KR100893332B1 - Composition for restraining white rust and treating method of galvannealed steel pipe using it - Google Patents

Abstract

The present invention is based on 100 parts by weight of pure water, 30 to 45 parts by weight of phosphate, 5 to 15 parts by weight of potassium phosphate as a pH buffer, 3 to 15 parts by weight of ethylene diamine tetra acetic acid (EDTA), and nitrile It relates to anti-whitening composition comprising 3 to 15 parts by weight of rotriacetic acid (NTA).

In addition, the present invention, after diluting the anti-whitening composition to 0.1 ~ 0.4w / v% with cooling water in a cold bath for steel pipe hot dip galvanizing, after impregnating the pipe galvanized in the cooling water, the pipe is dried, the pipe It relates to a method of treating the composition on a galvanized pipe, to which the anti-whitening composition is applied.

Anti-whitening composition, galvanized

Description

Composition for restraining white rust and treating method of galvannealed steel pipe using it}

The present invention relates to a phosphate-based anti-whitening composition for galvanized steel pipes and a surface treatment method of galvanized steel pipes using the same.

In recent years, regulations on heavy metals such as chromium have been tightened due to environmental regulations of developed countries. Accordingly, each manufacturer has been devoted to developing a substitute for chromic acid solution which was treated to prevent white rust of galvanized steel pipe. Chromium, which has the lowest cost and excellent corrosion resistance, has been avoided as a highly toxic substance to humans, and also has a considerable treatment cost in waste water treatment. Galvanized steel pipes have corrosion resistance that suppresses corrosion of the steel pipes by sacrificial anodization of zinc, but have also caused complaints from customers due to the occurrence of white rust of zinc which is coated on the surface of the steel pipes. In order to prevent this, the chromic acid solution has been conventionally used, but the chromic acid solution has been restricted due to various environmental regulations. Hexavalent chromic acid and trivalent chromic acid have been used for the chromic acid treatment method.

However, since the material having corrosion resistance comparable to chromium is difficult to be found in the existing material system, and the treatment method must be treated without changing the existing plating process, many plating plants use chromic acid which is harmful to the environment or human body, but is inexpensive. It has been used continuously.

Therefore, the inventor of the present invention, in order to solve the problem according to the conventional chromic acid treatment method, as a result of repeated studies, the phosphate-based anti-whitening agent according to the present invention, which does not use chromium at all, has been developed.

An object of the present invention has a corrosion resistance comparable to chromium, and provides an environmentally friendly anti-whitening composition and a processing method capable of treating white rust without changing any existing processes since chromium and heavy metals are not added at all.

The present invention is based on 100 weight of pure water, 30 to 45 parts by weight of phosphate, 5 to 15 parts by weight of potassium phosphate as a pH buffer, 3 to 15 parts by weight of ethylene diamine tetra acetic acid (EDTA) It provides a white rust preventive composition comprising 3-15 parts by weight, and nitrilotriacetic acid (NTA).

In addition, the present invention provides a galvanized pipe to which the anti-whitening composition is applied.

In addition, the present invention after diluting the anti-whitening composition to 0.1 ~ 0.4w / v% with a cooling water in a cooling tank for hot-dip galvanizing, impregnated with a pipe galvanized in the cooling water, and then drying the pipe, Provided is a method of treating the composition on a galvanized pipe, to which the anti-whitening composition is applied.

Hereinafter, the present invention will be described in more detail.

The anti-whitening composition of the present invention was based on 100 parts by weight of pure water, based on 30 to 45 parts by weight of phosphate having excellent reactivity with zinc. The idea is that it is excellent and environmentally friendly. However, it is necessary to supplement the corrosion resistance by adding a few special additives in terms of phosphate itself, which cannot sufficiently secure the corrosion resistance of chromium, and also uses 100% solution or the amount of application as the general chromate. In addition, since a large amount of metal ions are present in the cooling water and are easily precipitated as salts, which not only impair the appearance of the plating, but also have a harmful effect on the corrosion resistance and turbidity of the cooling water, zinc is added by adding 5 to 15 parts by weight of potassium phosphate salt as a buffer. The plated steel pipe was allowed to stabilize in an aqueous solution of cooling water. This can be assessed by the management of the conductivity.

In addition, in order to improve the stability of zinc materials and Dorothes, the addition of a metal ion sequestrant combined with metal ions in the aqueous solution to form a chelate complex to suppress the turbidity of the cooling water, which is very fine dissolved ions and zinc-based metal powder Since the back is not removed by a filter or the like, this passivation operation should be performed ultimately. When the chelate complex is formed, the metal ion acts to prevent precipitation by other indicators, and 3-15 parts by weight of ethylene diamine tetra acetic acid (EDTA) and nitrilotrile as the metal ion blocking agent. 3-15 parts by weight of acetic acid (NTA) was added.

In the anti-whitening composition of the present invention, when it contains less than the minimum value of each component, the anti-whitening effect is not preferable because it is inadequate, and when the maximum value of each component is exceeded, The prevention effect is reduced and undesirable.

In addition, the treatment method of the present invention, after diluting the anti-rust composition to 0.1 ~ 0.4w / v% with cooling water in a steel pipe hot dip galvanizing cooling tank, and then impregnated the pipe galvanized in the cooling water, After drying, the galvanized pipe is dried with cooling water and then applied to the steel pipe so that the adhesion amount of the composition is preferably 10 to 100 mg / m 2.

Normally, the melting point of zinc is around 450 ℃, and when it reaches the cooling water, it is usually not easy to handle at about 280 ~ 350 ℃, so it is cooled in the cooling water tank and the temperature is about 300 ℃. Therefore, the anti-whitening agent diluted in the cooling water bath must react with zinc at this temperature. Of course, if the temperature is low, the white rust preventive effect is lowered because it does not react with the white rust inhibitor in the cooling water tank.

In the treatment method of the present invention, the concentration of the anti-whitening solution is preferably 0.1 to 0.4 w / v%, and when the concentration is less than 0.1 w / v%, the anti-whitening effect is extremely low, and the concentration is more than 0.4 w / v%. In the case of the problem of staining on the surface of the pipe due to the concentration gradient due to the role and workability of the chelating agent and the pH buffer agent occurs, work management within this range is required.

In the salt spray test and outdoor exposure test of the following examples, the corrosion resistance can be confirmed. By the method of the present invention, a galvanized pipe coated with a white rust preventive composition having corrosion resistance against white rust can be obtained in a white rust generation within 5% in a 3 hour salt spray test and a corrosion resistance test for 30 days in an outdoor exposure.

Hereinafter, it demonstrates concretely by the manufacture example and the Example of this invention. However, the following Preparation Examples and Examples are intended to aid the understanding of the present invention, and are not intended to limit the scope of the present invention in any way.

Production Example  One

30 parts by weight of phosphate, 10 parts by weight of potassium phosphate, 5 parts by weight of ethylene diamine tetra acetic acid (EDTA), and 3 parts by weight of nitrilotriacetic acid (NTA) were added to 100 parts by weight of pure water. Anti-whitening composition was prepared.

Production Example  2

To 70 parts by weight of pure water, 40 parts by weight of phosphate, 15 parts by weight of potassium phosphate, 10 parts by weight of ethylene diamine tetra acetic acid (EDTA), and 10 parts by weight of nitrilotriacetic acid (NTA) were added. Pure water was further added to 100 parts by weight to prepare an anti-whitening composition of Preparation Example 2.

Production Example  3

30 parts by weight of phosphate, 5 parts by weight of potassium phosphate, 3 parts by weight of ethylene diamine tetra acetic acid (EDTA), and 3 parts by weight of nitrilotriacetic acid (NTA) were added to 100 parts by weight of pure water. Anti-whitening composition was prepared.

Production Example  4

100 parts by weight of pure water was added 45 parts by weight of phosphate, 15 parts by weight of potassium phosphate, 15 parts by weight of ethylene diamine tetra acetic acid (EDTA), and 15 parts by weight of nitrilotriacetic acid (NTA). An anti-whitening composition was prepared.

Production Example  5

Prepared by adding 37 parts by weight of phosphate, 8 parts by weight of potassium phosphate, 12 parts by weight of ethylene diamine tetra acetic acid (EDTA), and 12 parts by weight of nitrilotriacetic acid (NTA) based on 100 parts by weight of pure water. The anti-whitening composition of Example 1 was prepared.

Example  One

In this embodiment, in order to measure the reactivity of the composition of the present invention and zinc of the zinc steel pipe, the pipe temperature was set from 200 ° C to 350 ° C to measure the amount of white rust generated over time.

After adding the anti-whitening composition prepared in Preparation Example 1 to the steel pipe hot-dip galvanizing cooling tank, the concentration of the composition in the cooling water was 0.4w / v%, and the zinc-plated pipe was dried through the cooling water, and Preparation Example 1 It was applied to the steel pipe so that the deposition amount of the composition of 50mg / ㎡ was carried out plating cooling process. The cooling water temperature at this time was set to 70 ~ 90 ℃ as the field conditions, the pipe used is a 32A white pipe. In addition, in Examples 1 to 3, in contrast to these, using a Cr acid treatment agent in place of the anti-whitening composition of Preparation Example 1, a comparative composition was prepared using the same conditions as above.

The measurement results are shown in Table 1 below.

Test Pipe outer diameter Pipe temperature (℃) Impregnation time (sec) White Cheek Occurrence (Test Piece of Each Case: 4EA) 1h 2h 3h Composition of Preparation Example 1 Test result by pipe temperature 32A 200 30 85% 100% 100% 250 30 0% 0% 5% 300 30 0% 0% 0% 350 30 0% 0% 0% Comparative Example Cr Acid Treatment Agent Test result by pipe temperature 32A 200 30 50% 70% 100% 250 30 30% 50% 70% 300 30 5% 10% 20% 350 30 0% 5% 15%

* Test conditions: Korean Industrial Standard-Chlorine Spray Test Method KS D9502; Concentration of anti-whitening composition 0.4%, cooling water temperature 80 ℃

As shown in Table 1, in the case of the composition of the present invention, it can be seen that the reactivity of the composition and zinc coated on the pipe at 200 ° C. is not good, and the temperature of the pipe shows excellent corrosion resistance at 250 ° C. or higher. It was. In the case of the Cr acid treatment agent which is a comparative example, the temperature is generally low in view of the reactivity and applicability of chromium.

Example  2

In this example, the corrosion resistance according to the concentration of the composition of the present invention at a test temperature of 300 ℃ was measured.

The plating cooling process was performed in the same manner as in Example 1 except that the test temperature was set to 300 ° C. and the concentration of the anti-whitening composition of Preparation Example 1 was set at 0.05 to 0.6 w / v%.

The measurement results are shown in Table 2 below.

Test Pipe outer diameter Concentration (w / v%) Impregnation time (sec) White Cheek Occurrence (Test Piece of Each Case: 4EA) 1h 2h 3h Composition of Preparation Example 1 Test result by concentration 32A 0.05 30 5% 20% 70% 0.1 30 0% 0% 5% 0.4 30 0% 0% 0% 0.6 30 0% 0% 0% Comparative Example Cr Acid Treatment Agent Test result by concentration 32A 0.05 30 20% 40% 100% 0.1 30 10% 25% 80% 0.4 30 5% 15% 30% 0.6 30 0% 5% 15%

* Test conditions: Korean Industrial Standard-Chlorine Spray Test Method KS D9502

As shown in Table 2, the concentration of the composition of Preparation Example 1 exhibited a poor result significantly exceeding 5% of the white rust generated as a requirement for corrosion resistance, even when exceeding 0.4w / v% of the same level of corrosion resistance Only represented. Accordingly, the standard operating conditions can be seen that it is preferable to set the concentration of the composition of the present invention to 0.1 to 0.4w / v%.

Example  3

In this example, the cooling water turbidity was measured according to the number of times at the test temperature of 300 ℃. This is the purpose of the test as an evaluation for the deterioration of corrosion resistance during precipitation and cloudiness of salts.

The test temperature was 300 ° C, and the plating cooling process was performed in the same manner as in Example 2, except that the concentration of the anti-whitening composition of Preparation Example 1 was set at 0.05 to 0.6 w / v%. Was performed.

The measurement results are shown in Tables 3a and 3b.

Test Pipe outer diameter Concentration (w / v%) Impregnation time (sec) Test Piece of Each Case: 4EA 5 times 10th 20 times Composition of Preparation Example 1 Stain / salt (20 consecutive test results) 32A 0.05 30 0% 0% 0% 0.1 30 0% 0% 0% 0.4 30 0% 0% 0% 0.6 30 5% 20% 40% Comparative Example Cr Acid Treatment Agent Stain / salt (20 consecutive test results) 32A 0.05 30 0% 0% 0% 0.1 30 0% 0% 10% 0.4 30 15% 35% 50% 0.6 30 30% 35% 80%

* Test conditions: Korean Industrial Standard-Chlorine Spray Test Method KS D9502

Test Pipe outer diameter Concentration (w / v%)) Impregnation time (sec) White Cheek Occurrence (Test Piece of Each Case: 4EA) 1h 2h 3h Composition of Preparation Example 1 Stain / salt (20 consecutive test results) 32A 0.05 30 5% 25% 80% 0.1 30 0% 0% 10% 0.4 30 0% 0% 5% 0.6 30 0% 0% 0% Comparative Example Cr Acid Treatment Agent Stain / salt (20 consecutive test results) 32A 0.05 30 20% 50% 100% 0.1 30 10% 45% 100% 0.4 30 15% 25% 40% 0.6 30 10% 15% 30%

* Test conditions: Korean Industrial Standard-Chlorine Spray Test Method KS D9502

As can be seen in Tables 3a and 3b, the composition of the present invention was able to produce a white rust preventive agent without contamination of the cooling water even in about 20 tests. During field work, continuous inflow of pipes and zinc and roads from the pipes flow into the cooling water, which eventually reacts with the anti-whitening agent, deteriorating the intrinsic properties of the anti-whitening agent and reducing the corrosion resistance. This causes problems such as greatly deteriorating the appearance of the pipe due to reattachment and precipitation of salts. Therefore, by using the anti-whitening composition of the present invention, it can be seen that the effects such as preventing the re-adhesion of the salt when used continuously. The test results demonstrated good corrosion resistance, ie less than 5% white rust in a 3 hour salt spray test, even in 20 or more continuous operations.

As can be seen from the above, the composition of the present invention is an environmentally friendly and excellent anti-whitening effect that does not contain any chromium and heavy metals, and by the treatment method using the composition, without changing any existing plating process at all By the efficient method, white rust can be treated in a large amount, and a corrosion resistant treatment method of a galvanized steel pipe having excellent white rust corrosion resistance can be obtained.

Claims (3)

30 to 45 parts by weight of phosphate, 5 to 15 parts by weight of potassium phosphate as a pH buffer, 3 to 15 parts by weight of ethylene diamine tetra acetic acid (EDTA), and nitrilotriacetic acid (based on 100 parts by weight of pure water) NTA) Anti-whitening composition containing 3-15 weight part. Galvanized pipe to which the anti-whitening composition according to claim 1 is applied. After diluting the anti-whitening composition according to claim 1 with 0.1 to 0.4 w / v% of cooling water in a hot dip galvanizing cooling bath, and then impregnating the galvanized pipe in the cooling water, the pipe is dried to the pipe. A method of treating said composition on galvanized pipes, wherein said composition is applied to an anti-whitening composition.