TWI476389B - Quickly evaluate the method of resisting the rust resistance of steel strip - Google Patents

Description

Method for quickly evaluating the rust resistance of a bandaged steel strip

The invention relates to a method for evaluating rust resistance, in particular to a method for quickly evaluating the rust resistance of a bandaged steel strip.

The banding steel strip is a kind of steel strip used for bundling large objects such as wood, paper, stone, steel, welded pipe, etc., and the mechanical properties must be flexible and continuous, and must have considerable rust resistance during storage. If the steel strip is rusted, not only does the appearance of the steel strip affect the selling phase, but the generated rust easily contaminates the packaged object. Therefore, in addition to the machine requirements of various types of banding steel strips, the production plant must also be rust-proof, the most common way is blue and wax. The bluening is to uniformly heat the steel strip at a high temperature to form a uniform oxide film on the surface; the wax is coated with a wool felt containing oil wax or water wax when the blue belt is cooled and cooled below a certain temperature to make the blue layer The surface has a layer of oil wax or water wax attached, which has the effect of lubricating and also has anti-rust effect.

The storage of the products bundled by the bandaged steel strip is mostly stored in the factory. It can be distinguished from the rust resistance of the bandaged steel strip in about one or two months. The rust easily will cause the customer to have a bad impression on the manufacturer, so the production resistance The rust-resistant steel band is a problem that manufacturers have been working on.

Traditionally, researchers who bandaged steel strips have evaluated their rust resistance by exposing them directly to the plant for a month or two. However, this method is too time consuming. In recent years, the evaluation method has gradually moved toward laboratory accelerated corrosion tests, such as the literature. Evaluation of Corrosion Resistance of Blue-coated Steel Strips [Wu Zongfeng, Zhang Yaonan, Lin Si-Ning, Tu Ruifan, Anti-corrosion Engineering, Vol. 26, No. 2 (2012), pp. 81-88] records: salt spray, electrochemical communication Two kinds of accelerated corrosion tests of impedance and three kinds of test methods for actual exposure are used to evaluate the rust resistance of the bandaged steel strips produced by two different manufacturers. The two accelerated corrosion tests can compare the rust resistance of the bandaged steel strips produced by two different manufacturers. Sexuality, but lacks the correspondence between the two accelerated corrosion tests and the actual exposure. The salt spray method cannot know how long it takes to obtain the degree of corrosion equivalent to the actual exposure, and the way of electrochemical AC impedance can only be different. The rust resistance between steels is good or bad.

Another constant temperature and humidity wettability test is to set the temperature in the test chamber to 50 ° C and the relative humidity to 98%. Then put the test strips in the test chamber and observe the rust conditions of different exposure times. ASTMD610 (American Society for Testing and Materials' Test Method for Evaluating the Degree of Corrosion of Painted Steel Surfaces) is evaluated for corrosion grade (as shown in Figure 6 for the percentage of corrosion on the surface of ASTM D610 test piece and corrosion grade), showing 7 days of wetting. The level of corrosion generated is equivalent to the corrosion level of the actual exposure for two months, which means that the wetting for 7 days can be used as an accelerated corrosion test method for evaluating the rust resistance of the wrapped steel strip, and if the corrosion level is more than 5 during this period, Its actual rust resistance should be accepted by customers who use bandaged steel strips and is a common method for assessing the rust resistance of bandaged steel strips.

However, the above-mentioned constant temperature and humidity wettability test can be used as a method for evaluating the rust resistance of the wrapped steel strip. However, in the research process of the manufacturer's rust resistance improvement of the wrapped steel strip, the steel materials for each process change must be Test the rust resistance in the shortest time, and the test strips of each steel strip need to be run separately. The way to wait for 7 days of wet evaluation is still too time consuming, so there is still a need to develop a way to quickly assess the rust resistance of the banded steel strip in a shorter period of time to speed up the production process of the banded steel strip.

In order to solve the existing deficiencies and limitations of the method for evaluating the rust resistance of the steel strip, the main object of the present invention is to provide a method for quickly evaluating the rust resistance of the wrapped steel strip.

The invention solves the method for quickly evaluating the rust resistance of a wrapped steel strip proposed by the prior art problem, comprising: a sampling step: respectively forming a plurality of wrapped steel strips into two test pieces, and measuring one of the test pieces by a circuit potential method, Taking out the stable value of the open circuit potential of the test piece with time, another test piece of the constant temperature and humidity wet test is used to evaluate the corrosion resistance level of the other test piece; the calculation step: using a plurality of test strips for wrapping the steel strip The stable value of the open circuit potential is taken as the value of the X-axis and the corrosion resistance level as the value of the Y-axis to obtain a plurality of coordinate points, and the regression equation is calculated by linear regression calculation of the values of the plurality of coordinate points; and the evaluation step: The test strip is to be tested, and the test piece is measured by the open circuit potential method, and the stable value of the open circuit potential of the test piece changes with time is obtained, and the stable value is substituted into the regression. The equation yields the corresponding corrosion resistance grade, and the corrosion resistance rating of the wrapped steel strip to be tested is evaluated.

Preferably, in the sampling step, the other test piece is tested by constant temperature and humidity wetness, and another test piece is placed in a test chamber with a temperature setting of 50 ° C and a relative humidity setting of 98% for 7 days. The corrosion resistance rating was evaluated.

Preferably, in the sampling step, in the sampling step, when one of the test pieces is measured by the open circuit potential method, a saturated calomel electrode is used as a reference electrode, and the test piece is immersed in a normal temperature of 0.1 M NaCl + 0.1 M Na _{2 .} In the SO ₄ aqueous solution, the open circuit potential of the test piece is measured by an open circuit potential method; in the evaluation step, when the test piece is measured by the open circuit potential method, a saturated calomel electrode is used as a reference electrode, and The sheet to be tested was immersed in an aqueous solution of 0.1 M NaCl + 0.1 M Na ₂ SO ₄ at room temperature, and the open circuit potential of the sheet to be tested was measured by an open circuit potential method.

Preferably, the stable value of the open circuit potential of the to-be-tested piece of the present invention is a value that finally measures the change in the open circuit potential within 5x10 ^-6 Volts/Sec.

The sampling step and the calculation step of the present invention can be calculated by sampling the regression equation before the evaluation step. When the rust resistance of any of the wrapped steel strips is to be evaluated, since the open circuit potential of the test piece is measured within a few hours The stable value can be obtained, and the stable value of the open potential circuit of the test piece can be substituted into the regression equation to obtain the corresponding corrosion resistance level, so that the rust resistance of the different bandage steel strips can be quickly evaluated, thereby speeding up the bandaging of the steel strip. Production process.

10‧‧‧ Trend Line

1 is a flow chart of the steps of a method in accordance with a preferred embodiment of the present invention.

2 is a graph showing the open circuit potential-corrosion resistance level of different wrapped steel strips in an embodiment of the preferred embodiment of the present invention.

Figure 3 is a time-potential coordinate diagram of a test strip of a banded steel strip with oil wax and unoiled wax.

Figure 4 is a time-potential coordinate plot of an unwashed and cleaned wrapped steel strip test piece.

Figure 5 is a time-potential coordinate plot of an unannealed and batch annealed wrapped strip test piece.

Fig. 6 is a comparison table of the percentage of corrosion amount on the surface of the existing ASTM D610 test piece and the corrosion level.

The laboratory has a measurement technique called open circuit potential (OCP) method, which directly measures the potential of the test piece in the solution relative to the reference electrode (ie, the open circuit potential) as a function of time, by interpreting the aforementioned open circuit. A curve of potential versus time to determine the corrosion resistance of the sheet to be tested or the porosity of the scale. For example, when the sheet to be tested is bare, the measured value of the stable open circuit potential can be used as an evaluation of the piece to be tested. The index of corrosion resistance in the solution, if the test piece is a steel containing scale, the rate of change in the circuit potential with time can be known as the porosity of the scale.

The invention applies the foregoing open circuit potential method measurement technology, which is a method for quickly evaluating the rust resistance of a wrapped steel strip. As shown in the flow chart of the method shown in FIG. 1, the method steps of the present invention include: a sampling step: A plurality of coated steel strips were respectively made into two test pieces, and one of the test pieces was measured by an open circuit potential (OCP) method, and the test piece was immersed in a 0.1 M NaCl + 0.1 M Na ₂ SO ₄ aqueous solution at normal temperature, and the reference electrode was set. Saturated calomel electrode (SCE), measured the stable value of the open circuit potential of the test piece with time, that is, the final measured value of the open circuit potential is within 5x10 ^-6 Volts/Sec, and Another test piece of the constant temperature and humidity test was placed, and another test piece was placed in a test chamber with a temperature setting of 50 ° C and a relative humidity setting of 98% for 7 days, and then the surface corrosion amount of the ASTM D610 test piece shown in FIG. The corrosion resistance rating of the other test piece was evaluated by the percentage and corrosion rating table.

Calculation step: taking the stable value of the open circuit potential of the plurality of wrapped steel strip test pieces as the value of the X-axis and the corrosion resistance level as the value of the Y-axis to obtain the coordinate points of the plurality of wrapped steel strip test pieces, with a plurality of coordinate points The numerical value is calculated by linear regression to obtain a regression equation.

Evaluation step: a test piece to be tested is prepared from the wrapped steel strip to be tested, and the test piece is measured by an open circuit potential (OCP) method, and the test piece is immersed in a normal temperature of 0.1 M NaCl + 0.1 M Na ₂ SO ₄ In the aqueous solution, the reference electrode is set to a saturated calomel electrode (SCE), and the stable value of the open circuit potential of the to-be-tested piece changes with time is measured, that is, the change of the open circuit potential is finally measured at 5×10 ^-6 Volts. Within the value of /Sec, the stable value of the open circuit potential of the film to be tested is substituted into the regression equation to obtain the corresponding corrosion resistance level, and the corrosion resistance of the bandaged steel strip to be tested is evaluated by the corrosion resistance level.

When performing the sampling step of the preferred embodiment of the present invention, for example, two test pieces respectively made of 16 different wrapped steel strips are used to measure the stable value of the open circuit potential of one of the test pieces by the method of the sampling step described above. After the other test piece of the same banded steel strip is subjected to the constant temperature and humidity wettability test, a variety of dressing steel strips are obtained after the corrosion resistance level is determined according to the percentage of surface corrosion of the ASTM D610 test piece and the corrosion level comparison table shown in FIG. The stable value of the open circuit potential of the test piece is taken as the value of the X-axis and the corrosion resistance level is taken as the value of the Y-axis. The two values of the test piece of each of the above-mentioned wrapped steel strips are plotted in the coordinate diagram of the open circuit potential-corrosion resistance level. 2, will open the circuit potential - The corrosion resistance coordinate map plots 16 coordinate points.

Since the 0.1 M NaCl + 0.1 M Na ₂ SO ₄ aqueous solution selected is a suitable aqueous solution when performing the sampling step described above, the stable value of the open circuit potential (OCP) of the test piece relative to the saturated calomel electrode (SCE) It will be reached within 1 to 2 hours, which will shorten the sampling time.

Then, when the calculation steps are performed on the values of the 16 kinds of wrapped steel strip samples, the numerical values of the plurality of coordinate points shown in FIG. 2 are linearly regressed to obtain a regression equation, and the trend line 10 of the regression equation is drawn. In the graph of the open circuit potential-corrosion resistance level, as shown in Fig. 2, it can be seen from the positive slope of the trend line 10 that although the corrosion resistance level of the test piece of the open potential circuit (OCP) is less than -0.6V, Scattered, but still shows that the stability value of the open potential circuit (OCP) is positively correlated with the corrosion resistance level. It is indeed feasible to verify the method for evaluating the rust resistance of the present invention.

Finally, the evaluation step is to prepare a to-be-tested piece from the wrapped steel strip to be tested, and measure the to-be-tested piece by the method of the foregoing evaluation step to obtain a stable value of the open circuit potential of the to-be-tested piece after changing with time. The stable value after the circuit potential of the chip to be tested changes with time is substituted into the regression equation to obtain a corresponding corrosion resistance level, and the corrosion resistance level of the wrapped steel strip to be tested is evaluated by the corrosion resistance level.

Since the 0.1 M NaCl + 0.1 M Na ₂ SO ₄ aqueous solution selected is an appropriate aqueous solution when performing the evaluation step described above, the open circuit potential (OCP) of the test piece relative to the saturated calomel electrode (SCE) is stable. The value will be reached within 1 to 2 hours, which will shorten the evaluation time.

Let's look at Figure 3 to Figure 5, in which Figure 3 is a test strip of the banded steel strip with the oil wax and the oil-free wax after the bluening of the same alloy material. The rust resistance of wax is better than the rust resistance of unoiled wax. The time-potential coordinate diagram of the open potential circuit measurement is respectively carried out. Figure 4 is the test of the banding steel strip which is unwashed and cleaned after the bluening of the same alloy material. The film (uncleaned rust resistance is better than the rust resistance of cleaning), the time-potential coordinate diagram of the open potential circuit measurement, and the blanking of the same alloy material after unbluening and batch annealing The steel strip test piece (unannealed rust resistance is superior to the rust resistance of batch annealing), respectively, the time-potential coordinate map of the open potential circuit measurement; as shown in the above FIG. 3 to FIG. 5, after fixing the alloy material The value of the open potential circuit of the test piece of the banded steel strip with better rust resistance is higher than the open circuit value of the test piece of the banded steel strip with poor rust resistance, that is, the value of the open circuit potential is positively correlated with the rust resistance. It is indeed feasible to verify that the method of the present invention samples the regression equation to evaluate the rust resistance.

Claims (5)

A method for quickly evaluating the rust resistance of a bandaged steel strip, the steps comprising: a sampling step: respectively forming a plurality of wrapped steel strips into two test pieces, measuring one of the test pieces by a circuit potential method, and obtaining an open circuit of the test piece The stable value of the potential change with time, and another test piece of the constant temperature and humidity wet test, the corrosion resistance grade of the other test piece is evaluated; the calculation step: the stable value of the open circuit potential of the plurality of wrapped steel strip test pieces is taken as The value of the X-axis and the corrosion resistance level are used as the value of the Y-axis to obtain a plurality of coordinate points. The regression equation is calculated by linear regression calculation of the values of the plurality of coordinate points; and the evaluation step: the braided steel strip to be tested is produced. A test piece is taken out, and the test piece is measured by an open circuit potential method, and a stable value of the open circuit potential of the test piece changes with time is obtained, and the stable value is substituted into the regression equation to obtain a corresponding corrosion resistance level. The corrosion resistance of the bandaged steel strip to be tested is evaluated by the corrosion resistance level. A method for rapidly evaluating the rust resistance of a bandaged steel strip as described in claim 1, wherein in the sampling step, when the other test piece is wetted by constant temperature and humidity, the other test piece is set at a temperature of 50 ° C, The corrosion resistance level was evaluated after placing in a test chamber with a humidity setting of 98% for 7 days. A method for rapidly evaluating the rust resistance of a bandaged steel strip as described in claim 1 or 2, wherein in the sampling step, when one of the test pieces is measured by an open circuit potential method, a saturated calomel electrode is used as a reference electrode, and The test piece was immersed in an aqueous solution of 0.1 M NaCl + 0.1 M Na ₂ SO ₄ at normal temperature, and the open circuit potential of the test piece was measured by an open circuit potential method; in the evaluation step, the test was performed by an open circuit potential method. In the test piece, a saturated calomel electrode is used as a reference electrode, and the test piece is immersed in an aqueous solution of 0.1 M NaCl + 0.1 M Na ₂ SO ₄ at room temperature, and the open circuit of the test piece is measured by an open circuit potential method. Potential. A method for quickly evaluating the rust resistance of a bandaged steel strip according to claim 1 or 2, wherein a stable value of an open circuit potential of the test piece and the test piece is a final measurement of an open circuit potential change at 5x10 ^-6 Values within Volts/Sec. A method for quickly evaluating the rust resistance of a bandaged steel strip according to claim 3, wherein a stable value of the open circuit potential of the test piece and the test piece is a final measurement of an open circuit potential change at 5x10 ^-6 Values within Volts/Sec.