TW201723232A - Rust-removal composition and acidic rust-removal method using same which comprises: phosphoric aqueous solution, polyacid, polyol aqueous solution, polyphosphate, corrosion inhibitor, surfactant and water - Google Patents

Abstract

A rust-removal composition having a pH value in the ranges of 0~2, and comprising: phosphoric aqueous solution, polyacid, polyol aqueous solution, polyphosphate, corrosion inhibitor, surfactant and water, wherein the corrosion inbitor composition does not contain the inorganic acid except for the phosphoric acid. The present invention also provides an acidic rust-removal method using the abovementioned rust-removal composition. The rust-removal composition in this invention does not contain the inorganic acid capable of causing air pollution and damages to the operation staff, thereby effectively removing rust skins on the miscellaneous steel species and capable of being recycled only through filtration.

Description

Derusting composition and acid descaling method using same

The present invention relates to a rust removing composition and an acid rust removing method using the same, and particularly to a rust removing composition mainly composed of phosphoric acid and an acidic rust removing method using the same.

In high-temperature processes (such as hot rolling or annealing, other heat treatments, etc.), steel may form a layer of black scale, the main component of which is iron oxide and metal oxides formed by other metal elements in the steel. This black scale does not only affect the appearance of the steel, but also has an effect on subsequent processing. Therefore, a step of removing the scale is usually included in the processing of the steel.

The commonly used method of removing scale is pickling. For the scale which is difficult to remove, some auxiliary treatment (such as salt bath treatment, electric rust removal, mechanical treatment) is needed to improve the rust removal efficiency. Acids commonly used for pickling include sulfuric acid, nitric acid, hydrochloric acid, and the like. For example, CN 101423924 refers to a degreasing and pickling one-step hot dip zinc treatment process comprising adding octylphenol ethoxylate, hexamethylenetetramine and water to a hydrochloric acid wash treated prior to hot dip zinc processing. However, such a pickling process is prone to problems such as incomplete pickling or excessive pickling in actual use, and the difference in pickling degree may seriously affect the appearance of the steel. For example, the steel surface may have many holes which are not smooth and not bright. In addition, the acid itself and the gases produced by the acid (such as NO, NO ₂ , hydrochloric acid vapor, etc.) may cause environmental pollution and endanger the health of the operator.

In view of the above problems with the acid solution, a phosphoric acid-based lotion has been developed, for example, US Pat. - diethyl thiourea, nonionic surfactant, organic solvent and amine. Due to the use of organic solvents, the aforementioned patents may volatilize during operation and cause air pollution.

No. 5,011,551 discloses a composition for converting a surface of a corroded steel material into a substrate suitable for application of an organic coating comprising an aliphatic alcohol, phosphoric acid, basic nitrate, tannic acid, zinc nitrate and a surfactant. Although this patent can form a layer of phosphate coating on the surface of the steel material suitable for subsequent coating of the organic coating, this method must take more man-hours, is not economical, and the nitrate is converted into nitrogen oxides in the solution. Causes air pollution.

It can be understood from the above description that there is still a great room for improvement in the removal of scale components based on phosphoric acid, in line with economic and environmental protection requirements.

Accordingly, it is an object of the present invention to provide a rust-removing composition which is capable of efficiently removing scales of various steel grades, is environmentally friendly, is easy to recycle, and does not endanger the health of the operator.

Thus, the rust-removing composition of the present invention has a pH range of 0 to 2 and comprises: an aqueous solution of phosphoric acid, a polybasic acid, an aqueous solution of a polyhydric alcohol, a polyphosphate, a corrosion inhibitor, a surfactant, and water, wherein the rust-removing composition It does not contain inorganic acids other than phosphoric acid.

Another object of the present invention is to provide an acid rust removing method which is highly environmentally friendly and has high removal efficiency.

Accordingly, the acidic descaling method of the present invention comprises the following steps: (A) providing a heat-treated steel material having a surface containing scale; and (B) immersing the steel material in the rust-removing composition as described above.

The effect of the invention is that the rust-removing composition of the invention does not contain any reagents which may harm the environment or the operator (especially inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, etc.), and can be efficiently and efficiently composed of special components. It removes the scale of various steel grades and has the advantage of easy recycling. The acid rust removing method of the present invention can efficiently remove the scale of various types of heat-treated steel materials by using the above-described rust removing composition, and obtain a steel material having a smooth surface and bright light.

The contents of the present invention will be described in detail below:

The rust removing composition of the present invention has a pH range of 0 to 2 and contains an aqueous phosphoric acid solution, a polybasic acid, an aqueous polyhydric alcohol solution, a polyphosphate, a corrosion inhibitor, and a surfactant.

Preferably, the rust-removing composition has a pH range of 0.7 to 1.2.

The aqueous phosphoric acid solution is composed of phosphoric acid and water. The concentration of the aqueous phosphoric acid solution can be adjusted according to actual needs. In a specific example of the present invention, the concentration of the aqueous phosphoric acid solution is 85 wt%.

The polybasic acid generally refers to an organic acid having two or more acid groups; preferably, the polybasic acid is selected from the group consisting of citric acid, tartaric acid, malic acid, maleic acid, oxalic acid, and phthalic acid. Or a combination of the foregoing. In a specific embodiment of the invention, the polybasic acid is citric acid or tartaric acid.

Preferably, the aqueous polyol solution is composed of a polyol and water, and the polyol is generally an alcohol having two or more alcohol groups; preferably, the polyol is selected from polyvinyl alcohol. Ethylene glycol, propylene glycol, glycerin, sugar alcohol, tannic acid or a combination of the foregoing. The concentration range of the aqueous polyol solution can be adjusted according to actual needs. In a specific example of the present invention, the concentration of the aqueous polyol solution is 5% by weight.

Preferably, the polyphosphate is selected from the group consisting of polyphosphates, pyrophosphates or a combination of the foregoing. The polyphosphate is for example but not limited to sodium tripolyphosphate. The pyrophosphate salt is, for example but not limited to, trisodium pyrophosphate.

Preferably, the corrosion inhibitor is selected from the group consisting of thiourea, hexamethylenetetramine or a combination of the foregoing. In a specific embodiment of the invention, the corrosion inhibitor is hexamethylenetetramine.

Preferably, the surfactant is selected from sodium dodecylbenzene sulfonate, polyoxyethylene ether or a combination of the foregoing. In a specific embodiment of the invention, the surfactant is sodium dodecylbenzene sulfonate.

Preferably, the aqueous solution of phosphoric acid is used in an amount ranging from 0.1 to 95 parts, and the amount of the polybasic acid is from 0.1 to 10 parts, and the amount of the aqueous solution of the polyhydric alcohol is in the range of 100 parts by weight based on the total weight of the rust-removing composition. 0.1 to 10 parts, the polyphosphate is used in an amount ranging from 0.1 to 10 parts, the corrosion inhibitor is used in an amount ranging from 0.1 to 5 parts, and the surfactant is used in an amount ranging from 0.1 to 5 parts, and the balance is water. And the concentration of the aqueous phosphoric acid solution was 85 wt%, and the concentration of the aqueous polyhydric alcohol solution was 5 wt%.

The acidic descaling method of the present invention comprises the following steps: (A) providing a heat-treated steel material having a surface containing scale; and (B) immersing the steel material in the rust-removing composition as described above.

Preferably, the heat-treated steel material of the step (A) is heat-treated carbon steel, alloy steel or stainless steel.

Preferably, this step (B) is carried out at a temperature ranging from 20 to 80 °C.

The steel material treated by the acidic descaling method of the present invention can be further subjected to general phosphate coating treatment and saponification treatment, and the scale on the surface of the steel material is reacted with phosphoric acid to form iron phosphate precipitate in the rust removing composition of the present invention. It can be taken out by filtration, and the rust-removing composition can be further recovered.

The invention is further illustrated by the following examples, but it should be understood that this embodiment is intended to be illustrative only and not to be construed as limiting.

< Example >

The following examples and comparative examples were taken separately using the steel types listed in Table 1 below:

Table 1 The steels of the above different steel grades form black scale on the surface after heat treatment.

[ Example 1] An aqueous phosphoric acid solution having a weight percentage of 85 wt% was mixed with water to obtain an aqueous phosphoric acid solution having a pH of about 0.7. Taking 95.8 parts of an aqueous phosphoric acid solution and adding 1 part of citric acid and 1 part of an aqueous solution of polyvinyl alcohol (the weight average molecular weight of polyvinyl alcohol is 100,000, and 5 g of polyvinyl alcohol is formulated into 100 g of an aqueous solution to obtain a polyethylene having a concentration of 5 wt%. An aqueous alcohol solution), 1 part sodium pyrophosphate, 0.5 part hexamethylenetetramine and 0.5 part sodium sodium dodecyl sulfate, and finally 0.2 parts by weight of a 85 wt% aqueous phosphoric acid solution at room temperature. The mixture was stirred to obtain a rust-removing composition having a pH of 0.7 ± 0.05.

[ Comparative Example 1] A phosphoric acid aqueous solution having a weight percentage of 85 wt% of phosphoric acid and water was adjusted to have a pH of about 0.7 ± 0.05.

[ Test ] The different steel grades listed in Table 2 below were respectively immersed in the rust-removing composition of Example 1 and the phosphoric acid aqueous solution of Comparative Example 1, and the immersion temperature was set to 30 ± 1 ° C, and the scale was completely self-recorded. The time required for the steel to separate.

Table 2

From the results of Table 2, it is understood that the rust-removing composition of Example 1 can effectively remove scales in a short period of time.

[ Examples 2 and 3] The remaining preparation procedures of Examples 2 and 3 were carried out except that the phosphoric acid aqueous solutions having pH values of 0.3 and 1.5 were respectively adjusted while adjusting the pH values of the rust removing compositions to 0.3 ± 0.05 and 1.5 ± 0.05, respectively. The same as in the first embodiment.

[ Comparative Examples 2 to 5] A phosphoric acid aqueous solution having a weight percentage of 85 wt% of phosphoric acid and water was adjusted to have a pH of 0.3 ± 0.05, 1.5 ± 0.05, and 2.5 ± 0.05, respectively, that is, Comparative Examples 2, 3, and 5, respectively. Aqueous phosphoric acid solution. Further, a phosphoric acid aqueous solution having a pH of 2.5 was prepared, and the pH of the rust-removing composition was adjusted to 2.5 ± 0.05. The rest of the preparation procedure of Comparative Example 4 was the same as in Example 1, and finally the rust-removing composition of Comparative Example 4 was obtained.

[ Test ] The steel materials of the steel grade 1010AK were respectively immersed in the rust removing compositions of Examples 1 to 3 and the aqueous phosphoric acid solutions of Comparative Examples 1 to 5 listed in Table 3 below, and the immersion temperature was set to 30 ± 1 ° C. , record the time required for the scale to completely separate from the steel.

table 3

From the results of Table 3, it is understood that the rust-removing compositions of Examples 1 to 3 can effectively remove scales in a short period of time. When the pH of the rust-removing composition is more than 2 (as in Comparative Examples 4 and 5), the removal time of the scale will increase, and even the scale may not be effectively removed.

[ Example 4] except that a phosphoric acid aqueous solution having a pH of 0.9 was prepared, citric acid was replaced with tartaric acid, sodium pyrophosphate was replaced with sodium tripolyphosphate, and the pH of the rust-removing composition was adjusted to 0.9 ± 0.05, respectively. The rest of the preparation procedure of Example 4 was the same as in Example 1.

[ Comparative Example 6] A phosphoric acid aqueous solution having a weight percentage of 85 wt% of phosphoric acid and water was adjusted to have a pH of 0.9 ± 0.05.

[ Test 1] The different steel grades listed in Table 4 below were respectively immersed in the rust-removing composition of Example 4 and the phosphoric acid aqueous solution of Comparative Example 6, and the immersion temperature was set to 60 ± 1 ° C, and the scale was completely recorded. The time required to separate the steel.

Table 4

From the results of Table 4, it was found that the rust-removing composition of Example 4 can effectively remove the scale in a short period of time.

[ Test 2] The steel of the steel grade 1010AK was respectively immersed in the rust-removing composition of Example 4 and the phosphoric acid aqueous solution of Comparative Example 6, and the immersion temperature was set to 25 ± 1 ° C, 45 ± 1 ° C, 60 ± 1 The time required for the scale to completely separate from the steel was recorded at ° C and 75 ± 1 ° C. The results are shown in Table 5 below.

table 5

From the results of Table 5, it was found that the rust-removing composition of Example 4 can effectively remove scales in a short period of time. And when the immersion temperature increases, the removal time of the scale will be shortened.

[ Test 3] The steel materials of the steel types 304 and 430 were respectively immersed in the rust removing composition of Example 4 and the phosphoric acid aqueous solution of Comparative Example 6, and the immersion temperature was set to 50 ± 1 ° C, and the scale was completely separated from the steel. The time required, the results are shown in Table 6.

Table 6

From the results of Table 6, it is understood that the rust-removing composition of Example 4 can effectively remove scales in a short period of time.

In summary, the rust-removing composition of the present invention does not contain any reagents (especially inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, etc.) which may harm the environment or the operator, and can effectively remove various kinds of components through special composition. The scale of different steel grades has the advantage of easy recycling. The acid rust removing method of the present invention can efficiently remove the scale of various types of heat-treated steel materials by using the above-described rust removing composition, and obtain a steel material having a smooth surface and bright light.

However, the above is only the embodiment of the present invention, and the scope of the invention is not limited thereto, and all the equivalent equivalent changes and modifications according to the scope of the patent application and the patent specification of the present invention are still The scope of the invention is covered.

Claims (10)

A rust removing composition having a pH range of 0 to 2 and comprising: an aqueous phosphoric acid solution; a polybasic acid; an aqueous polyhydric alcohol solution; a polyphosphate; a corrosion inhibitor; a surfactant; and water; wherein the rust removing composition is not Contains inorganic acids other than phosphoric acid. The descaling composition according to claim 1, wherein the polyphosphate is selected from the group consisting of polyphosphates, pyrophosphates or a combination thereof. The rust removing composition according to claim 1, wherein the polybasic acid is selected from the group consisting of citric acid, tartaric acid, malic acid, maleic acid, oxalic acid, phthalic acid or a combination thereof. The rust removing composition according to claim 1, wherein the aqueous polyhydric alcohol solution is composed of water and a polyhydric alcohol selected from the group consisting of polyvinyl alcohol, ethylene glycol, propylene glycol, glycerin, sugar alcohol, and single Nitrate or a combination of the foregoing. The rust removing composition according to claim 1, wherein the corrosion inhibitor is selected from the group consisting of thiourea, hexamethylenetetramine or a combination thereof. The rust removing composition according to claim 1, wherein the surfactant is selected from sodium dodecylbenzenesulfonate, polyoxyethylene ether or a combination thereof. The rust removing composition according to claim 1, wherein the aqueous phosphoric acid solution is used in an amount ranging from 0.1 to 95, and the polybasic acid is used in an amount ranging from 0.1 to 10, based on 100 parts by total of the rust removing composition. The polyhydric aqueous solution is used in an amount ranging from 0.1 to 10 parts, the polyphosphate is used in an amount ranging from 0.1 to 10 parts, the corrosion inhibitor is used in an amount ranging from 0.1 to 5 parts, and the surfactant is used in an amount ranging from 0.1 to 10 parts by weight. 0.1 to 5 parts, and the balance is water, and the concentration of the aqueous phosphoric acid solution is 85 wt%, and the concentration of the aqueous solution of the polyol is 5 wt%. An acid descaling method comprising the steps of: (A) providing a heat-treated steel material having a surface containing scale; and (B) immersing the steel material in the rust-removing composition according to any one of claims 1 to 7. in. The acidic descaling method according to claim 8, wherein the step (B) is carried out at a temperature ranging from 20 to 80 °C. The acidic descaling method according to claim 8, wherein the heat-treated steel material is heat-treated carbon steel, alloy steel or stainless steel.