KR101275019B1 - Oxide film remover for improvement in the quality of electro painting and removing method of oxide film - Google Patents

Abstract

PURPOSE: An oxide film remover and an oxide film removing method for improving electro-painting quality are provided to effectively remove a heat-affected oxide film formed on a metal surface by using the oxide film remover of a chelating agent, thereby improving corrosion resistance of painting quality. CONSTITUTION: An oxide film remover for improving electro-painting quality is obtained by using 2-20 w/v% chelating agent which has pH 2-7 when diluted with a solvent and is measured by a 0.1N-KMnO4 thermal oxidation-reduction titration method, in order to remove an oxide film generated on a metal surface in an electro-painting process. The chelating agent is formed in a way that the consumption of 0.1N-NaOH for 5 ml sample of the oxide film remover is 5-30 ml. The chelating agent material is selected among EDTA(Ethylene Diamine Tetra Acetic Acid), DTPA(Diethylene Triamine Penta Acetic Acid), NTA(Nitrilotri Acetic Acid), HEDTA(Hydroxyethyl Ethylenediamine Triacetic Acid), HEDPA(Hydroxyethylidene Diphosphoric Acid), and phosphorous acid. [Reference numerals] (a) Before process; (b) After process; (c) After salt water spreading test

Description

FIELD OF THE INVENTION [0001] The present invention relates to an oxide film remover and an oxide film removal method for improving electrodeposition coating quality,

TECHNICAL FIELD The present invention relates to an oxide film remover and an oxide film remover which can effectively remove oxidized traces or weld soot during metal processing to improve the quality of the phosphate film and electrodeposition coating.

In the electro painting, the cleanliness of the material has an absolute effect on the corrosion resistance after painting. Therefore, in order to perform the electrodeposition coating, first the removal of the oxide film formed on the metal surface and the cleaning (degreasing) of the oil flow are performed, and then the phosphate film is coated and the electrodeposition coating is performed. As an example of an implementation process for the electrodeposition coating, there are procedures such as the following: an electrolysis step, a preliminary degreasing, a main degreasing, a water washing, a surface conditioning, a phosphate coating, a water washing, a pure water, an electrodeposition painting, .

Phosphate coating is one of the widely used methods for pretreatment of metals. It is to chemically treat the metal surface to form a compound coating with high stickiness and stability on its surface. It is well known in the art that phosphate coating is an essential requirement to enhance the physical properties of the coating, such as adhesion, durability, corrosion resistance and flex resistance, in the subsequent metal coating process. Before such a phosphate coating treatment, Etc., most of the surface conditioning treatment using the surface modifier is performed. An example of the liquid phase adjusting agent used for the surface adjusting treatment is the Korean Patent Registration No. 101084 entitled " Liquid Surface Conditioning Agent ", which is a patentee of the present application.

When the above-mentioned metal coating, metal plating, or other metal surface treatment is performed, an oxide film (scale) containing rust adversely affecting the formation of the metal surface film on the metal surface occurs unexpectedly. There are typical examples of the oxide film formed by welding heat affected part, rust, oil burning phenomenon, etc. Oil burning phenomenon occurs when the oil coated on the steel sheet for rust prevention or press is used for the process such as waiting time or welding And the like.

In the case of most metallic steel sheets such as iron and zinc materials, an oxide film (scale) as shown in Fig. 1 is generated on the metal surface of the heat affected portion due to welding or other external environmental factors.

If the phosphate coating treatment is carried out without removing the oxide film formed on the metal surface, the ginseng salt coating particles may fail to contact the film forming standard value (for example, 2 to 10 탆) The coating film particles are formed to cause disorder, and eventually adversely affect the electrodeposition coating process. It is also a factor that causes the salt water spray test and salt water composite corrosion test to fail.

Conventional techniques for removing the oxide film include a treatment method using strong acid (HCl, H ₂ SO ₄ , H ₃ PO ₄ ) or a shot blasting method. In the case of strong acid, It is practically difficult to apply the process to the process due to corrosion of the equipment, and the shot blast process can be applied to a small amount but it is not applicable to a large quantity continuous process.

Accordingly, an object of the present invention is to provide a method of forming an electrodeposited coating on a metal material by removing an oxide film adhered to or oxidized from a metal material (steel, zinc, or aluminum) before electrodeposition coating, An oxide film removing agent and an oxide film removing method.

According to the above object, the present invention uses a metal chelate compound (hereinafter referred to as "chelating agent") for removing an oxide film formed on a metal surface.

More specifically, the present invention relates to a chelating agent having a pH of 2 to 7 and a chelating agent capable of being measured by 0.1N-KMnO ₄ thermal oxidation-reduction titration when diluted in a solvent for removal of an oxide film formed on a metal surface in an electrodeposition coating step, v% to obtain an oxide film remover, and the amount of 0.1 N-NaOH consumed per 5 ml of the oxide film remover sample is 5 to 30 ml.

The chelating agent may be selected from the group consisting of EDTA (ethylene diamine tetra acetic acid), DTPA (diethylenetriamine penta acetic acid), NTA (nitrilotriacetic acid), HEDTA (hydroxyethyl ethylenediamine triacetic acid), HEDPA (hydroxyethylidene diphosphoric acid) Acid).

In the present invention, the chelating agent is used to dry a bath in one of the boiling step, the degreasing step, the boiling step and the degreasing common step of the electrodeposition coating pretreatment step to remove the oxide film formed on the metal surface.

The present invention uses a chelating agent to remove an oxide film of a heat-affected part formed on a metal surface, thereby improving the corrosion resistance of the coating quality. In the conventional process, the oxide film remover of a chelating agent It is advantageous to use existing facilities without additional process expansion.

In addition, since the oxidizing agent of the present invention is not strongly acidic, it does not cause damage to the equipment or the transfer device, and does not adversely affect the working environment due to the absence of odor and gas (gas) 1 to 10 minutes). Furthermore, when working at low temperature or neutral, there is an advantage that the oxide film can be removed without causing corrosion in a composite material such as a rust-preventive galvanized steel sheet or aluminum.

1 is a photograph showing an oxide film formed on a metal surface,
FIG. 2 and FIG. 3 are graphs and a result table showing the result of analysis of an oxide film formed on a heat affected zone by welding (CO ₂ welding and MAG welding) on a metal surface by EDX (Energy Dispersive X-ray spectroscopy)
FIG. 4 is a photograph showing the process of electrodeposition coating in the state that an oxide film is present on the metal surface and showing the unsatisfactory quality after 720 hours of the salt spray test,
FIG. 5 is a photograph showing the state before and after the treatment with the chelating agent oxide film remover according to the present invention and the state after the electrolytic coat agent treated with the oxide film remover after the salt spray test. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

An example of a process for electrodeposition coating is described in detail in Table 1 below.

fair
division Tansei Spare
Degreasing This skim
washing Suesse
1,2 surface
adjustment Phosphate coating Suesse
3,4 Pure three Electroplating
stamp Sob Processing time (min) 1.5 0.5 2 0.5 0.5 2 0.5 0.5 2 10 Temperature (℃) 45 ± 5 45 ± 5 45 ± 5 Room temperature Room temperature 45 ± 5 Room temperature Room temperature 30 ± 5 180 use
drugs water Degreasing agent Degreasing agent water surface
Adjusting agent Encapsulation water water varnish

purpose Material temperature
Rising and dirt
Cleaning oil
Cleaning oil Surface medicine
remove
(wash)
Surface activation
Film formation Surface medicine
remove
(wash) Surface medicine
very
remove
(wash)
stamp
Paint fixation

The electrodeposition coating as described in Table 1 and the chemicals applied to this process can not remove the oxide film on the surface of the metal material. As a result of performing the electrodeposition coating by following the procedure of the above process with the oxide film, As can be seen from the photograph of FIG. 4, the salt spray test results in dissatisfaction. That is, rust occurred in the electrodeposited deposit.

However, it is impossible to remove the oxide film by a method such as acid treatment or shot blasting in advance due to the nature of the above-mentioned process. As already mentioned in the Background of the Invention section of the present specification, the acid treatment involves the scattering of the acid gas, the durability of the apparatus and the transportation equipment, and the poor working environment, And the shot blast method can not be applied because it can not be continuously operated in large quantities.

Therefore, it is necessary to remove the oxide film formed on the metal surface while applying any chemical to any of the above processes. The present inventor has accomplished the object of the present invention by chelating metal ions in the oxide film and dissolving them in solution.

First, the present inventors analyzed the state of an oxide film formed on a metal surface.

One example of the result of analyzing by EDX (Energy Dispersive X-ray spectroscopy) that the oxide film (scale) as shown in Fig. 1 was generated on the metal surface of the heat affected portion due to welding to the metal plate or other external environmental factors 2 and 3, respectively.

FIG. 2 shows the state of the oxide film of the heat affected zone when the steel is welded to the steel material, and FIG. 3 shows the state of the oxide film and the analysis result in the case of the zinc oxide coated steel sheet.

As can be seen from the analysis table of FIG. 2 and FIG. 3, it can be seen that the oxide film contains iron (Fe), zinc (Zn) and manganese (Mn).

Therefore, the inventor of the present invention believed that when metal chelating (solubilizing) the compound contained in the oxide film, impurities such as phosphorus (P), which is naturally oxidized, are dissolved, .

When the chelating agent used as an example is E.D.T.A. (EthylendiaminetetraAcetate), the mechanism is presumed to be as follows.

Where M ^{n +} ; Metal ions in the oxide film of heat welding site, that is, Fe, Zn, Mn and so on.

However, chelating agents such as E. D.T.A (Ethylenediaminetetra Acetic Acid), D.T.P.A (Diethylene TriaminepentaAcetic Acid), and N.T.A (Nitrilotriacetic Acid) have a problem that their solubility in water is generally low (usually less than 2%).

According to the results of experiments conducted by the inventors of the present invention, when a chelating agent having a high solubility in water, that is, a chelating agent dissolving in water and 2 to 20 w / v% of the chelate metal salt, dissolves impurities such as phosphorus (P) contained in the oxide film The oxide film on the metal surface could be removed.

In order to increase the solubility in water, it is possible to find a universal method of converting to an alkali salt (Na or K), but this is an alkaline chloride chelating agent. The alkaline chlorinated chelating agent has a hydrogen ion concentration index of 2 to 20 w / v%, that is, a pH of 8 to 11, which can not be removed by the present inventor.

The present inventors have found that when a chelating agent is dissolved using a weak acid such that the concentration of chelating agent (amount of chelating agent dissolved in water) is 2 to 20 w / v% in acidic or neutral (pH 2 to 7) Satisfactory results were obtained as an oxide film remover in accordance with the object of the present invention.

The weak acids used here include phosphoric acid, acetic acid, lactic acid, citric acid, and tartaric acid.

In addition, chelating agents that are well soluble in water, such as HEDTA (HydroxyetherEthylenDiamineTriAceticAcid) and HEDPA (HydroxyEthylidenDiPhosphoricAcid) or phosphorous acid, can be mixed with alkali or alkaline salts such as NaOH, KOH, Sodium 2,3 Phosphate, The pH was adjusted with diethanol amine or triethanol amine. Also, according to the present invention, the chelating agent well soluble in water can be measured by its KMnO ₄ thermal oxidation-reduction titration method.

The use of the chelate oxide remover of the present invention thus obtained can be included in one of the pretreatment process, the degassing process, the degassing process, the common bathing process, and the degassing process.

The preferred use process of the chelate oxide film remover is a bathing process or a degreasing cleaning process. In the case of tanning, a chelating agent having a pH of 2 to 7 and a concentration of 2 to 20 w / v% as an oxide film removing agent is used as a bathing tank, The process is to use humidification.

As a result of the treatment with the oxide film remover of the present invention, the metal surface on which the pre-treatment oxide film was generated as shown in FIG. 5 (a) was a clean material as shown in FIG. 5 (b) As shown in the photograph of FIG. 5 (c), the results were satisfactory without corrosion.

Specific examples of the oxide film remover of the chelating agent according to the present invention are shown in the table of Table 2 below.

Example
Chemical name One 2 3 4 5 6 ① E.D.T.A (g) 20 ② D.T.P.A (g) 50 ③ N.T.A (g) 10 ④ HEDTA (g) 50 50 50 100 ⑤ HEDPA (g) 50 50 50 ⑥ The phosphorous acid (g) 150 ⑦ Acid (g) 30 - - 30 - - ⑧ Alkali agent (g) 10
(pH adjustment) 5
(pH adjustment) 20
(pH adjustment) 15
(pH adjustment) 50
(pH adjustment) 50
(pH adjustment) ⑨ water Fill the remaining amount 1ℓ Fill the remaining amount 1ℓ Fill the remaining amount 1ℓ Fill the remaining amount 1ℓ Fill the remaining amount 1ℓ Fill the remaining amount 1ℓ ⑩ Concentration (w / v%) 3 5 10 10 15 20 ⑪ management point 30 25 20 15 10 5 pH 2 ± 0.5 3 ± 0.5 4 ± 0.5 5 ± 0.5 6 ± 0.5 7 ± 0.5 Processing time 1 minute 30 seconds 2 minutes 2 minutes 2 minutes 2 minutes 10 minutes Treatment temperature 20 25 35 45 55 55

here,

① E.D.T.A; Ethylendiaminetetra Acetic Acid

② D.T.P.A; DiethyleneTriaminepentaAcetic Acid

③ N.T.A; NitrilotriaceticAcid

④ HEDTA; Hydroxyether ethylendiamine TriAceticAcid

⑤ HEDPA; HydroxyethylideneDiphosphoric Acid

⑥ Phosphouous Acid; H₃PO₃

⑦ Acid; Phosphoric Acid, Acetic Acid, Lactic Acid, Citric Acid and Tartaric Acid were used.

⑧ Alkali agent is used to neutralize excess acid and adjust pH. Use NaOH, KOH, Na alkaline salt (eg sodium sulphate, sodium triphosphate), K alkaline salt (potassium diphosphate, potassium triphosphate), diethanol amine or triethanol amine Respectively.

⑨ water; Use general industrial water and add the remaining amount to 1 liter.

⑩ Concentration (w / v%); The content of chelating agent is indicated and the measurement method is as follows.

First, take 10 g of the sample solution, take it into a 100 ml volumetric flask, fill it with distilled water to the marking, mix well, add 10 ml each into two 100 ml triangular fritts, and add one of them to the titration column (A) of 0.1N-KMnO₄ The other one is used for titration at room temperature 0.1N-KMnO₄ (B). The chelating agent is not oxidized by 0.1N-KMnO4 at room temperature, so it is not consumed and only oxidized by heat.

* Titration 0.1N-KMnO4 titration method (A): Add 30 ml of distilled water to a 100 ml triangular fryer prepared for measurement, boil, add 6 ml of 1: 1 H2SO4, titrate with 0.1N-KMnO4 reagent, And the number of consumed ml is called 'A'.

For another measurement, 30 ml of distilled water was added to a 100 ml triangular fountain, added with 2 ml of 1: 1 H2SO4, titrated with 0.1N-KMnO4 reagent at room temperature, and ending pink for 30 seconds or longer. Quot; B ".

therefore,

Concentration (w / v%) = (A - B) x 0.6

⑪ management point (point); The amount of 0.1N-NaOH consumed per 5 ml of the sample solution is an important management technique for the maintenance of the liquid. The specific measurement method is as follows.

That is, 5 ml of the sample solution was accurately sampled with a massholl pipette, transferred to a 250 ml Erlenmeyer flask, and 50 ml of distilled water was added thereto. 3 ~ 5 drops of phenolphaleine was added dropwise to the solution and then titrated with 0.1 N NaOH. The point representing the pink color is the end point, and the number of the consumed ml is called the point of management.

Referring to Table 2, it can be seen that the amount of 0.1 N NaOH consumed per 5 ml of the chelating agent sample is 5 to 30 ml as an oxide film remover of the present invention.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. Therefore, the scope of the present invention should not be limited by the described embodiments, but should be determined by the scope of claims and equivalents thereof.

Claims (4)

In order to remove the oxide film formed on the metal surface in the electrodeposition coating process, an oxide film remover is obtained by diluting the solvent with 2 to 20 w / v% of a chelating agent having a pH of 2 to 7 and a 0.1N-KMnO ₄ thermal oxidation-reduction titration method , And the amount of 0.1 N NaOH is 5 to 30 ml per 5 ml of the oxide film removing agent sample.
The chelating agent of claim 1, wherein the chelating agent is selected from the group consisting of ethylene diamine tetraacetic acid (EDTA), diethylenetriamine penta acetic acid (DTPA), nitrilotriacetic acid (NTA), hydroxyethylenediamine triacetic acid (HEDTA), hydroxyethylidene diphosphoric acid (HEDPA) , Phosphorous acid (phosphorous acid).
The method of claim 1 or 2, wherein the chelating agent has a solubility in water and is selected from the group consisting of phosphoric acid, acetic acid, lactic acid, citric acid, Wherein Tartaric Acid is selectively used as an antioxidant.
Characterized by removing the oxide film formed on the surface of the metal by using a chelating agent oxide film remover as set forth in any one of claims 1 to 3 for bathing in one of the bathing step, the degreasing step, the boiling step and the degreasing common step of the electrodeposition coating pretreatment step An oxide film removal method for improving electrodeposition coating quality.

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