CN104264141A - Normal-temperature thick-film zinc phosphide phosphating solution and experimental method for determining component proportions - Google Patents

Abstract

The invention discloses a normal-temperature thick-film zinc phosphide phosphating solution and an experimental method for determining component ratios. The normal-temperature thick-film zinc phosphide phosphating solution comprises: Zn(H ₂ PO ₄ ) ₂ 70g/L, Zn(NO ₃ ) ₂ 100g/L, NaNO ₂ 0.6g/L, Ni(NO ₃ ) ₂ 6g/L, Ce(NO ₃ ) _3.6 (H ₂ O) 10g/L, citric acid 1.5g/L , OP emulsifier 1ml/L, time 20min; the experimental method for determining the component ratio of the room temperature thick film zinc phosphide phosphating solution includes: solution preparation, phosphating film preparation, and performance testing. The normal temperature thick film zinc phosphide phosphating solution obtained by using this component has a dark gray phosphating film without hanging ash, and the film layer is evenly and continuously covered; the relationship between film weight and film thickness is about 1:1, and the average The film weight exceeds 18.13g/L, and the obtained phosphating film is a heavy-duty film, which is mainly used for anti-corrosion of storage parts; the phosphating film has fine crystals, small porosity, good corrosion resistance, and excellent corrosion resistance of the film layer.

Description

A normal-temperature thick-film zinc phosphide phosphating solution and an experimental method for determining the proportion of components

technical field

The invention belongs to the technical field of zinc-based phosphating solutions, in particular to a normal-temperature thick-film zinc-based phosphating solution and an experimental method for determining component ratios.

Background technique

Phosphating treatment can be widely used in various industries, such as automobiles, machinery, shipbuilding, home appliances, military industry, aviation, etc. After years of development, phosphating technology has made many new achievements. In particular, the scope of application of phosphating has been greatly expanded, and phosphating has become an indispensable and important technology for steel processing, anti-corrosion, and decoration. In many chemical surface conversion treatment processes, phosphating treatment occupies a very important position. However, the traditional phosphating solution has high temperature, high energy consumption, and high cost. Although some phosphating solutions have low temperature, the film-forming effect is not good, especially as a thick phosphating film with anti-corrosion properties, the corrosion resistance is not good. .

Contents of the invention

The purpose of the embodiments of the present invention is to provide a normal-temperature thick-film zinc phosphide phosphating solution and an experimental method for determining the proportion of components, aiming at solving the problem of high-temperature phosphating solution cost, high energy consumption, and low-temperature phosphating solution film thickness. Thin, loose film formation, poor corrosion resistance.

The embodiment of the present invention is achieved in this way, a normal temperature thick film zinc phosphide phosphating solution, the normal temperature thick film zinc phosphide phosphating solution includes: Zn(H ₂ PO ₄ ) ₂ 70g/L, Zn(NO ₃ ) ₂ 100g/L, NaNO ₂ 0.6g/L, Ni(NO ₃ ) ₂ 6g/L, Ce(NO ₃ ) ₃ .6(H ₂ O) 10g/L, citric acid 1.5g/L, OP emulsification Dose 1ml/L, time 20min.

The preparation method of the solution: put 2/3 of the total volume of distilled water in a one-liter beaker, first add 1.5g of citric acid, stir it with a glass rod to dissolve, then mix 70g of zinc dihydrogen phosphate, 100g of zinc nitrate, 0.6 Add 1g of sodium nitrite, 6g of nickel nitrate and 10g of cerium nitrate respectively, fully stir to dissolve, finally add 1ml of OP emulsifier and mix evenly, pour the mixed solution into a 1L volumetric flask, add water to constant volume, stir well, and set aside .

Another object of the present invention is to provide a kind of experimental method of determining component ratio of thick film zinc phosphide phosphating solution at normal temperature, the experimental method of determining component ratio of this normal temperature thick film zinc phosphide phosphating solution comprises the following steps:

Step 1, solution preparation, according to the specified process parameters, the solution preparation is carried out. During the preparation process, the error caused by the weighing should be reduced, numbered and ready for use;

Step 2: Preparation of phosphating film. After numbering the treated samples, control the temperature of the water bath at 30°C, place the beaker of phosphating solution in the water bath for 20 minutes, and then put the samples into different ingredients In the phosphating solution, after the time is up, the samples are taken out, dried, and then passivated;

Step 3, performance test, measure the thickness of the film layer with a coating thickness gauge; test the corrosion resistance of the film layer with the drop method, dipping method and polarization curve method; evaluate the wear resistance with a surface performance tester; measure with the weight loss method Membrane weight; Evaluate the porosity of membrane layer by potassium ferricyanide solution filter paper method; Measure the acidity and total acidity of phosphating solution by acid-base titration.

Further, the process parameters of step one are as follows:

Orthogonal experiment phosphating solution: Zn(H ₂ PO ₄ ) ₂ 30～70g/L, Zn(NO ₃ ) ₂ 40～100mL/L, NaNO ₂ 0.2-1.0g/L, Ce(NO ₃ ) ₃ .6 (H ₂ O) 10g/L, citric acid 2.0g/L, Ni(NO ₃ ) ₂ 4g/L, OP emulsifier 1.0ml/L, time 20-30min, temperature 30℃;

Single factor experiment phosphating solution: Zn(H ₂ PO ₄ ) ₂ orthogonal optimal value, Zn(NO ₃ ) ₂ orthogonal optimal value, NaNO ₂ orthogonal optimal value, Ce(NO ₃ ) ₃ .6( H ₂ O) 8-12g/L, citric acid 0-3.0g/L, Ni(NO ₃ ) ₂ 0-12g/L, OP emulsifier 1.0ml/L, time orthogonal optimal value, temperature 30℃;

Membrane removal solution: chromium trioxide 50g/L, 70-90°C, 15min;

Treatment passivation solution: chromium trioxide 2g/L, 70-90°C, 3-5min;

Surface adjustment solution: 5g/L oxalic acid solution, 1min;

Porosity measurement solution: potassium ferricyanide 10g/L, sodium chloride 15g/L;

NaOH drip liquid: sodium hydroxide 4g/L;

CuSO ₄ drip solution: copper sulfate pentahydrate 41g/L, sodium chloride 35g/L, 0.1N hydrochloric acid 13ml/L.

Further, the experimental method for determining the component ratio of the normal-temperature thick-film zinc phosphide phosphating solution specifically includes: sample grinding, surface adjustment, phosphating, passivation, drying, performance testing; sample grinding, surface adjustment, phosphating , passivation, and performance testing require deionized water rinse.

Further, the quality evaluation method for the appearance of the phosphating film: observe the phosphating film in a place with good light. The color of the phosphating film on zinc-based steel is from light gray to dark gray or black. A good phosphating film should be continuous, uniform, complete, dense, There are no metal bright spots, no serious ash, scratch lightly with fingernails, you can see obvious scratches, poor quality phosphating film is rough, crisp and loose with rust spots or serious ash.

Further, film thickness and film weight test methods:

After phosphating, select 5 points with uniform intervals from left to right on both sides of the steel sheet, measure the film thickness of these 10 points with a film thickness meter, check whether the film is uniform, and then take the average value and record it as the film thickness; The weight of the film can be measured by the weight loss method. Take the dry test piece after phosphating, weigh it with an electronic analytical balance, record the mass m1 of the test piece, and put the test piece into the film removal solution under the specified conditions to remove the film; Immediately wash with deionized water, dry quickly, and weigh; record the weight as m ² , measure the length and width of the test piece with a vernier caliper to calculate the area S:

G=(m ₁ -m ₂ )×10 ⁴ /S

G-weight of phosphating film per unit area (g/m ² );

m1-sample mass before film removal (g);

m ₂ - mass of sample after film removal (g);

S - total surface area (cm ² ) of the phosphating sample.

Further, the corrosion resistance test method:

The corrosion resistance of phosphating film is tested by copper sulfate drop method and 3% sodium chloride immersion method. In addition, the polarization curve analyzes the corrosion resistance of phosphating film from the electrochemical point of view;

① Copper sulfate drop method:

Under normal temperature conditions, drop a drop of copper sulfate spot solution on the phosphating film sample, start the stopwatch at the same time, and record the time for the spot solution to change from sky blue to light red. The longer the time, the better the corrosion resistance of the phosphating film;

② 3% sodium chloride impregnation method:

Submerge the phosphating test piece in 3% sodium chloride solution at room temperature, take it out for observation at intervals until rust spots appear, the longer the rust spots appear, the better the corrosion resistance of the phosphating film;

③ Polarization curve:

The self-corrosion potential of the polarization curve indicates the corrosion tendency of the material. The more negative the potential, the greater the corrosion tendency, and the self-corrosion current density i _corr indicates the speed of the corrosion rate. The larger the i _corr , the faster the corrosion rate. i _corr is the current density value corresponding to the tangent intersection of the Tafel zone of the cathodic polarization curve and the anodic polarization curve. The self-corrosion potential is the initial potential value of the polarization curve.

Further, the porosity test method:

Take a piece of 20mm×50mm filter paper, soak the test solution and paste it on the phosphating film to be tested and wait for 1 minute; place 3 phosphating test pieces side by side, remove the filter paper and check the number of blue spots; the thickness of the phosphating film requires no Greater than 3 points.

Further, the test method of wear resistance:

Place the phosphating sample in the multifunctional surface performance tester, set the speed, load, test time, and test radius parameters before starting the test, process the data with software, make a friction-time curve, and obtain the average friction coefficient. The smaller the coefficient of friction, the better the anti-friction performance, that is, the better the wear resistance.

The embodiment of the present invention is to provide a phosphating solution formula with good stability, long film-forming time, high-quality film thickness, and good corrosion resistance at room temperature. With this formula, a film layer of 20 μm can be obtained on the steel surface, with an average film thickness of 20 μm. It weighs 18.13g/cm ² ; it provides the test technology and method of corrosion resistance and wear resistance of thick and heavy phosphate film.

The normal-temperature thick-film zinc phosphide phosphating solution provided by the invention and the experimental method for determining the proportion of components adopt the normal-temperature thick-film zinc phosphide phosphating solution obtained by this component, and the formed phosphating film is dark gray, without Hanging ash, the film layer is evenly and continuously covered completely; the relationship between film weight and film thickness is about 1:1, and the average film weight reaches 18.13g/L. The obtained phosphating film is a heavy-duty film, which is mainly used for corrosion protection of storage parts; The crystal is dense, the porosity is small, the corrosion resistance is good, and the film layer has excellent corrosion resistance. The present invention optimizes the formula of the phosphating process through orthogonal experiments and single factor experiments, and uses various methods to check the performance of the film layer, and obtains a dark gray appearance, fine grains on the surface, no hanging ash, and a thickness of about 20 μm. Thick phosphating film with a film weight of more than 18g/m ² has good corrosion resistance, and the process is simple, the film forming temperature is low, and the energy consumption is small.

Description of drawings

Fig. 1 is the flow chart of the experimental method for determining the component ratio of the normal temperature thick film zinc phosphide phosphating solution provided by the embodiment of the present invention;

Fig. 2 is an electrode potential polarization curve diagram provided by an embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The application principle of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

The zinc-based phosphating solution for thick film phosphating at room temperature in the embodiment of the present invention includes: Zn(H ₂ PO ₄ ) ₂ 70g/L, Zn(NO ₃ ) ₂ 100g/L, NaNO ₂ 0.6g/L, Ni(NO ₃ ) ₂ 6g/L, Ce(NO ₃ ) ₃ .6(H ₂ O) 10g/L, citric acid 1.5g/L, OP emulsifier 1ml/L, time 20min.

The preparation method of the solution: put 2/3 of the total volume of distilled water in a one-liter beaker, first add 1.5g of citric acid, stir it with a glass rod to dissolve, then mix 70g of zinc dihydrogen phosphate, 100g of zinc nitrate, 0.6 Add 1g of sodium nitrite, 6g of nickel nitrate and 10g of cerium nitrate respectively, fully stir to dissolve, finally add 1ml of OP emulsifier and mix evenly, pour the mixed solution into a 1L volumetric flask, add water to constant volume, stir well, and set aside .

As shown in Figure 1, the experimental method for determining the component ratio of the normal temperature thick film zinc phosphide phosphating solution of the embodiment of the present invention comprises the following steps:

S101: Prepare the solution. Prepare the solution according to the specified process parameters. During the preparation process, reduce the error caused by weighing, number it, and wait for use;

S102: Preparation of phosphating film. After numbering the treated samples, control the temperature of the water bath at 30°C, put the beaker of phosphating solution in the water bath and let it stand for 20 minutes, and then put the samples into phosphorus of different components. in the solution. After the time is up, the samples are taken out, dried, and then passivated.

S103: Performance test, measure the thickness of the film layer with a coating thickness gauge; test the corrosion resistance of the film layer with the drop method, dipping method and polarization curve method; evaluate the wear resistance with a surface performance tester; measure the film layer with the weight loss method weight; the porosity of the film layer was evaluated by the potassium ferricyanide solution filter paper method; the acidity and total acidity of the phosphating solution were measured by the acid-base titration method.

The technological parameter of step S101 is as follows:

Orthogonal experiment phosphating solution: Zn(H ₂ PO ₄ ) ₂ 30～70g/L, Zn(NO ₃ ) ₂ 40～100mL/L, NaNO ₂ 0.2-1.0g/L, Ce(NO ₃ ) ₃ .6 (H ₂ O) 10g/L, citric acid (2.0g/L), Ni(NO ₃ ) ₂ (4g/L), OP emulsifier (1.0ml/L), time 20-30min, temperature 30℃.

Single factor experiment phosphating solution: Zn(H ₂ PO ₄ ) ₂ (orthogonal optimal value), Zn(NO ₃ ) ₂ (orthogonal optimal value), NaNO ₂ (orthogonal optimal value), citric acid ( 0-3.0g/L), Ni(NO ₃ ) ₂ (0-12g/L), Ce(NO ₃ ) ₃ .6(H ₂ O)(8-12g/L), OP emulsifier (1.0ml/ L), time (orthogonal optimal value), temperature 30°C.

Membrane removal solution: chromium trioxide 50g/L, 70-90°C, 15min;

Treatment passivation solution: chromium trioxide 2g/L, 70-90°C, 3-5min;

Surface adjustment solution: 5g/L oxalic acid solution, 1min;

Porosity measurement solution: potassium ferricyanide 10g/L, sodium chloride 15g/L;

NaOH drip liquid: sodium hydroxide 4g/L;

CuSO ₄ drip solution: copper sulfate pentahydrate 41g/L, sodium chloride 35g/L, 0.1N hydrochloric acid 13ml/L.

The specific steps are as follows:

(1) Experimental process:

Sample grinding→surface adjustment→phosphating→passivation→drying→performance test (except after drying, deionized water rinse is required between other steps);

(2) Process parameters:

Orthogonal experiment phosphating solution: Zn(H ₂ PO ₄ ) ₂ 30～70g/L, Zn(NO ₃ ) ₂ 40～100mL/L, NaNO ₂ 0.2-1.0g/L, Ce(NO ₃ ) ₃ .6 (H ₂ O) (10g/L), citric acid (2.0g/L), Ni(NO ₃ ) ₂ (4g/L), OP emulsifier (1.0ml/L), time 20-30min, temperature 30℃ .

Single factor experiment phosphating solution: Zn(H ₂ PO ₄ ) ₂ (orthogonal optimal value), Zn(NO ₃ ) ₂ (orthogonal optimal value), NaNO ₂ (orthogonal optimal value), citric acid ( 0-3.0g/L), Ni(NO ₃ ) ₂ (0-12g/L), Ce(NO ₃ ) ₃ .6(H ₂ O)(8-12g/L), OP emulsifier (1.0ml/ L), time (orthogonal optimal value), temperature 30°C.

Membrane removal solution: chromium trioxide 50g/L, 70-90°C, 15min;

Treatment passivation solution: chromium trioxide 2g/L, 70-90°C, 3-5min;

Surface adjustment solution: 5g/L oxalic acid solution, 1min;

Porosity measurement solution: potassium ferricyanide 10g/L, sodium chloride 15g/L;

NaOH drip liquid: sodium hydroxide 4g/L;

CuSO ₄ drip solution: copper sulfate pentahydrate 41g/L, sodium chloride 35g/L, 0.1N hydrochloric acid 13ml/L;

(3) Solution preparation, according to the process parameters in step (2), carry out solution preparation. During the preparation process, the errors caused by weighing should be minimized, numbered and ready for use.

(4) Preparation of phosphating film. After numbering the pre-treated samples, control the temperature of the water bath at 30°C, put the beaker of phosphating solution in the water bath for 20 minutes, and then put the samples into different components. in the phosphating solution. After the time is up, the samples are taken out, dried, and then passivated.

(5) performance test, measure the thickness of the film layer with a coating thickness gauge; use the drop method, the dipping method and the polarization curve method to test the corrosion resistance of the film layer; evaluate the wear resistance with the surface performance tester; measure with the weight loss method Membrane weight; Evaluate the porosity of membrane layer by potassium ferricyanide solution filter paper method; Measure the acidity and total acidity of phosphating solution by acid-base titration.

Phosphating film quality evaluation method of the present invention comprises:

1. Appearance:

Observe the phosphating film in a place with good light. The color of the phosphating film on zinc-based steel is from light gray to dark gray or black. A good phosphating film should be continuous, uniform, complete, dense, without metal bright spots, and without serious ash. If you scratch it with your fingernail, you can see obvious scratches. Poor quality phosphating film is rough, crisp, rusty or seriously dusty;

2. Film thickness and film weight test:

After phosphating, select 5 points with uniform intervals from left to right on both sides of the steel sheet, measure the film thickness of these 10 points with a film thickness meter, check whether the film is uniform, and then take the average value and record it as the film thickness. The weight of the film can be measured by the weight loss method. Take the dry test piece after phosphating, weigh it with an electronic analytical balance, record the mass m ₁ of the test piece, and put the test piece into the film removal solution under the specified conditions to remove the film. Immediately after removing the membrane, rinse with deionized water, dry quickly, and weigh. Record its weight as m ₂ , measure the length and width of the test piece with a vernier caliper to calculate the area S:

G=(m ₁ -m ₂ )×10 ⁴ /S

G-weight of phosphating film per unit area (g/m ² );

m ₁ - mass of the sample before film removal (g);

m ₂ - mass of sample after film removal (g);

The total surface area of S-phosphating sample (cm ² );

3. Corrosion resistance test:

The corrosion resistance test of phosphating film is mainly copper sulfate drip method and 3% sodium chloride immersion method. In addition, the polarization curve can analyze the corrosion resistance of phosphating film from the electrochemical point of view.

① Copper sulfate drop method

Under normal temperature conditions, drop a drop of copper sulfate spot solution on the phosphating film sample, start the stopwatch at the same time, and record the time when the spot solution changes from sky blue to light red. The longer the time, the better the corrosion resistance of the phosphating film.

②3% sodium chloride impregnation method

Submerge the phosphating test piece in 3% sodium chloride solution at room temperature, and take it out for observation at regular intervals until rust spots appear. The longer the time for rust spots to appear, the better the corrosion resistance of the phosphating film.

③Polarization curve

The polarization curve is a method to quickly determine the corrosion rate and corrosion tendency of metals. The self-corrosion potential of the polarization curve indicates the corrosion tendency of the material. The more negative the potential, the greater the corrosion tendency, and the self-corrosion current density i _corr indicates the corrosion tendency. The speed of the speed, the larger the i _corr , the faster the corrosion speed. i _corr is the current density value corresponding to the tangent intersection of the Tafel zone of the cathodic polarization curve and the anodic polarization curve. The self-corrosion potential is the initial potential value of the polarization curve.

4. Porosity test

Take a piece of 20mm×50mm filter paper, soak it with the test solution and paste it on the phosphating film to be tested (place 3 phosphating test pieces side by side) and wait for 1 min, then remove the filter paper and check the number of blue spots. Thick phosphating film requires no more than 3 points per square centimeter.

5. Wear resistance test

Place the phosphating sample in the multifunctional surface performance tester, set the speed, load, test time, test radius and other parameters before starting the test, process the data with software, make a friction-time curve, and obtain the average friction coefficient , the smaller the friction coefficient, the better the anti-friction performance, that is, the better wear resistance.

The technical effect of the present invention is further illustrated by the following experimental results and analysis:

1. Orthogonal experiment results and analysis:

Table 1 Orthogonal Experimental Results: Orthogonal Experimental Results are shown in Table 1, and the data adopts the method of range analysis; as can be seen from Table 1: (1) Analysis is based on the thickness of the phosphating film, because it is the phosphorus used for corrosion protection Generally speaking, the thickness of the phosphating film is proportional to the corrosion resistance, so the thicker the film, the better. From the visual analysis of the R1 data in Table 1, it can be clearly seen that the four factors are all important to the phosphating film. Thickness has an effect, but the degree of influence is not the same. The larger the value of R, the greater the degree of influence of this factor on film thickness. From the data, it can be concluded that the order of influence on film thickness is Zn(H ₂ PO ₄ ) ₂ concentration>Zn(NO ₃ ) ₂ concentration>phosphating time>NaNO ₂ concentration, from the K value analysis trend, it can be seen that with the increase of Zn(H ₂ PO ₄ ) ₂ and Zn(NO ₃ ) ₂ , phosphorus The thickness of the chemical film layer increased, and with the increase of phosphating time and the increase of NaNO ₂ content, the film thickness first increased and then decreased. It can be seen from the inability to form a film and the change trend of the film thickness in the first group of experiments. The influence of the film layer is great, too little main salt can not form a phosphating film at room temperature, the best combination of film thickness obtained is: Zn(H ₂ PO ₄ ) ₂ 70g/L, Zn(NO ₃ ) ₂ 100g/L , NaNO ₂ 0.6g/L, time 25min;

Table 1 Orthogonal experiment results

6. Based on the analysis of copper sulfate dripping time, it can be seen from the R2 data in Table 1 that the influence of the two main salts is still the largest, and the degree of time influence is relatively small. The order of influence is Zn(NO ₃ ) ₂ concentration>Zn(H ₂ PO ₄ ) ₂ concentration > NaNO ₂ concentration > phosphating time. From the K value analysis trend, it can be seen that the drip time increases with the increase of Zn(H ₂ PO ₄ ) ₂ and Zn(NO ₃ ) ₂ dosage, which is As the concentration of the main salt is higher, the thicker the phosphating film is formed, and the dripping time is longer; with the increase of NaNO ₂ , the dripping time first increases and then decreases _. Phosphating has a promoting effect at a very low concentration. Excessive dosage will cause passivation of the metal surface and affect the formation of the film; the drop time decreases with the decrease of phosphating time because the phosphating film is etched by acid due to too long time. If it becomes rough and porous, the optimal level combination of the obtained copper sulfate dripping time is: Zn(H ₂ PO ₄ ) ₂ 70g/L, Zn(NO ₃ ) ₂ 100g/L, NaNO ₂ 0.6g/L, time 20min;

In general, the main salt Zn(H ₂ PO ₄ ) ₂ concentration and Zn(NO ₃ ) ₂ concentration have the greatest impact on the phosphating film, followed by the accelerator NaNO ₂ content also played a very important role, phosphating The influence of time on film thickness and copper sulfate dripping time is different. Through the previous analysis, the best phosphating film formula can be selected based on the corrosion resistance of the film layer and copper sulfate dripping time as indicators as follows:

The best formula for film thickness: Zn(H ₂ PO ₄ ) ₂ 70g/L, Zn(NO ₃ ) ₂ 100g/L, NaNO ₂ 0.6g/L, Ni(NO ₃ ) ₂ 4g/L, citric acid 2g/L , Ce(NO ₃ ) ₃ .6(H ₂ O) 10g/L, OP emulsifier 1ml/L, time 25min and temperature 30℃;

The best formula for copper sulfate dropping time: Zn(H ₂ PO ₄ ) ₂ 70g/L, Zn(NO ₃ ) ₂ 100g/L, NaNO ₂ 0.6g/L, Ni(NO 3 ) 2 4g/L, Ce(NO ₃ ) ₂ 4g/L, ₃ ) _3.6 (H ₂ O) 10g/L, citric acid 2g/L, OP emulsifier 1ml/L, time 20min, temperature 30℃;

7. Performance comparison of the best formula:

According to the optimal formula of film thickness obtained in 1 and the optimal formula of copper sulfate dripping, samples were prepared respectively and various performance tests were carried out, and their corrosion resistance and electrode potential diagrams were measured respectively (as shown in table 2 between the best formulas) Compare with Figure 2 Electrode Potential Polarization Curve), compare, analyze, and select the better formula in the two to prepare for the next step of single factor experiment, which can further optimize the process formula of the conversion coating;

Table 2 Comparison of corrosion resistance performance of the best formulations

The final formula of the present invention is:

The final optimized formula was selected by orthogonal experiment and single factor experiment: Zn(H ₂ PO ₄ ) ₂ 70g/L, Zn(NO ₃ ) ₂ 100g/L, NaNO ₂ 0.6g/L, Ni(NO ₃ ) ₂ 6g /L, citric acid 1.5g/L, Ce(NO ₃ ) ₃ .6(H ₂ O) 10g/L, OP emulsifier 1ml/L, time 20min. Under phosphating to form a film, measure its film thickness and copper sulfate dropping time and take pictures with a metallographic microscope.

Table 3 Effect of surface adjustment on the performance of phosphating film

It can be seen from Table 3 that both the film thickness and the copper sulfate dripping time of the film formed with surface adjustment are about twice that of without surface adjustment. It can be seen that the importance of surface adjustment can be analyzed, and the film formed under surface adjustment It can be clearly seen that the needle-shaped crystals are interlaced, but no obvious crystals can be seen in the film formed without surface adjustment. The formation of a large number of needle-shaped crystals indicates that after surface adjustment, the crystallization of the phosphating film is faster and more, so the film is thicker. The coverage of a large number of crystals makes the phosphating film finer and denser, so the corrosion resistance of the film layer can be greatly improved.

Final formula performance test result of the present invention is:

First, appearance: the phosphating film formed by this phosphating solution is dark gray, without hanging ash, and the film layer is evenly and continuously covered;

Second, film thickness and film weight: as shown in Table 4;

Table 4 final formula film thickness and film weight

The relationship between film weight and film thickness is about 1:1, and the average film weight exceeds 18.87g/L. The obtained phosphating film is a heavy-duty film, which is mainly used for anti-corrosion of storage parts;

Third, corrosion resistance test: corrosion resistance is still evaluated by copper sulfate dripping time and sodium chloride immersion time, and compared with national standards;

Table 5 final formula corrosion resistance test

It can be seen from Table 5 that the corrosion resistance of the final formula is slightly better than that of the formula obtained in the previous orthogonal experiment. The copper sulfate drop reached 295s, and the immersion time of 3% sodium chloride was more than 3 hours, and the corrosion resistance reached the national standard;

Fourth, porosity:

The number of blue points on the filter paper is 25, the area of the filter paper is 10cm ² , and the number of blue points per unit area is 2.5 points/cm ² , which meets the requirement of not more than 3 points/cm ² . The porosity is small and the corrosion resistance is good, which is also the reason for the different dripping time of copper sulfate on the same test piece, but the anti-corrosion phosphating film must also have certain pores, because if the phosphating metal is protected with anti-rust oil, choose a A phosphating film with a certain gap can make the oil penetrate into the pores well;

Fifth, wear resistance:

Table 6 final formulation wear resistance test data (without surface adjustment)

Table 7 final formulation wear resistance test data (surface adjustment)

The workpiece after phosphating will inevitably have friction in transportation engineering, so it is meaningful to test its wear resistance. In the experiment, the film with surface adjustment and the film without surface adjustment are tested for friction, and the difference in wear resistance between the two is compared;

A small friction coefficient indicates good friction reduction, that is, good wear resistance. Since the friction test takes a long time and the friction process is divided into three stages, it is more scientific to use the average friction coefficient to measure wear resistance. From Table 6 and Table 7 The average friction coefficient of the phosphating film without surface adjustment is 0.5349; the average friction coefficient of the phosphating film with surface adjustment is 0.4813, indicating that the surface adjustment can improve the wear resistance of the phosphating film;

Sixth, free acidity and acidity:

The free acidity is the concentration of free hydrogen ions in the phosphating solution, and the total acidity refers to the sum of all ion concentrations that can react with hydroxide ions in the phosphating solution. In actual production, the total acidity is often used to measure the main salt concentration of the phosphating solution. Free acidity is used to measure PH. If a phosphating film is to be formed at room temperature, both must be controlled within a certain range. The influence of some main salt unit additions on total acidity and acidity can be found in the data. Therefore, in production, it is very convenient to supplement the main salt by measuring the initial free acidity and total acidity of the phosphating solution;

The measurement of free acidity and total acidity adopts the titration method, and the unit is "point". Take 10ml of phosphating solution, use methyl orange and phenolphthalein as indicators respectively, and titrate to the end point with a 0.1N sodium hydroxide solution alkaline burette. The number of milliliters consumed by sodium oxide is the number of acidity points, and the free acidity of the final formula measured by the experiment is 4 points, and the total acidity is 85 points.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (9)

1. a normal temperature phosphorization of thick film Zinc phosphating solution, is characterized in that, this normal temperature phosphorization of thick film Zinc phosphating solution comprises: Zn (H ₂pO ₄) ₂70g/L, Zn (NO ₃) ₂100g/L, NaNO ₂0.6g/L, Ni (NO ₃) ₂6g/L, Ce (NO ₃) ₃.6 (H ₂o) 10g/L, citric acid 1.5g/L, OP emulsifying agent 1ml/L, time 20min;

Compound method: the distilled water putting into cumulative volume 2/3 in 1L beaker, first add the citric acid of 1.5g, stirring with glass stick makes it dissolve, then 70g primary zinc phosphate, 100g zinc nitrate, 0.6g Sodium Nitrite, 6g nickelous nitrate and 10g cerous nitrate are added respectively, abundant stirring and dissolving, the OP emulsifying agent finally adding 1ml mixes, and is poured into by mixed solution in 1L volumetric flask, add water after constant volume and stir evenly, stand-by.

2. an experimental technique for normal temperature phosphorization of thick film Zinc phosphating solution determination component ratio, is characterized in that, the experimental technique of this normal temperature phosphorization of thick film Zinc phosphating solution determination component ratio comprises the following steps:

Step one, solution preparation, according to Zn (H ₂pO ₄) ₂70g/L, Zn (NO ₃) ₂100g/L, NaNO ₂0.6g/L, Ni (NO ₃) ₂6g/L, Ce (NO ₃) ₃.6 (H ₂o) 10g/L, citric acid 1.5g/L, OP emulsifying agent 1ml/L, time 20min;

Compound method: the distilled water putting into cumulative volume 2/3 in 1L beaker, first add the citric acid of 1.5g, stirring with glass stick makes it dissolve, then 70g primary zinc phosphate, 100g zinc nitrate, 0.6g Sodium Nitrite, 6g nickelous nitrate and 10g cerous nitrate are added respectively, abundant stirring and dissolving, the OP emulsifying agent finally adding 1ml mixes, mixed solution is poured in 1L volumetric flask, add water after constant volume and stir evenly, stand-by, carry out solution preparation, in process for preparation, reduce the error that weighing brings, be numbered, stand-by;

Step 2, prepared by phosphatize phosphate coat, after the sample processed is numbered, bath temperature is controlled at 30 DEG C, hold Phosphating Solution beaker and leave standstill 20min in water-bath, then sample is put into respectively the Phosphating Solution of heterogeneity, the time takes out sample respectively to rear, carry out drying treatment, and then carry out Passivation Treatment;

Step 3, performance test, measures thicknesses of layers with coating thickness tester; With topical application, the solidity to corrosion of pickling process and method of polarization curve test rete; Wear resistance is evaluated with surface property tester; Film weight is measured by weight-loss method; With potassium ferricyanide solution filter paper method evaluation rete porosity; Phosphating Solution acidity and total acidity is surveyed by acid base titration.

3. the experimental technique of normal temperature phosphorization of thick film Zinc phosphating solution determination component ratio as claimed in claim 2, it is characterized in that, the processing parameter of step one is as follows:

Orthogonal experiment Phosphating Solution: Zn (H ₂pO ₄) ₂30 ~ 70g/L, Zn (NO ₃) ₂40 ~ 100mL/L, NaNO ₂0.2-1.0g/L, Ce (NO ₃) ₃.6 (H ₂o) 10g/L, citric acid 2.0g/L, Ni (NO ₃) ₂4g/L, OP emulsifying agent 1.0ml/L, time 20 ~ 30min, temperature 30 DEG C;

Experiment of single factor Phosphating Solution: Zn (H ₂pO ₄) ₂orthogonal optimum value, Zn (NO ₃) ₂orthogonal optimum value, NaNO ₂orthogonal optimum value, Ce (NO ₃) ₃.6 (H ₂o) 8-12g/L, citric acid 0-3.0g/L, Ni (NO ₃) ₂0-12g/L, OP emulsifying agent 1.0ml/L, time quadrature optimum value, temperature 30 DEG C;

Membrane removal liquid: chromium trioxide 50g/L, 70-90 DEG C, 15min;

Process passivating solution: chromium trioxide 2g/L, 70-90 DEG C, 3-5min;

Surface adjustment liquid: 5g/L oxalic acid solution, 1min;

Gaging hole porosity solution: Tripotassium iron hexacyanide 10g/L, sodium-chlor 15g/L;

NaOH drip liquid: sodium hydroxide 4g/L;

CuSO ₄point dropping liquid: cupric sulfate pentahydrate 41g/L, sodium-chlor 35g/L, 0.1N hydrochloric acid 13ml/L.

4. the experimental technique of normal temperature phosphorization of thick film Zinc phosphating solution determination component ratio as claimed in claim 2, it is characterized in that, the experimental technique of this normal temperature phosphorization of thick film Zinc phosphating solution determination component ratio specifically comprises: sample polishing, surface adjustment, phosphatization, passivation, drying, performance test; Sample polishing, surface adjustment, phosphatization, passivation, performance test need deionized water rinsing.

5. the experimental technique of normal temperature phosphorization of thick film Zinc phosphating solution determination component ratio as claimed in claim 2, it is characterized in that, the grade estimation method of phosphatize phosphate coat outward appearance: observe phosphatize phosphate coat in the place of well lighted, zinc system steel iron phosphatising film color from light gray to dark-grey or black, good phosphatize phosphate coat answer continuous uniform, complete, fine and closely woven, without metal bright spot, without serious dust.

6. the experimental technique of normal temperature phosphorization of thick film Zinc phosphating solution determination component ratio as claimed in claim 2, is characterized in that, thickness and film are resurveyed method for testing:

After phosphatization, steel disc tow sides respectively from left to right choose uniform 5 points in interval, measure the thickness of these 10 points with film thickness gauge, and whether inspection film forming is even, then average and be designated as thickness; Film is reused weight-loss method and is measured, and gets the dry test piece after phosphatization, weighs with electronic analytical balance, record test piece quality m ₁, test piece is put under prescribed conditions the membrane removal of membrane removal liquid; Washed with de-ionized water is used immediately except after complete film, dry rapidly, weigh; Record weight is m ₂, calculate area S by vernier caliper measurement test piece length and width:

G＝(m ₁-m ₂)×10 ⁴/S

G-unit surface phosphatize phosphate coat weight (g/m ²);

M ₁sample mass (g) before-membrane removal;

M ₂sample mass (g) after-membrane removal;

Total surface area (the cm of S-phosphatization sample ²).

7. the experimental technique of normal temperature phosphorization of thick film Zinc phosphating solution determination component ratio as claimed in claim 2, is characterized in that, solidity to corrosion testing method:

The test of phosphatize phosphate coat solidity to corrosion adopts copper sulfate topical application and 3% sodium-chlor pickling process, and polarization curve is from electrochemistry angle analysis phosphatize phosphate coat solidity to corrosion quality in addition;

1. copper sulfate topical application:

Under normal temperature condition, drip copper sulfate point dropping liquid, start stopwatch simultaneously, record a dropping liquid and become the pink time by sky blue to phosphatize phosphate coat sample, time longer explanation phosphatize phosphate coat solidity to corrosion is better;

2. 3% sodium-chlor pickling process:

Under room temperature, the test piece after phosphatization is immersed in 3% sodium chloride solution, takes out observation at set intervals, to when occurring rust staining, occur that the rust staining time solidity to corrosion of longer explanation phosphatize phosphate coat is better;

3. polarization curve:

The corrosion potential of polarization curve indicates the corrosion tendency of material, and the more negative explanation corrosion tendency of current potential is larger, and corrosion current density i _corrindicate the speed of corrosion speed, i _corrlarger, illustrate that corrosion speed is faster, i _corrbe current density value corresponding to the point of intersection of tangents in the Ta Feier district of cathodic polarization curve and anodizing curve, namely corrosion potential is the initial potential value of polarization curve.

8. the experimental technique of normal temperature phosphorization of thick film Zinc phosphating solution determination component ratio as claimed in claim 2, is characterized in that, porosity testing method:

Get 20mm × 50mm filter paper, soak into and detect liquid and be posted on tested phosphatize phosphate coat and wait for 1min; By placed side by side for the test piece after 3 pieces of phosphatizations, take off filter paper and check Bluepoint number; Require that Bluepoint number is not more than every square centimeter and is not more than 3 points.

9. the experimental technique of normal temperature phosphorization of thick film Zinc phosphating solution determination component ratio as claimed in claim 2, is characterized in that, wear resisting property testing method:

Phosphatization sample is placed in multifunction surface ability meter, set rotating speed, load, test duration, start test after testing radius parameter, with software data processing, make friction force-time curve, draw average friction coefficient, the less explanation antifriction performance of frictional coefficient is good, and namely wear resisting property is good.