TWI527938B - Rapidly electrolytic rust removal method - Google Patents

Description

Rapid electric rust removal method

The invention relates to a rapid electric derusting method, in particular to a method for removing scale on steel surface by using a persulfate compound as an electrolyte.

Steel refers to an alloy containing iron as the main element and having a carbon content between 0.2% and 2.1%, and containing other elements such as manganese, chromium, nickel, vanadium and tungsten; for example, stainless steel, carbon steel, alloy steel….

Among them, stainless steel, in addition to chromium and iron, also contains different components such as nickel, carbon, molybdenum (Mo), titanium (Ti), strontium (Ac), selenium (Se), and developed a series of different Stainless steel. Stainless steel is a stable and strong chrome-rich oxidized film layer formed on the surface to prevent oxygen atoms from continuously infiltrating into oxidation and thus resisting rust. Capability; therefore, stainless steel has unique strength, high wear resistance, superior corrosion resistance and resistance to rust, which is why stainless steel has a high commercial value.

However, in some environments, such as the coastal chlorine-containing atmosphere, when the film layer is continuously destroyed, the oxygen atoms in the air or liquid will continuously penetrate into the stainless steel. The iron atoms in the stainless steel form loose iron oxide, and the stainless steel The surface is rusted. Therefore, it is not any kind of stainless steel, it can resist corrosion and rust in any environment.

In addition, the stainless steel production process includes an annealing and pickling stage. The annealing system heats the stainless steel in order to recrystallize the microstructure of the stainless steel to enhance its strength and ductility. However, during the annealing process, the stainless steel surface may form an undesired black oxide layer (ie, scale); these scales must be removed, otherwise it is not only unsightly, but also requires the next cold-rolling paint. In the case of stainless steel, such as bonding, it will affect the effect and quality of subsequent processing steps, so it is necessary to remove the scale efficiently.

At present, the method for removing the scale may be mechanical or chemical, or may be supplemented by other treatment methods such as salt bath, electrolysis, and other mechanical forces to enhance the rust removal effect; wherein the mechanical method is such as rolling Method, grinding method, sand blasting method, etc.; chemical methods such as pickling, which is to dip the steel into the pickling solution, so that the steel is in the pickling solution by the scale in the continuous conveying process The chemical reaction can be carried out to wash the scale; however, the pickling solution used in the pickling method is usually a strong inorganic acid (hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid), which is easy to cause pollution and damage to the environment.

For example, if nitric acid is used for the pickling process, nitrate wastes and nitrogen oxides (NO _x ) such as nitrogen monoxide (NO) and nitrogen dioxide (NO ₂ ) are generated during the reaction. substance. If hydrochloric acid is used for the pickling process, the acid mist of hydrochloric acid will pollute the air, which will affect the quality of the working environment on the spot. The acid mist of hydrochloric acid may also corrode the machine in the factory, and the concentration of hydrochloric acid used is too high or the treatment time is too long. The surface of the steel causes excessive corrosion, which easily affects the appearance of the steel or reduces the smoothness and flatness of the steel surface.

In addition, the pickling waste liquid formed after pickling generally contains oxides of heavy metals such as iron, chromium and nickel, and these oxides may cause impact on the environment, and special treatment is required to remove them, and the pickling liquid It can not be reused; the current improvement method is to separate and separate metal ions by acid-base neutralization method, and to treat the solidified and dried metal ion-containing sludge by burying method, but the area for burying sludge containing metal ions is limited. In addition to the cost, it also pollutes the soil and is difficult to handle properly.

Nowadays, the inventors have provided a green environmental protection concept and a quick processing method in view of the significant harm caused by the acid washing liquid itself and its waste liquid to the environment and human health, and the slow processing speed to remove the stainless steel scale.

The main object of the present invention is to provide a rapid electric rust-removing method which utilizes an oxidizing electrolyte to infiltrate and dissolve acid corrosion resistance, and is interposed between high-chromium oxide scale and steel, and is closely packed with scale. Combined low chromium content metal layer (chrome empty After the layer is dissolved, the low chromium content metal layer can be removed together with the upper layer of scale to achieve a fast and good descaling effect.

The above-mentioned main object of the present invention is achieved by the following specific technical means: a rapid electric rust-removing method comprising the following steps: Step 1: using a steel material having a surface containing scale as an anode, and placing a persulfate-containing material Electrolytic treatment in the acidic electrolyte of the root compound; and step 2: applying an external force to the steel containing the scale on the surface, the rust is detached from the surface of the steel to complete the rust removal, and a surface is free of scale Steel.

The rapid electric derusting method as described above, wherein the steel material is a chromium-containing alloy steel or stainless steel.

The rapid electric rust removing method as described above, wherein the persulfate-containing compound is sodium peroxodisulfate (Na ₂ S ₂ O ₈ ), potassium persulfate (K ₂ S ₂ O ₈ ) or ammonium persulfate [( One of NH ₄ ) ₂ S ₂ O ₈ ].

The rapid electric rust removing method as described above, wherein the concentration of the persulfate-containing compound is in the range of 10 to 70%.

The rapid electric rust removing method as described above, wherein the step is performed at a pH of less than 2.

The rapid electric derusting method as described above, wherein the step is performed at a temperature of 25 to 80 °C.

The rapid electric rust removing method as described above, wherein the current density of the step 1 is 15 to 60 A/dm ² .

The rapid electric rust removing method as described above, wherein the external force applied in the second step is one of brush grinding, wiping, rinsing, and ultrasonic oscillating.

The advantages of the rapid electric rust removal method of the present invention are:

1. The steel obtained by the rust removing method of the present invention has a smooth and bright surface, and does not need to be subjected to surface treatment such as polishing, so that the procedure is more simplified and time-saving.

2. The method of the present invention does not use chemical substances (such as inorganic strong acids) which have environmental protection and safety concerns, and the amount of hexavalent chromium generated can meet the national standard. Compared with the traditional rust removal method of the strong acid pickling liquid, the present invention has It can avoid the effect of waste acid treatment and the problem of corrosion of people's employees and equipment.

3. The present invention uses sodium peroxodisulphate (Na ₂ S ₂ O ₈ ), potassium persulfate (K ₂ S ₂ O ₈ ) or ammonium persulfate [(NH ₄ ) ₂ S ₂ O ₈ ] as an electrolyte. The rust removal completion time only takes 3 to 5 minutes, and the rust removal completion time required for Na ₂ SO ₄ as the electrolyte is 20 minutes, which has the effect of reducing the time required by at least 4 times.

(S1)‧‧‧Step one

(S2)‧‧‧Step 2

First figure: flow chart of processing steps of the present invention

Figure 2: Schematic diagram of the surface of the steel without electric rust removal

The third figure: a schematic diagram of the surface of the steel material after the rust removal is completed in one embodiment of the present invention

Fourth: Schematic diagram of the surface of the steel material after the rust removal is completed in the second embodiment of the present invention

Figure 5: Schematic diagram of the surface of the steel in which the rust removal is completed in the three specific embodiments of the present invention

Figure 6: Schematic diagram of the surface of the steel with sodium sulfate as the electrolyte

For a more complete and clear disclosure of the technical content, the purpose of the invention and the effects thereof achieved by the present invention, it is explained in detail below, and please refer to the drawings and drawings:

Please refer to the first figure, which is a flow chart of the steps of the rapid electric derusting method of the present invention, which comprises the following steps: Step 1 (S1): using a steel having a surface containing scale and being a chromium-containing alloy steel or stainless steel as an anode. And placed in an acidic electrolyte containing persulfate compound Electrolytic treatment; and step 2 (S2): applying an external force to the surface of the steel containing the scale, the rust is detached from the surface of the steel to complete the rust removal, and a steel having no surface on the surface is obtained.

Wherein, the concentration of the persulfate-containing compound described in the first step (S1) is in the range of 10 to 70%, and the electrolysis is performed in the range of the pH value of less than 2, and the operation of electrically derusting is performed at 25 to 80. The temperature is set at a temperature of °C, and the current density at the time of electrolysis is 15 to 60 A/dm ² .

Wherein, the external force applied in the second step (S2) may be one of brushing, wiping, rinsing, and ultrasonic oscillating.

The invention adopts an acidic electrolyte containing a persulfate compound, and the component thereof generates a chemical substance having a high oxidizing ability when reacting at the electrode, and functions to dissolve the chrome depletion layer, and a large amount of gas generated by electrolysis can cause the oxidized scale to fall off. In particular, high-alloy rust scales of superalloys and stainless steels are different from ordinary carbon steels. The high chromium content of the components and the high affinity of chromium and oxygen make the scales produced by surface oxidation rich in high density and very chemical. Stable chrome oxide, of course, between the high chromium oxide scale and the base metal (steel) is a low chromium content metal layer (chromium depletion layer), which is tightly bonded to the scale. Moreover, the low chromium content metal layer has a low acid attack resistance. Therefore, the present invention can dissolve the low chromium content metal layer by infiltration into the upper chromium layer which is tightly combined with the low chromium content metal layer by oxidizing the electrolyte solution. Remove.

The invention may be further exemplified by the specific examples, but is not intended to limit the scope of the invention in any way.

<Example 1>

First, the steel used in this embodiment is 300 series stainless steel; this stainless steel is purchased from Tangrong Stainless Steel Co., model SS304 (please refer to the second figure). The stainless steel is used as an anode and placed in an electrolyte containing 10% sodium persulfate (Na ₂ S ₂ O ₈ ) (pH < 2), and then the anode and the cathode (stainless steel metal) are electrically connected to one. The power supply device obtains an electrolysis device for performing an electrolysis reaction (the temperature of the electrolyte is about 60 ° C, generally, the higher the temperature, the better the electrolysis effect), and the current density used in electrolysis is 15 A/dm ² ; After 3 minutes of treatment, the electrolytically treated stainless steel was taken out and placed in an ultrasonic oscillator for 60 seconds, and then the stainless steel surface was wiped off to obtain a smooth polished stainless steel (see the third figure).

<Embodiment 2>

In this embodiment, the same steel conditions, electrolyte temperature, electrolysis treatment time, shaking time, electrolysis equipment, current density and flow rate during electrolysis are used; and the electrolyte selected in the embodiment is 10% potassium persulfate. (K ₂ S ₂ O ₈ ) electrolyte (pH <2); smooth polished stainless steel made from the above conditions (see Figure 4).

<Example 3>

In this embodiment, the same steel conditions, electrolyte temperature, electrolysis treatment time, shaking time, electrolysis equipment, current density and flow rate during electrolysis are used; and the electrolyte selected in this embodiment is 10% ammonium persulfate. Electrolyte [(NH ₄ ) ₂ S ₂ O ₈ ] (pH <2); smooth polished stainless steel material prepared by the above conditions (see Figure 5).

<Comparative example>

The comparative example uses the same steel conditions as in the first embodiment, the electrolyte temperature and the electrolysis equipment, the current density and the flow during electrolysis; and the electrolyte selected in the comparative example is a sodium sulphate Na ₂ SO ₄ electrolyte containing 16%; Stainless steel made from the above conditions (see Figure 6).

According to the results of the electric rust removal of the above embodiments, the results of the rust removal were further analyzed (see Table 1); the results showed that 10% sodium persulfate (Na ₂ S ₂ O) ₈ ) After the stainless steel electric rust-removing reaction for the electrolyte, the surface roughness of the prepared stainless steel is 1.285, the gloss is 5.1, the time required for rust removal is 3 minutes, and the potassium persulfate at 10% concentration (K _{2 )} S ₂ O ₈ ) After the stainless steel electric rust-removing reaction for the electrolyte, the surface roughness of the prepared stainless steel is 2.53, the gloss is 2.52, the time required for rust removal is 3 minutes, and the ammonium persulfate at 10% concentration [(NH ₄ ) ₂ S ₂ O ₈ ] After the stainless steel electric rust-removing reaction was carried out for the electrolyte, the surface roughness of the prepared stainless steel was 1.965, the gloss was 2.18, and the time required for rust removal was 5 minutes; After the stainless steel electric derusting reaction was carried out with 16% sodium sulfate (Na ₂ SO ₄ ) as the electrolyte, the surface roughness of the prepared stainless steel was 1.61, the gloss was 5.5, and the time required for the rust removal was 20 minutes; It can be seen that the electrolysis method of the present invention can indeed be used in a short period of time. The steel surface scale is removed in the room, and a steel surface having a smooth and bright surface is obtained, that is, the method used in the present invention has a better rust removal efficiency.

The above is only a part of the embodiments of the present invention, and is not intended to limit the present invention. It is intended to be included in the scope of the present invention.

In summary, the embodiments of the present invention can achieve the expected use efficiency, and the specific technical means disclosed therein have not been seen in similar products, nor have they been disclosed before the application, and have completely complied with the patent law. The regulations and requirements, the application for invention patents in accordance with the law, and the application for review, and the grant of patents, are truly sensible.

(S1)‧‧‧Step one

(S2)‧‧‧Step 2

Claims (3)

A rapid electric rust removing method, comprising the following steps: Step 1: using a steel material with a surface containing a scale as an anode, and placing a pH value less than 2 and containing sodium persulfate (Na ₂ S ₂ O ₈ ), persulfuric acid Electrolysis at a temperature of 25 to 80 ° C in an acidic electrolyte containing potassium (K ₂ S ₂ O ₈ ) or ammonium persulfate [(NH ₄ ) ₂ S ₂ O ₈ ] in a concentration range of 10 to 70% Treatment, electrolysis uses a current density of 15~60A/dm ² ; and step 2: applies an external force to the surface of the steel containing the scale, so that the scale is detached from the surface of the steel to complete the derusting, and obtain a Steel with no surface on the surface. The rapid electric derusting method according to the first aspect of the invention, wherein the steel material is a chromium-containing alloy steel or stainless steel. The method of claim 1, wherein the external force applied in the second step comprises one of brushing, wiping, rinsing, and ultrasonic oscillating.