A galvanizing method for building scaffold steel pipes and its application

Abstract

The application discloses a kind of building scaffold steel pipe galvanizing method, comprising the following steps: S1: pretreatment;The steel pipe to be plated is pretreated;S2: auxiliary plating;After pretreatment, the steel pipe is immersed in auxiliary plating agent;S3: hot dip galvanizing;After the steel pipe after auxiliary plating is dried, it is immersed in zinc liquid;S4: cooling;After the steel pipe after galvanizing is cooled;S5: passivation;After the steel pipe after cooling is immersed in passivation liquid, it is dried.The galvanized steel pipe of the application has excellent salt fog resistance, weather resistance and moisture resistance, and the building scaffold steel pipe galvanized steel pipe of the application can replace traditional chromium-containing galvanized steel pipe, is environmentally friendly and harmless, has considerable industrial value and social value.

Description

TECHNICAL FIELD

[0001] The application relates to a galvanizing process technical field, and belongs to the technical field of C23C2 / 06, in particular to a building scaffold steel pipe galvanizing method and application thereof. BACKGROUND

[0002] Since steel is easy to rust in air, water or soil, even completely damaged, the annual loss of steel caused by corrosion accounts for about 1 / 10 of the entire steel production, so it is necessary to adopt the method of coating and plating protective layer to protect steel from corrosion, and hot-dip galvanizing is one of the methods. Galvanizing is an effective method to improve the atmospheric corrosion resistance of steel, but in a humid environment, the galvanized layer is easy to corrode, and white loose corrosive substances are formed on the surface or the color becomes dull, which seriously affects the performance of the galvanized part. Therefore, the galvanized layer needs to be passivated to cover a protective film on the surface of the zinc layer.

[0003] The hot-dip galvanizing process generally includes the following steps: pickling, cleaning, plating aid, hot-dip galvanizing, cooling and passivation. Among them, the traditional passivation is to use hexavalent chromium chromate for passivation treatment, but the problem of poor salt mist corrosion resistance and poor weather resistance will occur.

[0004] Patent CN113088853A discloses a hot-dip galvanizing process for high-strength fasteners, which improves the corrosion resistance of the passivation film and increases the wear resistance, but the weather resistance still needs to be strengthened. SUMMARY

[0005] In order to solve the above problems, the first aspect of the application provides a building scaffold steel pipe galvanizing method, which comprises the following steps:

[0006] S1: pretreatment; oil removal and rust removal are performed on the steel pipe to be plated to obtain a pretreated steel pipe;

[0007] S2: plating aid; the pretreated steel pipe is immersed in a plating aid;

[0008] S3: hot-dip galvanizing; the steel pipe after the plating aid is dried at 100-120 DEG C and then immersed in a zinc liquid with a temperature of 430-460 DEG C.

[0009] S4: cooling; the galvanized steel pipe is cooled to 25-28 DEG C;

[0010] S5: passivation; the cooled steel pipe is immersed in a passivation liquid, washed with water and naturally dried.

[0011] Preferably, the plating aid in the step S2 is a mixture of a chloride salt and a citrate salt.

[0012] Further preferably, the citrate salt is sodium citrate.

[0013] Preferably, the plating auxiliary agent comprises, by mass concentration, 10-15 g / L of aluminum chloride, 5-10 g / L of potassium chloride, 15-25 g / L of ammonium chloride, and 3-7 g / L of citrate.

[0014] Further preferably, the plating auxiliary agent, measured by mass concentration, includes 10-15 g / L of aluminum chloride, 7-9 g / L of potassium chloride, 20-25 g / L of ammonium chloride, and 5-7 g / L of citrate.

[0015] Further preferably, the plating auxiliary agent, calculated by mass concentration, includes 12 g / L of aluminum chloride, 8 g / L of potassium chloride, 23 g / L of ammonium chloride, and 6 g / L of citrate.

[0016] Further preferably, the specific steps of the preparation method of the plating flux are as follows: aluminum chloride, potassium chloride, ammonium chloride and citrate are added into a stirring tank according to mass concentration, and stirred for 2-5 minutes to obtain the flux.

[0017] Preferably, the passivation solution in step S5 comprises, by weight, 5-15 parts of film-forming aid, 5-10 parts of inorganic salt, 5-10 parts of corrosion inhibitor, 1-10 parts of nano-oxide, 0.1-2 parts of complexing agent, 2-12 parts of surfactant, and the balance is water.

[0018] Further preferably, the passivation solution in step S5 comprises, by weight, 5-10 parts of film-forming aid, 5-8 parts of inorganic salt, 5-10 parts of corrosion inhibitor, 1-5 parts of nano-oxide, 0.1-1 parts of complexing agent, 2-10 parts of surfactant, and the balance is water.

[0019] Further preferably, the passivation solution in step S5 comprises, by weight, 8 parts of film-forming aid, 7 parts of inorganic salt, 6 parts of corrosion inhibitor, 3 parts of nano-oxide, 0.4 parts of complexing agent, 8 parts of surfactant, and the balance is water.

[0020] Further preferably, the complexing agent includes at least one of hydroxyethylidene diphosphonic acid, nitrilotriacetic acid, aminotrimethylene phosphoric acid, hydroxyacetic acid, methylene diphosphonic acid, ethylenediaminetetramethylene phosphoric acid, ethylenediaminetetraacetic acid, and tartaric acid.

[0021] Further preferably, the complexing agent is a mixture of ethylenediaminetetraacetic acid and tartaric acid, with a mass ratio of 1:2.

[0022] Preferably, the weight ratio of the film-forming aid, the inorganic salt and the corrosion inhibitor is (5-10): (5-8): (5-10).

[0023] More preferably, the weight ratio of the film-forming aid, the inorganic salt and the corrosion inhibitor is (7-9): (6-8): (5-8).

[0024] The applicant has found that when the weight ratio of phytic acid, molybdate, and 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole is (7-9):(6-8):(5-8), the salt spray corrosion resistance of the passivation film is improved. It is speculated that: the phytic acid forms a phytic acid passivation film on the surface of the substrate. When 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole is added, the phytic acid passivation film becomes denser and more uniform. After that, molybdate is added, and the molybdate ions and chloride ions in the molybdate compete for adsorption at the surface defects of the passivation film, thereby enhancing the pitting corrosion resistance of the passivation film and further improving the salt spray resistance of the passivation film. At the same time, under the combined action of nano-silica, the complexing agent tartaric acid and EDTA, not only the salt spray resistance of the passivation film is guaranteed, but also its weather resistance and moisture and heat resistance are improved.

[0025] More preferably, the weight ratio of the film-forming aid, the inorganic salt and the corrosion inhibitor is 8:7:6.

[0026] Further preferably, the film-forming aid includes at least one of phytic acid, phosphoric acid, potassium dihydrogen phosphate, lactic acid and oxalic acid, the inorganic salt includes at least one of molybdate, silicate, titanate, zirconium salt and nitrate, and the corrosion inhibitor includes at least one of triethanolamine borate, polyethylene glycol borate, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole and diethanolamine.

[0027] More preferably, the film-forming aid is phytic acid, the inorganic salt is molybdate, the molybdate is sodium molybdate, and the corrosion inhibitor is 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole.

[0028] Preferably, the nano-oxide is nano-silicon dioxide, and the average particle size of the nano-silicon dioxide is 10-50 nm.

[0029] More preferably, the average particle size of the nano-silicon dioxide is 10-30 nm.

[0030] More preferably, the average particle size of the nano-silica is 20 nm.

[0031] Preferably, the surfactant is a quaternary ammonium salt cationic surfactant.

[0032] Further preferably, the quaternary ammonium salt cationic surfactant is propylene [(octaamidopropyl dimethyl / octadecamidopropyl dimethyl) chloride / ammonium bromide].

[0033] The applicant found that when the quaternary ammonium cationic surfactant is a propane group [(octaamidopropyl dimethyl / octadecanoylpropyl dimethyl) chloride / ammonium bromide], the weather resistance of the passivation film is further improved. The applicant speculates that since the propane group [(octaamidopropyl dimethyl / octadecanoylpropyl dimethyl) chloride / ammonium bromide] is a diquaternary ammonium salt, it undergoes chelate adsorption with the iron matrix, resulting in a close arrangement between the adsorbed molecules, preventing oxygen molecules from diffusing into the steel matrix, thereby further improving the weather resistance of the passivation film.

[0034] Preferably, the auxiliary plating temperature in step S2 is 60-80° C., and the auxiliary plating time is 5-8 minutes.

[0035] More preferably, the auxiliary plating temperature in step S2 is 60-70° C., and the auxiliary plating time is 5-7 minutes.

[0036] More preferably, the auxiliary plating temperature in step S2 is 65° C., and the auxiliary plating time is 6 minutes.

[0037] Preferably, the passivation time in step S5 is 0.5-2 min, and the passivation temperature is 22-32°C.

[0038] More preferably, the passivation time in step S5 is 0.5-1.5 min, and the passivation temperature is 22-28°C.

[0039] Further preferably, the passivation time in step S5 is 1 min and the passivation temperature is 25°C.

[0040] The present invention also includes a method for preparing the passivation solution, which comprises the following steps:

[0041] The film-forming aid, inorganic salt, corrosion inhibitor, nano-oxide, complexing agent and surfactant are mixed and stirred according to parts by weight to obtain the product.

[0042] The applicant has found that when the weight ratio of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, molybdate, and phytic acid is (7-9):(6-8):(5-8), the salt spray corrosion resistance of the passivation film is improved. It is speculated that: the phytic acid forms a phytic acid passivation film on the surface of the substrate. When 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole is added, the phytic acid passivation film becomes denser and more uniform. After that, molybdate is added, and the molybdate ions and chloride ions in the molybdate compete for adsorption at the surface defects of the passivation film, thereby enhancing the pitting corrosion resistance of the passivation film and further improving the salt spray resistance of the passivation film. At the same time, under the combined action of nano-silica, the complexing agent tartaric acid and EDTA, not only the salt spray resistance of the passivation film is guaranteed, but also its weather resistance and moisture and heat resistance are improved.

[0043] The second aspect of the application provides a building scaffold steel pipe galvanizing method for the building scaffold steel pipe.

[0044] Beneficial effects:

[0045] The application improves the corrosion resistance of the passivation film by optimizing the weight ratio of 2-(2'-hydroxy-5'-tert-octylphenyl) benzotriazole, molybdate and phytic acid. Under the joint action of nano-silicon dioxide, complexing agent tartaric acid and EDTA, not only the salt spray resistance of the passivation film is ensured, but also the weather resistance and moisture resistance are improved. In addition, propylene [(octylamide propyl dimethyl / amido octadecyl propyl dimethyl) chloride / bromide] is selected as a quaternary ammonium salt cationic surfactant, which further improves the weather resistance of the passivation film. The building scaffold steel pipe galvanizing steel pipe of the application can replace the traditional chromium-containing galvanized steel pipe, is environmentally friendly and harmless, and has considerable industrial value and social value. Embodiment

[0046] Example 1

[0047] A building scaffold steel pipe galvanizing method, comprising the following steps:

[0048] S1: pretreatment; the steel pipe to be plated is subjected to oil removal and rust removal to obtain a pretreated steel pipe;

[0049] S2: plating aid; the pretreated steel pipe is immersed in a plating aid at 65 DEG C for 6 min;

[0050] S3: hot dip galvanizing; the steel pipe after plating aid is dried at 110 DEG C for 10 min and then immersed in a zinc liquid at a temperature of 450 DEG C for 5 min.

[0051] S4: cooling; the galvanized steel pipe is cooled to 26 DEG C;

[0052] S5: passivation; the cooled steel pipe is immersed in a passivation liquid, the passivation temperature is 25 DEG C, the passivation time is 1 min, and the steel pipe is naturally dried after being washed with water for three times.

[0053] The plating aid comprises aluminum chloride 12 g / L, potassium chloride 8 g / L, ammonium chloride 23 g / L and sodium citrate 6 g / L in terms of mass concentration.

[0054] The preparation method of the plating aid comprises the following specific steps: aluminum chloride, potassium chloride, ammonium chloride and citrate are added to a stirred tank containing 1 L of water in terms of mass concentration, and the plating aid is obtained after being stirred for 4 min.

[0055] The passivation liquid in the step S5 comprises the following raw materials in terms of weight parts: film forming aid 8 parts, inorganic salt 7 parts, corrosion inhibitor 6 parts, nano-oxide 3 parts, complexing agent 0.4 parts, surfactant 8 parts, and the balance is water.

[0056] The film forming aid is phytic acid.

[0057] The inorganic salt is sodium molybdate.

[0058] The corrosion inhibitor is 2-(2'-hydroxy-5'-tert-octylphenyl) benzotriazole.

[0059] The weight ratio of the three of the film forming aid, the inorganic salt and the corrosion inhibitor is 8:7:6.

[0060] The nano-oxide is nano-silicon dioxide, the average particle size of the nano-silicon dioxide is 20 nm, and the nano-silicon dioxide is purchased from Tianxing New Material, and the model is TSP-H10.

[0061] The complexing agent is a mixture of ethylenediaminetetraacetic acid and tartaric acid, and the mass ratio of the two is 1:2.

[0062] The surfactant is propylene [(octylamide propyl dimethyl / octadecylamide propyl dimethyl) chloride / bromide ammonium], and is purchased from Zhengzhou Yihe Fine Chemical Co., Ltd.

[0063] The application also comprises a preparation method of the passivation solution, and the specific steps are as follows:

[0064] The film forming aid, the inorganic salt, the corrosion inhibitor, the nano-oxide, the complexing agent and the surfactant are mixed and stirred for 20 min according to weight parts, and then the passivation solution is obtained.

[0065] Example 2

[0066] A building scaffold steel pipe galvanizing method, comprising the following steps:

[0067] S1: pretreatment; the steel pipe to be plated is subjected to oil removal and rust removal to obtain a pretreated steel pipe;

[0068] S2: plating aid; the pretreated steel pipe is immersed in a plating aid at 65 DEG C for 6 min;

[0069] S3: hot dip galvanizing; the steel pipe after plating aid is dried at 110 DEG C for 10 min, and then immersed in a zinc liquid at a temperature of 450 DEG C for 5 min.

[0070] S4: cooling; the galvanized steel pipe is cooled to 26 DEG C;

[0071] S5: passivation; the cooled steel pipe is immersed in a passivation solution, the passivation temperature is 25 DEG C, the passivation time is 1 min, and the steel pipe is naturally dried after being washed with water for three times.

[0072] The plating aid comprises aluminum chloride 12 g / L, potassium chloride 8 g / L, ammonium chloride 23 g / L and sodium citrate 6 g / L in terms of mass concentration.

[0073] The preparation method of the plating aid agent comprises the following specific steps: aluminum chloride, potassium chloride, ammonium chloride and citrate are added into a stirred tank containing 1L of water according to mass concentration, and the plating aid agent is obtained after stirring for 4 minutes.

[0074] The passivation liquid in the step S5 comprises the following raw materials in parts by weight: 7 parts of film forming aid, 6 parts of inorganic salt, 5 parts of corrosion inhibitor, 3 parts of nano oxide, 0.4 parts of complexing agent, 8 parts of surfactant, and the rest is water.

[0075] The film forming aid is phytic acid.

[0076] The inorganic salt is sodium molybdate.

[0077] The corrosion inhibitor is 2-(2'-hydroxy-5'-tert-octyl phenyl) benzotriazole.

[0078] The weight ratio of the film forming aid, the inorganic salt and the corrosion inhibitor is 7:6:5.

[0079] The nano oxide is nano silicon dioxide, the average particle size of the nano silicon dioxide is 20nm, and the nano silicon dioxide is purchased from Tianxing New Material and the model is TSP-H10.

[0080] The complexing agent is a mixture of ethylenediaminetetraacetic acid and tartaric acid, and the mass ratio of the two is 1:2.

[0081] The surfactant is propylene [(octylamide propyl dimethyl / octadecylamide propyl dimethyl) chloride / bromide ammonium], which is purchased from Zhengzhou Yihe Fine Chemical Co., Ltd.

[0082] The application further comprises a preparation method of the passivation liquid, and the specific steps are as follows:

[0083] The film forming aid, the inorganic salt, the corrosion inhibitor, the nano oxide, the complexing agent and the surfactant are mixed and stirred for 20 minutes to obtain the passivation liquid.

[0084] Example 3

[0085] A building scaffold steel pipe galvanizing method comprises the following steps:

[0086] S1: pretreatment; the steel pipe to be plated is subjected to oil removal and rust removal to obtain a pretreated steel pipe;

[0087] S2: plating aid; the pretreated steel pipe is immersed in a plating aid agent at 65 DEG C for 6 minutes;

[0088] S3: hot dip galvanizing; the steel pipe after plating aid is dried at 110 DEG C for 10 minutes and then immersed in zinc liquid at a temperature of 450 DEG C for 5 minutes.

[0089] S4: cooling; the galvanized steel pipe is cooled to 26 DEG C.

[0090] S5: passivation; the cooled steel pipe is immersed into a passivation solution, the passivation temperature is 25 DEG C, the passivation time is 1 min, and the steel pipe is naturally dried after being washed with water for three times.

[0091] The plating aid includes aluminum chloride 12 g / L, potassium chloride 8 g / L, ammonium chloride 23 g / L and sodium citrate 6 g / L in terms of mass concentration.

[0092] The preparation method of the plating aid comprises the following specific steps: aluminum chloride, potassium chloride, ammonium chloride and citrate are added into a stirred tank containing 1 L of water in terms of mass concentration, and the plating aid is obtained after being stirred for 4 min.

[0093] The passivation solution in the step S5 comprises the following raw materials in terms of weight parts: film forming aid 8 parts, inorganic salt 7 parts, corrosion inhibitor 6 parts, nano oxide 10 parts, complexing agent 0.4 parts, surfactant 5 parts, and the balance is water.

[0094] The film forming aid is phytic acid.

[0095] The inorganic salt is sodium molybdate.

[0096] The corrosion inhibitor is 2-(2'-hydroxy-5'-tert-octylphenyl) benzotriazole.

[0097] The weight ratio of the film forming aid, the inorganic salt and the corrosion inhibitor is 8:7:6.

[0098] The nano oxide is nano silicon dioxide, the average particle size of the nano silicon dioxide is 20 nm, and the nano silicon dioxide is purchased from Tianxing New Material and the model is TSP-H10.

[0099] The complexing agent is a mixture of ethylenediaminetetraacetic acid and tartaric acid, and the mass ratio of the two is 1:2.

[0100] The surfactant is propylene [(octylamide propyl dimethyl / octadecylamide propyl dimethyl) chloride / bromide ammonium], which is purchased from Zhengzhou Yihe Fine Chemical Co., Ltd.

[0101] The application further comprises a preparation method of the passivation solution, and the specific steps are as follows:

[0102] The film forming aid, the inorganic salt, the corrosion inhibitor, the nano oxide, the complexing agent and the surfactant are mixed and stirred for 20 min in terms of weight parts, and then the passivation solution is obtained.

[0103] Comparative Example 1

[0104] A building scaffold steel pipe galvanizing method comprises the following steps:

[0105] S1: pretreatment; the steel pipe to be plated is subjected to oil removal and rust removal to obtain a pretreated steel pipe;

[0106] S2: assistant plating; the pretreated steel pipe is immersed in an assistant plating agent at 65 DEG C for 6 min;

[0107] S3: hot dip galvanizing; the steel pipe after assistant plating is dried at 110 DEG C for 10 min and then immersed in a zinc liquid at 450 DEG C for 5 min.

[0108] S4: cooling; the galvanized steel pipe is cooled to 26 DEG C;

[0109] S5: passivation; the cooled steel pipe is immersed in a passivation liquid, the passivation temperature is 25 DEG C, the passivation time is 1 min, and the steel pipe is washed with water for three times and then naturally dried.

[0110] The assistant plating agent comprises aluminum chloride 12 g / L, potassium chloride 8 g / L, ammonium chloride 23 g / L and sodium citrate 6 g / L in terms of mass concentration.

[0111] The preparation method of the assistant plating agent comprises the following specific steps: aluminum chloride, potassium chloride, ammonium chloride and citrate are added into a stirred tank containing 1 L of water in terms of mass concentration, and the assistant plating agent is obtained after stirring for 4 min.

[0112] The passivation liquid in the step S5 comprises the following raw materials in terms of weight parts: film forming aid 4 parts, inorganic salt 7 parts, corrosion inhibitor 11 parts, nano oxide 3 parts, complexing agent 0.4 parts, surfactant 8 parts, and the rest is water.

[0113] The film forming aid is phytic acid.

[0114] The inorganic salt is sodium molybdate.

[0115] The corrosion inhibitor is 2-(2'-hydroxy-5'-tert-octyl phenyl) benzotriazole.

[0116] The weight ratio of the film forming aid, the inorganic salt and the corrosion inhibitor is 4:7:11.

[0117] The nano oxide is nano silicon dioxide, the average particle size of the nano silicon dioxide is 20 nm, and the nano silicon dioxide is purchased from Tianxing New Material and the model is TSP-H10.

[0118] The complexing agent is a mixture of ethylenediaminetetraacetic acid and tartaric acid, and the mass ratio of the two is 1:2.

[0119] The surfactant is propylene [(octylamide propyl dimethyl / ammonium chloride / bromide)] and is purchased from Zhengzhou Yihe Fine Chemicals Co., Ltd.

[0120] The application further comprises a preparation method of the passivation liquid, and the specific steps are as follows:

[0121] The film forming aid, inorganic salt, corrosion inhibitor, nano-oxide, complexing agent and surfactant are mixed and stirred for 20 minutes by weight parts, and then the film forming aid is obtained.

[0122] Comparative Example 2

[0123] A galvanizing method for building scaffold steel pipes, comprising the following steps:

[0124] S1: pretreatment; the steel pipe to be plated is subjected to oil removal and rust removal to obtain a pretreated steel pipe;

[0125] S2: plating aid; the pretreated steel pipe is immersed in a plating aid at 65°C for 6 minutes;

[0126] S3: hot dip galvanizing; the steel pipe after plating aid is dried at 110°C for 10 minutes and then immersed in a zinc liquid at a temperature of 450°C for 5 minutes.

[0127] S4: cooling; the galvanized steel pipe is cooled to 26°C;

[0128] S5: passivation; the cooled steel pipe is immersed in a passivation liquid, the passivation temperature is 25°C, the passivation time is 1 minute, and the steel pipe is naturally air-dried after being washed with water three times.

[0129] The plating aid comprises aluminum chloride 12g / L, potassium chloride 8g / L, ammonium chloride 23g / L, and sodium citrate 6g / L in terms of mass concentration.

[0130] The preparation method of the plating aid comprises the following specific steps: aluminum chloride, potassium chloride, ammonium chloride, and citrate are added to a stirred tank containing 1L of water in terms of mass concentration, and the plating aid is obtained after being stirred for 4 minutes.

[0131] The passivation liquid in step S5 comprises the following raw materials in terms of weight parts: film forming aid 8 parts, inorganic salt 7 parts, corrosion inhibitor 6 parts, nano-oxide 3 parts, complexing agent 0.4 parts, surfactant 15 parts, and the balance is water.

[0132] The film forming aid is phytic acid.

[0133] The inorganic salt is sodium molybdate.

[0134] The corrosion inhibitor is 2-(2'-hydroxy-5'-tert-octylphenyl) benzotriazole.

[0135] The weight ratio of the film forming aid, inorganic salt, and corrosion inhibitor is 8:7:6.

[0136] The nano-oxide is nano-silicon dioxide, the average particle size of the nano-silicon dioxide is 20nm, and the nano-silicon dioxide is purchased from Tianxing New Material, model TSP-H10.

[0137] The complexing agent is a mixture of ethylenediaminetetraacetic acid and tartaric acid, and the mass ratio of the two is 1:2.

[0138] The surfactant is sodium dodecyl benzene sulfonate.

[0139] The application also includes a preparation method of the passivation solution, and the specific steps are as follows:

[0140] The film-forming aid, inorganic salt, corrosion inhibitor, nano oxide, complexing agent and surfactant are mixed and stirred for 20 min according to the weight parts, and then the passivation solution is obtained.

[0141] Comparative Example 3

[0142] A galvanizing method for a building scaffold steel pipe, comprising the following steps:

[0143] S1: pretreatment; the steel pipe to be plated is subjected to oil removal and rust removal to obtain a pretreated steel pipe;

[0144] S2: plating aid; the pretreated steel pipe is immersed in a plating aid at 65 DEG C for 6 min;

[0145] S3: hot dip galvanizing; the steel pipe after the plating aid is dried at 110 DEG C for 10 min and then immersed in a zinc liquid at a temperature of 450 DEG C for 5 min.

[0146] S4: cooling; the galvanized steel pipe is cooled to 26 DEG C;

[0147] S5: passivation; the cooled steel pipe is immersed in a passivation solution, the passivation temperature is 25 DEG C, the passivation time is 1 min, and the steel pipe is naturally dried after being washed with water for three times.

[0148] The plating aid comprises, by mass concentration, 12 g / L of aluminum chloride, 8 g / L of potassium chloride, 23 g / L of ammonium chloride and 6 g / L of sodium citrate.

[0149] The preparation method of the plating aid comprises the following specific steps: aluminum chloride, potassium chloride, ammonium chloride and citrate are added into a stirred tank containing 1 L of water according to the mass concentration, and the plating aid is obtained after being stirred for 4 min.

[0150] The passivation solution in the step S5 comprises, by weight, film-forming aid 8 parts, inorganic salt 7 parts, corrosion inhibitor 6 parts, nano oxide 13 parts, complexing agent 0.4 parts, surfactant 8 parts, and the rest is water.

[0151] The film-forming aid is phytic acid.

[0152] The inorganic salt is sodium molybdate.

[0153] The corrosion inhibitor is 2-(2'-hydroxy-5'-tert-octylphenyl) benzotriazole.

[0154] The weight ratio of the film forming aid, the inorganic salt and the corrosion inhibitor is 8:7:6.

[0155] The nano-oxide is nano-silica, the average particle size of the nano-silica is 20 nm, and the nano-silica is purchased from Tianxing New Material, and the model is TSP-H10.

[0156] The complexing agent is a mixture of ethylenediaminetetraacetic acid and tartaric acid, and the mass ratio of the two is 1:1.

[0157] The surfactant is propylene [(octylamide propyl dimethyl / octadecylamide propyl dimethyl) chloride / bromide ammonium], which is purchased from Zhengzhou Yihe Fine Chemical Co., Ltd.

[0158] The application also includes a preparation method of the passivation solution, and the specific steps are as follows:

[0159] The film forming aid, the inorganic salt, the corrosion inhibitor, the nano-oxide, the complexing agent and the surfactant are mixed and stirred for 20 min according to weight parts, and then the passivation solution is obtained.

[0160] Performance Evaluation

[0161] (1) Corrosion resistance: The corrosion resistance test of the galvanized steel pipe adopts neutral salt spray accelerated corrosion test, adopts JH-60 type salt spray corrosion test box, and is executed according to GB / T10125-2012 'Artificial atmosphere corrosion test salt spray test'

[0162] ; test medium: chemical pure NaCl deionized water solution, medium concentration 50g / l, pH value 6.5;

[0163] Test temperature: 35±2℃; salt spray deposition amount: 1-2ml / h·80cm2; test sample placement: the experimental surface is at an angle of 30° to the vertical direction; test period: 24h as a period, continuous spraying in each period, and continuous observation for 3 periods. The test sample is checked once before the end of each period, and the checking time is not more than 30min, and the change of the corrosion area of the test sample with time is observed and recorded.

[0164] (2) Weather resistance: the passivated galvanized steel pipe is placed in the outdoor natural environment, the appearance is observed every 2 months, and the observation is continuously carried out for 6 months. According to the following standards, the surface is bright, no white rust, no black spot, and then it is qualified, and if slight white rust or slight black spot is generated or obvious white rust or obvious black spot is generated, it is unqualified.

[0165] Table 1

[0166] Test Item Corrosion Resistance (h) Weather Resistance (month) Example 1 72 6 Example 2 72 6 Example 3 72 6 Comparative Example 1 48 4 Comparative Example 2 24 2 Comparative Example 3 48 6

Claims

1. A method for galvanizing a steel pipe for a building scaffold, characterized in that: The following steps are involved: S1: Pretreatment: pre-treat the steel pipe to be plated; S2: Plating flux: immerse the pretreated steel pipe in the plating flux; S3: Hot dip galvanizing: drying the galvanized steel pipe and then immersing it in zinc solution; S4: Cooling: Cooling the galvanized steel pipe; S5: Passivation: immerse the cooled steel pipe in the passivation solution and dry it; The passivation solution in step S5 comprises, by weight, 5-15 parts of a film-forming aid, 5-10 parts of an inorganic salt, 5-10 parts of a corrosion inhibitor, 1-10 parts of a nano-oxide, 0.1-2 parts of a complexing agent, 2-12 parts of a surfactant, and the balance being water; The film-forming aid is phytic acid, the inorganic salt is sodium molybdate, and the corrosion inhibitor is 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole; the weight ratio of the phytic acid, molybdate, and 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole is (7-9):(6-8):(5-8); The surfactant is a quaternary ammonium salt cationic surfactant; The quaternary ammonium salt cationic surfactant is propylene [(octaamidopropyl dimethyl / octadecamidopropyl dimethyl) chloride / ammonium bromide].

2. A galvanizing method for building scaffolding steel pipe according to claim 1, characterized in that: The plating flux in step S2 is a mixture of chloride and citrate.

3. A galvanizing method for a building scaffold steel pipe according to claim 2, characterized in that: The plating auxiliary agent comprises, by mass concentration, 10-15 g / L of aluminum chloride, 5-10 g / L of potassium chloride, 15-25 g / L of ammonium chloride, and 3-7 g / L of citrate.

4. A galvanizing method for building scaffolding steel pipe according to claim 1, characterized in that: The nano-oxide is nano-silicon dioxide, and the average particle size of the nano-silicon dioxide is 10-50 nm.

5. A galvanizing method for building scaffolding steel pipe according to claim 1, characterized in that: The auxiliary plating temperature in step S2 is 60-80° C., and the auxiliary plating time is 5-8 minutes.

6. A galvanizing method for building scaffolding steel pipes according to claim 1, characterized in that: The passivation time in step S5 is 0.5-2 minutes, and the passivation temperature is 22-32°C.

7. Use of the galvanizing method for building scaffolding steel pipes according to any one of claims 1 to 6 on building scaffolding steel pipes.