CN112782347A - Method for detecting degreasing performance of degreasing agent for cold-rolled hot-galvanized substrate - Google Patents
Method for detecting degreasing performance of degreasing agent for cold-rolled hot-galvanized substrate Download PDFInfo
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Abstract
The invention discloses a method for detecting degreasing performance of a degreasing agent for a cold-rolled hot-galvanized substrate, and mainly solves the technical problems that the degreasing performance of the existing degreasing agent for the cold-rolled hot-galvanized substrate cannot be accurately detected and the detection precision is low. The invention discloses a method for detecting degreasing performance of a degreasing agent for a cold-rolled hot-galvanized substrate, which comprises the following steps: 1) preparing a sample; 2) preparing a copper ammonia solution; 3) preparing iron powder; 4) preparing a mixed solution of a degreasing agent and iron powder; 5) soaking the sample by using the mixed solution; 6) and evaluating the degreasing performance of the degreasing agent. The method of the invention has simple operation, no need of expensive equipment, low working strength and accurate detection result.
Description
Technical Field
The invention relates to a method for detecting degreasing performance of a degreasing agent, in particular to a method for detecting degreasing performance of a degreasing agent for a cold-rolled hot-dip galvanized substrate, and belongs to the technical field of metal material detection and analysis.
Background
After hot galvanizing, the steel plate forms a bright surface with certain corrosion resistance. The hot dip galvanized steel sheet is widely applied to household appliances, buildings and the like, and the domestic yield exceeds 1 hundred million tons every year.
During the production process of the hot-dip base plate, the surface of the hot-dip base plate can not be stained with anti-rust oil, rolling oil and the like, the iron powder caused by surface friction during rolling is also remarkably dropped, during hot-dip, the residual oil on the surface of the base plate influences the binding force of coating elements and a steel base plate, and the iron powder causes the condition that the coating has uneven spangles. Thereby affecting the appearance quality and the processing performance of the plating plate. Before hot-dipping, residual oil and iron powder are generally removed by a degreasing process.
The principle of degreasing and iron removal of degreasing fluid is as follows: in the production process, technological process grease including antirust oil, lubricating oil and the like is adhered to the surface of the cold-rolled substrate, iron powder and oil in the rolling process are mixed together and adhered to the surface of the substrate, and the degreasing process is a process which takes mechanical cleaning as an auxiliary process in aqueous solution and takes the oil and the iron powder away from the substrate.
Since the oil is not soluble in water, it is necessary to use a degreasing agent in the cleaning process, which usually consists of an alkaline solution and a surfactant, wherein the alkaline solution is used for saponification, and the oil of animal or vegetable oils reacts with a strong base to form water-soluble salts of alcohols and acids, such as:
CH3COOCH2CH3+NaOH→CH3COONa+CH3CH2OH
part of oil belongs to mineral oil, namely hydrocarbon, can not perform saponification reaction, and a surfactant is required to be added for degreasing, wherein one end of a surfactant molecule is hydrophilic phase, the other end is lipophilic phase, and when the molecules are directionally arranged on an oil-water interface, a head group with larger polarity extends to a water phase; the nonpolar carbon hydrogen bond penetrates into the oil phase, and the hydrophilic phase completely surrounds the internal phase oil, so that the oil is taken away from the surface of the substrate to form a stable O/W type emulsion.
Surfactants that can be used for degreasing can be classified into two types, anionic and nonionic, according to the type of hydrophilic group, and the anionic surfactant generates hydrophobic anions after dissociating in water. The anionic surfactant is divided into four categories of carboxylate, sulfate ester salt, sulfonate and phosphate ester salt, and has the characteristics of good decontamination, foaming, dispersion, emulsification, wetting and the like. The nonionic surfactant is soluble in water without dissociation, and has lipophilic groups substantially the same as those of the ionic surfactant, and hydrophilic groups mainly composed of a certain number of oxygen-containing groups (such as hydroxyl groups and polyoxyethylene chains). The nonionic surfactant is not present in an ionic state in the solution, so that it has high stability, is not easily affected by the presence of strong electrolyte, is not easily affected by acid and alkali, can be mixed with other surfactants for use, has good compatibility, has good solubility in various solvents, and does not strongly adsorb on the solid surface.
Because the iron powder is mixed with grease and adhered to the surface of the substrate, the iron powder will be separated from the surface after the grease is removed, so the iron removal is also part of the degreasing process. Iron atoms on the surface of the iron powder easily lose outer layer electrons in the solution and become ferrous ions Fe2+And therefore, has a positive charge.
The surface of the substrate is generally provided with positive charges, the anionic surfactant is provided with negative charges and is easily adsorbed on the surface of the substrate, so that the substrate cleaning is facilitated, but the iron powder is also provided with positive charges, the iron powder is easily adsorbed on the surface when the anionic surfactant is adopted, the removal of the iron powder is not facilitated, the nonionic surfactant does not have the problems but is high in price, the other factor influencing the cleaning effect of the iron powder is the content of potassium hydroxide, the rinsing effect is good when the content of the potassium hydroxide is high, but the oil removal effect is reduced due to high conductivity, so that the influence factor of the iron removal capacity is relatively complex, and the experiment is needed to.
In order to further improve the cleanliness of the hot-dip plated substrate, a plurality of researches are carried out at home and abroad on degreasing processes, and devices such as electrolytic degreasing, degreasing combined scrubbing, electric spraying and the like are put into application in different production lines. At present, the degreasing effect of degreasing fluid can be realized by detecting the oil content of degreased board surface, but the method is complex, needs special equipment, is complex to operate and needs long time, and has high detection difficulty and low general precision due to the low oil content of the degreased board surface; because the iron powder on the plate surface has little influence on the mechanical and corrosion resistance of the hot-dip plated plate (mainly influences the appearance), the iron removal effect is not regarded for a long time, and no proper detection method is available. In the industry, due to the lack of effective technical means, the effects of degreasing and iron removal in a degreasing process cannot be accurately detected, and certain influence is caused on the stability of the surface quality of a hot-dip product.
Disclosure of Invention
The invention aims to provide a method for detecting degreasing performance of a degreasing agent for a cold-rolled hot-galvanized substrate, which mainly solves the technical problems that the degreasing performance of the existing degreasing agent for the cold-rolled hot-galvanized substrate cannot be accurately detected and the detection precision is low; the method can accurately detect the removing capability of the degreasing agent on the residual oil and the residual iron on the surface of the cold-rolled hot-dip galvanized substrate.
The technical idea of the invention is that degreasing fluid is adjusted to be alkalescent by carbon dioxide and heated to a set temperature, treated test iron powder is added, a sample plate is cleaned in the degreasing fluid for a certain time, and the degreasing and iron removal capacity of the degreasing fluid is judged by observing the area of the water membrane on the surface of the sample plate and the adhesion degree of the iron powder.
The invention adopts the technical scheme that a method for detecting the degreasing performance of a degreasing agent for a cold-rolled hot-dip galvanized substrate comprises the following steps:
1) preparing a sample, and cutting out a cold-rolled hot-dip galvanized substrate sample, wherein the length of the sample is 20-30cm, and the width of the sample is 10-15 cm;
2) preparing a copper ammonia solution, adding 100mL of a copper sulfate solution with the mass volume concentration of 40g/L into a 400mL beaker, then dropwise adding 150g/L of ammonia water until light blue basic copper sulfate precipitate is generated, and continuously dropwise adding the ammonia water until the precipitate is completely dissolved; the mass volume concentration of the copper ammonium sulfate in the copper ammonium solution is 57 g/L;
3) preparing iron powder, adding 800mL of oxalic acid with the mass volume concentration of 50g/L into a 1000mL beaker, adding 20g of degreased iron powder, stirring and cleaning for 5-20min, filtering, and cleaning residual oxalic acid; transferring the filtered iron powder into a copper ammonia solution, stirring and dispersing, standing for 10-30min, filtering, cleaning the copper ammonia solution on the surface of the iron powder by using ethanol, and drying for later use;
4) preparing a mixed solution of a degreasing agent and iron powder, adding 800mL of the degreasing agent into a 1000mL beaker, heating the degreasing agent to 40-80 ℃, adding 0.067mL of phenolphthalein with the mass volume concentration of 10g/L into the degreasing agent, introducing carbon dioxide until the solution turns red, controlling the pH value of the solution to be 8-10, and then adding 2-4g of iron powder;
5) soaking the sample by using the mixed solution, stirring to enable the iron powder to be suspended in the solution, soaking the sample in the mixed solution along the long edge direction for 10-20s, taking out the sample from the mixed solution, observing the quantity of the iron powder on the surface of the sample by naked eyes, and recording the quantity of the iron powder on the surface of the sample; washing the sample with water for 20 s; vertically standing the cleaned sample for 15-30s, and observing and recording the ratio of the area of the water membrane on the surface of the sample to the total immersion area;
5) soaking the sample by using the mixed solution, stirring to enable the iron powder to be suspended in the solution, soaking the sample in the mixed solution along the long edge direction for 10-20 seconds, taking out the sample from the mixed solution, observing the quantity of the iron powder on the surface of the sample by naked eyes, and recording the quantity of the iron powder on the surface of the sample; washing the sample with water; vertically standing the cleaned sample for 15-30s, and observing and recording the ratio of the area of the water membrane on the surface of the sample to the total immersion area;
6) evaluating the degreasing performance of the degreasing agent, namely evaluating the iron removal capacity of the degreasing agent according to the amount of iron powder on the surface of a sample, wherein the iron removal performance of the degreasing agent is excellent when the total iron powder number on two surfaces of the sample is less than or equal to 3, the iron removal performance of the degreasing agent is qualified when the total iron powder number on two surfaces of the sample is 4-6, and the iron removal performance of the degreasing agent is unqualified when the total iron powder number on two surfaces of the sample is more than 6; evaluating the degreasing performance of the degreasing agent according to the ratio of the area of the water film on the surface of the sample to the total immersed area, evaluating that the degreasing performance of the degreasing agent is excellent if the ratio of the sum of the areas of the water films on the two sides of the sample to the total immersed area is more than or equal to 70%, evaluating that the degreasing performance of the degreasing agent is qualified if the ratio of the sum of the areas of the water films on the two sides of the sample to the total immersed area is 30-70%, and evaluating that the degreasing performance of the degreasing agent is unqualified if the ratio of the sum of the.
Furthermore, the particle size of the iron powder is 3-10 μm.
The degreasing agent is aqueous solution, the main components of the degreasing agent comprise a mixture of sodium hydroxide and potassium hydroxide with the mass volume concentration of 10-30g/L and a surfactant with the mass volume concentration of 1-20g/L, and the degreasing agent is used for removing residual oil and iron powder attached to the surface of the cold-rolled hot-dip zinc substrate.
The technical scheme of the invention is based on the following researches of the applicant:
the applicant finds that the effect of the degreasing agent in removing residual oil and iron powder is related to factors such as alkali concentration, alkali type and surfactant type in the degreasing solution, and is also related to factors such as degreasing temperature and time in actual production, and the effect is best evaluated by simulating field process conditions.
And (3) evaluating the degreasing agent, namely putting the hot-dip base plate into the degreasing agent at a specified temperature to serve as a basic measure for simulating a degreasing process. Because the temperature has obvious influence on the degreasing efficiency, the degreasing temperature of different hot-dip production lines is between 40 ℃ and 80 ℃. In order to correctly evaluate the degreasing effect under the field process conditions, the test temperature is consistent with the production temperature. In addition, the time for placing the sample plate in the degreasing fluid and the relative speed of the sample plate and the degreasing fluid have a large influence on the degreasing effect, the placing time is generally 10-20 seconds, the simulated degreasing time is short when the unit speed is high, and the time for simulated degreasing is long when the unit speed is low. In addition, the evaluation of the oil removal and iron removal capacity has the following characteristics: for the evaluation of oil removal capability, alkali and surfactant have degreasing effect, but the price difference between the alkali and the surfactant is large, the alkali is hundreds yuan/ton, and the surfactant is thousands to tens of thousands yuan/ton. The quantity of alkali in different types of degreasing fluids is close, and the using concentration is about 10g/L-30g/L, so if the quality of the degreasing fluid is to be evaluated, the degreasing effect of the surfactant is mainly evaluated, the degreasing effect of the shielded alkali is considered, and the degreasing fluid is adjusted to be alkalescent by adopting a method of introducing carbon dioxide. The phenolphthalein indicator is red at a pH of 8-10, and colorless both above and below. The degreasing solution is originally strong in alkalinity, the pH value is about 13, after a drop of phenolphthalein is added into the degreasing solution, the pH value is reduced after carbon dioxide is introduced, the degreasing solution becomes red after the pH value is 8-10, and the introduction of the carbon dioxide can be stopped, so that the degreasing performance of the alkali is shielded, and the influence on degreasing evaluation caused by introducing more impurities is avoided. The reaction formula is as follows:
CO2+2NaOH＝Na2CO3+H2O
the phenolphthalein is used as an acid-base indicator, the use concentration is generally 10g/L, the use amount has no great influence on the actual effect, generally 1 drop is added, in a laboratory, 1mL of aqueous solution is generally considered to be about 15 drops, and therefore 1 drop of phenolphthalein is generally 0.067 mL.
The oil content of the substrate before degreasing is 100mg/m2Above, after degreasing, the concentration is generally 1mg/m2The following are generally used in a long time and measured by an infrared method after washingThe detection accuracy is difficult to ensure. Other ways of evaluating whether the resid has been removed need to be considered. After degreasing, the residual oil on the surface generally exists as an oil film, the thickness of the residual oil is about tens of nanometers, and because the oil and the water cannot be compatible with each other, when the oil film exists, the substrate is immersed in water and the surface degreasing liquid is washed, and then the continuous water film cannot be formed on the surface, so that the substrate can be immersed in water and extracted after degreasing, whether the water film on the surface of the substrate is continuous and the area of the residual water film can be used as evaluation measures for whether the degreasing is complete, and the situation that the surface oil content is low can be evaluated. From experimental experience, it can be seen that 100% of the water film area is not possible due to the influence of the edge effect, but when the degreasing effect is good, 70% or more of the water film area can be ensured, even 90% or more regardless of the cost, but after the degreasing agent test of a general production line, the water film area is about 50% or more, sometimes 30% or more, and the result does not actually influence the production from experience, but if the water film area is 30% or less, it indicates that a continuous oil film still exists on the surface of the degreased steel plate, and the continuous oil film affects the continuity of the zinc-iron alloy layer during hot-dipping, so the degreaser is considered to be unqualified.
And (3) evaluating the iron removal capacity, namely using rolled iron powder for evaluating the iron removal capacity, wherein the detection shows that the particle size of the rolled iron powder is in normal distribution, the peak value is about 6 micrometers, 95 percent of the particle size is between 3 and 10 micrometers, and the rolled iron powder is difficult to directly obtain. In the production, the iron powder cleaned by the degreasing process influences the continuous degreasing effect, so a magnetic filter is arranged below a degreasing tank and used for collecting the iron powder, the iron powder is used as a material for iron removal evaluation, however, the iron powder obtained on site usually has been stored for a period of time, the surface of the iron powder is oxidized, the iron powder is different from rolled iron powder, the iron powder is difficult to be directly used for evaluating the iron removal effect, the iron powder is treated by oxalic acid, the surface oxidation film is removed, and the reactivation of the iron powder is realized, and the equation is as follows:
Fe2O3+3H2C2O4＝2FeC2O4↓+2CO2↑+3H2O
oxalic acid is a commonly used rust remover for removing an oxide layer on the surface of iron powder, the cleaning time of the rust remover is related to the thickness of the oxide layer on the surface, generally, the cleaning time is 5 to 20 minutes, and the dissolution of metal iron cannot be caused even if the cleaning time is long.
However, the treated iron powder and the steel substrate have the same color, and whether the iron powder and the steel substrate are attached to the surface of the substrate or not can not be easily seen in the test, copper sulfate and ammonia water are used for synthesizing a copper ammonia solution, and the equation is as follows:
CuSO4+4NH3·H2O＝[Cu(NH3)4]SO4+4H2O
copper salt can perform a displacement reaction with iron, and because the reaction speed is high usually, the coating is black, compared with the common copper salt, the cuprammonium solution can slowly react with iron, and the displacement coating is bright red and is easy to identify:
Fe+[Cu(NH3)4]2++2H2O→Cu↓+2NH3+2NH4 ++Fe(OH)2↓
the displacement reaction takes about 24 hours to complete, and is generally soaked in the cuprammonium solution for 10-30 minutes, so that the surface is dyed on one hand, and the residual iron powder is not influenced to participate in the experiment on the other hand. The treated iron powder is put into degreasing fluid, the iron powder is suspended in the solution after stirring, the hot-dip coated substrate is taken out after being cleaned in the solution, and the number of the iron powder adhered to the surface is observed, so that whether the degreasing fluid is easy to adsorb the iron powder or how the iron removal efficiency is high can be judged. Research shows that the iron removing effect is mainly related to the components of the degreasing fluid, the general potassium hydroxide has better rinsing performance, the iron removing performance is better when the electronegativity of the surfactant is lower, but the price of the potassium hydroxide and the surfactant is higher. For the degreasing solution with better performance, iron powder is not adhered to the surface of the steel plate after cleaning, or 1-2 degreasing solutions with poorer performance are adhered to the surface of the steel plate after cleaning. After hot-dipping, iron powder is nucleated on the surface to cause regional uneven spangles. The uneven spangles only affect the appearance and do not affect the performance, and common high-end users pay more attention to the uneven spangles.
Compared with the prior art, the invention has the following positive effects: 1. the method can effectively evaluate the oil removing capability of the degreasing fluid. 2. The method can evaluate the iron removal capacity of the degreasing fluid and realize technical breakthrough. 3. The method is simple and convenient to operate, does not need special equipment, and has low working strength.
Detailed Description
The invention is further described below with reference to specific examples.
In example 1, the speed of a certain low-speed hot galvanizing production line is 50m/s, the degreasing temperature is 40 ℃, and detection shows that the degreasing solution contains 15g/L of sodium hydroxide and 3g/L of surfactant by adopting a certain low-cost degreasing solution.
A method for detecting degreasing performance of a degreasing agent for a cold-rolled hot-dip galvanized substrate comprises the following steps:
1) preparing a sample, and cutting out a cold-rolled hot-dip galvanized substrate sample, wherein the length of the sample is 20cm, and the width of the sample is 10 cm;
2) preparing a copper ammonia solution, adding 100mL of copper sulfate solution with the mass volume concentration of 40g/L into a 400mL beaker, then dropwise adding ammonia water with the volume concentration of 150g/L until light blue basic copper sulfate precipitate is generated, and continuously dropwise adding ammonia water until the precipitate is completely dissolved, thus obtaining a dark blue solution containing copper ammonia complex ions, namely copper sulfate ammonia ([ Cu (NH) in the copper ammonia solution3)4]SO4) The mass volume concentration of the active carbon is 57 g/L;
3) preparing iron powder, adding 800mL of oxalic acid with the mass volume concentration of 50g/L into a 1000mL beaker, taking 20g of degreased iron powder from a magnetic filter of a hot galvanizing degreasing production line, adding the degreased iron powder into the beaker, stirring and cleaning for 10 minutes, filtering, and cleaning residual oxalic acid on the iron powder; transferring the iron powder into a copper ammonia solution, stirring and dispersing, standing for 10 minutes, filtering and cleaning, removing surface moisture by using ethanol, and drying for later use;
4) preparing a mixed solution of a degreasing agent and iron powder, adding 800mL of the degreasing agent into a 1000mL beaker, heating the degreasing agent to 40 ℃, adding 0.067mL of phenolphthalein with the mass volume concentration of 10g/L into the degreasing agent, introducing carbon dioxide gas until the solution is reddish, and adding 2g of the treated iron powder into the degreasing agent;
5) soaking the sample by using the mixed solution, stirring the degreasing agent to enable the iron powder to be suspended in the solution, putting the substrate into the degreasing agent along the long edge, keeping for 20 seconds, taking out, observing and recording the amount of the iron powder on the surface; cleaning the surface of the substrate with water for 20 seconds, standing vertically for 20 seconds, and observing and recording the ratio of the area of the surface water film to the total immersion area;
6) evaluating the degreasing performance of the degreasing agent, wherein the total iron powder on two surfaces of the hot-dip base plate is 3; the proportion of the sum of the areas of the water films on the two surfaces to the total immersion area is 55 percent, which is qualified oil removing capability and excellent iron removing capability.
Example 2, a certain hot galvanizing line speed is 100m/s, the degreasing temperature is 60 ℃, and a certain degreasing agent is adopted. The detection shows that the content of sodium hydroxide in the degreasing agent is 20g/L, and the content of the surfactant is 8 g/L.
A method for detecting degreasing performance of a degreasing agent for a cold-rolled hot-dip galvanized substrate comprises the following steps:
1) preparing a sample, and cutting out a cold-rolled hot-dip galvanized substrate sample, wherein the length of the sample is 30cm, and the width of the sample is 15 cm;
2) preparing a copper ammonia solution, adding 100mL of copper sulfate solution with the mass volume concentration of 40g/L into a 400mL beaker, then dropwise adding ammonia water with the volume concentration of 150g/L until light blue basic copper sulfate precipitate is generated, and continuously dropwise adding ammonia water until the precipitate is completely dissolved, thus obtaining a dark blue solution containing copper ammonia complex ions, namely copper sulfate ammonia ([ Cu (NH) in the copper ammonia solution3)4]SO4) The mass volume concentration of the active carbon is 57 g/L;
3) preparing iron powder, adding 800mL of oxalic acid with the mass volume concentration of 50g/L into a 1000mL beaker, taking 20g of degreased iron powder from a magnetic filter of a hot galvanizing degreasing production line, adding the degreased iron powder into the beaker, stirring and cleaning for 20 minutes, filtering, and cleaning residual oxalic acid; transferring the filtered iron powder into a copper ammonia solution, stirring and dispersing, standing for 20 minutes, filtering, removing the moisture on the surface of the iron powder by using ethanol, and drying for later use;
4) preparing a mixed solution of a degreasing agent and iron powder, adding 800mL of the degreasing agent into a 1000mL beaker, heating the degreasing agent to 60 ℃, adding 0.067mL of phenolphthalein with the mass volume concentration of 10g/L into the degreasing agent, introducing carbon dioxide gas until the solution is reddish, heating the degreasing agent to 60 ℃, and adding 3g of treated iron powder into the degreasing agent;
5) soaking the sample by using the mixed solution, stirring the degreasing agent to enable the iron powder to be suspended in the solution, putting the degreasing agent into the substrate along the long edge, keeping for 15 seconds, taking out, observing and recording the amount of the iron powder on the surface; washing the surface of the substrate with water for 20 seconds, vertically standing for 15 seconds, and observing and recording the ratio of the area of the surface water film to the total immersion area;
6) evaluating the degreasing performance of the degreasing agent, wherein the total number of two sides of iron powder on the hot-dip coated substrate is 5; the proportion of the sum of the areas of the water films on the two sides to the total immersion area is 35 percent, and the water films are qualified in oil removal capacity and iron removal capacity.
Example 3, a hot dip galvanizing line speed was 150m/s, a degreasing temperature was 80 ℃, and a degreasing solution was used.
Detection shows that the degreasing fluid contains 10g/L of sodium hydroxide, 5g/L of potassium hydroxide and 15g/L of surfactant.
A method for detecting degreasing performance of a degreasing agent for a cold-rolled hot-dip galvanized substrate comprises the following steps:
1) preparing a sample, and cutting out a cold-rolled hot-dip galvanized substrate sample, wherein the length of the sample is 30cm, and the width of the sample is 15 cm;
2) preparing a copper ammonia solution, adding 100mL of copper sulfate solution with the mass volume concentration of 40g/L into a 400mL beaker, then dropwise adding ammonia water with the volume concentration of 150g/L until light blue basic copper sulfate precipitate is generated, and continuously dropwise adding ammonia water until the precipitate is completely dissolved, thus obtaining a dark blue solution containing copper ammonia complex ions, namely copper sulfate ammonia ([ Cu (NH) in the copper ammonia solution3)4]SO4) The mass volume concentration of the active carbon is 57 g/L;
3) preparing iron powder, adding 800mL of oxalic acid with the mass volume concentration of 50g/L into a 1000mL beaker, taking 20g of degreased iron powder from a hot-dip degreasing production line under a magnetic filter, putting the degreased iron powder into the beaker, stirring and cleaning for 5 minutes, filtering, and cleaning residual oxalic acid; transferring the filtered iron powder into a copper ammonia solution, stirring and dispersing, standing for 20 minutes, filtering, removing surface moisture by using ethanol, and drying for later use;
4) preparing a mixed solution of a degreasing agent and iron powder, adding 800mL of the degreasing agent into a 1000mL beaker, heating the degreasing agent to 80 ℃, adding 0.067mL of phenolphthalein with the mass volume concentration of 10g/L into the degreasing agent, introducing carbon dioxide gas until the solution is reddish, and adding 4g of treated iron powder into the degreasing agent;
5) soaking the sample by using the mixed solution, stirring the degreasing agent to enable the iron powder to be suspended in the solution, putting the substrate into the degreasing agent along the long edge, keeping for 10 seconds, taking out, observing and recording the amount of the iron powder on the surface; washing the surface of the substrate with water for 20 seconds, vertically standing for 30 seconds, and observing and recording the ratio of the surface water film area to the total area;
6) evaluating the degreasing performance of the degreasing agent, wherein the total iron powder on two surfaces of the hot-dip base plate is 0 particle; the proportion of the sum of the areas of the water films on the two sides to the total immersion area is 80 percent, and the water film is good in oil removing capability and good in iron removing capability.
In addition to the above embodiments, the present invention may have other embodiments. All technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.
Claims (3)
1. A method for detecting degreasing performance of a degreasing agent for a cold-rolled hot-dip galvanized substrate is characterized by comprising the following steps:
1) preparing a sample, and cutting out a cold-rolled hot-dip galvanized substrate sample, wherein the length of the sample is 20-30cm, and the width of the sample is 10-15 cm;
2) preparing a copper ammonia solution, adding 100mL of a copper sulfate solution with the mass volume concentration of 40g/L into a 400mL beaker, then dropwise adding 150g/L of ammonia water until light blue basic copper sulfate precipitate is generated, and continuously dropwise adding the ammonia water until the precipitate is completely dissolved; the mass volume concentration of the copper ammonium sulfate in the copper ammonium solution is 57 g/L;
3) preparing iron powder, adding 800mL of oxalic acid with the mass volume concentration of 50g/L into a 1000mL beaker, adding 20g of degreased iron powder, stirring and cleaning for 5-20min, filtering, and cleaning residual oxalic acid; transferring the filtered iron powder into a copper ammonia solution, stirring and dispersing, standing for 10-30min, filtering, cleaning the copper ammonia solution on the surface of the iron powder by using ethanol, and drying for later use;
4) preparing a mixed solution of a degreasing agent and iron powder, adding 800mL of the degreasing agent into a 1000mL beaker, heating the degreasing agent to 40-80 ℃, adding 0.067mL of phenolphthalein with the mass volume concentration of 10g/L into the degreasing agent, introducing carbon dioxide until the solution turns red, controlling the pH value of the solution to be 8-10, and then adding 2-4g of iron powder;
5) soaking the sample by using the mixed solution, stirring to enable the iron powder to be suspended in the solution, soaking the sample in the mixed solution along the long edge direction for 10-20s, taking out the sample from the mixed solution, observing the quantity of the iron powder on the surface of the sample by naked eyes, and recording the quantity of the iron powder on the surface of the sample; washing the sample with water for 20 s; vertically standing the cleaned sample for 15-30s, and observing and recording the ratio of the area of the water membrane on the surface of the sample to the total immersion area;
6) evaluating the degreasing performance of the degreasing agent, namely evaluating the iron removal capacity of the degreasing agent according to the amount of iron powder on the surface of a sample, wherein the iron removal performance of the degreasing agent is excellent when the total iron powder number on two surfaces of the sample is less than or equal to 3, the iron removal performance of the degreasing agent is qualified when the total iron powder number on two surfaces of the sample is 4-6, and the iron removal performance of the degreasing agent is unqualified when the total iron powder number on two surfaces of the sample is more than 6; evaluating the degreasing performance of the degreasing agent according to the ratio of the area of the water film on the surface of the sample to the total immersed area, evaluating that the degreasing performance of the degreasing agent is excellent if the ratio of the sum of the areas of the water films on the two sides of the sample to the total immersed area is more than or equal to 70%, evaluating that the degreasing performance of the degreasing agent is qualified if the ratio of the sum of the areas of the water films on the two sides of the sample to the total immersed area is 30-70%, and evaluating that the degreasing performance of the degreasing agent is unqualified if the ratio of the sum of the.
2. The method for detecting the degreasing agent degreasing performance of the cold-rolled hot-galvanized substrate as claimed in claim 1, wherein the particle size of the iron powder is 3-10 μm.
3. The method for detecting the degreasing agent degreasing performance of the cold-rolled hot-galvanized substrate as claimed in claim 1, wherein the degreasing agent is an aqueous solution, the main components of the degreasing agent comprise a mixture of sodium hydroxide and potassium hydroxide with a mass volume concentration of 10-30g/L, and a surfactant with a mass volume concentration of 1-20 g/L.
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