CN110359036B - Phosphating process for steel pipe - Google Patents
Phosphating process for steel pipe Download PDFInfo
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- CN110359036B CN110359036B CN201910803179.7A CN201910803179A CN110359036B CN 110359036 B CN110359036 B CN 110359036B CN 201910803179 A CN201910803179 A CN 201910803179A CN 110359036 B CN110359036 B CN 110359036B
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
- C23C22/40—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing molybdates, tungstates or vanadates
- C23C22/42—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing molybdates, tungstates or vanadates containing also phosphates
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Abstract
The invention discloses a phosphating process of a steel pipe, which relates to a steel pipe treatment process and comprises the following steps: s1, oil and rust removal treatment; s2, washing with water; s3, phosphating; s4, drying; each liter of phosphating solution comprises the following components in parts by weight: 30-40 parts of phosphoric acid; 20-25 parts of zinc oxide; 0.2-0.3 part of sodium chlorate; 0.2-0.3 part of sodium molybdate; 0.2-0.4 part of sodium m-nitrobenzenesulfonate; 0.5-1.0 part of phosphating auxiliary agent; adjusting the pH value to 2.0-3.5 by ammonia water. The invention has the following advantages: through the combined cooperation of all components in the system, the phosphating process can be carried out at normal temperature, and the phosphating solution does not contain harmful substances such as nitrate, nitrite and heavy metal, and has no pollution to the operating environment and no harm to operators.
Description
Technical Field
The invention relates to a steel pipe treatment process, in particular to a phosphating process of a steel pipe.
Background
Phosphating is a process in which chemical and electrochemical reactions form a phosphate chemical conversion film, referred to as a phosphating film. The purpose of the phosphorization is mainly as follows: the base metal is protected, and the metal is prevented from being corroded to a certain extent; the primer is used for priming before painting, and the adhesive force and the corrosion resistance of a paint film layer are improved.
Chinese patent publication No. CN109013704A discloses a seamless steel tube manufacturing process, which comprises the following steps: a. heating; b. perforating; c. acid pickling treatment: pickling the pipe material by using a pickling solution; d. and (3) phosphating treatment: in the step of carrying out phosphating treatment on the pipe material after the pickling, phosphating treatment is carried out on the pipe material by adopting phosphating solution; e. saponification treatment: saponifying the pipe material by using saponification liquid; f. slowly cooling; g. cold rolling; h. annealing; i. checking operation; j. straightening; k. cutting: and cutting the straightened pipe material into steel pipes with the length meeting the specification. Wherein the pickling solution is a sulfuric acid solution with the mass fraction of 18-22%, the pickling temperature is 40-60 ℃, and the pickling time is 20-40 minutes; the phosphating solution contains zinc dihydrogen phosphate with the concentration of 40g/L and zinc nitrate with the concentration of 55g/L, the phosphating temperature is 50-75 ℃, and the phosphating treatment time is 8-15 minutes; the saponification liquid comprises 80g/L sodium stearate, saponification temperature is 60-75 deg.C, and saponification time is greater than or equal to 5 min.
In the technical scheme, the phosphorization treatment process needs to be carried out under the heating condition of 50-75 ℃, on one hand, the energy consumption is high, on the other hand, the temperature in a processing workshop is high, so that the working environment of workers is severe and needs to be improved.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a steel pipe phosphating process which can be used for phosphating steel pipes at normal temperature.
In order to achieve the purpose, the invention provides the following technical scheme:
a phosphorization process of a steel pipe comprises the following steps,
s1, oil and rust removal treatment;
s2, washing with water;
s3, phosphating;
s4, drying;
each liter of phosphating solution comprises the following components in parts by weight:
adjusting the pH value to 2.0-3.5 by ammonia water.
By adopting the technical scheme, phosphoric acid and zinc oxide are main film forming substances, and before phosphating, three-stage ionization equilibrium reaction of free phosphoric acid and a series of ionization and hydrolysis dynamic equilibrium reaction of zinc oxide with the phosphoric acid exist in phosphating solution. After the steel pipe is immersed in the phosphating solution, the anodic oxidation process of Fe occurs on the surface to generate Fe (H)2PO4)2、Zn(H2PO4)2、Zn3(PO4)2·4H2O and Zn2Fe(PO4)2·4H2And O and other substances, when the phosphating reaction is carried out until the concentrations of the substances reach respective solubility products, the insoluble phosphate forms crystal nuclei on active points on the surface of the steel pipe, and the crystal nuclei are continuously extended and grown to the periphery of the surface to form crystals by taking the crystal nuclei as centers until a continuous and uniform phosphating film is formed on the surface of the steel pipe.
Sodium chlorate has strong aging property, plays a role in accelerating cathode depolarization, and canCan accelerate the film forming speed of phosphorization and obviously improve the corrosion resistance of a phosphorized film. Sodium molybdate is used as an accelerant, has the passivation and purification functions, and can improve the corrosion resistance of the phosphating film.
In the process of phosphorization, the catalyst can play the roles of oxidizing agent, corrosion inhibitor, complexing agent and reducing the weight of the film layer. Because of the fact that
Can form various condensed polyacid ions by the condensation of oxygen polyhedron at the same point or edge, and the basic structural unit is octahedral MoO in the polyacid anion structure of molybdenum6When it is reacted with an orthophosphate salt,
regular tetrahedron is immediately MoO6Octahedral enclosure, i.e. filling of heteroatoms in the centre of the polyacid ion to form a heteropolyacid: phosphomolybdic acid (H)3PO4·12MoO3·30H2O). Coordinated MoO of molybdenum in phosphomolybdic acid3Much more active in the molecule than in free molybdic acid or normal molybdate; in a solution containing an inorganic acid, the phosphate reacts with the aforementioned phosphomolybdic acid to produce a salt of complex phosphomolybdic acid. Phosphomolybdates, in turn, have a strong oxidizing effect on many inorganic and organic compounds. The strong oxidation accelerates the anodic oxidation process of the surface of the steel pipe, and the complex phosphomolybdate ions (heteropoly acid ions) can promote depolarization of the surface of the cathode, have a synergistic effect with sodium chlorate, improve the density of micro-current, and partially seal the surface of the anode, so that the area ratio of the cathode to the anode is increased, and the phosphating speed is greatly accelerated. The heteropoly acid is adsorbed on the surface of the steel pipe or embedded in the micropores of the phosphating film, so that a more compact arrangement is generated, and the quality of the phosphating film is improved.
The sodium m-nitrobenzenesulfonate and sodium chlorate can be used together to promote the growth of crystal nucleus and improve the stability of the phosphating film. The pH value of the system is regulated and controlled by ammonia water to control the free acidity, so that the phenomena of obvious hydrogen evolution, rough phosphating film or weak hydrogen evolution and over-thin phosphating film are avoided. Through the combined cooperation of all components in the system, the phosphating process can be carried out at normal temperature, and the phosphating solution does not contain harmful substances such as nitrate, nitrite and heavy metal, and has no pollution to the operating environment and no harm to operators.
Furthermore, each liter of phosphating solution comprises 25 to 30 parts by weight of zinc dihydrogen phosphate.
By adopting the technical scheme, the zinc dihydrogen phosphate can also play roles in stabilizing the pH value of the solution and adjusting the total acidity while participating in the phosphorization.
Furthermore, each liter of phosphating solution comprises 0.1 to 0.3 portion of sodium fluoride according to the weight portion.
By adopting the technical scheme, the sodium fluoride has double functions of buffering and promoting, and the fluorine ions have great electronegativity and are easily combined with the hydrogen ions in a covalent bond form to generate hydrofluoric acid, so that the hydrogen ions are released when the free acidity of the solution is reduced, the buffering effect is strong, the overvoltage of hydrogen is reduced, the depolarization effect of a cathode is achieved, and the promotion effect on the film forming process is achieved.
Further, citric acid is adopted as the phosphating assistant.
By adopting the technical scheme, in the phosphating process, part of ferrous ions can generate ferric ions under the oxidation action, and further Fe (PO) is generated4)3The sediment affects the phosphorization film forming speed and the film forming quality. The citric acid as the compounding agent can effectively complex ferric ions and reduce sediments. Meanwhile, the weak acidity of the citric acid can also increase active points on the surface of the organism and promote the initial formation of a phosphorization crystal nucleus, so that the effect of refining the film layer is achieved, and the phosphorization film is more compact.
Furthermore, each liter of phosphating solution comprises 0.1 to 0.2 portion of 1-octyl mercaptan by weight portion.
By adopting the technical scheme, the 1-octyl mercaptan has good wettability and adsorptivity, the film forming uniformity is improved, and the thickness and the corrosion resistance of a phosphating film can be effectively improved. In addition, the 1-octanethiol can also cooperate with citric acid to reduce sediments so as to further improve the quality of the phosphating film.
Furthermore, each liter of phosphating solution comprises 100.3 to 0.5 portion of emulsifier OP-100 by weight.
By adopting the technical scheme, the OP-10 can be directionally arranged and adsorbed on the interface between the phosphating solution and the metal, the surface tension of the steel pipe is reduced, and the wettability of the phosphating solution on the surface of the steel pipe is improved, so that the pretreatment requirement is reduced, and the film forming is accelerated. Meanwhile, the method can inhibit the separation of hydrogen, slow down the reduction of the total acidity of the phosphating solution and play a role in stabilizing the phosphating solution. In addition, OP-10 can also improve the cathode polarization, which is beneficial to obtaining a fine-crystal phosphating film so as to improve the compactness of the phosphating film. In addition, under the action of 1-octanethiol, the addition amount of OP-10 can be effectively reduced.
Furthermore, each liter of phosphating solution comprises 0.1 to 0.2 portion of hydroxylamine sulfate according to the weight portion.
By adopting the technical scheme, the hydroxylamine sulfate can reduce iron ions generated by oxidation into ferrous ions, and is beneficial to P film Zn2Fe(PO4)2·4H2A phosphate film having a high O content is formed to improve the quality of the phosphate film. Meanwhile, the hydroxylamine sulfate can also reduce the electrode potential of Fe through coordination adsorption, so that Fe has a greater dissolving tendency, and the forming speed of the phosphating film is accelerated.
In conclusion, the invention has the following beneficial effects:
1. phosphoric acid and zinc oxide are main film forming substances, and before phosphating, three-stage ionization equilibrium reaction of free phosphoric acid and a series of ionization and hydrolysis dynamic equilibrium reaction of zinc oxide with the phosphate exist in phosphating solution. After the steel pipe is immersed in the phosphating solution, the anodic oxidation process of Fe occurs on the surface to generate Fe (H)2PO4)2、Zn(H2PO4)2、Zn3(PO4)2·4H2O and Zn2Fe(PO4)2·4H2O and the like, and when the phosphating reaction is carried out until the concentrations of the substances reach respective solubility products, the insoluble phosphate forms crystal nuclei on active points on the surface of the steel pipe and takes the crystal nuclei as the centerContinuously extending and growing to the periphery of the surface to form crystals until a continuous and uniform phosphating film is formed on the surface of the steel pipe.
2. The sodium chlorate has stronger aging property, plays a role in accelerating the depolarization of the cathode, can accelerate the film forming rate of the phosphating and obviously improves the corrosion resistance of the phosphating film. The sodium m-nitrobenzenesulfonate and sodium chlorate can be used together to promote the growth of crystal nucleus and improve the stability of the phosphating film. The pH value of the system is regulated and controlled by ammonia water to control the free acidity, so that the phenomena of obvious hydrogen evolution, rough phosphating film or weak hydrogen evolution and over-thin phosphating film are avoided. Through the combined cooperation of all components in the system, the phosphating process can be carried out at normal temperature, and the phosphating solution does not contain harmful substances such as nitrate, nitrite and heavy metal, and has no pollution to the operating environment and no harm to operators.
3. The sodium fluoride has double functions of buffering and promoting, and the fluorine ions have great electronegativity and are easily combined with the hydrogen ions in a covalent bond form to generate hydrofluoric acid, so that the hydrogen ions are released when the free acidity of the solution is reduced, the sodium fluoride has a strong buffering effect, and meanwhile, the overvoltage of hydrogen is reduced, the cathode depolarization effect is realized, and the film forming process is promoted.
The 4.1-octanethiol has good wettability and adsorptivity, and can effectively improve the thickness and corrosion resistance of a phosphating film while improving the uniformity of the formed film. In addition, the 1-octanethiol can also cooperate with citric acid to reduce sediments so as to further improve the quality of the phosphating film.
OP-10 can be directionally arranged and adsorbed on the interface between the phosphating solution and the metal, so that the surface tension of the steel pipe is reduced, and the wettability of the phosphating solution on the surface of the steel pipe is improved, thereby reducing the requirements of pretreatment and accelerating film formation. Meanwhile, the method can inhibit the separation of hydrogen, slow down the reduction of the total acidity of the phosphating solution and play a role in stabilizing the phosphating solution. In addition, OP-10 can also improve the cathode polarization, which is beneficial to obtaining a fine-crystal phosphating film so as to improve the compactness of the phosphating film. In addition, under the action of 1-octanethiol, the addition amount of OP-10 can be effectively reduced.
6. Hydroxylamine sulfate can reduce iron ions generated by oxidation into ferrous ions, and is beneficial to the P film Zn2Fe(PO4)2·4H2A phosphate film having a high O content is formed to improve the quality of the phosphate film. Meanwhile, the hydroxylamine sulfate can also reduce the electrode potential of Fe through coordination adsorption, so that Fe has a greater dissolving tendency, and the forming speed of the phosphating film is accelerated.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following drawings and examples.
Examples
Example 1
A phosphating process of a steel pipe, as shown in figure 1, comprises the following steps:
s1, oil and rust removal treatment;
s2, washing with water;
s3, phosphating;
s4, drying;
the components of each liter of phosphating solution are shown in the table 1 in parts by weight, and the pH is adjusted to 2.0 by adopting ammonia water.
Wherein the phosphating assistant adopts citric acid.
Example 2
The difference from example 1 is that the components of each liter of phosphating solution are shown in table 1 in parts by weight, and the pH is adjusted to 3.0 with ammonia water.
Example 3
The difference from example 1 is that the components of phosphating solution per liter are shown in table 1 in parts by weight, and the pH is adjusted to 3.5 with ammonia.
Example 4
The difference from the example 2 is that the components of the phosphating solution are shown in the following table 1 in parts by weight.
Example 5
The difference from the example 2 is that the components of the phosphating solution are shown in the following table 1 in parts by weight.
Example 6
The difference from the example 2 is that the components of the phosphating solution are shown in the following table 1 in parts by weight.
Wherein the emulsifier OP-10 is replaced by sodium dodecyl sulfate.
Example 7
The difference from the example 2 is that the components of the phosphating solution are shown in the following table 1 in parts by weight.
Example 8
The difference from the example 2 is that the components of the phosphating solution are shown in the following table 1 in parts by weight.
Wherein, tartaric acid is adopted as the phosphating auxiliary agent.
Comparative example
Comparative example 1
The difference from the example 2 is that the components of the phosphating solution are shown in the following table 1 in parts by weight.
Comparative example 2
The difference from the example 2 is that the components of the phosphating solution are shown in the following table 1 in parts by weight.
Performance test
And (3) corrosion resistance test: the samples were subjected to corrosion resistance tests by the dropping method described in appendix D of GB 6807-86 phosphating treatment technical Condition before painting of Steel works, the formulation of the test solution was 41g/L anhydrous copper sulfate, 35g/L sodium chloride and 13ml/L hydrochloric acid (0.1N), a drop of the test solution was dropped on the phosphating surface at 15-25 deg.C while a stopwatch was started, the time for which the drop turned pale yellow or reddish from sky blue was observed, and the time was recorded as shown in Table 2.
And (3) appearance inspection: according to an appearance inspection method in GB 6807-86 technical conditions for phosphating treatment before painting of steel workpieces, appearance observation is carried out on a sample, and the observation result is shown in Table 2.
TABLE 1 (phosphating solution prescription table)
TABLE 1 continuation
Table 2 (test table)
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.
Claims (5)
1. A phosphating process of a steel pipe is characterized by comprising the following steps: comprises the following steps of (a) carrying out,
s1, oil and rust removal treatment;
s2, washing with water;
s3, phosphating;
s4, drying;
each liter of phosphating solution comprises the following components in parts by weight:
30-40 parts of phosphoric acid;
20-25 parts of zinc oxide;
0.2-0.3 part of sodium chlorate;
0.2-0.3 part of sodium molybdate;
0.2-0.4 part of sodium m-nitrobenzenesulfonate;
0.5-1.0 part of phosphating auxiliary agent;
0.1-0.2 part of 1-octyl mercaptan;
emulsifier OP-100.3-0.5 part;
adjusting the pH value to 2.0-3.5 by ammonia water.
2. A process for phosphating a steel tube according to claim 1, characterized in that: each liter of phosphating solution comprises 25 to 30 portions of zinc dihydrogen phosphate according to the parts by weight.
3. A process for phosphating a steel tube according to claim 1, characterized in that: each liter of phosphating solution comprises 0.1 to 0.3 portion of sodium fluoride according to the weight portion.
4. A process for phosphating a steel tube according to claim 1, characterized in that: the phosphating assistant adopts citric acid.
5. A process for phosphating a steel tube according to claim 1, characterized in that: each liter of phosphating solution comprises 0.1 to 0.2 portion of hydroxylamine sulfate according to the weight portion.
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Denomination of invention: A phosphating process for steel pipes Effective date of registration: 20220523 Granted publication date: 20210730 Pledgee: China Minsheng Banking Corp Wenzhou branch Pledgor: Zhejiang Fengye Group Co.,Ltd. Registration number: Y2022980006078 |