Phosphating solution for titanium and titanium alloy and phosphating method

Abstract

The invention relates to the technical field of titanium and titanium alloy surface treatment, in particular to a phosphating solution for titanium and titanium alloy and a phosphating method.The phosphating solution is prepared from phosphate containing phosphate ions, fluoride containing fluoride ions, oxalic acid, potassium dodecyl benzene sulfonate and a solvent; and the titanium and titanium alloy base material is subjected to acid pickling and surface activating treatment by using a surface conditioning agent before phosphating treatment. By using the phosphating solution prepared by the invention and the phosphating method, a uniform phosphating film with a honeycomb structure can be formed on the surface of titanium and titanium alloy, so that the adhesive force of a lubricating coating can be improved subsequently, the lubricating coating and the surface of the titanium alloy can be uniformly combined, and the upsetting galling of a fastener can be effectively prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of surface treatment of titanium and titanium alloys, and particularly relates to a phosphating solution and a phosphating method for titanium and titanium alloys. Background Art

[0002] Due to a series of advantages such as low density, high strength, good corrosion resistance, and excellent biocompatibility, titanium and titanium alloys have been widely used in many fields such as aerospace, medical devices, chemical industry, and automobiles. However, the surface of titanium and titanium alloys is relatively smooth and its surface activity is low. When performing subsequent treatments such as painting, electroplating, and bonding, the adhesion of the coating or plating layer is poor and it is easy to fall off, thus affecting the quality and service life of the product.

[0003] Fastener titanium alloy coil wire needs to be coated with lubricating coatings such as molybdenum disulfide, graphite, and tungsten disulfide to achieve continuous upsetting of fasteners. Fasteners such as TC16 titanium alloy pallet nuts and TB9 titanium alloy blind rivets are usually prepared by cold upsetting, with a large amount of deformation and multiple upsetting operations, requiring high anti-load capacity and bonding force for the dry film lubricating coating. The surface pretreatment methods before coating the titanium alloy bar wire include polishing, sandblasting, and phosphating. Polishing controls the surface roughness through the grit size of the sand belt. If the grit is coarser, the surface roughness after polishing is larger, which is not conducive to subsequent upsetting lubrication. If the surface roughness after polishing is small, it is not conducive to the combination of the subsequent lubricating coating and the titanium alloy surface. Both sandblasting and phosphating are beneficial to improving the bonding force of the subsequent dry film lubricating coating. There are a large number of phosphating solution formulations and phosphating methods for ferrous metals or aluminum alloys. The manganese-based, zinc-based, iron-based, zinc-calcium-based, and ternary phosphating agents disclosed for ferrous metals and aluminum alloys have problems of poor control of the film layer thickness and loose phosphating film when applied to titanium alloys.

[0004] Chinese invention patent with the publication number CN103498138A discloses a phosphating treatment method before coating of titanium alloy fasteners, and discloses a phosphating solution including sodium phosphate, sodium fluoride, and glacial acetic acid. After treating the surface of the titanium alloy fastener material with this phosphating solution, a loose and porous structure is obtained. However, for the phosphating before coating of titanium and titanium alloy bar wire used for upsetting fasteners, a homogeneous and fine honeycomb structure phosphating film needs to be formed to achieve the purpose of improving the coating bonding force. This phosphating film needs to be finely designed and controlled, and the film formation needs to be uniform to prevent uneven bonding force of the subsequent coating, resulting in the problem of scoring during the upsetting process of fasteners.

[0005] In view of the problem that the existing phosphating solution is not easy to form a uniform honeycomb structure phosphating film on the surface of titanium alloy wire, and the bonding force between the subsequent lubricating coating and the titanium alloy surface is poor, which further leads to the problem of scoring during the upsetting process of fasteners, the present invention designs a phosphating solution formulation and a phosphating method. Summary of the Invention

[0006] To solve the above problems, the present invention provides a phosphating solution and a phosphating method for titanium and titanium alloys. By using a promoter in the phosphating solution and activating the titanium and titanium alloys with a surface conditioner before phosphating, a uniform honeycomb-structured phosphating film can be formed on the surface of the titanium and titanium alloys, which is beneficial to improving the adhesion of the subsequent lubricating coating, enabling the lubricating coating to be uniformly combined with the surface of the titanium alloy, and effectively preventing the upsetting and galling of fasteners.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A phosphating solution for titanium and titanium alloys, which is composed of the following components: a phosphate containing phosphate ions, a fluoride containing fluoride ions, a promoter, a surfactant, and a solvent.

[0009] Preferably, the phosphate containing phosphate ions in the phosphating solution is potassium phosphate, the fluoride containing fluoride ions is potassium fluoride and hydrofluoric acid, the promoter is oxalic acid, the surfactant is potassium dodecylbenzenesulfonate, and the solvent is deionized water.

[0010] Preferably, the phosphating solution is prepared from potassium phosphate at a concentration of 40 - 60 g / L, potassium fluoride at a concentration of 15 - 25 g / L, hydrofluoric acid at a concentration of 4 - 8 g / L, oxalic acid at a concentration of 1 - 3 g / L, potassium dodecylbenzenesulfonate at a concentration of 2 - 4 g / L, and deionized water.

[0011] Preferably, the hydrofluoric acid is hydrofluoric acid with a concentration of 40%.

[0012] A phosphating method for a phosphating solution for titanium and titanium alloys, comprising the following steps:

[0013] Step 1, pickling the titanium and titanium alloy substrate without oxide scale on the surface, then cleaning and drying it, and transferring it to the surface conditioner for standing;

[0014] Step 2, drying the titanium and titanium alloy substrate after standing in Step 1, and performing phosphating treatment in the phosphating solution; during phosphating, monitor the pH value, free acidity, total acidity, and the ratio of total acidity to free acidity of the phosphating solution.

[0015] Preferably, in Step 1, the acid solution ratio during pickling is HNO3:HF:H2O = 1:7:14, and the pickling time is 3 - 7 min.

[0016] Preferably, in Step 1, the surface conditioner is prepared by adding titanium phosphate colloid to deionized water to form a titanium phosphate solution.

[0017] Preferably, the particle size of the titanium phosphate colloid is 15 - 80 nm; the concentration of the titanium phosphate solution is 0.1% - 0.6%, and the pH value is 8.5 - 9.7.

[0018] Preferably, in step 2, the pH value of the phosphating solution is 2.2 to 3.5; the free acidity of the phosphating solution is ≥ 3 points.

[0019] Preferably, in step 2, the total acidity of the phosphating solution: free acidity is 1:20 to 1:27.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) In the present invention, a surface conditioner is used to activate titanium and titanium alloy before phosphating. The surface conditioner adopts a weakly alkaline titanium phosphate solution, which can promote the crystallization refinement and densification of the phosphating film, improve the film-forming property, and shorten the phosphating time.

[0022] (2) In the phosphating solution of the present invention, a promoter and a surfactant are used. The promoter oxalic acid is beneficial to promoting the phosphating reaction to form a dense and fine phosphating film; the surfactant potassium dodecylbenzenesulfonate can improve the permeability and wettability of the phosphating solution, which is beneficial to the uniform distribution of the phosphating film and reduces foam generation.

[0023] (3) Potassium phosphate used in the phosphating solution of the present invention has better solubility at room temperature compared with sodium phosphate. The positively charged potassium ions formed by the secondary hydrolysis and the hydrolysis of potassium fluoride can promote the formation of phosphating film crystal nuclei and grain refinement, accelerating the normal temperature phosphating process; the solvents used are all deionized water, avoiding the influence of calcium ions and magnesium ions in tap water on the stability of colloidal particles and phosphating solution.

[0024] In summary, the phosphating solution of the present invention is different from traditional zinc-based, manganese-based, and iron-based phosphating agents. This phosphating solution, combined with the phosphating method provided by the present invention, can form a dense film layer on the surface of titanium and titanium alloy. Moreover, the process is simple, suitable for subsequent coating of a lubricating coating on the phosphating film, improving the adhesion of the lubricating coating, enabling the uniform combination of the lubricating coating and the titanium alloy surface, and effectively preventing the upsetting and galling of fasteners. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of the phosphating solution and phosphating method for titanium and titanium alloy of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] The following further details the present application with reference to the drawings and embodiments. The following further details the specific embodiments of the present invention, but the present invention is not limited to these embodiments. Any improvement or substitution based on the basic spirit of this embodiment still falls within the scope protected by the claims of the present invention.

[0027] Refer to Figure 1, the phosphating solution for titanium and titanium alloys provided by the present invention is prepared from potassium phosphate with a concentration of 40 - 60 g / L, potassium fluoride with a concentration of 15 - 25 g / L, hydrofluoric acid with a concentration of 4 - 8 g / L, oxalic acid with a concentration of 1 - 3 g / L, potassium dodecylbenzenesulfonate with a concentration of 2 - 4 g / L, and deionized water; wherein, the hydrofluoric acid is hydrofluoric acid with a concentration of 40%.

[0028] The present invention also provides a phosphating method for the phosphating solution of titanium and titanium alloys, comprising the following steps:

[0029] Step 1, place the titanium and titanium alloy substrate with a polished, buffed, or sandblasted surface without oxide scale in an acid pickling tank for acid pickling. The acid solution ratio is HNO3:HF:H2O = 1:7:14, the acid pickling temperature is room temperature, the acid pickling time is 3 - 7 min. Immediately after acid pickling, rinse with deionized water and blow dry the surface water stains with compressed air. After drying, transfer the titanium and titanium alloy substrate to the tank solution of the surface conditioner and let it stand for 2 - 3 min for surface activation in 2 - 15 min (the shorter the time, the better);

[0030] This tank solution is prepared by adding titanium phosphate colloid with a particle diameter of 15 - 80 nm to deionized water to form a titanium phosphate solution with a concentration of 0.1% - 0.6%; control the pH value of this titanium phosphate solution at 8.5 - 9.7.

[0031] The pH value of the surface conditioner tank solution is regulated by the flowing overflow method, that is, by injecting the titanium phosphate solution prepared according to the concentration provided by the present invention into one end of the tank, so that the used titanium phosphate solution flows out of the tank, detect the pH value of the tank solution, and keep the pH value of this titanium phosphate solution in the tank at 8.5 - 9.7 all the time.

[0032] Step 2, blow dry the titanium and titanium alloy substrate obtained in Step 1 with compressed air, transfer it to the tank of the phosphating solution and vibrate for 5 min - 15 min. The phosphating temperature is 25°C - 40°C. During phosphating, monitor the pH value, free acidity, total acidity, and the ratio of total acidity to free acidity of the phosphating solution; wherein, the pH value of the phosphating solution is 2.2 - 3.5, the free acidity of the phosphating solution ≥ 3 points, and the ratio of total acidity to free acidity of the phosphating solution = 1:20 - 1:27;

[0033] The method for measuring the free acidity points is: take 10 mL of the phosphating solution and add it to a conical flask, then add 20 mL of deionized water, and then add 1 - 2 drops of bromophenol blue indicator. Titrate with 0.1 mol / L standard NaOH solution. The number of milliliters of the standard NaOH solution consumed when the solution turns blue is the number of free acidity points;

[0034] The method for measuring the total acidity points is as follows: Take 10 mL of the phosphating solution and add it to a conical flask, then add 20 mL of deionized water. Next, add 1 - 2 drops of phenolphthalein indicator, and titrate with a 0.1 mol / L standard NaOH solution. The number of milliliters of the standard NaOH solution consumed when the solution turns pink is the number of points of the total acidity.

[0035] Step 3: Immerse the phosphated titanium and titanium alloy substrate obtained in Step 2 in a cleaning tank filled with deionized water, and blow it dry with compressed air after taking it out of the tank.

[0036] Example 1

[0037] A phosphating solution for titanium and titanium alloys is prepared by sequentially adding 400 g of potassium phosphate, 150 g of potassium fluoride, 40 g of hydrofluoric acid with a concentration of 40%, 10 g of oxalic acid, and 20 g of potassium dodecylbenzenesulfonate to 10 L of deionized water, and stirring until completely dissolved.

[0038] The phosphating method of the phosphating solution for titanium and titanium alloys in this example includes the following steps:

[0039] Step 1: Place the titanium and titanium alloy substrate with a polished, buffed, or sandblasted surface without scale in a pickling tank for pickling. The acid solution ratio is HNO3:HF:H2O = 1:7:14, the pickling temperature is room temperature, the pickling time is 3 min. After pickling, immediately rinse with deionized water and blow dry the water stains on the surface with compressed air. After drying, transfer the titanium and titanium alloy substrate to the bath solution of the surface conditioner and let it stand for 2 min for surface activation;

[0040] The bath solution is prepared by adding 10 mL of titanium phosphate colloid with a particle diameter of 15 - 80 nm to 10 L of deionized water to form a 0.1% titanium phosphate solution, and controlling the pH value of the titanium phosphate solution to be 8.5 - 9.7; The pH value of the bath solution is regulated by the flowing overflow method, that is, by injecting the titanium phosphate solution configured according to the concentration provided by the present invention at one end of the tank and flowing out the used titanium phosphate solution for regulation;

[0041] Step 2: Blow dry the titanium and titanium alloy substrate obtained in Step 1 with compressed air, transfer it to the tank of the phosphating solution, vibrate and keep it for 15 min. The phosphating temperature is 25°C - 30°C. During phosphating, the pH value of the phosphating solution is 2.2 - 3.5, the free acidity of the phosphating solution ≥ 3 points, and the ratio of the total acidity to the free acidity of the phosphating solution is 1:20 - 1:24;

[0042] Step 3: Immerse the phosphated titanium and titanium alloy substrate obtained in Step 2 in a cleaning tank filled with deionized water, and blow it dry with compressed air after taking it out of the tank.

[0043] Example 2

[0044] A phosphating solution for titanium and titanium alloys, which is prepared by sequentially adding 500 g of potassium phosphate, 200 g of potassium fluoride, 60 g of hydrofluoric acid with a concentration of 40%, 20 g of oxalic acid, and 30 g of potassium dodecylbenzenesulfonate into 10 L of deionized water and stirring until completely dissolved.

[0045] The phosphating method of the phosphating solution for titanium and titanium alloys in this embodiment includes the following steps:

[0046] Step 1: Place the titanium and titanium alloy substrates with a polished, buffed, or sandblasted surface without scale in an acid pickling tank for pickling. The acid solution ratio is HNO3:HF:H2O = 1:7:14, the pickling temperature is room temperature, the pickling time is 5 min. After pickling, immediately rinse with deionized water and blow dry the surface water stains with compressed air. After drying, transfer the titanium and titanium alloy substrates to the bath solution of the surface conditioner and let them stand for 2 min for surface activation in 8 min.

[0047] This bath solution is prepared by adding 30 mL of titanium phosphate colloid with a particle diameter of 15 - 80 nm into 10 L of deionized water to form a titanium phosphate solution with a concentration of 0.3%, and controlling the pH value of this titanium phosphate solution to be 8.5 - 9.7. The pH value of the bath solution is regulated by the flowing overflow method, that is, by injecting the titanium phosphate solution configured according to the concentration provided by the present invention at one end of the tank and flowing out the used titanium phosphate solution for regulation.

[0048] Step 2: Blow dry the titanium and titanium alloy substrates obtained in Step 1 with compressed air, transfer them to the phosphating solution tank, vibrate and keep for 10 min. The phosphating temperature is 30°C - 35°C. During phosphating, the pH value of the phosphating solution is 2.2 - 3.5, the free acidity of the phosphating solution ≥ 3 points, and the total acidity of the phosphating solution: free acidity = 1:22 - 1:25.

[0049] Step 3: Immerse the titanium and titanium alloy substrates phosphated in Step 2 in a cleaning tank, which contains deionized water, and blow dry with compressed air after taking them out of the tank.

[0050] Example 3

[0051] A phosphating solution for titanium and titanium alloys, which is prepared by sequentially adding 600 g of potassium phosphate, 250 g of potassium fluoride, 80 g of hydrofluoric acid with a concentration of 40%, 30 g of oxalic acid, and 40 g of potassium dodecylbenzenesulfonate into 10 L of deionized water and stirring until completely dissolved.

[0052] The phosphating method of the phosphating solution for titanium and titanium alloys in this embodiment includes the following steps:

[0053] Step 1: Place the titanium and titanium alloy substrate with a polished, buffed, or sandblasted surface without scale in a pickling tank for pickling. The acid solution ratio is HNO3:HF:H2O = 1:7:14, the pickling temperature is room temperature, the pickling time is 7 minutes. After pickling, immediately rinse with deionized water and blow dry the water stains on the surface with compressed air. After drying, transfer the titanium and titanium alloy substrate to the bath solution of the surface conditioner and let it stand for 3 minutes for surface activation for 15 minutes;

[0054] This bath solution is prepared by adding 60 mL of titanium phosphate colloid with a particle diameter of 15 - 80 nm to 10 L of deionized water to form a titanium phosphate solution with a concentration of 0.6%. Control the pH value of this titanium phosphate solution at 8.5 - 9.7; The pH value of the bath solution is regulated by the flowing overflow method, that is, by injecting the titanium phosphate solution configured according to the concentration provided by the present invention into one end of the tank and flowing out the used titanium phosphate solution for regulation;

[0055] Step 2: Blow dry the titanium and titanium alloy substrate obtained in Step 1 with compressed air, transfer it to the tank of the phosphating solution, vibrate and keep it for 5 minutes. The phosphating temperature is 35°C - 40°C. During phosphating, the pH value of the phosphating solution is 2.2 - 3.5, the free acidity of the phosphating solution ≥ 3 points, and the total acidity of the phosphating solution: free acidity = 1:24 - 1:27;

[0056] Step 3: Place the titanium and titanium alloy substrate after phosphating in Step 2 in a cleaning tank for impregnation. The cleaning tank contains deionized water, and after taking it out of the tank, blow dry it with compressed air.

[0057] The phosphating solution for titanium and titanium alloy prepared by the present invention does not require subsequent sealing and passivation treatment, the process is simple, and the formed phosphating film has good compactness; After coating a molybdenum disulfide coating on this phosphating film, continuous upsetting of fasteners can be realized. Compared with directly coating a molybdenum disulfide coating on the surface of titanium and titanium alloy, the adhesion of the lubricating coating is improved, and it can effectively prevent scratching and flaking during the upsetting of fasteners.

Claims

1. A phosphating solution for titanium and titanium alloys, characterized in that, The phosphating solution consists of the following components: phosphate containing phosphate ions, fluoride containing fluoride ions, accelerator, surfactant, and solvent.

2. The phosphating solution for titanium and titanium alloy according to claim 1, characterized in that, In the phosphating solution, the phosphate containing phosphate ions is potassium phosphate, the fluoride containing fluoride ions is potassium fluoride and hydrofluoric acid, the accelerator is oxalic acid, the surfactant is potassium dodecylbenzenesulfonate, and the solvent is deionized water.

3. The phosphating solution for titanium and titanium alloys according to claim 2, characterized in that, The phosphating solution is prepared from potassium phosphate at a concentration of 40 - 60 g / L, potassium fluoride at 15 - 25 g / L, hydrofluoric acid at 4 - 8 g / L, oxalic acid at 1 - 3 g / L, potassium dodecylbenzenesulfonate at 2 - 4 g / L, and deionized water.

4. The phosphating solution for titanium and titanium alloys according to claim 3, characterized in that, The hydrofluoric acid is hydrofluoric acid with a concentration of 40%.

5. The phosphating method of the phosphating solution for titanium and titanium alloys according to any one of claims 1-4, characterized in that, It includes the following steps: Step 1: Pickle the titanium and titanium alloy substrate without oxide scale on the surface, then clean and dry it, and transfer it to the surface conditioner for standing. Step 2: Dry the titanium and titanium alloy substrate after standing in Step 1, and carry out phosphating treatment in the phosphating solution; during phosphating, monitor the pH value, free acidity, total acidity, and the ratio of total acidity to free acidity of the phosphating solution.

6. The phosphating method of the phosphating solution for titanium and titanium alloys according to claim 5, characterized in that, In Step 1, the acid solution ratio during pickling is HNO3:HF:H2O = 1:7:14, and the pickling time is 3 - 7 minutes.

7. The phosphating method of the phosphating solution for titanium and titanium alloys according to claim 5, characterized in that, In Step 1, the surface conditioner is prepared by adding titanium phosphate colloid to deionized water to form a titanium phosphate solution.

8. The phosphating method of the phosphating solution for titanium and titanium alloys according to claim 7, characterized in that, The particle size of the titanium phosphate colloid is 15 - 80 nm; the concentration of the titanium phosphate solution is 0.1% - 0.6%, and the pH value is 8.5 - 9.

7.

9. The phosphating method of the phosphating solution for titanium and titanium alloys according to claim 1, characterized in that, In Step 2, the pH value of the phosphating solution is 2.2 - 3.5; the free acidity of the phosphating solution is ≥ 3 points.

10. The phosphating method of the phosphating solution for titanium and titanium alloy according to claim 1, characterized in that, In Step 2, the ratio of total acidity to free acidity of the phosphating solution is 1:20 - 1:27.

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