Phosphating process for steel surfaces

Abstract

The application relates to the field of steel processing, and discloses a steel surface phosphating treatment process, which comprises the following steps: (1) obtaining cleaned steel; (2) preparing a pretreatment liquid; (3) preparing a phosphating liquid; (4) pretreatment; and (5) phosphating treatment; the treatment process performs phosphating treatment on the surface of the steel, can form a phosphating layer with high corrosion resistance, the phosphating layer can greatly block the corrosion of corrosion factors on the surface of the steel, the pretreatment can further improve the bonding force between the phosphating layer and the steel, thereby effectively avoiding the peeling problem of the phosphating layer, improving the service life of the phosphating layer, and better providing protection for the steel.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of steel processing, in particular to a steel surface phosphating process. BACKGROUND

[0002] Phosphating is a common pretreatment technology, which should belong to chemical conversion film treatment in principle, and is mainly applied to steel surface phosphating, and non-ferrous metal (such as aluminum and zinc) parts can also be applied to phosphating.

[0003] Phosphating is a process of forming a phosphate chemical conversion film through chemical and electrochemical reactions, and the formed phosphate conversion film is called phosphating film.

[0004] The main purposes of phosphating are to provide protection to the base metal, to prevent corrosion of the metal to some extent, to provide a primer before painting to improve the adhesion and corrosion resistance of the paint film, and to play a role in reducing friction and lubrication in metal cold working process.

[0005] Steel is a material of a certain shape, size and performance made by pressing steel ingot, billet or steel. Most steel processing is through pressing to make the processed steel (billet, ingot, etc.) produce plastic deformation. According to the different processing temperatures of steel, it can be divided into cold working and hot working.

[0006] Steel is widely used and involves multiple fields. However, steel has poor corrosion resistance, so it is easily eroded by various corrosion factors during use, causing continuous corrosion of steel parts, a significant decrease in quality, and a shortened service life.

[0007] Therefore, surface treatment is performed before the use of steel to improve the performance of steel, and phosphating treatment of steel is a common treatment method. However, the existing phosphating treatment process has limited improvement in the corrosion resistance of steel, and cannot meet the needs of some special corrosion prevention fields.

[0008] Therefore, we propose a steel surface phosphating treatment process to solve the problems in the prior art. SUMMARY

[0009] (I) Technical problems solved

[0010] In view of the deficiencies of the prior art, the present application provides a steel surface phosphating treatment process.

[0011] (II) Technical solutions

[0012] In order to achieve the above purpose, the present application provides the following technical solutions:

[0013] The steel surface phosphating treatment process comprises the following steps:

[0014] (1) The surface of the steel is polished, and then the steel is cleaned multiple times, dried after cleaning, and the cleaned steel is obtained;

[0015] (2) Prepare the pretreatment solution: add dilute hydrochloric acid to the maleic anhydride solution, adjust the temperature to 55-60℃, and mix uniformly under stirring and insulation to obtain the pretreatment solution;

[0016] (3) Prepare the phosphating solution: add phosphoric acid, sodium nitrate, modifier, rare earth nitrate, zinc nitrate, and sodium fluoride to deionized water in sequence, and mix uniformly under stirring to obtain the phosphating solution;

[0017] (4) Pretreatment: soak the cleaned steel of step (1) in the pretreatment solution, water bath insulation, immersion treatment, then take out, wash with water to neutral, dry, and get the pretreated steel;

[0018] (5) Phosphating treatment: add the pretreated steel obtained in step (4) and the phosphating solution to the reaction kettle, then adjust the temperature to 78-85℃, vacuum, immersion treatment for 8-10min, then take out, wash with pure water to neutral, then blow dry.

[0019] As a further technical solution, the polishing treatment in step (1) is carried out with 250 mesh and 400 mesh sandpaper in sequence, and the polishing time is 10 min.

[0020] As a further technical solution, the multiple cleaning in step (1) is carried out with water, ethanol and acetone in sequence, and the cleaning time is 5-7 min each time.

[0021] As a further technical solution: the volume ratio of the dilute hydrochloric acid and the maleic anhydride solution is 2:1;

[0022] The concentration of hydrochloric acid is 1.5 mol / L;

[0023] The concentration of maleic anhydride is 0.12 mol / L.

[0024] As a further technical solution: the content of each component in the phosphating solution is: phosphoric acid 9-12g / L, sodium nitrate 2-3g / L, modifier 1.2-1.6g / L, rare earth nitrate 0.09-0.12g / L, zinc nitrate 3-5g / L, and sodium fluoride 1.2-1.8g / L.

[0025] As a further technical solution, the modifier is a mixture of hydroxylamine sulfate and nano silicon dioxide particles;

[0026] The mass ratio of hydroxylamine sulfate and nano silicon dioxide particles is 3:1.

[0027] As a further technical solution, the water bath incubation temperature in step (4) is 80-85 DEG C, and the pretreatment time of the steel immersed in the pretreatment solution is 45-50 min.

[0028] As a further technical solution: in step (5), the mixing mass ratio of the pretreated steel and the phosphating solution is 20:1.

[0029] As a further technical solution: in step (5), the vacuum degree of vacuumizing is 0.05 Pa.

[0030] Wherein, the drying is carried out by nitrogen blowing.

[0031] The steel is phosphated by the prepared phosphating solution, a dense phosphating layer is formed on the surface of the steel, the phosphating layer has a uniform thickness, and the corrosion resistance of the steel is greatly improved after the formation of the phosphating layer.

[0032] The components of the phosphating solution are optimally proportioned, so that the film forming rate of the steel during phosphating is moderate, neither too fast nor too slow, a dense phosphating layer with uniform thickness can be formed, if the phosphating speed is too fast, the phosphating layer is too thick, the internal particles are coarse, the structure has many cracks, the continuity is poor, the structure is loose, and the corrosion factor can penetrate into the surface of the steel, thereby corroding the steel, and if the phosphating speed is too slow, the phosphating layer is too small and easy to fall off, and the service life is short.

[0033] The modifier is introduced, which has a more positive promoting effect on the structure of the phosphating layer, the internal particles of the phosphating layer are smaller and more dense, thereby greatly improving the corrosion resistance of the phosphating layer.

[0034] A certain amount of nano-silicon dioxide particles are introduced into the modifier, which can increase the thickness of the phosphating layer, fill the interstitial gap, improve the density of the structure, and thereby improve the blocking effect of the phosphating layer on the corrosion medium.

[0035] (Three) beneficial effects

[0036] Compared with the prior art, the present application provides a steel surface phosphating process, which has the following beneficial effects:

[0037] The present application processes the surface of the steel by phosphating, which can form a phosphating layer with high corrosion resistance, and the existence of the phosphating layer can greatly block the corrosion of the corrosion factor on the surface of the steel, and the pretreatment can further improve the bonding force between the phosphating layer and the steel, thereby effectively avoiding the problem of phosphating layer falling off, improving the service life of the phosphating layer, and better providing protection for the steel. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application. Embodiment 1

[0039] The steel surface phosphating process comprises the following steps:

[0040] (1) The steel is subjected to surface polishing treatment, and then is subjected to multiple cleaning treatment, and after the cleaning is completed, drying is performed to obtain cleaned steel; the polishing treatment is polishing treatment with 250-mesh and 400-mesh sandpaper in sequence, and the polishing time is 10 min; the multiple cleaning is cleaning of the steel with water, ethanol and acetone in sequence, and the cleaning time is 5 min each time

[0041] (2) A pretreatment solution is prepared: dilute hydrochloric acid is added to a maleic anhydride solution, the temperature is adjusted to 55°C, and the mixture is uniformly stirred and kept at temperature to obtain the pretreatment solution; the volume ratio of the dilute hydrochloric acid to the maleic anhydride solution is 2:1;

[0042] The concentration of the hydrochloric acid is 1.5 mol / L;

[0043] The concentration of the maleic anhydride is 0.12 mol / L.

[0044] (3) A phosphating solution is prepared: phosphoric acid, sodium nitrate, a modifier, rare earth nitrate, zinc nitrate and sodium fluoride are sequentially added to deionized water, and the mixture is uniformly stirred to obtain the phosphating solution; the content of each component in the phosphating solution is: phosphoric acid 9 g / L, sodium nitrate 2 g / L, modifier 1.2 g / L, rare earth nitrate 0.09 g / L, zinc nitrate 3 g / L, and sodium fluoride 1.2 g / L; the modifier is a mixture of hydroxylamine sulfate and nano-silicon dioxide particles;

[0045] The mixing mass ratio of the hydroxylamine sulfate to the nano-silicon dioxide particles is 3:1.

[0046] (4) Pretreatment: the cleaned steel in step (1) is soaked in the pretreatment solution, water bathed and kept at temperature, immersed and treated, then taken out, washed with water to neutral, and dried to obtain pretreated steel; the water bath temperature is 80°C, and the pretreatment time of the steel soaked in the pretreatment solution is 45 min.

[0047] (5) Phosphating treatment: the pretreated steel material obtained in step (4) is added to a reaction kettle with phosphating solution, then the temperature is adjusted to 78℃, vacuum is extracted, immersion treatment is performed for 8 min, then it is taken out, washed with pure water until neutral, and then dried, and the pretreated steel material is obtained; the mass ratio of the pretreated steel material to the phosphating solution is 20:1; the vacuum degree of vacuum extraction is 0.05 Pa;

[0048] The drying is performed by blowing nitrogen. Example 2

[0049] The steel surface phosphating treatment process comprises the following steps:

[0050] (1) The steel material is subjected to surface polishing treatment, and then the steel material is subjected to multiple cleaning treatment, and after cleaning, drying is performed to obtain a cleaned steel material; the polishing treatment is performed by using 250-mesh and 400-mesh sandpaper for polishing treatment in sequence, and the polishing time is 10 min; the multiple cleaning is performed by using water, ethanol and acetone in sequence for cleaning the steel material, and the cleaning time is 6 min each time

[0051] (2) Preparation of pretreatment solution: dilute hydrochloric acid is added to a maleic anhydride solution, the temperature is adjusted to 56℃, and the mixture is uniformly stirred and mixed under heat preservation to obtain a pretreatment solution; the volume ratio of dilute hydrochloric acid to maleic anhydride solution is 2:1.

[0052] The concentration of the hydrochloric acid is 1.5 mol / L.

[0053] The concentration of the maleic anhydride is 0.12 mol / L.

[0054] (3) Preparation of phosphating solution: phosphoric acid, sodium nitrate, modifier, rare earth nitrate, zinc nitrate and sodium fluoride are sequentially added to deionized water, and the mixture is uniformly stirred and mixed to obtain a phosphating solution; the content of each component in the phosphating solution is: phosphoric acid 10 g / L, sodium nitrate 2.5 g / L, modifier 1.3 g / L, rare earth nitrate 0.10 g / L, zinc nitrate 3.5 g / L, and sodium fluoride 1.4 g / L; the modifier is a mixture of hydroxylamine sulfate and nano silicon dioxide particles;

[0055] The mass ratio of the hydroxylamine sulfate to the nano silicon dioxide particles is 3:1.

[0056] (4) Pretreatment: the cleaned steel material in step (1) is soaked in the pretreatment solution, water bath heat preservation is performed, immersion treatment is performed, then it is taken out, washed with water until neutral, and dried to obtain a pretreated steel material; the water bath heat preservation temperature is 82℃, and the pretreatment time of the steel material soaked in the pretreatment solution is 46 min.

[0057] (5) Phosphating treatment: the pretreated steel material obtained in step (4) is added to a reaction kettle with phosphating solution, then the temperature is adjusted to 80°C, vacuum is extracted, immersion treatment is performed for 9 min, then it is taken out, washed with pure water until neutral, and then dried, and the pretreated steel material is obtained; the mixing mass ratio of the pretreated steel material and the phosphating solution is 20:1; the vacuum degree of vacuum extraction is 0.05 Pa;

[0058] The drying is performed by using nitrogen. Example 3

[0059] The steel surface phosphating treatment process comprises the following steps:

[0060] (1) The steel material is subjected to surface polishing treatment, and then the steel material is subjected to multiple cleaning treatment, and after cleaning, drying is performed to obtain a cleaned steel material; the polishing treatment is performed by using 250-mesh and 400-mesh sandpaper for polishing treatment in sequence, and the polishing time is 10 min; the multiple cleaning is performed by using water, ethanol and acetone in sequence for cleaning the steel material, and the cleaning time is 6 min each time

[0061] (2) Preparation of pretreatment solution: dilute hydrochloric acid is added to a maleic anhydride solution, the temperature is adjusted to 58°C, and the mixture is uniformly stirred and mixed under heat preservation to obtain a pretreatment solution; the mixing volume ratio of dilute hydrochloric acid and maleic anhydride solution is 2:1.

[0062] The concentration of the hydrochloric acid is 1.5 mol / L.

[0063] The concentration of the maleic anhydride is 0.12 mol / L.

[0064] (3) Preparation of phosphating solution: phosphoric acid, sodium nitrate, modifier, rare earth nitrate, zinc nitrate and sodium fluoride are sequentially added to deionized water, and the mixture is uniformly stirred and mixed to obtain a phosphating solution; the content of each component in the phosphating solution is: phosphoric acid 11 g / L, sodium nitrate 2.8 g / L, modifier 1.5 g / L, rare earth nitrate 0.11 g / L, zinc nitrate 4 g / L, and sodium fluoride 1.5 g / L; the modifier is a mixture of hydroxylamine sulfate and nano silicon dioxide particles;

[0065] The mixing mass ratio of the hydroxylamine sulfate and the nano silicon dioxide particles is 3:1.

[0066] (4) Pretreatment: the cleaned steel material in step (1) is soaked in the pretreatment solution, water bath heat preservation is performed, immersion treatment is performed, then it is taken out, washed with water until neutral, and dried to obtain a pretreated steel material; the water bath heat preservation temperature is 82°C, and the pretreatment time of the steel material soaked in the pretreatment solution is 48 min.

[0067] (5) Phosphating treatment: the pretreated steel material obtained in step (4) is added into a reaction kettle with phosphating solution, then the temperature is adjusted to 81℃, vacuum is extracted, and immersion treatment is performed for 9 min, then it is taken out, washed with pure water until neutral, and then dried, and the pretreated steel material and the phosphating solution are mixed in a mass ratio of 20:1; the vacuum degree of vacuum extraction is 0.05 Pa;

[0068] The drying is performed by using nitrogen. Example 4

[0069] A steel surface phosphating treatment process, comprising the following steps:

[0070] (1) The steel material is subjected to surface polishing treatment, and then the steel material is subjected to multiple cleaning treatment, and after cleaning, drying is performed to obtain a cleaned steel material; the polishing treatment is performed by using 250-mesh and 400-mesh sandpaper for polishing treatment in sequence, and the polishing time is 10 min; the multiple cleaning is performed by using water, ethanol and acetone in sequence for cleaning the steel material, and the cleaning time is 7 min each time

[0071] (2) Preparation of pretreatment solution: dilute hydrochloric acid is added to a maleic anhydride solution, the temperature is adjusted to 60℃, and the mixture is uniformly stirred and mixed under heat preservation to obtain a pretreatment solution; the volume ratio of dilute hydrochloric acid to maleic anhydride solution is 2:1;

[0072] The concentration of the hydrochloric acid is 1.5 mol / L;

[0073] The concentration of the maleic anhydride is 0.12 mol / L.

[0074] (3) Preparation of phosphating solution: phosphoric acid, sodium nitrate, modifier, rare earth nitrate, zinc nitrate and sodium fluoride are sequentially added to deionized water, and the mixture is uniformly stirred and mixed to obtain a phosphating solution; the content of each component in the phosphating solution is: phosphoric acid 12 g / L, sodium nitrate 3 g / L, modifier 1.6 g / L, rare earth nitrate 0.12 g / L, zinc nitrate 5 g / L, and sodium fluoride 1.8 g / L; the modifier is a mixture of hydroxylamine sulfate and nano silicon dioxide particles;

[0075] The mixing mass ratio of the hydroxylamine sulfate and the nano silicon dioxide particles is 3:1.

[0076] (4) Pretreatment: the cleaned steel material in step (1) is soaked in the pretreatment solution, water bathed and heat preserved, immersed and treated, then taken out, washed with water until neutral, and dried to obtain a pretreated steel material; the water bath heat preservation temperature is 85℃, and the pretreatment time of the steel material soaked in the pretreatment solution is 50 min.

[0077] (5) phosphating treatment: the pretreated steel material obtained in step (4) is added into a reaction kettle with phosphating solution, then the temperature is adjusted to 85℃, vacuum is extracted, and immersion treatment is performed for 10 min, then it is taken out, washed with pure water until neutral, and then dried with nitrogen, so as to obtain the phosphating steel material; the mixing mass ratio of the pretreated steel material and the phosphating solution is 20:1; the vacuum degree of the vacuum extraction is 0.05 Pa;

[0078] The drying is performed by using nitrogen.

[0079] Comparative Example 1

[0080] On the basis of Example 1, the pretreatment liquid is not used, and the rest of the technical solutions are the same as those in Example 1.

[0081] Comparative Example 2

[0082] On the basis of Example 1, no modifier is added in the phosphating solution, and the rest of the technical solutions are the same as those in Example 1.

[0083] Test

[0084] The 45 steel material is used as the test object of the steel material, the sample with a specification of 10 cm x 20 cm x 5 mm is used, the example and the comparative method are used for treatment respectively, then the corrosion resistance is detected, the steel material treated by the example and the comparative method is used as the working electrode, the platinum electrode is used as the auxiliary electrode, the saturated mercury electrode is used as the reference electrode, the electrolytic solution is the NaCl solution with a mass fraction of 5.0%, the Tafel curve of the electrode sample is measured, the scanning range of the control test potential is open circuit potential ± 1.5 V, and the scanning frequency is set to 0.5 mV / s, so as to obtain the self-corrosion potential.

[0085] Table 1

[0086]

[0087] As shown in Table 1, the steel material treated by the method has a lower corrosion potential, which indicates that the corrosion resistance of the steel material treated by the method is greatly improved.

[0088] Based on the sample in Example 1, the influence of the concentration of different modifiers in the phosphating solution on the corrosion resistance of the treated steel material is compared.

[0089] Table 2

[0090]

[0091] As shown in Table 2, by introducing the modifier into the phosphating solution in the process, the corrosion resistance of the steel material after phosphating treatment can be improved, and different concentrations of the modifier have different influences on the phosphating performance of the steel material.

[0092] Continue the test, detect the self-corrosion current of the sample of the example and the comparative example:

[0093] Table 3

[0094]

[0095] As shown in Table 3, the self-corrosion current of the steel material after the process of the application is low, which indicates that the corrosion resistance of the steel material after the process of the application is greatly improved.

[0096] Although the embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A phosphate treatment process for steel surfaces, characterized in that, Includes the following steps: (1) The steel is surface-grinding and then cleaned multiple times. After cleaning, it is dried to obtain cleaned steel. (2) Preparation of pretreatment solution: Add dilute hydrochloric acid to maleic anhydride solution, adjust the temperature to 55-60℃, keep warm and stir to mix evenly to obtain pretreatment solution; (3) Preparation of phosphating solution: Phosphoric acid, sodium nitrate, modifier, rare earth nitrate, zinc nitrate and sodium fluoride are added to deionized water in sequence and stirred until evenly mixed to obtain phosphating solution; (4) Pretreatment: Immerse the steel cleaned in step (1) in the pretreatment solution, keep it warm in a water bath, immerse it, then take it out, rinse it with clean water until it is neutral, and dry it to obtain the pretreated steel. (5) Phosphating treatment: Add the pretreated steel obtained in step (4) and phosphating solution to the reactor, then adjust the temperature to 78-85℃, vacuum, immerse for 8-10 minutes, then take it out, wash with pure water until neutral, and then blow dry. The volume ratio of the dilute hydrochloric acid and maleic anhydride solution is 2:

1. The concentration of the dilute hydrochloric acid is 1.5 mol / L; The concentration of maleic anhydride is 0.12 mol / L; The modifier is a mixture of hydroxylamine sulfate and nano-silica particles; The mass ratio of hydroxylamine sulfate to nano-silica particles is 3:

1.

2. The steel surface phosphating treatment process according to claim 1, characterized in that, The polishing process described in step (1) involves polishing with 250-grit and 400-grit sandpaper in sequence, with each polishing time being 10 minutes.

3. The steel surface phosphating treatment process according to claim 1, characterized in that, The multiple cleaning steps in step (1) involve sequentially cleaning the steel with water, ethanol, and acetone, with each cleaning session lasting 5-7 minutes.

4. The steel surface phosphating treatment process according to claim 1, characterized in that: The phosphating solution contains the following components: phosphoric acid 9-12 g / L, sodium nitrate 2-3 g / L, modifier 1.2-1.6 g / L, rare earth nitrate 0.09-0.12 g / L, zinc nitrate 3-5 g / L, and sodium fluoride 1.2-1.8 g / L.

5. The steel surface phosphating treatment process according to claim 1, characterized in that, In step (4), the water bath temperature is 80-85℃, and the pretreatment time for immersing the steel in the pretreatment solution is 45-50 minutes.

6. The steel surface phosphating treatment process according to claim 1, characterized in that: In step (5), the mass ratio of the pretreated steel to the phosphating solution is 20:

1.

7. The steel surface phosphating treatment process according to claim 1, characterized in that: The vacuum level in step (5) is 0.05 Pa; Nitrogen gas is used for drying.

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