阅读说明：本技术 一种钢材热浸镀锌后处理方法 (Post-treatment method for hot dip galvanizing of steel ) 是由 石全中 唐本标 于 2021-09-01 设计创作，主要内容包括：本发明公开了一种钢材热浸镀锌后处理方法,包括以下步骤：水冷：将制件从锌浴中取出后进行水冷,以防止在缓慢冷却时合金层的过量生长导致灰暗镀层；钝化：以防止制件在储运过程中产生腐蚀,包括以下步骤：a.将钝化液放入钝化槽中；b.调节钝化槽中钝化液的温度和pH值；c.将水冷后的制件直接放入钝化槽中,钝化一段时间后,漂洗烘干；其中钝化液包括以下按重量份数配比的原料：丙基三甲基硅烷10份～20份,钼磷酸铵10份～15份,钼酸钠20份～50份,纳米二氧化硅0.01份～0.2份,有机缓蚀剂5份～20份,表面活性剂5份～10份,水80份～120份。本发明制备所得的钢材钝化后的镀层性能优异,并且其能达到使用六价铬作为钝化液钝化后所得的制件镀层的耐腐蚀性能。(The invention discloses a post-treatment method for hot dip galvanizing of steel, which comprises the following steps: water cooling: taking the workpiece out of the zinc bath, and then carrying out water cooling to prevent a dark plating layer caused by excessive growth of an alloy layer during slow cooling; passivation: the method for preventing the corrosion of the parts in the storage and transportation process comprises the following steps: a. putting the passivation solution into a passivation tank; b. adjusting the temperature and the pH value of the passivation solution in the passivation tank; c. directly putting the water-cooled workpiece into a passivation tank, passivating for a period of time, rinsing and drying; the passivation solution comprises the following raw materials in parts by weight: 10 to 20 portions of propyl trimethyl silane, 10 to 15 portions of ammonium molybdate, 20 to 50 portions of sodium molybdate, 0.01 to 0.2 portion of nano silicon dioxide, 5 to 20 portions of organic corrosion inhibitor, 5 to 10 portions of surfactant and 80 to 120 portions of water. The steel prepared by the invention has excellent performance of the passivated plating layer, and can achieve the corrosion resistance of the workpiece plating layer obtained by passivating by using hexavalent chromium as a passivating solution.)

1. A steel hot-dip galvanizing post-treatment method is characterized by comprising the following steps:

step (1), water cooling: taking the workpiece out of the zinc bath, and then carrying out water cooling to prevent a dark plating layer caused by excessive growth of an alloy layer during slow cooling;

passivating in step (2): the method for preventing the corrosion of the parts in the storage and transportation process comprises the following steps:

a. Putting the passivation solution into a passivation tank;

b. adjusting the temperature and the pH value of the passivation solution in the passivation tank;

c. directly putting the water-cooled workpiece into a passivation tank, passivating for a period of time, rinsing and drying;

the passivation solution comprises the following raw materials in parts by weight:

10 to 20 portions of propyl trimethylsilane, 10 to 15 portions of ammonium molybdate, 20 to 50 portions of sodium molybdate,

0.01 to 0.2 portion of nano silicon dioxide, 5 to 20 portions of organic corrosion inhibitor,

5 to 10 parts of surfactant and 80 to 120 parts of water.

2. The steel material hot-dip galvanizing post-treatment method according to claim 1, characterized in that: in the step (2) b, the temperature of the passivation solution is 20-40 ℃, and the pH value is 2-3.

3. The steel material hot-dip galvanizing post-treatment method according to claim 1, characterized in that: in the step (2) c, the passivation time is 2 min-3 min.

4. The steel material hot-dip galvanizing post-treatment method according to claim 1, characterized in that: in the step (2) c, the rinsing time is 10 s-30 s.

5. The steel material hot-dip galvanizing post-treatment method according to claim 1, characterized in that: in the step (2) c, the drying temperature is 40-60 ℃.

6. The steel material hot-dip galvanizing post-treatment method according to claim 1, characterized in that: the organic corrosion inhibitor is at least one of ethylene diamine tetraacetic acid-2 sodium salt, aminodimethylidene phosphoric acid, hydroxyl ethylidene diphosphonic acid, polyol phosphate and thiourea.

7. The steel material hot-dip galvanizing post-treatment method according to claim 1, characterized in that: the surfactant is at least one of nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether and sodium dodecyl benzene sulfonate.

Technical Field

The invention relates to the technical field of hot-dip galvanizing, in particular to a post-treatment method for hot-dip galvanizing of steel.

Background

Steel materials, which are most widely used in industry, are subject to corrosion to various degrees when used in environments such as atmosphere, seawater, soil, and building materials. Statistically, the annual loss of ferrous material from corrosion worldwide can account for approximately 1/3 of its total production. In order to ensure the normal use of steel products and prolong the service life of the steel products, the corrosion protection technology of steel has been generally regarded by people.

The hot dip galvanizing is one of the most effective means for delaying the environmental corrosion of steel materials, and is to dip the steel products with their surfaces cleaned and activated into molten zinc liquid, and to plate a zinc alloy coating with good adhesion on the steel products through the reaction and diffusion between iron and zinc. Compared with other metal protection methods, the hot-dip galvanizing process has incomparable advantages in the protection characteristic of the combination of the physical barrier and the electrochemical protection of the plating layer, the bonding strength of the plating layer and the substrate, the compactness, the durability, the maintenance-free property and the economical efficiency of the plating layer and the adaptability of the plating layer to the shape and the size of a product.

At present, hot-dip galvanized products mainly comprise steel plates, steel strips, steel wires, steel pipes and the like, wherein the proportion of the hot-dip galvanized steel plates is the largest. For a long time, the hot dip galvanizing process is popular with people due to its low galvanizing cost, excellent protective characteristics and beautiful appearance, and is widely applied to the fields of automobiles, buildings, household appliances, chemical industry, machinery, petroleum, metallurgy, light industry, traffic, electric power, aviation, ocean engineering and the like.

When the parts require long periods of storage and transportation, the parts should be passivated to prevent corrosion during storage and transportation, the corrosion product of which is commonly referred to as white rust. The traditional passivation treatment is mainly hexavalent chromium passivation mainly based on chromate, and the most common treatment method is to immerse a plated workpiece into 0.1-0.2% sodium dichromate or chromic anhydride solution. However, the discharge of waste liquid containing hexavalent chromium is more and more strictly controlled due to the high toxicity and carcinogenicity of hexavalent chromium. Therefore, in recent years, the development and production of chromium-free passivation solution are becoming more popular internationally, and the development is moving towards inorganic salts and organic matters.

In the prior art, common chromium-free passivation can be divided into inorganic matter passivation and organic matter passivation, wherein the inorganic matter passivation comprises molybdate, silicate and the like, and the problems of thin film layer and difficult control of film forming uniformity exist; the organic matter passivation comprises the problem that the corrosion resistance of a workpiece is poor and cannot reach the corrosion resistance of hexavalent chromium due to the existence of acrylic resin.

Disclosure of Invention

The invention aims to provide a post-treatment method for hot dip galvanizing of steel, which is used for solving the technical problem that a finished piece after chromium-free passivation in the prior art has poor corrosion resistance.

In order to achieve the above object, an embodiment of the present invention provides a method for post-treatment of hot-dip galvanizing of a steel material, comprising the steps of:

(1) water cooling: taking the workpiece out of the zinc bath, and then carrying out water cooling to prevent a dark plating layer caused by excessive growth of an alloy layer during slow cooling;

(2) passivation: the method for preventing the corrosion of the parts in the storage and transportation process comprises the following steps:

a. putting the passivation solution into a passivation tank;

b. adjusting the temperature and the pH value of the passivation solution in the passivation tank;

c. directly putting the water-cooled workpiece into a passivation tank, passivating for a period of time, rinsing and drying;

the passivation solution comprises the following raw materials in parts by weight:

10 to 20 portions of propyl trimethylsilane, 10 to 15 portions of ammonium molybdate, 20 to 50 portions of sodium molybdate,

0.01 to 0.2 portion of nano silicon dioxide, 5 to 20 portions of organic corrosion inhibitor,

5 to 10 parts of surfactant and 80 to 120 parts of water.

In one preferable scheme of the invention, in the step (2) b, the temperature of the passivation solution is 20-40 ℃, and the pH value is 2-3.

In one preferable embodiment of the present invention, in the step (2) c, the passivation time is 2min to 3 min.

In a preferred embodiment of the present invention, the rinsing time in step (2) c is 10 to 30 seconds.

In one preferable scheme of the invention, in the step (2) c, the drying temperature is 40-60 ℃.

In a preferred embodiment of the present invention, the organic corrosion inhibitor is at least one of ethylenediamine tetraacetic acid-2 sodium salt, aminodimethylidene phosphoric acid, hydroxyethylidene diphosphonic acid, polyol phosphate and thiourea.

In one preferable scheme of the invention, the surfactant is at least one of nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether and sodium dodecyl benzene sulfonate.

In summary, the invention has the following advantages:

1. the steel prepared by the invention has excellent corrosion resistance and surface quality of the coating, simple formula, low cost and easy operation of the passivation method.

2. The corrosion resistance of the coating of the steel prepared by the passivation solution can reach the corrosion resistance of a workpiece passivated by hexavalent chromate.

Detailed Description

Example 1

A steel hot-dip galvanizing post-treatment method comprises the following steps:

(1) water cooling: taking the workpiece out of the zinc bath, and then carrying out water cooling to prevent a dark plating layer caused by excessive growth of an alloy layer during slow cooling;

(2) passivation: to prevent the corrosion of the product during storage and transportation, the corrosion product is usually called white rust, comprising the following steps:

a. Putting the passivation solution into a passivation tank;

b. adjusting the temperature and the pH value of the passivation solution in the passivation tank, adjusting the temperature of the passivation solution to 20-40 ℃, and adjusting the pH value to 2-3;

c. directly putting the water-cooled workpiece into a passivation tank, passivating for 2-3 min, rinsing and drying for 10-30 s at the drying temperature of 40-60 ℃;

the passivation solution comprises the following raw materials in parts by weight:

15 parts of propyl trimethylsilane, 12.5 parts of ammonium molybdate, 35 parts of sodium molybdate,

0.1 part of nano silicon dioxide, 12.5 parts of organic corrosion inhibitor hydroxy ethylidene diphosphonic acid,

7.5 parts of surfactant nonylphenol polyoxyethylene ether and 100 parts of water;

the examples 2, 3 and 4 are the same as the example 1 in the hot dip galvanizing post-treatment method, except that the passivation solutions of the examples 2, 3 and 4 and the example 1 are different in the compounding ratio in passivation.

Specific components and formulation ratios of the passivation solutions of example 1, example 2, example 3 and example 4 are shown in table 1;

table 1: specific components and proportions of passivation solutions of example 1, example 2, example 3 and example 4

5 comparative examples were set, comparative example 1, comparative example 2, comparative example 3, comparative example 4 and comparative example 5 respectively.

Comparative examples 1, 2, 3, 4 and 5 are the same as example 1 in hot-dip galvanizing post-treatment, except that the components and the proportions of the passivation solutions of comparative examples 1, 2, 3 and 4 and example 1 are different in passivation.

The specific components and proportions of the passivation solutions of comparative examples 1, 2, 3, 4 and 5 are shown in table 2:

table 2: specific components and proportions of passivation solutions of comparative examples 1, 2, 3, 4 and 5

Experimental detection

The steel prepared in the examples and the comparative examples is subjected to performance tests on the passivated coating, including the corrosion resistance rating and the corrosion resistance of the coating.

The corrosion resistance rating of the coating is according to GB/T6461-2002 rating of samples and test pieces after corrosion tests of metals and other inorganic coatings on metal substrates, and the protection rating can be divided into 10 grades according to the performance of the samples and the test pieces, wherein the performance is better when the grade is higher.

The corrosion resistance of the coating is tested by neutral salt spray test according to GB/T10125-1997 on the passivated hot dip galvanized sheet. The specific method comprises the following steps: and (4) continuously spraying for 120h, observing the area with the white rust, and calculating the percentage of the area with the white rust by a grid drawing method. According to the invention, the samples are respectively immersed in 5% sodium chloride solution for 30 days, and the area percentage of the white rust after a certain time is observed.

The test results of the performance of the passivated coating layer of the steels prepared in the examples and the comparative examples are shown in Table 3:

table 3: results of testing performance of passivated coating layer of steel prepared in the examples and comparative examples

As can be seen from table 3: the corrosion resistance of the plating layer obtained after the steel is passivated in passivating solutions with different components and proportions is greatly different. The steel prepared by the embodiment of the invention has excellent performance of a passivated plating layer, the protection rating according to GB/T6461-2002 can reach 9 grades, and the white rust area percentage is less than 5 percent after the steel is soaked in a 5 percent sodium chloride solution for 30 days. The steel prepared in the comparative example 1 of the invention has poor performance of a passivated coating, the protection rating grade according to GB/T6461-2002 is 5, and the white rust area percentage reaches 17.0 percent after the steel is soaked in a 5 percent sodium chloride solution for 30 days; the steel prepared in the comparative example 2 of the invention has poor performance of a passivated coating, the protection rating grade according to GB/T6461-2002 is 5, and the white rust area percentage reaches 16.8 percent after the steel is soaked in a 5 percent sodium chloride solution for 30 days; the steel prepared in the comparative example 3 has poor performance of a passivated coating, the protection rating grade according to GB/T6461-2002 is 5, and the white rust area percentage reaches 17.9 percent after the steel is soaked in a 5 percent sodium chloride solution for 30 days; the steel prepared in the comparative example 4 of the invention has poor performance of a passivated coating, the protection rating grade according to GB/T6461-2002 is 8, and the white rust area percentage is 5.2% after the steel is soaked in a 5% sodium chloride solution for 30 days; the steel prepared in the comparative example 5 of the invention has excellent performance of the passivated plating layer, the protection rating grade according to GB/T6461-2002 is 9, and the white rust area percentage is only 4.3 percent after the steel is soaked in a 5 percent sodium chloride solution for 30 days.

By comparing examples 2-4 with example 1, it can be seen that: the protective rating and the corrosion resistance of the passivated coatings of the steel products prepared in the examples 2-4 and the steel product prepared in the example 1 according to GB/T6461-2002 are not greatly different and have no obvious change. Therefore, the steel prepared by the embodiment of the invention in the same components and a certain proportioning range has excellent coating performance after passivation.

By comparing the doping of nano-silica in the passivation solution in example 1 with the non-doping of nano-silica in the passivation solution in comparative example 1, it can be seen that: compared with the steel prepared by adding nano-silica into the passivation solution in the comparative example 1 and not adding nano-silica into the passivation solution, the steel prepared by adding nano-silica into the passivation solution in the example 1 has the advantages that the protection rating grade and the corrosion resistance of the coating according to GB/T6461-2002 are greatly different, and the example 1 is superior to the comparative example 1. Therefore, the nano silicon dioxide is doped into the passivation solution of the invention, so that the corrosion resistance of the passivated plating surface can be improved.

By comparing the incorporation of sodium molybdate in the passivation solution of example 1 with the absence of sodium molybdate in the passivation solution of comparative example 2, it can be seen that: the protection rating and the corrosion resistance of the coating according to GB/T6461-2002 of the passivated coating of the steel prepared by doping the sodium molybdate into the passivating solution in the example 1 are greatly different from those of the steel prepared by not doping the sodium molybdate into the passivating solution in the comparative example 2, and the corrosion resistance of the coating is remarkably changed, and the example 1 is better than the comparative example 2. Therefore, the corrosion resistance of the passivated plating surface can be improved by adding sodium molybdate into the passivating solution.

By comparing the addition of propyltrimethylsilane to the passivation solution of example 1 with the absence of propyltrimethylsilane in the passivation solution of comparative example 3, it can be seen that: example 1 the steel material obtained by adding propyltrimethylsilane into the passivation solution and the steel material obtained by not adding propyltrimethylsilane into the passivation solution in the comparative example 3 have larger differences of the protection rating grade and the corrosion resistance of the coating according to GB/T6461-2002 after passivation, and have obvious changes, and the example 1 is better than the comparative example 3. Therefore, the corrosion resistance of the passivated plating surface can be improved by doping propyltrimethylsilane into the passivation solution.

By comparing the surfactant nonylphenol polyoxyethylene ether doped in the passivation solution in example 1 with the surfactant not doped in the passivation solution in comparative example 4, it can be seen that: example 1 and comparative example 4. the steel prepared by adding the surfactant to the passivation solution has the advantages that the passivated coating has the protection rating grade and the corrosion resistance according to GB/T6461-2002, but the difference is not large and has no significant change, and example 1 is better than comparative example 4. Therefore, the invention shows that the addition of the surfactant in the passivation solution has an influence on the protection grade and the corrosion resistance of the passivated plating layer, but has little influence.

By comparing examples 1-4 with comparative example 5, it can be seen that: the steel products prepared in the examples 1-4 and the comparative example 5 have the passivated coatings with the protection rating grades according to GB/T6461-2002 and the corrosion resistance of the coatings which are not greatly different and have no obvious change, and the examples 1-4 are superior to the comparative example 5. Thus, it is demonstrated that the steel products prepared in examples 1-4 of the present invention have a passivation coating with a protection grade and corrosion resistance comparable to those of a coating passivated with hexavalent chromium.

Therefore, the passivated plating layer of the steel prepared by the invention has excellent performance, and the corrosion resistance of the workpiece plating layer obtained by passivating the steel by using hexavalent chromium as a passivating solution can be achieved; according to the invention, propyl trimethylsilane, nano silicon dioxide and sodium molybdate are added into the passivation solution, so that the corrosion resistance of the passivated plating layer can be greatly improved.