An electroplating layer stripping solution, its preparation method and application

Abstract

This invention provides an electroplating layer stripping solution, its preparation method, and its application. The electroplating layer stripping solution of this invention comprises fluoride, concentrated nitric acid, chloride, dicarboxylic acid compounds, hydroxy polycarboxylic acid compounds, urea, and glycolic acid or glycolate. This electroplating layer stripping solution can simultaneously strip chromium, nickel, and copper plating layers in one step, simplifying the process. The stripping process is easy to control and will not damage the substrate material. Furthermore, the stripping solution does not contain cyanide, meeting environmental protection requirements. This invention also provides a preparation method and application of the electroplating layer stripping solution.

Description

Technical Field

[0001] This invention belongs to the field of metal surface treatment technology, specifically relating to an electroplating layer stripping solution, its preparation method, and its application. Background Technology

[0002] When the Cu-Ni-Cr electroplating coating on the surface of magnesium alloy materials is defective, it is necessary to peel off the coating and then re-plat it. Traditional peeling methods have the following drawbacks: each metal coating requires a different chemical solution for peeling, and multiple coatings cannot be peeled off simultaneously. Therefore, the process is complex and difficult to operate.

[0003] Electrolysis is used to strip nickel plating, which is fast but can easily corrode the magnesium alloy material due to changes in the concentration of the chemical solution, especially in thinner areas, making the stripping process difficult to control. Cyanide is used to strip copper plating; this substance is highly toxic and does not meet environmental protection requirements.

[0004] Therefore, a new electroplating stripping solution still needs to be developed. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, the present invention provides an electroplating stripping solution that can simultaneously strip chromium, nickel, and copper plating layers in one step, simplifying the process.

[0006] The present invention also provides a method for preparing an electroplating layer stripping solution.

[0007] The present invention also provides a method for peeling off the electroplated layer on the surface of a magnesium alloy material.

[0008] A first aspect of the present invention provides an electroplating layer stripping solution, the components of which include fluoride, concentrated nitric acid, chloride, dicarboxylic acid compounds, hydroxy polycarboxylic acid compounds, urea, and glycolic acid or glycolate.

[0009] The electroplating layer stripping solution of the present invention has at least the following beneficial effects:

[0010] Generally, different chemicals are required for each type of metal plating to be stripped, making the process complex and difficult to operate. For example, when stripping nickel plating, electrolysis is used, which, although faster, can easily corrode magnesium alloys due to variations in the chemical concentration, especially in thinner plating areas, making the stripping process difficult to control. Stripping copper plating involves the use of cyanide, a highly toxic substance that does not meet environmental protection requirements.

[0011] The electroplating stripping solution of the present invention can simultaneously strip chromium, nickel and copper plating layers in one step, making the process simpler.

[0012] The electroplating layer stripping solution of this invention allows for easy control of the stripping process without damaging the substrate material. Furthermore, the stripping solution is cyanide-free, meeting environmental protection requirements.

[0013] in:

[0014] The role of fluorides is to provide fluoride ions to form a non-soluble protective film of magnesium fluoride, ensuring that magnesium alloy materials do not suffer from over-corrosion.

[0015] Concentrated nitric acid is used to oxidize and dissolve nickel and copper metal plating, ensuring successful removal.

[0016] The main function of chlorides is to provide chloride ions to dissolve chromium metal plating.

[0017] The role of dicarboxylic acid compounds is to assist in providing dissolved acid, maintaining the acidity of the drug solution, and extending the service life of the drug solution.

[0018] Hydroxypolycarboxylic acid compounds act as complexing agents, forming complexes with dissolved chromium, nickel, and copper metals to improve the stability of the stripping solution.

[0019] The role of urea is to act as an accelerator. When removing nickel plating, the removal speed is relatively slow, and adding a small amount can appropriately increase the removal speed.

[0020] Glycolic acid or glycolate acts as an accelerator, maintaining the copper dissolution rate during the removal of copper plating.

[0021] According to some embodiments of the present invention, the components, by mass percentage, comprise:

[0022] Fluorides: 20wt%–40wt%

[0023] Concentrated nitric acid: 10wt%~20wt%,

[0024] Chloride: 2wt%–5wt%,

[0025] Dicarboxylic acid compounds: 10wt%~20wt%,

[0026] Glycolic acid or glycolate: 1wt%–2wt%,

[0027] Hydroxypolycarboxylic acid compounds: 5wt%–10wt%,

[0028] Urea: 0.1wt%~0.5wt%,

[0029] The remainder is water.

[0030] The role of water is to act as a solvent, providing a carrier for the solution.

[0031] According to some embodiments of the present invention, the components, by mass percentage, comprise:

[0032] Fluorides: 25wt%–35wt%,

[0033] Concentrated nitric acid: 14wt%~16wt%,

[0034] Chloride: 3wt%–4wt%

[0035] Dicarboxylic acid compounds: 14wt%~16wt%,

[0036] Glycolic acid or glycolate: 1.4 wt%–1.8 wt%.

[0037] Hydroxypolycarboxylic acid compounds: 6wt%–8wt%,

[0038] Urea: 0.2wt%~0.4wt%,

[0039] The remainder is water.

[0040] According to some embodiments of the present invention, the fluoride includes at least one of ammonium bifluoride and potassium fluoride.

[0041] According to some embodiments of the present invention, the concentrated nitric acid includes nitric acid with a concentration of about 68%.

[0042] According to some embodiments of the present invention, the dicarboxylic acid compound includes at least one of oxalic acid and malonic acid.

[0043] According to some embodiments of the present invention, the glycolate includes at least one of glycolic acid, sodium glycolate, and potassium glycolate.

[0044] According to some embodiments of the present invention, the hydroxypolycarboxylic acid compound includes at least one of citric acid, tartaric acid, malic acid, and lactic acid.

[0045] A second aspect of the present invention provides a method for preparing the electroplating layer stripping solution, comprising the following steps: mixing the components according to the specified proportions.

[0046] The method for preparing the electroplating layer stripping solution of the present invention has at least the following technical effects:

[0047] The preparation method of the electroplating layer stripping solution of the present invention does not require complex process control or expensive equipment, and can be easily realized for large-scale industrial production.

[0048] The preparation method of the electroplating layer stripping solution of the present invention uses readily available raw materials and has low cost.

[0049] A third aspect of the present invention provides a method for peeling off an electroplated layer on the surface of a magnesium alloy material, comprising the following steps: immersing the workpiece to be peeled in the electroplated layer peeling solution of the present invention.

[0050] The method for peeling off the electroplated layer on the surface of magnesium alloy materials according to the present invention has at least the following technical effects:

[0051] The electroplating stripping solution of the present invention can simultaneously strip chromium, nickel and copper plating layers in one step, making the process simpler.

[0052] The electroplating layer stripping solution of this invention allows for easy control of the stripping process without damaging the substrate material. Furthermore, the stripping solution is cyanide-free, meeting environmental protection requirements.

[0053] According to some embodiments of the present invention, the workpiece to be peeled off includes a magnesium alloy substrate, the surface of which is provided with a copper plating layer, a nickel plating layer and a chromium plating layer.

[0054] According to some embodiments of the present invention, the immersion time is 20 min to 40 min.

[0055] According to some embodiments of the present invention, a method for removing electroplated layers from the surface of magnesium alloy materials may include two main steps: stripping and activation. The stripping step, performed in the electroplating stripping solution of the present invention, can simultaneously remove chromium, nickel, and copper plating layers in one step. Immersion stripping is used; as long as the temperature is controlled between 20°C and 30°C, the solution will not damage the material. The activation step mainly targets the removal of a thick magnesium fluoride film layer that forms on the surface of the magnesium alloy material after the stripping step, so that the magnesium alloy surface is in an activated state, which facilitates subsequent rework according to the normal process flow.

[0056] The method for peeling the electroplated layer on the surface of magnesium alloys in this invention is simpler, easier to control, does not damage the material, and uses more environmentally friendly chemicals compared to traditional peeling methods.

[0057] According to some embodiments of the present invention, the stripping process of the electroplated layer on the magnesium alloy surface can be as follows:

[0058] Defective magnesium alloy electroplating products → peeling → water washing → activation → water washing → drying → observation of magnesium alloy surface condition.

[0059] In this process, stripping involves immersing the defective magnesium alloy electroplated product in the electroplating layer stripping solution of the present invention.

[0060] The number of water washes after peeling and activation can each be 3 times.

[0061] The overall process for reworking defective magnesium alloy electroplated products can be summarized as follows:

[0062] Defective magnesium alloy electroplating products → peeling → 3 water washes → activation → 3 water washes → acid etching → surface conditioning → zinc immersion → cyanide-free copper base coat → pyrometallurgical copper → acid copper → semi-bright nickel → full-bright nickel → decorative chromium → drying → observation or inspection of magnesium alloy surface condition.

[0063] The electroplating process for magnesium alloy raw materials can be as follows:

[0064] Magnesium alloy blank → hot dipping for degreasing → water washing 3 times → acid etching → surface conditioning → zinc immersion → cyanide-free copper base coat → pyrometallurgical copper → acid copper → semi-bright nickel → full-bright nickel → decorative chromium → drying → observation or inspection of magnesium alloy surface condition.

[0065] The acid etching and surface conditioning processes need to be repeated 1 to 2 times to ensure that surface impurities are removed more thoroughly and cleanly, which significantly improves the adhesion of subsequent coatings.

[0066] It should be noted that pure water is used for rinsing between each process, and rinsing can be performed two or more times.

[0067] Acid copper, semi-bright nickel, and fully bright nickel are neutralized and activated using 8-10% sulfuric acid.

[0068] The purpose of hot dipping degreasing is to remove oil and dirt from the surface of the workpiece. The formula can be:

[0069] Sodium hydroxide 20g / L~50g / L,

[0070] Sodium phosphate 5g / L~10g / L,

[0071] OP emulsifier 1g / L-5g / L

[0072] The operating conditions can be: temperature: 50℃~60℃, time: 3min~6min.

[0073] The purpose of stripping is to remove defective electroplating layers from the surface cleanly without damaging the material. The stripping solution of this invention is used. Operating conditions can be: temperature: 20℃~30℃; time: until complete stripping, approximately 20min~40min. The operation method is immersion.

[0074] The purpose of activation is to remove the magnesium fluoride film layer formed after stripping, thereby reactivating the material so that it can be directly reworked to obtain a good product. The activation solution formula can be:

[0075] Sodium gluconate: 30g / L~50g / L

[0076] Sodium hydroxide: 120g / L~160g / L

[0077] Sodium nitrate: 20g / L~30g / L

[0078] HEDP sodium salt: 20g / L~3g / L.

[0079] The operating conditions can be: temperature: 50℃~60℃, time: 1min~3min.

[0080] The purpose of acid etching is to soften the oxide layer on the surface of the workpiece. The acid etching solution formula can be:

[0081] Phosphoric acid: 10g / L~20g / L

[0082] Organophosphonic acid (HEDP): 12 g / L~25 g / L

[0083] Sodium nitrate: 1g / L~3g / L.

[0084] The operating conditions can be: temperature: 15℃~30℃, time: 0.5min~1.5min.

[0085] The purpose of surface conditioning is to remove surface impurities and oxides, forming a uniform, thin magnesium hydroxide film on the surface and controlling the zinc replacement rate. The solution formulation used for surface conditioning can be:

[0086] Sodium hydroxide: 120g / L~160g / L

[0087] Sodium nitrate: 20g / L~30g / L.

[0088] The operating conditions can be: temperature: 50℃~65℃, time: 1min~3min.

[0089] The purpose of zinc immersion is to deposit a fine zinc layer on the substrate surface, increasing the surface potential and enhancing the adhesion between the substrate and the coating. The solution formulation used for zinc immersion can be:

[0090] Zinc sulfate: 40g / L~45g / L

[0091] Potassium pyrophosphate: 50g / L~60g / L

[0092] Sodium glycine: 5g / L~10g / L

[0093] Sodium fluoride: 5g / L~8g / L

[0094] Sodium acetate: 20g / L~25g / L

[0095] Sodium nitrate: 5g / L~10g / L.

[0096] The operating conditions can be as follows: temperature: 50℃~65℃, time: 1.5min~3.5min, pH: 9.5~11.0.

[0097] The purpose of cyanide-free copper priming is to serve as a pre-plated copper layer. The solution significantly inhibits copper replacement in the zinc plating layer and rapidly deposits a uniform and fine copper layer, which is crucial for ensuring adhesion between the plating layer and the substrate. The solution formulation for cyanide-free copper priming can be as follows:

[0098] Copper sulfate: 40g / L~50g / L

[0099] HEDP potassium salt: 180g / L~200g / L

[0100] Diethylenetriamine: 80 g / L~100 g / L

[0101] Potassium carbonate: 80g / L~100g / L

[0102] 2-Mercaptobenzothiazole: 0.2 g / L~0.25 g / L,

[0103] Sodium benzenesulfinate: 2.5g / L~3g / L.

[0104] The operating conditions are as follows: temperature: 15℃~30℃, time: approximately 10 min, pH: 9.0~9.6, current: 1.5A / dm³. 2 ~3A / dm 2 .

[0105] The purpose of pyroplating copper plating is to rapidly increase the thickness of the copper plating layer, achieving a uniform and bright appearance, while simultaneously preventing subsequent acidic plating solutions from corroding the substrate. The solution formulation for pyroplating copper plating can be as follows:

[0106] Copper pyrophosphate: 75g / L~95g / L

[0107] Potassium pyrophosphate: 280g / L~350g / L

[0108] Ammonia (28%): 2ml / L~5ml / L.

[0109] The operating conditions are as follows: temperature: 55℃~60℃, time: approximately 20 min, pH: 8.5~8.9, current: 1.5A / dm³. 2 ~2.5A / dm 2 .

[0110] The purpose of acid copper is to create decorative and protective glossy coatings. The solution formulation for acid copper can be:

[0111] Copper sulfate: 180g / L~240g / L

[0112] Sulfuric acid: 60g / L~80g / L

[0113] RP-980MU: 5ml / L~7ml / L

[0114] RP-980A: 0.5ml / L~0.7ml / L

[0115] RP-980B: 0.15ml / L~0.3ml / L.

[0116] Operating conditions can be as follows: Temperature: 15℃~30℃, Time: approximately 15 minutes, Current: 3A / dm 2 ~5A / dm 2 .

[0117] The purpose of semi-bright nickel is to work in combination with fully bright nickel to improve protective performance. The solution formulation for semi-bright nickel can be:

[0118] Nickel sulfate: 240 g / L~300 g / L

[0119] Nickel chloride: 50 g / L~65 g / L

[0120] Boric acid: 40g / L~55g / L

[0121] RN-3110Mu:4.0ml / L~8.0ml / L,

[0122] RN-3110A: 0.6ml / L~0.8ml / L

[0123] RN-664: 0.4ml / L~0.8ml / L.

[0124] The operating conditions can be as follows: temperature: 50℃~60℃, time: approximately 15 min, pH: 4.0~4.4, current: 3A / dm³. 2 ~5A / dm 2 .

[0125] The purpose of full-brightness nickel plating is to create a decorative and protective glossy finish. The solution formulation for full-brightness nickel plating can be:

[0126] Nickel sulfate: 240 g / L~300 g / L

[0127] Nickel chloride: 50 g / L~65 g / L

[0128] Boric acid: 40g / L~55g / L

[0129] RN-781: 0.3ml / L~0.5ml / L

[0130] RN-672PT: 6ml / L~8ml / L

[0131] RN-664: 0.4ml / L~0.8ml / L.

[0132] The operating conditions are as follows: temperature: 50℃~60℃, time: approximately 15 min, pH: 4.2~4.6, current: 3A / dm³. 2 ~5A / dm 2 .

[0133] The purpose of decorative chrome plating is to improve the corrosion resistance and surface hardness of the coating, and enhance its wear resistance. The solution formulation used for decorative chrome plating can be:

[0134] Chromic acid: 180g / L~220g / L

[0135] Sulfuric acid: 0.8 g / L~1.2 g / L

[0136] RM-86: 20ml / L~28ml / L.

[0137] The operating conditions are as follows: temperature: 30℃~40℃, time: approximately 2.5 min, current: 8A / dm². 2 ~15A / dm 2 . Detailed Implementation

[0138] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0139] In some embodiments of the present invention, the present invention provides an electroplating layer stripping solution, the components of which include fluoride, concentrated nitric acid, chloride, dicarboxylic acid compounds, hydroxy polycarboxylic acid compounds, urea, and glycolic acid or glycolate.

[0140] It should be noted that, generally speaking, different chemicals are required for each type of metal plating to be stripped, making the process complex and difficult to operate. For example, when stripping nickel plating, an electrolytic method is used. Although the stripping speed is faster, it is easy for changes in the concentration of the chemicals to corrode the magnesium alloy material, especially in areas where the plating is relatively thin, making the stripping process difficult to control. Stripping copper plating involves the use of cyanide, a highly toxic substance, which does not meet environmental protection requirements.

[0141] However, the electroplating stripping solution of the present invention can simultaneously strip chromium, nickel and copper plating layers in one step, making the process simpler.

[0142] Furthermore, the electroplating layer stripping solution of the present invention allows for easy control of the stripping process without damaging the substrate material. Simultaneously, the stripping solution does not contain cyanide, meeting environmental protection requirements.

[0143] The components of the electroplating layer stripping solution of the present invention are:

[0144] The role of fluorides is to provide fluoride ions to form a protective film of magnesium fluoride, ensuring that magnesium alloy materials do not suffer from over-corrosion.

[0145] Concentrated nitric acid is used to oxidize and dissolve nickel and copper metal plating, ensuring successful removal.

[0146] The main function of chlorides is to provide chloride ions to dissolve chromium metal plating.

[0147] The role of dicarboxylic acid compounds is to assist in providing dissolved acid, maintaining the acidity of the drug solution, and extending the service life of the drug solution.

[0148] Hydroxypolycarboxylic acid compounds act as complexing agents, forming complexes with dissolved chromium, nickel, and copper metals to improve the stability of the stripping solution.

[0149] The role of urea is to act as an accelerator. When removing nickel plating, the removal speed is relatively slow, and adding a small amount can appropriately increase the removal speed.

[0150] Glycolic acid or glycolate acts as an accelerator, maintaining the copper dissolution rate during the removal of copper plating.

[0151] In some embodiments of the present invention, the components, by mass percentage, include:

[0152] Fluorides: 20wt%–40wt%

[0153] Concentrated nitric acid: 10wt%~20wt%,

[0154] Chloride: 2wt%–5wt%,

[0155] Dicarboxylic acid compounds: 10wt%~20wt%,

[0156] Glycolic acid or glycolate: 1wt%–2wt%,

[0157] Hydroxypolycarboxylic acid compounds: 5wt%–10wt%,

[0158] Urea: 0.1wt%~0.5wt%,

[0159] The remainder is water.

[0160] The role of water is to act as a solvent, providing a carrier for the solution.

[0161] In some embodiments of the present invention, the components, by mass percentage, include:

[0162] Fluorides: 25wt%–35wt%,

[0163] Concentrated nitric acid: 14wt%~16wt%,

[0164] Chloride: 3wt%–4wt%

[0165] Dicarboxylic acid compounds: 14wt%~16wt%,

[0166] Glycolic acid or glycolate: 1.4 wt%–1.8 wt%.

[0167] Hydroxypolycarboxylic acid compounds: 6wt%–8wt%,

[0168] Urea: 0.2wt%~0.4wt%,

[0169] The remainder is water.

[0170] In some embodiments of the present invention, the fluoride includes at least one of ammonium bifluoride and potassium fluoride.

[0171] In some embodiments of the present invention, concentrated nitric acid includes nitric acid with a concentration of about 68%.

[0172] In some embodiments of the present invention, the dicarboxylic acid compound includes at least one of oxalic acid and malonic acid.

[0173] In some embodiments of the present invention, glycolate includes at least one of glycolic acid, sodium glycolate, and potassium glycolate.

[0174] In some embodiments of the present invention, the hydroxypolycarboxylic acid compound includes at least one of citric acid, tartaric acid, malic acid, and lactic acid.

[0175] In some other embodiments of the present invention, the present invention provides a method for preparing an electroplating layer stripping solution, comprising the following steps: mixing the components according to the specified ratio.

[0176] It is understood that the preparation method of the electroplating layer stripping solution of the present invention does not require complex process control or expensive equipment, and is easy to achieve large-scale industrial production.

[0177] The preparation method of the electroplating layer stripping solution of the present invention uses readily available raw materials and has low cost.

[0178] In some other embodiments of the present invention, the present invention provides a method for peeling off an electroplated layer on the surface of a magnesium alloy material, comprising the following steps: immersing the workpiece to be peeled in the electroplated layer peeling solution of the present invention.

[0179] It should be noted that the electroplating stripping solution of the present invention can simultaneously strip chromium, nickel and copper plating layers in one step, making the process simpler.

[0180] Furthermore, the electroplating layer stripping solution of the present invention allows for easy control of the stripping process and will not damage the substrate material. At the same time, the stripping solution does not contain cyanide, meeting environmental protection requirements.

[0181] In some embodiments of the present invention, the workpiece to be peeled off includes a magnesium alloy substrate, the surface of which is provided with a copper plating layer, a nickel plating layer and a chromium plating layer.

[0182] In some other embodiments of the present invention, the immersion time is 20 min to 40 min.

[0183] In other embodiments of the present invention, the method for removing the electroplated layer on the surface of magnesium alloy materials may include two main steps: stripping and activation. The stripping step, performed in the electroplating stripping solution of the present invention, can simultaneously remove chromium, nickel, and copper plating layers in one step. Immersion stripping, as long as the temperature is controlled between 20°C and 30°C, will not damage the material. The activation step mainly targets the removal of the relatively thick magnesium fluoride film layer formed on the surface of the magnesium alloy material after the stripping step, so that the magnesium alloy surface is in an activated state, which is beneficial for subsequent rework according to the normal process flow.

[0184] The method for peeling the electroplated layer on the surface of magnesium alloys in this invention is simpler, easier to control, does not damage the material, and uses more environmentally friendly chemicals compared to traditional peeling methods.

[0185] In other embodiments of the present invention, the stripping process of the electroplated layer on the magnesium alloy surface can be as follows:

[0186] Defective magnesium alloy electroplating products → peeling → water washing → activation → water washing → drying → observation of magnesium alloy surface condition.

[0187] In this process, stripping involves immersing the defective magnesium alloy electroplated product in the electroplating layer stripping solution of the present invention.

[0188] The number of water washes after peeling and activation can each be 3 times.

[0189] The overall process for reworking defective magnesium alloy electroplated products can be summarized as follows:

[0190] Defective magnesium alloy electroplating products → peeling → 3 water washes → activation → 3 water washes → acid etching → surface conditioning → zinc immersion → cyanide-free copper base coat → pyrometallurgical copper → acid copper → semi-bright nickel → full-bright nickel → decorative chromium → drying → observation or inspection of magnesium alloy surface condition.

[0191] The electroplating process for magnesium alloy raw materials can be as follows:

[0192] Magnesium alloy blank → hot dipping for degreasing → water washing 3 times → acid etching → surface conditioning → zinc immersion → cyanide-free copper base coat → pyrometallurgical copper → acid copper → semi-bright nickel → full-bright nickel → decorative chromium → drying → observation or inspection of magnesium alloy surface condition.

[0193] The acid etching and surface conditioning processes need to be repeated 1 to 2 times to ensure that surface impurities are removed more thoroughly and cleanly, which significantly improves the adhesion of subsequent coatings.

[0194] It should be noted that pure water is used for rinsing between each process, and rinsing can be performed two or more times.

[0195] Acid copper, semi-bright nickel, and fully bright nickel are neutralized and activated using 8-10% sulfuric acid.

[0196] The purpose of hot dipping degreasing is to remove oil and dirt from the surface of the workpiece. The formula can be:

[0197] Sodium hydroxide 20g / L~50g / L,

[0198] Sodium phosphate 5g / L~10g / L,

[0199] OP emulsifier 1g / L-5g / L

[0200] The operating conditions can be: temperature: 50℃~60℃, time: 3min~6min.

[0201] The purpose of stripping is to remove defective electroplating layers from the surface cleanly without damaging the material. The stripping solution of this invention is used. Operating conditions can be: temperature: 20℃~30℃; time: until complete stripping, approximately 20min~40min. The operation method is immersion.

[0202] The purpose of activation is to remove the magnesium fluoride film layer formed after stripping, thereby reactivating the material so that it can be directly reworked to obtain a good product. The activation solution formula can be:

[0203] Sodium gluconate: 30g / L~50g / L

[0204] Sodium hydroxide: 120g / L~160g / L

[0205] Sodium nitrate: 20g / L~30g / L

[0206] HEDP sodium salt: 20g / L~3g / L.

[0207] The operating conditions can be: temperature: 50℃~60℃, time: 1min~3min.

[0208] The purpose of acid etching is to soften the oxide layer on the surface of the workpiece. The acid etching solution formula can be:

[0209] Phosphoric acid: 10g / L~20g / L

[0210] Organophosphonic acid (HEDP): 12 g / L~25 g / L

[0211] Sodium nitrate: 1g / L~3g / L.

[0212] The operating conditions can be: temperature: 15℃~30℃, time: 0.5min~1.5min.

[0213] The purpose of surface conditioning is to remove surface impurities and oxides, forming a uniform, thin magnesium hydroxide film on the surface and controlling the zinc replacement rate. The solution formulation used for surface conditioning can be:

[0214] Sodium hydroxide: 120g / L~160g / L

[0215] Sodium nitrate: 20g / L~30g / L.

[0216] The operating conditions can be: temperature: 50℃~65℃, time: 1min~3min.

[0217] The purpose of zinc immersion is to deposit a fine zinc layer on the substrate surface, increasing the surface potential and enhancing the adhesion between the substrate and the coating. The solution formulation used for zinc immersion can be:

[0218] Zinc sulfate: 40g / L~45g / L

[0219] Potassium pyrophosphate: 50g / L~60g / L

[0220] Sodium glycine: 5g / L~10g / L

[0221] Sodium fluoride: 5g / L~8g / L

[0222] Sodium acetate: 20g / L~25g / L

[0223] Sodium nitrate: 5g / L~10g / L.

[0224] The operating conditions can be as follows: temperature: 50℃~65℃, time: 1.5min~3.5min, pH: 9.5~11.0.

[0225] The purpose of cyanide-free copper priming is to serve as a pre-plated copper layer. The solution significantly inhibits copper replacement in the zinc plating layer and rapidly deposits a uniform and fine copper layer, which is crucial for ensuring adhesion between the plating layer and the substrate. The solution formulation for cyanide-free copper priming can be as follows:

[0226] Copper sulfate: 40g / L~50g / L

[0227] HEDP potassium salt: 180g / L~200g / L

[0228] Diethylenetriamine: 80 g / L~100 g / L

[0229] Potassium carbonate: 80g / L~100g / L

[0230] 2-Mercaptobenzothiazole: 0.2 g / L~0.25 g / L,

[0231] Sodium benzenesulfinate: 2.5g / L~3g / L.

[0232] The operating conditions are as follows: temperature: 15℃~30℃, time: approximately 10 min, pH: 9.0~9.6, current: 1.5A / dm³. 2 ~3A / dm 2 .

[0233] The purpose of pyroplating copper plating is to rapidly increase the thickness of the copper plating layer, achieving a uniform and bright appearance, while simultaneously preventing subsequent acidic plating solutions from corroding the substrate. The solution formulation for pyroplating copper plating can be as follows:

[0234] Copper pyrophosphate: 75g / L~95g / L

[0235] Potassium pyrophosphate: 280g / L~350g / L

[0236] Ammonia (28%): 2ml / L~5ml / L.

[0237] The operating conditions are as follows: temperature: 55℃~60℃, time: approximately 20 min, pH: 8.5~8.9, current: 1.5A / dm³. 2 ~2.5A / dm 2 .

[0238] The purpose of acid copper is to create decorative and protective glossy coatings. The solution formulation for acid copper can be:

[0239] Copper sulfate: 180g / L~240g / L

[0240] Sulfuric acid: 60g / L~80g / L

[0241] RP-980MU: 5ml / L~7ml / L

[0242] RP-980A: 0.5ml / L~0.7ml / L

[0243] RP-980B: 0.15ml / L~0.3ml / L.

[0244] Operating conditions can be as follows: Temperature: 15℃~30℃, Time: approximately 15 minutes, Current: 3A / dm 2 ~5A / dm 2 .

[0245] The purpose of semi-bright nickel is to work in combination with fully bright nickel to improve protective performance. The solution formulation for semi-bright nickel can be:

[0246] Nickel sulfate: 240 g / L~300 g / L

[0247] Nickel chloride: 50 g / L~65 g / L

[0248] Boric acid: 40g / L~55g / L

[0249] RN-3110Mu:4.0ml / L~8.0ml / L,

[0250] RN-3110A: 0.6ml / L~0.8ml / L

[0251] RN-664: 0.4ml / L~0.8ml / L.

[0252] The operating conditions can be as follows: temperature: 50℃~60℃, time: approximately 15 min, pH: 4.0~4.4, current: 3A / dm³. 2 ~5A / dm 2 .

[0253] The purpose of full-brightness nickel plating is to create a decorative and protective glossy finish. The solution formulation for full-brightness nickel plating can be:

[0254] Nickel sulfate: 240 g / L~300 g / L

[0255] Nickel chloride: 50 g / L~65 g / L

[0256] Boric acid: 40g / L~55g / L

[0257] RN-781: 0.3ml / L~0.5ml / L

[0258] RN-672PT: 6ml / L~8ml / L

[0259] RN-664: 0.4ml / L~0.8ml / L.

[0260] The operating conditions are as follows: temperature: 50℃~60℃, time: approximately 15 min, pH: 4.2~4.6, current: 3A / dm³. 2 ~5A / dm 2 .

[0261] The purpose of decorative chrome plating is to improve the corrosion resistance and surface hardness of the coating, and enhance its wear resistance. The solution formulation used for decorative chrome plating can be:

[0262] Chromic acid: 180g / L~220g / L

[0263] Sulfuric acid: 0.8 g / L~1.2 g / L

[0264] RM-86: 20ml / L~28ml / L.

[0265] The operating conditions are as follows: temperature: 30℃~40℃, time: approximately 2.5 min, current: 8A / dm². 2 ~15A / dm 2 .

[0266] The technical solution of the present invention will be better understood below with reference to specific embodiments.

[0267] Example 1

[0268] An electroplating layer stripping solution was prepared, with the following components per 100 wt%:

[0269] Ammonium bifluoride: 20 wt%

[0270] Concentrated nitric acid: 10 wt%

[0271] Sodium chloride: 2wt%

[0272] Malonic acid: 10wt%

[0273] Glycolic acid: 1 wt%,

[0274] Citric acid: 5wt%,

[0275] Urea: 0.1 wt%

[0276] The remainder is water.

[0277] The preparation method is as follows: In a 1L stirring container, add 100mL of deionized water, first slowly add concentrated nitric acid (68%) and stir to dissolve evenly, then add ammonium fluoride, potassium chloride, malonic acid, citric acid, glycolic acid and urea in sequence and stir to dissolve, and continue stirring for 30min. After the solution cools to between 20-30℃, add pure water to make up to 1L, stir evenly and it is ready for use.

[0278] Example 2

[0279] An electroplating layer stripping solution was prepared, with the following components per 100 wt%:

[0280] Ammonium bifluoride: 30 wt%

[0281] Concentrated nitric acid: 15 wt%

[0282] Sodium chloride: 3wt%,

[0283] Malonic acid: 15wt%,

[0284] Glycolic acid: 1.5 wt%,

[0285] Citric acid: 7wt%

[0286] Urea: 0.3 wt%

[0287] The remainder is water.

[0288] The preparation method is as follows: In a 1L stirring container, add 100mL of deionized water, first slowly add concentrated nitric acid (68%) and stir to dissolve evenly, then add ammonium fluoride, potassium chloride, malonic acid, citric acid, glycolic acid and urea in sequence and stir to dissolve, and continue stirring for 30min. After the solution cools to between 20-30℃, add pure water to make up to 1L, stir evenly and it is ready for use.

[0289] Example 3

[0290] An electroplating layer stripping solution was prepared, with the following components per 100 wt%:

[0291] Ammonium bifluoride: 40 wt%

[0292] Concentrated nitric acid: 20wt%

[0293] Sodium chloride: 5 wt%

[0294] malonic acid: 20wt%

[0295] Glycolic acid: 2wt%,

[0296] Citric acid: 10wt%

[0297] Urea: 0.5 wt%.

[0298] The remainder is water.

[0299] The preparation method is as follows: In a 1L stirring container, add 100mL of deionized water, first slowly add concentrated nitric acid (68%) and stir to dissolve evenly, then add ammonium fluoride, potassium chloride, malonic acid, citric acid, glycolic acid and urea in sequence and stir to dissolve, and continue stirring for 30min. After the solution cools to between 20-30℃, add pure water to make up to 1L, stir evenly and it is ready for use.

[0300] Example 4

[0301] An electroplating layer stripping solution was prepared, with the following components per 100 wt%:

[0302] Ammonium bifluoride: 20 wt%

[0303] Concentrated nitric acid: 10 wt%

[0304] Sodium chloride: 5 wt%

[0305] Malonic acid: 10wt%

[0306] Glycolic acid: 2wt%,

[0307] Citric acid: 5wt%,

[0308] Urea: 0.5 wt%.

[0309] The remainder is water.

[0310] The preparation method is as follows: In a 1L stirring container, add 100mL of deionized water, first slowly add concentrated nitric acid (68%) and stir to dissolve evenly, then add ammonium fluoride, potassium chloride, malonic acid, citric acid, glycolic acid and urea in sequence and stir to dissolve, and continue stirring for 30min. After the solution cools to between 20-30℃, add pure water to make up to 1L, stir evenly and it is ready for use.

[0311] Performance testing

[0312] The stripping solutions from Examples 1 to 4 were used to strip the electroplating layer from the surface of defective magnesium alloy electroplated products.

[0313] It should be noted that, apart from the different components of the stripping solution, the parameters of other processes and the reagents used, such as those used in activation and acid etching, are the same. All reagents are commercially available products.

[0314] The magnesium alloy substrate has copper plating, nickel plating, and chromium plating on its surface. The original magnesium alloy blank material is die-cast magnesium-aluminum alloy (AZ-91D), with dimensions of 60mm × 60mm × 3mm; the surface has been polished with 400-grit sandpaper to achieve a uniform and smooth finish.

[0315] The surface plating layer composition and thickness of defective magnesium alloy electroplated products are as follows: copper (20μm~25μm) / nickel (15μm~20μm) / chromium (0.2μm~0.5μm).

[0316] Determination of the appearance of the material after coating peeling

[0317] Visually observe the smoothness and corrosion of the surface after stripping, and score the results from 1 to 5. A higher score indicates a better result, and a lower score indicates a worse result.

[0318] Defective Magnesium Alloy Electroplating Products: Appearance and Adhesion Assessment

[0319] Appearance

[0320] The gloss and uniformity of the reworked surface are visually observed and judged on a scale of 1 to 5. A higher score indicates a better result, while a lower score indicates a worse result.

[0321] bonding force

[0322] Thermal shock test: Bake the electroplated workpiece at 200℃ for 60 minutes, then immediately immerse it in room temperature water for rapid cooling. Repeat the test three times. Observe whether the plating layer blisters or peels off in flakes. Evaluation method: "○" indicates no blistering and good adhesion; "△" indicates localized small blisters and average adhesion; "×" indicates severe blistering and very poor adhesion.

[0323] The magnesium alloy electroplated defective products stripped by the stripping solution in Example 1 showed that when the content of the formulation components was taken to a lower limit, the overall stripping speed of the coating slowed down, and it took 40 minutes to completely remove the coating. There was no pitting on the surface. After rework, the coating had a smooth and bright appearance and passed the adhesion test.

[0324] The magnesium alloy electroplated defective products stripped by the stripping solution in Example 2 were observed to have a moderate overall stripping speed when the content of the formulation components was taken as the middle value. It took 30 minutes to completely remove the coating and there was no pitting on the surface. After rework, the coating had a smooth and bright appearance and passed the adhesion test.

[0325] The magnesium alloy electroplated defective products stripped by the stripping solution in Example 3 showed that when the content of the formulation components was taken to the higher limit, the overall stripping speed of the coating was accelerated, and the time required for complete stripping was 20 minutes. There was no pitting on the surface. After rework, the coating had a smooth and bright appearance and passed the adhesion test.

[0326] The magnesium alloy electroplated defective products stripped by the stripping solution in Example 4 showed that when the content of the main components in the formula was taken to the lower limit and the accelerator was taken to the higher limit, the overall stripping speed of the coating was relatively faster. It took 30 minutes to completely remove the coating, and there was no pitting on the surface. After rework, the coating had a smooth and bright appearance and passed the adhesion test.

[0327] Comparative Example 1

[0328] The original raw material is a magnesium alloy workpiece, and the original raw material is electroplated to perform surface electroplating treatment.

[0329] Comparison results: The electroplated coating has a smooth and bright appearance, and the adhesion test is qualified.

[0330] Comparative Example 2

[0331] Magnesium alloy workpieces made from raw materials are first degreased by hot immersion, and then processed according to the rework process for defective magnesium alloy electroplating products. The deplating process is carried out by immersion for 20 minutes as in Implementation Case 3. Other processes and conditions are the same.

[0332] Comparison results: The magnesium alloy material has a smooth surface and no corrosion; after rework, the coating has a smooth and bright appearance, and the adhesion test is qualified.

[0333] Comparative Example 3

[0334] The traditional magnesium alloy electroplating layer stripping process is adopted. First, the surface coating is stripped clean, and then the surface electroplating treatment is carried out according to the original magnesium alloy blank material electroplating process.

[0335] The traditional electroplating layer stripping process is as follows:

[0336] Magnesium alloy electroplating defective products → Chromium stripping → 3 water washes → Nickel stripping → 3 water washes → Copper stripping → 3 water washes → Hot immersion degreasing → 3 water washes → Acid etching → Surface conditioning → Zinc immersion → Cyanide-free copper base coat → Copper plating → Acid copper plating → Semi-bright nickel plating → Bright nickel plating → Decorative chromium plating → Drying → Observation or testing.

[0337] Chromium stripping solution formulation and operating conditions:

[0338] Sodium hydroxide: 80 g / L

[0339] Cathode: Stainless steel (SUS304)

[0340] Temperature: 45℃

[0341] Voltage: 5V.

[0342] Nickel stripping solution formulation and operating conditions:

[0343] Hydrofluoric acid: 20%,

[0344] Sodium nitrate: 2%,

[0345] Cathode: Precision carbon plate,

[0346] Temperature: 25℃

[0347] Voltage: 5V.

[0348] Copper stripping solution formulation and operating conditions:

[0349] Potassium polysulfide: 55 g / L

[0350] Sodium hydroxide: 80 g / L

[0351] Sodium cyanide: 35g / L

[0352] Temperature: 45℃.

[0353] Comparison results: After the chromium plating was removed, the surface was intact with no over-corrosion. After the nickel plating was removed, some pitting corrosion into the magnesium alloy material appeared in areas where the copper plating was thin, with obvious corrosion products. After the copper plating was removed, the surface was smooth and corrosion-free except for a few pits that appeared during the nickel removal process. The reworked plating appearance was smooth and bright except for unevenness caused by corrosion in the low-electricity areas. Adhesion test: Except for small bubbles in the corrosion areas, the adhesion was satisfactory.

[0354] The results of the examples and comparative experiments are summarized in Table 1.

[0355] Table 1

[0356]

[0357] As can be seen from the table above, the surface condition and appearance after re-plating of the magnesium alloy surface electroplating layer stripping solution of the present invention are not significantly different from the effect after direct electroplating of the original blank. In contrast, the traditional step-by-step stripping method is prone to local corrosion of the material during stripping, and the corrosion area will fail the adhesion test after re-plating, which cannot fully meet the rework requirements.

[0358] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. An electroplating layer stripping solution, characterized by, The electroplating layer stripping liquid is used for stripping the plating chromium layer, the plating nickel layer and the plating copper layer on the surface of the magnesium alloy substrate at the same time, and the components are: Fluoride: 20wt%-40wt%, Concentrated nitric acid: 10wt%-20wt%, Chloride: 2wt%-5wt%, Dicarboxylic acid compound: 10wt%-20wt%, Glycolic acid or glycolate: 1wt%-2wt%, Hydroxyl polycarboxylic acid compound: 5wt%-10wt%, Urea: 0.1wt%-0.5wt%, The rest is water.

2. The electroplated layer stripping solution according to claim 1, characterized by The fluoride includes at least one of ammonium hydrogen fluoride and potassium fluoride.

3. The electroplated layer stripping solution according to claim 1, wherein The dicarboxylic acid compound includes at least one of oxalic acid and malonic acid.

4. The electroplated layer stripping solution according to claim 1, wherein The glycolate includes at least one of glycolic acid, sodium glycolate and potassium glycolate.

5. The electroplated layer stripping solution according to claim 1, wherein The hydroxyl polycarboxylic acid compound includes at least one of citric acid, tartaric acid, malic acid and lactic acid.

6. A method for producing the plating layer stripping solution according to any one of claims 1 to 5, characterized by, The method comprises the following steps: According to the proportion, the components are uniformly mixed.

7. A method for stripping an electroplated layer from a surface of a magnesium alloy material, characterized by, The method comprises the following steps: The workpiece to be stripped is immersed in the electroplating layer stripping liquid according to any one of claims 1-5.

8. The peeling method according to claim 7, characterized by, The workpiece to be stripped includes a magnesium alloy material substrate, and the magnesium alloy material substrate is provided with a plating copper layer, a plating nickel layer and a plating chromium layer.

9. The peeling method according to claim 7 or 8, characterized by, The immersion time is 20min-40min.

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