KR100781180B1 - The composition for preventing corrosion - Google Patents

Abstract

A corrosion inhibitor is provided to inhibit the activation of a corrosion layer by forming a passivation layer by the chemical reaction with a metal surface corrosion layer. A corrosion inhibitor comprises 55-65 wt% of orthophosphoric acid (44% H3PO4); 5-7 wt% of zinc nitrate (Zn(NO3)2.H2O); 6-8 wt% of aluminum nitrate (Al(NO3)3.9H2O); 4-5 wt% of potassium ferrocyanide (K4Fe(CN)6.3H2); 0.03-0.05 wt% of a nonionic surfactant; and the balance of desalted water. Preferably the nonionic surfactant comprises 86 % of polymer fluorochemical active; 12 % of nonfluorochemical active; and 2 % of a co-solvent.

Description

Corrosion Inhibitor {The composition for preventing corrosion}

1 is a magnified photograph of a scanning electron microscope on a metal surface,

   (A) is before the application of a corrosion inhibitor according to the invention,

   (B) is after the application of a corrosion inhibitor according to the present invention.

2 is a cross-sectional photograph of a passivation film layer generated after the application of a corrosion inhibitor according to the present invention,

   (A) the psalm,

   (B) the lower corrosion conversion layer,

   (C) is the upper corrosion conversion layer.

3 is an X-ray diffraction graph of the cross section of the passivation film layer generated after the application of the corrosion inhibitor according to the present invention.

4 is a photograph of the salt spray test results for the specimens that each produced a scratch on the surface,

   (A) is for the comparative example specimens subjected to top coat after shot blasting,

   (B) refers to a specimen coated with a corrosion inhibitor according to the present invention after shot blasting and subjected to a top coat,

   (C) refers to the specimen subjected to the corrosion inhibitor coating, coating and top coat after the shot blasting.

5 is a photograph showing the adhesion test results of each specimen,

   (A) is the reference specimen (ASTM D 4541 (2002)),

   (B) is an example specimen coated with a corrosion inhibitor,

   (C) is for comparative specimens,

   (D) is for another comparative specimen.

The present invention relates to a corrosion inhibitor, and more particularly, to a corrosion inhibitor which suppresses the corrosion layer formed due to the oxidation of the metal surface and at the same time creates a passivation film layer capable of preventing the oxidation of the metal surface without an additional process. will be.

Metal is an essential material for us to live in various fields such as large plants, machinery facilities, industrial facilities, bridges, water and sewage and gas facilities, automobiles, ships, and railways.

However, the metal is oxidized and corroded by the chemical reaction with the atmosphere, and the corrosion proceeds as the oxidizing action causes the corrosion layer formed on the metal surface to come off the metal surface.

Once corrosion occurs, the progress is so fast that the loss of metals due to corrosion reaches 10% of the total amount of metals every year, and as corrosion progresses, aging plant caused by industrialization causes loss of life and property loss. It hinders continuous industrial development and the economic loss is very large.

Various coating methods were used to prevent corrosion of the metal as described above.

In order to prevent the rust of iron products, there is a method of applying two consecutive layers of epoxy resin and fluorine compound on the oxidized metal surface with phosphoric acid, septic salt and red blood salt.

However, when the first two consecutive painting as described above, there is a disadvantage that the adhesion strength is weakened by the hassle and the first painting which has to go through two processes for the metal surface coating.

It also uses corrosion inhibitors, including orthophosphoric acid, water, zinc acetate, ethanol, tartaric acid, tannins, hepatitis, or red blood salts, which are characterized by the ability of phosphorus to prevent rusting of metals. Prevent corrosion.

In order to apply the corrosion inhibitor is required to remove the rust on the surface of the rusted product, when applying the surface of a large metal product with the corrosion inhibitor, there is a problem that the cleaning operation after application of the metal surface is difficult.

In addition, there are plating and coating to prevent corrosion by forming a protective film on the surface of the metal, and cathodic protection to prevent corrosion by connecting a metal with low corrosion resistance.

Plating and painting refers to coating with a thin layer of a different kind of metal or material such as paint for the purpose of improving the surface condition of the base metal. Cathodic protection is based on the principle that the coating layer is corroded instead of the base metal. It means that the coating layer having lower corrosion resistance than the base metal is formed on the surface.

However, the above-described plating surface treatment can prevent corrosion of the base metal, but nevertheless, the plating layer is not dense, and there is a gap between the metal forming the plating layer and the external environment such as fine pinholes in the plating layer. There is a disadvantage that the base metal is exposed to the external environment to cause corrosion by causing local corrosion to the conductive metal, the cost is increased due to the installation of special equipment.

In addition, the above-described coating surface treatment is complicated and cumbersome due to the necessity of several processes of performing the upper coating work after the lower coating work in order to suppress the corrosion formed on the metal surface, and the processing time increases, and the solvent of the paint Due to the volatile substances contained in it may adversely affect the health of the worker, the adhesion due to the coating is weakened, the adhesion of the paint is poor, there is a limit to the corrosion protection.

Moreover, the paint used to prevent corrosion by the surface treatment of the coating or plating as described above contains toxic substances such as formaldehyde or oxybenzene, which is harmful to the human body and may have a fatal effect on workers. There is a problem that pollutes the environment because it is not environmentally friendly.

In addition, the corrosion can be prevented by the cathodic protection, which is a method of preventing corrosion by using the ionization tendency between the base metal and the metal that is more reactive than the base metal, but the moisture in the atmosphere continues to oxidize the coating layer. When the base metal is incomplete and there is a space in contact with the external environment, or when the base metal is a non-metal than the plating metal, there is a problem that the corrosion of the selective material metal proceeds.

The present invention was devised to solve the problems of the conventional method for suppressing the formation of corrosion layer on the metal surface and the generation of the corrosion protection film, and can significantly shorten the time required for the metal surface treatment process. Even during use, it does not cause environmental pollution or adverse effects on the human body, and can simplify the pretreatment of the metal surface and convert the corrosion layer generated on the oxidized surface through chemical reaction to create the passivation layer, thereby effectively preventing metal corrosion. It is an object of the present invention to provide a corrosion inhibitor.

The object of the present invention is 55 to 65% by weight of orthophosphoric acid (44% H ₃ PO ₄ ), 5 to 7% by weight of zinc nitrate (Zn (NO ₃ ) ₂ H ₂ 0) and 6 to 8 Wt.% Aluminum nitrate (Al (NO ₃ ) ₃ .9H ₂ O), 4-5 wt.% Potassium iron cyanide (K ₄ FE (CN) ₆ .3H ₂ 0), and 0.03-0.05 wt. Achieved by a corrosion inhibitor mixed with ionic surfactant and residual demineralized water.

Corrosion inhibitor of the present invention is applied on the metal surface after the transformation of the corrosion layer of the metal surface to passivation to form a passivated coating layer, thereby suppressing the activity of the corrosion layer generated on the metal surface, excellent corrosion layer diffusion suppression function, external painting work In order to ensure the adhesion with the passivation coating layer external paint.

In addition, the corrosion inhibitor is not only an environmentally friendly water-soluble material that has no adverse effects on the environment, but also has a strong durability that is not broken by external vibration or impact, and the productivity and convenience of work are improved by a pretreatment batch process. By reducing the working time applied to the metal surface, it saves time and money.

Corrosion inhibitors having the above advantages include nonionic surfactants, orthophosphoric acid, zinc nitrate, aluminum nitrate, potassium iron cyanate and demineralized water.

The orthophosphoric acid (44% H ₃ PO ₄ ) is reacted with potassium iron cyanide (K ₄ FE (CN) ₆ .3H ₂ 0), also called potassium cyanide, to dissolve the oxidized corrosion layer, and Fe ₃ H ₈ (PO ₄ In the process of conversion to) to react with the zinc nitrate (Zn (NO ₃ ) ₂ · H ₂ 0), to form a zinc phosphate film on the surface.

At this time, the zinc phosphate film has a strong anticorrosive action on the surface of the corrosion layer is converted.

The aluminum nitrate (Al (NO ₃ ) ₃ .9H ₂ O) causes a change in potential occurring in the metals and components included in the corrosion inhibitor.

In addition, the non-ionic surfactant is composed of 86% polymer fluorochemical actives (Polymeric fluorochemical actives), 12% non-fluorochemical actives and 2% co-solvent (co-solvent) This removes the fat on the metal surface and increases the penetration pressure, allowing the corrosion inhibitor to penetrate into the corrosion layer of less than 0.5mm thickness to form a protective film at high speed.

In addition, the nonionic surfactant acts as an interfacial surface active material, maintains the same hygroscopicity of the coated surface, enhances adhesion, and creates a fundamental corrosion protection film of the metal.

Demineralized water is an additive mixed with the above components at a temperature of 20 ° C. to 30 ° C., and serves as a catalyst for causing a chemical reaction with the corrosion layer.

The mixed corrosion inhibitor as described above is applied to the metal surface to passivate the corrosion layer of the metal surface to form a passivation coating layer, the most important role in maintaining a strong passivation coating layer is the content of orthophosphoric acid.

If the orthophosphoric acid is less than 55% by weight, it is difficult to expect the performance of the passivated pickling layer because it does not change the oxide of the corrosive, and in excess of 65% by weight, Fe ₃ KH ₁₄ (PO ₄ ) ₈ 4H ₂ 0, KFe ₃ H _{When 8} (PO ₄ ) _{6 ·} 6H ₂ 0, cracks are formed on the surface abundantly, and the over-white phenomenon causes excessive white whites in the passivation layer, which causes obstacles to the upper coating work.

Since the content as described above greatly influences the performance of the corrosion inhibitor, it is important to observe the ratio of the component amount, and in the state where all of the above conditions are satisfied, the corrosion inhibitor increases the corrosion layer protection and the adhesive strength in the subsequent painting operation. It provides an advantageous condition to increase the.

Details of the above-described effects of the corrosion inhibitor of the present invention will be clearly understood through the following preferred embodiments of the present invention.

In order to investigate the effect of the corrosion inhibitor, the surface analysis of the passivation layer formed on the sample coated with the corrosion inhibitor, the performance evaluation on the corrosion diffusion and inhibition, and the adhesion test with the organic coating was performed.

First, in order to analyze the surface of the passivation film layer, a 10 mm × 10 mm size steel sheet specimen having a shot blasted according to ASTM D-610 was prepared and left in the air, and the corrosion inhibitor of the present invention was applied to the sample surface on which the corrosion layer was formed. And dried.

In this case, the corrosion inhibitor is 55 to 65% by weight of orthophosphoric acid, 5 to 7% by weight of zinc nitrate, 6 to 8% by weight of aluminum nitrate, 4 to 5% by weight of potassium iron cyanide, 0.03 to 0.05% by weight of nonionic surfactant is mixed with residual demineralized water.

In addition, the coating and drying, using the air spray mainly used in the general field to adjust the coating thickness and apply about 1 to 2 times, and proceeds to dry for about 12 hours or more in a general indoor environment, do not contact with moisture Be careful not to.

1 is a magnified photograph of a scanning electron microscope of the surface before and after the application of the corrosion inhibitor, (a) before the application of the corrosion inhibitor, (b) after the application of the corrosion inhibitor.

2 is a cross-sectional photograph of the passivation film layer formed after application of the corrosion inhibitor, (a) is a specimen, (b) a lower corrosion conversion layer, and (c) is an upper corrosion conversion layer.

The passivation layer is formed of a lower corrosion conversion layer (b), which is a lower layer of the passivation film formed by the first chemical reaction between the corrosion inhibitor and the corrosion layer, and a passivation film formed by the second chemical reaction between the corrosion inhibitor and the corrosion layer. It consists of an upper corrosion conversion layer (C) which is an upper layer.

The above-mentioned corrosion inhibitor is applied to the metal surface on which the corrosion layer is formed as described above, and the passivation film layer is used to find the surface constituent elements of the specimen having the passivation film layer including the corrosion conversion layer by a chemical reaction on the surface. The cross section of was analyzed by energy dispersive X-ray spectroscopy (EDS), the results are shown in Table 1.

ingredient weight% atom% C 5.78 10.86 O 43.34 61.12 Na 0.58 0.57 Al 0.23 0.19 P 21.50 15.66 K 0.71 0.41 Fe 26.74 10.80 Zn 1.12 0.39 Sum 100.00

Most of the elements constituting the surface of the specimen in which the passivation layer is formed are made of O, Fe, and P, and it can be seen that other elements are made in a very small amount.

In addition, in order to analyze the crystal structure of the specimen analyzed by the energy-dispersive X-ray spectroscopy, X-ray diffraction analysis was performed, and the analysis results are shown in FIG. 3.

As shown in FIG. 3, the resulting surface of the passivation layer is formed of Fe ₃ KH ₁₄ (P0 ₄ ) ₈ · 4H ₂ 0, (Fe _0.84 Al _0.16 ), which is formed by converting the corrosion layer due to the application of the corrosion inhibitor. By forming a passivation layer having a structural formula of 3KH ₁₄ (PO ₄ ) ₈ · 4H ₂ 0, Fe ₃ (NH ₄ ) H ₁₄ (PO ₄ ) ₈ · 4H ₂ O, the corrosion of the metal surface is suppressed and corrosion is prevented. You can prevent it.

Next, in order to confirm the performance of the corrosion generation and corrosion diffusion inhibiting ability of the passivation layer formed by chemical reaction with the corrosion layer formed on the metal surface, after each scratch is generated on the surface of the specimen, the salt spray test on the specimen Corrosion length and swelling from the scratch production start point were measured.

At this time, the salt spray test facility was INSTRON 5582, sprayed using the test solution 5% Nacl solution for 200 hours, 400 hours while maintaining the test temperature at 35 ℃, the test method was in accordance with ASTM B 117 (2003) .

As shown in FIG. 4, the specimens subjected only to shot blasting and top coat (a) were able to confirm that the corrosion progressed severely between the coating layers destroyed by the scratches, and to the shot blasting and corrosion inhibitor applied, undercoat, and top coat (c. ) Can confirm a clean surface state where the coating layer is not destroyed due to the strong durability of the passivation layer formed by the application of a bushing inhibitor and hardly progresses the corrosion.

In addition, the following results can be obtained as shown in Table 2 through the test methods of ASTM B 117 (2003) and ASTM D 1654 (1992) based on the above results.

Psalter Corrosion Diffusion Length ASTM grade (200h / 400h) Shot Blasting + Corrosion Inhibitor + Top Coating 0 mm RN.10 / RN.7 Shot blasting + corrosion layer + corrosion inhibitor + top coat 1.5mm RN.8 / RN.3 Short blasting + undercoat + top coat 6 mm RN.1 / RN.0

As shown in Table 2, the maximum corrosion diffusion length of the specimen without the corrosion inhibitor is different from the maximum corrosion diffusion length of the specimen coated with the corrosion inhibitor is about 6mm, the corrosion layer formed on the metal surface and the corrosion applied to the metal surface It can be seen that the passivation layer produced by the chemical reaction of the inhibitor inhibits the diffusion of corrosion.

That is, the lower corrosion converting layer (B) shown in FIG. 2, which was found in the cross section of the specimen coated with the corrosion inhibitor, forms a very strong bond with the metal surface by a chemical reaction generated during the formation of the passivation layer, thereby preventing initial corrosion. In addition to suppressing, it serves as a general undercoat that functions to prevent the spread of corrosion.

 Finally, a test was performed to compare the adhesion between the passivation layer formed by applying the corrosion inhibitor to the specimen and the top coat, and the adhesion between the rust preventive paint and the top coat used for conventional corrosion protection.

At this time, the adhesion test test apparatus is PATTI 110, the adhesive is used as a two-component epoxy adhesive in the state of maintaining the test rate of 1Mpa / sec, the test method was in accordance with ASTM D 4541 (2002).

FIG. 5 shows the results of adhesion by type of specimens, and according to the type of specimens, (A), (B), (C), and (D) are shown. Table 3 shows the results in detail.

Specimen Type How to make Result (rating, Mpa) Remarks Reference Specimen (ASTM D4541 (2002)) Coating after removing corrosion layer with wire brush 7.436 NORSOK Standard Paint Inter Adhesive More Than 5Mpa Comparative specimens coated with corrosion inhibitor (B) Mark about 10㎛ on the surface of the specimen with corrosion layer and dry it for 24h 6.332 Comparative specimen (C) 1.414 Other comparative specimens 0.806

As shown in FIG. 5 and Table 3, the reference specimen (ASTM D4541 (2002)) (a) and the test specimen coated with a corrosion inhibitor (b) has a relatively clean adhesive surface than the other specimens (c) and (d) It can be confirmed that the corrosion layer on the metal surface is removed to maintain a clean metal surface, or the corrosion layer on the metal surface is formed by a strong bond between the passivation layer formed on the metal surface coated with the corrosion inhibitor and the top coat. You can see a clean adhesive surface without being revealed.

As a result of this, since the corrosion layer is simply removed from the metal surface, or the corrosion inhibitor is applied to the corrosion layer formed on the metal surface, and the passivation layer is formed, the specimen has a strong adhesive strength with the top coat, so that the top coat is applied from the metal surface. Not only does it drop easily, it not only cleans the surface of the metal, but it also replaces the role of traditional undercoats, reducing work time, improving productivity, and reducing production costs.

In addition, the adhesive force test was conducted to further check the suitability of the industrial site to the adhesive force by checking the adhesive force using the cross cutter commonly used in the industrial field, the adhesive force tester (PATTI 110) as a first grade according to ASTM D 3359B. It was determined to be 5.7 Mpa when comparing the measurements.

As described above, the corrosion inhibitor of the present invention chemically reacts with the corrosion layer formed on the surface of the metal to form a passivation layer, thereby exerting a corrosion inhibitory effect on the metal while protecting the metal body to maintain the properties of the metal body, and external vibration. Or it has a strong durability without breaking even in impact, and can replace the role of the existing undercoat by the strong adhesion of the passivation layer itself, improve the productivity and convenience of the work in the pretreatment batch process, and shorten the working time You can save time and money.

Claims (2)

55 to 65 wt% orthophosphoric acid (44% H ₃ PO ₄ ), 5 to 7 wt% zinc nitrate (Zn (NO ₃ ) ₂ H ₂ 0), and 6 to 8 wt% aluminum nitrate (Al (NO ₃ ) ₃ · 9H ₂ O), 4 to 5% by weight of potassium iron cyanide (K ₄ FE (CN) ₆ · 3H ₂ 0), 0.03 to 0.05% by weight of anionic surfactant and residual demineralized water Corrosion inhibitor, characterized in that made. The method of claim 1, wherein the nonionic surfactant is composed of 86% polymer fluorochemical actives, 12% non-fluorochemical actives and 2% co-solvent Corrosion inhibitors, characterized in that.

Images