approximately 35 hours and failed the 48-hour CASS test. Therefore, the electroplating process described in this application can improve the pass rate of the 48-hour CASS test for electroplated automotive trim parts and enhance their corrosion resistance.

[0056] Combining Example 1 and Comparative Examples 1-3 with Table 6, it can be seen that the time for corrosion points to appear in Example 1 is much longer than that in Comparative Examples 1-3. This may be because: Example 1 uses the roughening solution prepared in Preparation Example 1, which contains potassium permanganate, potassium nitrate, and the complexing agent phytic acid. Comparative Example 1 uses the roughening solution prepared in Preparation Example 1, Comparative Example 2 uses the roughening solution prepared in Preparation Example 2, and Comparative Example 3 uses the roughening solution prepared in Preparation Example 3. Preparation Example 1 does not contain a complexing agent, Preparation Example 2 does not contain potassium nitrate, and Preparation Example 3 contains only potassium permanganate.

[0057] Potassium permanganate and potassium nitrate, acting as oxidizing agents, can perform micro-etching treatment on ABS, creating numerous micropores on the surface of ABS decorative parts and generating hydrophilic groups, facilitating metal deposition and improving the adhesion strength between the metal coating and the ABS plastic. Potassium permanganate is a strong oxidizing agent, while potassium nitrate is slightly weaker; their synergistic effect creates alternating, fine, and dense micropores on the surface of the ABS decorative parts, resulting in a stronger anchoring effect between the metal coating and the ABS plastic. The complexing agent can complex with the reduced manganese ions, enhancing the oxidation performance of the roughening solution and further improving the adhesion strength between the metal coating and the ABS plastic. The combined action of potassium permanganate, potassium nitrate, and the complexing agent improves the adhesion strength between the metal coating and the ABS plastic, thereby enhancing the corrosion resistance of automotive decorative electroplated parts.

[0058] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An electroplating process for automotive decorative parts, comprising pre-plating treatment and an electroplating process, wherein the pre-plating treatment process includes pretreatment and roughening, characterized in that: The roughening step includes immersing the pre-treated decorative parts in a roughening solution; The roughening solution contains the following components: potassium permanganate 15-30 g / L, potassium nitrate 3-8 g / L, complexing agent 1-3 g / L, with the remainder made up with water. The complexing agent is one or more of phytic acid, citric acid, ethylenediaminetetraacetic acid, and iminodisuccinic acid.

2. The electroplating process for automotive decorative parts according to claim 1, characterized in that: The mass ratio of potassium permanganate to potassium nitrate is (3-6):

1.

3. The electroplating process for automotive decorative parts according to claim 1, characterized in that: The roughening solution also contains 0.6-1.2 g / L sodium dodecylbenzenesulfonate.

4. The electroplating process for automotive decorative parts according to claim 1, characterized in that: The electroplating process includes semi-bright nickel plating, bright nickel plating, and microporous nickel plating. The electroplating solution used in the semi-bright nickel plating step contains 30-80 mg / L of potential difference stabilizer.

5. The electroplating process for automotive decorative parts according to claim 4, characterized in that: The potential difference stabilizer is one or more of acetic acid, aminoacetic acid, glycolic acid, nitric acid, and malonic acid.

6. The electroplating process for automotive decorative parts according to claim 5, characterized in that: The potential difference stabilizer is nitrilotriacetic acid and / or malonic acid.

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