JPH05500832A - Composition for inhibiting corrosion of ferrous metals and method for inhibiting corrosion thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Title of the invention: Composition for inhibiting corrosion of ferrous metals and method for inhibiting corrosion thereof The present invention provides novel and improved corrosion inhibiting compositions and ideas for biodegradable corrosion inhibitors. Novel uses for iron in the presence of aqueous media (susceptible to corrosion) An improved method for inhibiting corrosion of metal surfaces.

More specifically, the present invention combines an amino acid that has a corrosion inhibiting effect and an amino acid that is normally corrosive. Corrosion inhibitor effective in inhibiting corrosion of ferrous metals under service conditions in the presence of aqueous media The present invention relates to a method using a synthetic amino acid.

Description of related technology An important mechanism for protecting metals against corrosion degradation is through the use of inhibitors. is achieved. Unfortunately, such as formulations containing nitrogen and aromatic compounds, Certain common corrosion inhibitors are additives that inhibit corrosion in water-based heating and cooling systems. However, the disadvantage is that it is harmful to public health and the surrounding environment. It has been discovered that there are risks. Sedimentation of such potentially hazardous compounds or removal by other procedures is complicated and expensive. For example, Other corrosion inhibitors, such as Rom salts, have been banned because they are suspected of being carcinogenic. This is because there is. As a result, it is biologically compatible and/or biodegradable. It has become desirable to investigate the inhibitory properties of certain compounds. Such compounds are , non-toxic, easy to produce with high purity, and biodegradable. This dramatically reduces the tedious task of removing and recovering. Ami Limited uses of amino acids have been proposed.

For example, Nippon Kokoh's July 22, 1975 Japanese Patent No. Sho 5O-091546-A specifies that amines and amino acids or The mixture that requires these salts is dissolved in water to make a 20% aqueous solution. It has been disclosed that atmospheric corrosion of many ferrous metal and non-ferrous metal plates was suppressed when . The pH of the moisture adsorbed onto the metal plate above was about 5.5 or lower. It is believed that

However, as a result of examining ordinary amino acids in more detail, it was proven that this was a result of nurture. It was not revealed. For example, V.

``Amine as a corrosion inhibitor in aqueous hydrochloric acid solutions'' by Hluchan et al. Noic acid J (Workstoffund Korrosion, published in 1988) published in Vol. 39, pp. 512-517), a 1.0 molar salt with a pH of about 0 A study of 22 of the most common amino acids as inhibitors of corrosion of iron in acids It was conducted. In general, these amino acids that have inhibitory properties at acidic pH, Corrosion inhibiting effects were not proven to be effective enough for immediate industrial use. .

Amino acids with long hydrocarbon chains and amino acids or amino acids that grow additional amino groups Amino acids that have a group that can increase the electron density of the group are simply They merely showed a tendency to suppress their eating habits.

In particular, aspartic acid and glutamine are preferred amino acids for use in the present invention. The acid did not fall within the above "trend" range. According to the conclusion, these amino acids , has one amino group, a short carbon chain, and an additional carboxyl group Therefore, it is a particularly poor inhibitor.

Furthermore, it is inappropriate to use aspartic acid as an inhibitor under conditions higher than the pH of the acid. From a business perspective, this is seen as a drawback.

Aspartic acid can be inherently corrosive in somewhat alkaline pH conditions. Because it is known. K, Ramark ``Corrosion of Mild Steel and Copper in Sodium Chloride Solutions'' by Rishnaiah) The Role of Biologically Important Compounds J (Bulletine, 1986) on pages 7-10 of Volume 2 (January issue) of Electrochemistry magazine. Please refer to the publication). The paper states that aspartic acid is actually It is disclosed that corrosion was accelerated (inhibition efficiency -25.4%). Actually, dad Even in combination with a good corrosion inhibitor for mild steel, such as Verine, The presence of paragic acid kept the solution corrosive.

A related problem in industry is when fluids are in motion and exposed to aqueous environments. It is known to increase the corrosion rate of ferrous metals. Therefore, aqueous The extreme corrosive effects expected from amino acids such as aspartic acid in media , in motor vehicle cooling or heating systems where such media are in motion. If an amino acid such as be.

Therefore, amino acids like aspartic acid are non-toxic and biodegradable. Despite its existence, it has been avoided as a corrosion inhibitor.

Amino acids with only one amino group and an additional carboxyl group (e.g. . Aspartic acid) is used in a state where the amino acid is sufficiently ionized. A surprising and serendipitous discovery of a method for inhibiting corrosion of ferrous metals has opened the industry up. It fills a long-standing need. Furthermore, aqueous fluids are Corrosion inhibitors for ferrous metals that reduce the corrosion rate even in flowing conditions are unknown in the art. This brings about the improvement in question.

Summary of the invention Provides new and improved corrosion inhibiting compositions for ferrous metals in the presence of aqueous media This is the first object of the present invention.

Presents a new and improved method for inhibiting corrosion of ferrous metals in the presence of aqueous media. It is the main objective of the present invention to provide.

New and improved method for inhibiting corrosion of ferrous metals in the presence of aqueous media at rest It is another main object of the present invention to provide a method that allows

A novel method for inhibiting corrosion of ferrous metals in the presence of aqueous media in fluid or moving conditions It is yet another principal object of the present invention to provide an improved method.

Nurturing amino groups as corrosion inhibitors for ferrous metals in the presence of aqueous media It is a further object of the invention to provide new and improved methods of using amino acids. It is.

Other and further objects of the invention will be apparent from the description and claims that follow. Would.

Certain amino acids, particularly aspartic acid, are metallurgical in slightly alkaline aqueous media. is known to accelerate the corrosion of metals, but if sufficiently ionized under conditions of use. was found to function effectively as a corrosion inhibitor.

Such amino acids reduce the corrosion rate of ferrous metals by a factor of 100-1000. Surprise Interestingly, this corrosion inhibition effect improves as the fluid velocity increases. Ru.

Brief description of the drawing 2 in an aqueous solution at 90°C containing 1000 ppm aspartic acid at pH 1O. Real and imaginary impedance spectrum for a mild steel electrode rotating at 00 rpm A plot in numerical coordinates is shown in Figure 1.

9 at pH 10 without aspartic acid but with conductivity adjusted with sodium sulfate. Impedance for a mild steel electrode rotating at 20 OrIlm in an aqueous solution at 0 °C Figure 2 shows a plot of the real and imaginary coordinates of the spectrum.

The magnitude of the impedance spectrum for the mild steel electrodes in Figures 1 and 2 is plotted as a function of frequency. A plot against the number is shown in Figure 3.

Plot the phase angle against the logarithm of frequency for the mild steel electrodes shown in Figures 1 and 2. The result is shown in Figure 4.

Description of preferred embodiments Those useful in the present invention are amino acids having an amino group and salts thereof. Cal It is appropriate that the ratio of boxyl group/amino group is 1, but preferably these The compound is ``free J'' with more carboxyl groups than J amino groups, For example, it has two carboxyl groups and one amino group. The appropriate amino acid is represented, CH, C00H HooC-(-CH2-)arNH-: R3 represents Hl or -COOH, X and y each independently represent an integer from 1 to 3, and n represents an integer corresponding to the number of repeating aminoacyl units.

Examples of suitable compounds include glycine, polyglycine, aspartic acid, polyglycine, These are aspartic acid, glutamic acid, polyglutamic acid, and salts thereof.

Suitable salts include, but are not limited to, alkali metals, soluble alkaline earths, It is a salt of a similar metal and a 01-C4 alkylamine.

These compounds are readily available from many sources and are available through chemical synthesis and microbial development. It can be produced using any fermentation method.

These compounds inhibit corrosion when in their fully protonated cationic form. There is a tendency for it to become less effective as an agent, and as the pH increases from the acid side to the alkaline side. It actually gets worse as it accelerates corrosion. However, once these compounds are When sufficiently ionized under alkaline conditions of use, these compounds form ferrous metals. was found to dramatically reverse the corrosion rate. In general, the temperature and the specific compound used Depending on the material, a calcareous pH of at least about 8.9 is preferred. like this Under normal usage conditions, iron at equivalent pH conditions without these compounds The corrosion inhibitor of the present invention has a corrosion rate of 100 to 1000 compared to that of metals. When the concentration is low, it is 100 ppm, and when it is high, it is 5.0% by weight or more. (in an aqueous medium). Particularly preferably, the corrosion inhibitor of the invention is used at a concentration of about tooppm to about 3.3% by weight. However, corrosion inhibitors Concentrations in excess of 5.0% by weight of the corrosion inhibitor may also be used, if desired. It is judged that it can be used as long as it is not disadvantageous to the system in which it is used.

The corrosion-inhibiting effects of the compositions of the present invention are demonstrated at room temperature, i.e., at temperatures as low as about 25°C or less. It can also occur at temperatures as high as about 90°C or higher.

Temperature is known to accelerate the corrosion of metals, but even as temperatures rise, Beyond any effects on pH, the corrosion inhibition properties of the present invention are unaffected. This is particularly noteworthy. For example, the pH of this system can be determined by comparing the measured value at 90°C. Therefore, the value measured at 25°C may be reduced by one unit. of the amino acid The pK of the fully ionized state also decreases with increasing temperature. However, the temperature shadow The pH decreases to a value below the point at which the corrosion inhibitor is completely ionized. Unless otherwise noted, the compositions of the invention continue to remain effective.

In particularly preferred embodiments, the compositions of the invention are used in dynamic, flowing systems. It will be done. The rate of corrosion of ferrous metals in such systems increases with increasing flow velocity. It's surprising that it doesn't. In fact, as the flow velocity increases, corrosion The speed tends to be reduced to a significant extent. Typically, the composition of the invention or the absence of , the flow rate is, for example, 200 revolutions per minute (rpm) for a rotating cylindrical electrode. to about 11,000 rp, such aqueous medium is The presence of bodies results in an increase in the rate of corrosion of ferrous metals. This kind of corrosion The increase in velocity is what normally occurs with steel in water or other aqueous systems. decrease in oxygen , is often the rate-limiting step. This means that oxygen to the corroding surface This means that the mass transfer rate increases as the flow speed increases.

The pH of the aqueous medium under the conditions of use of the corrosion-inhibiting composition of the present invention may be at ambient or room temperature ( from about 8.9 to about 14, preferably from about 9.5 to about 1, when measured at about 25°C) There is no problem within the range of 2. Compositions of the invention, when measured at ambient or room temperature, Particularly preferred is use at a pH of about 10 or higher. But already mentioned As such, it is understood that pH changes depending on the temperature being measured.

Therefore, when the aqueous medium is acidic in nature, one preferred embodiment of the invention is to A suitable amino acid is used, preferably aspartic acid. its composition to bring the total pH of the aqueous medium to about 9.5 or higher, most preferably about 9.9 to 1 O or higher. Contains an effective amount of base to increase At such a pH, the amino acids are Exists in ionized form (conjugated base).

The steel billet was manufactured for use as an electrode in a rotating cylindrical electrode device. this device ``For Speed Sensitivity Testing'' by D. C. Silverman. Rotating cylindrical cage Cory-3ion Goku J (1984 “→Light←What” magazine, Volume 40, May issue, pages 220-226 (published in ).

The electrochemical impedance method is also used by D., C., Silverman. ) and J. E. Carrico (Carrico) [Electrochemical Impeders] Corrosion Methods - Practical Tools for Corrosion Prediction J (1988) 4 magazine, volume 44, May issue, pages 280-287). Ru.

The cylindrical electrode was made of mild steel (C1018). Seal this electrode with No. 600 silicon carbide sandpaper. and then immersed in the test solution. Also, this solution is heated to a desired temperature of 90”C. The electrode was then immersed in it. The electrode is attached to the cylindrical shaft, and after this immersed and set to rotate at 200 rpm to ensure turbulent conditions. . The water level is set at the top of the Rulon (registered trademark) (graphite-impregnated (tetrafluoroethylene), DuPont (E, 1. duPont de [Made by Nemours & Company] It is located in the middle of the spacer. to prevent hydrodynamic effects from interfering with the results and to ensure optimal flow and streamlines. sodium aspartate at pH 10 in a rotating cylinder apparatus. Obtained by exposing a mild steel electrode to the solution. sodium aspartate A pH of approximately 1000 ppm was obtained for B. However, asparagine Sodium sulfate is not present, and instead sodium sulfate (which is virtually non-corrosive) The same ionic strength was achieved using

By measuring the voltage between the copper electrode and the saturated calomel electrode, sample A and sample The corrosion potential of the copper electrode used for each of B was measured. For each of sample A and sample B The counter electrodes were rotated at different speeds for the same exposure time.

Polarization resistance was measured as described in the above-mentioned paper co-authored by Silverman and Kali: It was used to estimate the corrosion rate.

Corrosion rate is converted into erosion degree or corrosion loss in mils per year (mpy). Ta.

The impedance spectrum for the steel billet electrodes (sample A and sample B) is Each aqueous solution used for sample A and sample B at 20 Orpm using an electrode device. Obtained at pH 1O in the medium. These spectra (curves) are shown in Figures 1.2.3 and 4. The agreement between the calculated curve and the actual data indicates that the polarization resistance We prove that the model used to obtain the results is in good agreement with the actual results.

Localized nature of corrosion observed in static immersion tests under comparative conditions (example below) Test numbers 4 and 5) of 2 were not observed for the rotating cylindrical electrode. This behavior is , when a uniform velocity field exists, aspartic acid will advantageously cause corrosion to occur more uniformly. This suggests that it is possible to suppress the Furthermore, is the suppression effect uniform? It is suggested that it will increase. The end result of a smoother finish is the surface microstructure of the electrode. The nonuniformity of the structure was smaller than that of the static immersion specimen. . As such, the more uniform the speed and the smoother the surface of the steel, the better the surface The concentration of aspartic acid required to uniformly suppress corrosion in all parts of the I'll try it.

Table 1 (pH=1O, adjusted at 25°C) Exposure time Rotation speed Polarization resistance Estimated 0, 5 200 361 32.0 4 200 4530 2, 5 6 1000 13950 0.80 23 200 40160 0, 29 25 1000 138300 0, 0947 200 92340 0, 13 49 1000 2170800 0.0150 200 1103800 0 ．． 02 sample piece A (7) corrosion potential is -310 [IIV (S, C, E,)te.

The steel billet was manufactured for use as an electrode in a rotating cylindrical electrode device. this device ``For Speed Sensitivity Testing'' by D. C. Silverman. Rotating cylindrical basket Cor7Sion Kyoku J (1984 (7) rmJ magazine, Vol. 40, May issue, pp. 220-226) (published) in detail.

The electrochemical impedance method is also used by D., C., Silverman. ) and J. E. Carrico (Carrico), “Electrochemical Impeders” rCorrosion Method - A Practical Tool for Corrosion Prediction J (1988 rCorrosion J magazine, Volume 44, May issue, pages 280-287). Ru.

The cylindrical electrode was made of mild steel (C1018). Seal this electrode with No. 600 silicon carbide sandpaper. and then immersed in the test solution. Also, this solution has a desired temperature of 90'C. The electrode was then immersed in it. The electrode is attached to the cylindrical shaft, and after this immersed and set to rotate at 200 rpm to ensure turbulent conditions. . The water level is determined by the upper Rulon (registered trademark) [graphite-impregnated point] (tetrafluoroethylene), DuPont (E, 1. duPont de Manufactured by Nemours & Company) It is located in the middle of the spacer. to prevent hydrodynamic effects from interfering with the results and to ensure optimal flow and streamlines. 1) HIO's sodium aspartate was obtained by exposing a mild steel electrode to a liquid solution. sodium aspartate The pH of approximately 11000 pp was obtained for B. However, asparagine Sodium sulfate is not present, and instead sodium sulfate (which is virtually non-corrosive) The same ionic strength was achieved using

sample A and sample A by measuring the voltage between the steel electrode and the saturated calomel electrode. The corrosion potential of the steel electrode used for each of B was measured. For each of sample A and sample B The counter electrodes were rotated at different speeds for the same exposure time.

Polarization resistance was measured as described in the above-cited paper by Silberman and Carini, It was used to estimate the corrosion rate.

Corrosion rates were converted to erosion rates or corrosion losses in mils per year (mpY). .

The impedance spectrum for the steel billet electrodes (sample A and sample B) is Each aqueous solution used for sample A and sample B at 200 rpm using an electrode device. Obtained at pH 10 in These spectra (curves) are shown in Figures 1.2.3 and 4. The agreement between the calculated curve and the actual data indicates that the polarization resistance We prove that the model used to obtain the results is in good agreement with the actual results.

Localized nature of corrosion observed in static immersion tests under comparative conditions (example below) Test numbers 4 and 5) of 2 were not observed for the rotating cylindrical electrode. This behavior is , the presence of a uniform velocity field advantageously makes the aspartic acid corrosion more uniform. This suggests that it is possible to suppress the Furthermore, is the suppression effect uniform? It is suggested that it will increase. The end result of a smoother finish is the surface microstructure of the electrode. The nonuniformity of the structure was smaller than that of the static immersion specimen. . As such, the more uniform the speed and the smoother the surface of the steel, the better the surface The concentration of aspartic acid required to uniformly suppress corrosion in all parts of the I'll try it.

Table 1 Corrosion of mild steel at o 00 p p m (pH= (adjusted at 10.25°C) Exposure time Rotation speed Polarization resistance Estimated 0, 5 200 361 32.0 4 200 4530:15 6 1000 13950 0, 80 23 200 40160 0, 29 25 1000 138300 0, 0947 200 92340 0, 13 49 1000 2170800 0.0150 200 1103800 0 ．． The corrosion potential of 02 sample piece A (7) is -310 mV (S, C, E,).

Table 2 Corrosion of mild steel with sodium hydroxide (pH=lo, adjusted at 25°C) Exposure time Rotation speed Polarization resistance Estimated 0, 5 200 256 45 The corrosion potential of sample piece B is -630 mV (S, C, B,).

As shown in Tables 1 and 2, the corrosion of specimen A against sodium laginate The potential is -310 mV (S, C, E,), while aspartate sodium The corrosion potential of specimen B is -630 mV (S, C, E,) This difference in corrosion potential is due to the fact that sodium aspartate is This suggests that the tendency of the steel to oxidize the surface of the steel is large (,z').

However, the corrosion rate of each sample mentioned above has a contradictory relationship with this oxidation tendency. (to clarify) Between corrosion rates of sample A vs. sample B after the same exposure time Looking at the magnitude of the difference, aspartate suppresses corrosion by 100 to 1000 times. It proves that it does. Corrosion was observed in sample A (32 mpy) and sample B (45 mpy). mpy) also started at roughly the same rate, but with the presence of sodium aspartate. If the Ta.

Furthermore, in the absence of aspartate, the rotational speed, and hence the fluid velocity, increases As time passes, the corrosion rate increases for at least 24 hours in the experimental example. Probably (corrosion) No change was observed after 48 hours, probably because the product accumulated on the surface. This behavior is It is common for carbon steel and water. Is oxygen reduction the rate-limiting step? It is et al.

The rate of mass transfer of oxygen to the corroded surface often determines the corrosion rate; Velocity is adversely affected as corrosion products accumulate on the surface. However, asparagus In the presence of ginate, the corrosion rate did not increase with increasing flow rate. fruit Throughout the examples, the corrosion rate consistently decreased as the rotation speed increased. . The phenomenon of reduced corrosion rate obtained by increasing the flow rate is It appears to be reversible. The rotation speed was then lowered to 200 rpm. and demo (measured at exposure times 46-48, 49. and 50 hours, shown in Table 1) As can be seen from the corrosion rate), the corrosion rate increases as the fluid velocity increases to 11000 rpm. The speed of 0.13 mpy at 200 rpm, which the sample showed before the test, did not return. That's because there wasn't.

Therefore, the sodium salt of aspartic acid can react in an unexpected manner under basic conditions. It functions as a corrosion inhibitor for ferrous metals.

The impedance spectrum itself is studied as a function of rotational or fluid velocity. The rotating cylindrical electrode was used for over 48 hours. 200 rpm and 24 hours Plots under conditions after the test are shown in Tables 1.2.3 and 4.

Two plots of phase angle for mild steel in contact with sodium aspartate There is a peak. This is shown in FIG. Such behavior is explained by the fact that the relaxation time constant is This suggests that there are two types of intermediates that are strongly adsorbed in turn. Either the body or the tightly attached film are involved in the corrosion mechanism. This suggests that The high frequency peak is due to the intermediate adsorbed on the film. Due to the low frequency peaks are involved in the corrosion rate. Therefore, regarding the corrosion mechanism Without wishing to be bound by theory or to limit the invention in any way, However, even if the mechanism is not fully understood, aspartate It is believed that on forms some kind of adsorption layer on the metal surface. asparagus Some sort of adsorption layer exists on the metal surface when ginate ions are present. Further evidence that the aspartate ion is present under comparative conditions is given by a plot of the phase angle for mild steel. A plot like this (Fig. 4) suggests that only a corrosion reaction that transfers charge is occurring. do. Only one peak exists.

Dry and weigh. The specimens were then subjected to a static immersion test. changed The parameters and results obtained are shown in Table 3 below. The specimens are L-A, respectively. In a glass bottle containing about 600 cm3 (or CC) of Sunoku laginic acid test solution hung on a glass hook. This solution is mixed with deionized water and the desired aspartic acid concentration. It was prepared using aspartic acid in an amount sufficient to obtain the desired temperature. The hook above is for the bottle. It was attached by piercing the rubber stopper that seals the top. Inject the gas spray water from the side of the stopper. for aeration of a solution containing air saturated with water, excluding carbon dioxide. I blew into it. Place these bottles in a constant temperature bath maintained at a temperature of 90°C. Ta. The exposure time for these specimens was 5-7 days during which time the aspartic acid test solution Deionized water was added periodically to compensate for water loss due to evaporation at high temperatures. each The pH of the solution was adjusted at the beginning of the test using sodium hydroxide and kept at room temperature (RT, approx. 25°C) and the test temperature.

At the end of the specimen exposure time, remove the specimen from the solution and rinse it with soap solution. cleaned in an ultrasonic bath, rinsed with deionized water, rinsed with acetone, dried, and Weighed. For the surface of the specimen, after exposure, stereo Inspection was performed using a scope. Corrosion rate is determined by weight change (in aspartic acid solution) (before and after exposure) and then measure the degree of erosion or corrosion loss in lpy or g/h. It was estimated according to the method previously described by calculating. Significantly less corrosion If it is uniform and appears locally on a certain surface, the corrosion loss in duram units can be measured in terms of time. Only the value divided by the total exposure time is shown. The reason is that corrosion averaged over the entire surface area The corrosion rate is a factor that can affect the magnitude of corrosion if it occurs in a very localized area. This is because it is not shown accurately. However, Table 3 showing the results from the static immersion test shows that one In contrast to Tables 1 and 2, which show results from constant flow systems, under no flow conditions , the required concentration of aspartic acid needed to achieve the same level of corrosion inhibition increases. This proves that

Table 3 Total deception.

Table 3 (g) 迭) Threshold rope feeding reduction l Threshold expansion width Iitong strong weight loss.

Total number of grams per 1 total Example 3 The solution did not contain aspartic acid and only three steel specimens were subjected to static immersion tests. The method described in Example 2 was used, except that: Solution added sodium sulfate By doing so, it has the same conductivity as those containing aspartic acid. I adjusted it to sea urchin. By doing so, corrosion is contained in water of a given pH. Limited to corrosion caused by oxygen only. The results are shown in Table 4. without phosphoric acid Static immersion test results for mild steel Test pH total corrosion loss explanation Number mpy gden/h,' 1 8.0 @ RT 12.4 0.0987/119 7 over the entire surface ．． 1 Severe general corrosion at 90°C.

2 10.0 @ RT 21.4 0.1725/119 Over the entire surface 8.7 @ 90°C Severe general corrosion.

3 12.0 @ RT O, 300,0024/119 Initial appearance of pitting corrosion 1 0.4 Some stains with 190℃.

Total grams per total exposure time Comparing test numbers 2 and 3 in Table 3 with test number l in Table 4, when the pH is 8, corrosion The rate is higher with aspartic acid than without. This has a pH of 8 , aspartic acid does not provide any beneficial corrosion inhibiting effect and is instead a corrosion accelerator. This will help you confirm that you are working as a. Similar behavior was observed at pH 9.5. This is observed when the concentration of spalagic acid is 3% by weight (Test No. 10 in Table 3).

This behavior shows that when the pH is below 9.5, aspartic acid is completely or This is due to the fact that it does not exist in the ionized (conjugated base) form. this is , when the pH is higher than 9.5, e.g. 10 or higher, aspartic acid or 1 Even at concentrations as low as 1000 pp, no changes can be clearly demonstrated by observed changes. It will be done. At a concentration of 1% by weight and a pH of 10 (Test No. 9) under the static test conditions of Table 3. Virtually all corrosion disappears. Therefore, when the pH is measured at 90°C, it is 8.5~ In the range of about 9.0, that is, when the pH is 10 or more at room temperature (about 25°C), Spartic acid inhibits corrosion under static conditions, but at lower pH it inhibits corrosion. This increases or accelerates corrosion.

Test numbers 4 and 5) with a concentration of 101,000 pp in the range of pH 9.9 to lO At 5000pp01 (test number 8), some attack or corrosion was observed. The fact that aspartic acid does not inhibit corrosion at these concentrations does not mean The fact that there is a large area where corrosion or no evidence of corrosion is present indicates that asparagus This strongly suggests that lagic acid actually inhibits corrosion.

This apparent discrepancy is due to the fact that during immersion testing, under no-flow, i.e. static conditions, the specimen This is due to the fact that it is impossible to uniformly disperse aspartic acid.

Example 4 A steel specimen was prepared for use as an electrode in the rotating cylindrical electrode device described in Example 1. , in an aspartic acid solution containing 1000 ppm of aspartic acid, the pH is Three different levels (8, 10, and 12) were tested. The fourth test piece also The same procedure was carried out at pH 10 (for comparison). However, using aspartic acid without aspartic acid, the solution has the same conductivity as when aspartic acid is present. Adjustments were made with sodium sulfate. Corrosion is caused by the electrochemical impedance described in Example 1. Estimated using the S method. The results are shown in Table 5.

The electrochemical impedance spectrum was measured at 0.01 hertz (hz) after approximately 30 minutes. ) and estimated the corrosion rate under short-term exposure. Then the spectrum is , generated daily at 2 U Orpm to 0.001 hz. In addition, Spect The effect of fluid velocity on corrosion was We estimated the impact of The test was carried out at pH 8 using 11000 pp of aspartic acid. , 10° and 12 degrees, and further conducted at pH 10 without aspartic acid.

The magnitude of the perturbing voltage signal is small. (5 mV) to ensure linearity between perturbation and response. The above copper The electrode was pressed twice, before and after the experiment. The purpose of corrosion loss measurement is to This is because it is inferred by law. At pH 10, especially at pH 12, the corrosion loss is Note that it was affected by water leaking behind the. Polarization resistance is silver It is estimated using the circuit analog method shown in Figure 2 of the above-mentioned document co-authored by John Mann and Kaliguchi. Established.

The results of the rotating cylindrical electrode test show that under ideal conditions of fluid velocity, aspartic acid concentrations If the degree of Corrosion rate is small to about 1 to 0.5 mpy compared to 50 to 100 m1) y. This shows that it is possible to reduce the In the absence of aspartic acid, there is fluid movement As a result, the corrosion increases until the surface is completely corroded, and eventually the velocity of the fluid near the surface increases. It gets to the point where it starts to affect Rofeel. This trend is due to the fact that mild steel and low alloys in water Expected against corrosion of steel. However, at pH 9.5 or higher (measured at room temperature), asparagus When lagic acid is present, corrosion is reduced when there is fluid movement.

Example 5 This example shows that surfaces that have previously undergone corrosion can be protected with the corrosion inhibitors of the present invention. prove that The results shown in Table 6 demonstrate that in the rotating cylindrical electrode apparatus described in Example 1, , (has roughly the same conductivity as aspartic acid of 11,000 pp at pH 1o) ) 2000 ppm sodium sulfate and 50 ppm sodium chloride were added. Measured by exposing a previously corroded steel cylindrical electrode to deionized water It was done. In 24 hours, the electrode broke through significant corrosion loss and developed a reddish-brown rust layer.

It has an aspartic acid concentration of 500 ppm, and the pH is adjusted to about 10 with sodium hydroxide. The electrode was immersed in an aqueous solution that was adjusted and maintained under constant rotation. polarization Resistance increases rapidly over 24 hours and corrosion rate decreases with exposure time. It was shown that The corrosion rate was 11,000 pp as previously uncorroded. The values for electrodes exposed to paragic acid, e.g., do not decrease to the results shown in Table 1. It was. This difference suggests that the concentration was not optimal in this particular system. There is.

But more importantly, even 1000 ppm of aspartic acid Corrosion (even of previously corroded steel) can be inhibited under suitable conditions. This is an observation result.

Table 6 Exposure time Rotation speed Polarization resistance Corrosion rate, 17-19 200 87 (In Peedance 21 1000 182 method 81mpy) 0.5 200 610 22 1000 5400 Not measured 45 1000 > 10000 Example 6 A static immersion test was conducted as described in Example 2. However, glutamic acid, glycine, and Certain acids commonly used in antifreeze and antifreeze formulations were substituted for aspartic acid. . The parameters used and the results obtained are shown in Table 7.

Glutamic acid and glycine each exhibit similar behavior and corrosion inhibition to aspartic acid. It can be seen that this shows the system. Slightly more bleeding was observed on the test piece, but the corrosion loss was It was similar to that with aspartic acid at the same pH. Furthermore, these results indicate that Spartic acid, benzoic acid, sebacic acid (sebacic a) at 90°C cid) and octanoic acid. do. Are acids like the latter name commonly used in antifreeze formulations? The results for aspartic acid (test numbers 11 and 12 in Table 3 of Example 2) It is possible to use aspartic acid as a suitable replacement for acids such as shows. As can be seen from Table 7, the ammonium salt of aspartic acid is Salt does not seem to work well with. pH or aspartic acid (conjugated (as a base) at a pH lower than that at which it exists in fully ionized form , it drops to 7.7.

11 groan 9.4 [phase] ■γC1hυt3z<:=Meishiru Hanawa Yumbe Kokyu There are many places where there is no corrosion. 4 Glutamic acid +0.2@l? I’　-0,0220g/+19-WS, Extremely deep corrosion 11 9.4 [phase] (1) °C - evening rot 9 Some areas without corrosion Many 6 Glutamic acid 110@(company) <0.1 0.0 [X11/119 Corrosive -Table 7 (continued) 90'C-Remains 1 Transferable 1'Asparagi A Fujisha 1t each Total number of plums per 1 total V dew hour ■ Example 7 A static immersion test was conducted as described in Example 2. However, instead of aspartic acid, Concentrations of polyaspartic acid and (amino acid) from 2000 ppm to 3.3% polyasparagine hydroxamic acid (pol yaspartyl hydroxamic acid) was used. parameter The parameters and results are shown in Table 8. The concentration of 2000 ppm at this time is The concentration of carboxyl groups is similar to that of aspartic acid at 11,000 pp. It was selected for this purpose. The corrosion inhibiting effect is shown at pH 9.5 (90°) when measured at 25°C. When measured at C, the pH changed to approximately 8.4) or above. This is aspa All points on the surface that are very close to the pH threshold of lagic acid, resulting in an inhomogeneous surface. It is suggested that even larger amounts of polyaspartic acid are required to completely suppress the effect. . However, a significant degree of suppression was obtained at 2000 ppm. But rotation Under high fluid velocities such as those applied to electrodes, the corrosion-inhibiting properties of polyaspartic acid is expected to increase.

Polyasparagine hydroxamic acid does not contain amino groups, but At the same concentration as paragic acid, the corrosion inhibition effect was inferior.

Mild steel/Polyasparagine S size static ζ Cod anchorage C Moose anchor S wear amount at 90'C 7 1 fish more than the attendant ~ (1st day of school) There are many places where there is no corrosion. Q more rotten than acid Total number of plums per 1W Example 8 This example demonstrates that the compositions of the present invention are effective as corrosion inhibitors at relatively low temperatures. prove

A static immersion test on steel in pH 10 water was performed at 30°C as described in Example 2. , no inhibitor, 3% aspartic acid added, or 3% polyaspartic acid It was conducted under the condition that . The parameters and results are shown in Table 9. Asparagi Significant corrosion inhibition effect under relatively low temperature conditions for both polyaspartic acid and polyaspartic acid. (10, Ompy or decreased to less than 0, lmpy without local corrosion) Ta.

Total grams per total exposure time Therefore, in accordance with the present invention, a water-based It is clear that compositions and methods for inhibiting corrosion of ferrous metals in the presence of media have been provided. It is. Although the invention has been described with respect to a number of specific examples and embodiments, the invention is not limited to these, and there are many alternatives in light of the above explanation, It is understood that modifications and variations will be apparent to those skilled in the art. Therefore, the original All alternatives, partial modifications and variations that fall within the spirit and scope of the invention are expressly disclosed. Unfortunately, it is included.

Chestnut １　沣の箭岑51! I + gong street capture T size procedure amendment form October 23, 1992 1990 Patent Application No. 511875 Z invention name Corrosion inhibiting composition for ferrous metals and its corrosion inhibiting method 3, Person performing correction Relationship to the incident: Patent applicant Name: Monsando Company 4. Agent Address: 331 Shin-Otemachi Building, 2-2-1 Otemachi, 100 East Special Training Center Hei 3-ku 1+Takuto 7 f, IIP! 'f'-” IPIA C!D-C/J!1~,5 vノ λu So TFt3, LL, 9';).

r Scope of claims ■, In a composition for inhibiting corrosion of ferrous metals in the presence of an aqueous medium, HOOC-(-CH2-)aNH-.

X and y each independently represent an integer of 1 to 3, and n is an amount effective to suppress corrosion of ferrous metals according to Japanese Patent Application Publication No. 5-500832 (1 4) Indicates the repeating integer of aminoacyl units. ) and the amino acids indicated by (b) Effective in providing amino acids in a sufficiently ionized form under the conditions of use. amount of base and A corrosion inhibiting composition comprising.

2. The above amino acids, glycine, polyglycine, aspartic acid, polyaspa selected from the group consisting of lagic acid, glutamic acid, polyglutamic acid, and salts thereof; A composition according to claim 1, wherein the composition is selected from the group consisting of:

3. The amino acid according to claim 1, wherein the amino acid is aspartic acid and a salt thereof. Composition.

4. The amino acid is present in the aqueous medium at about 100 ppm to about 5.0 ppm under the conditions of use. Claim 1, wherein the amino acid is present in an amount sufficient to provide an amino acid concentration of greater than or equal to % by weight. composition.

5. The amino acid is present in an aqueous medium of about 11,000 pp to about 3.3 pp under conditions of use. of claim 4, wherein the amino acid concentration is present in a sufficient amount to provide an amino acid concentration of % by weight. Composition.

6. The base is an alkali metal hydroxide, an alkali metal carbonate, an alkali Earth metal hydroxides, ammonium hydroxides, and hydrorubyramine , the composition according to claim 1.

7. The composition according to claim 6, wherein the base is a hydroxide of an alkali metal. .

8. Whether the alkali metal hydroxide is sodium hydroxide or potassium hydroxide 8. The composition of claim 7, wherein the composition is selected from the group consisting of:

9. Claim 1, wherein the pH in the aqueous medium under the conditions of use is at least 8.9. Compositions as described in Section.

10. The pH in the aqueous medium under conditions of use is from about 8.9 to about 14, claim 9. Compositions as described in Section.

11. The pH in the aqueous medium is about 9.9 to about 12 when measured at room temperature. The composition according to item 1.

12. The pH of the aqueous medium is about 10 to about 11 when measured at room temperature. Composition according to item 1.

13. In a method for inhibiting corrosion of ferrous metal in the presence of an aqueous medium, the aqueous medium all over your body, (In the formula, R1 is H, H2N-CH-C-, or CH2C00H H2N-(-CH2-)A, R2 is HO-, HOOC-CH-NH -, or CH2C00H HOOC-(-CH2-') NH-X and y are each independently an integer from 1 to 3. indicate the number, and n is an amount of repeating arrangement of aminoacyl units effective to inhibit corrosion of ferrous metals. Show the number. ) and the amino acids indicated by (b) Effective in providing amino acids in a sufficiently ionized form under the conditions of use. amount of base and A method comprising adding.

14. The above amino acids, glycine, polyglycine, aspartic acid, polyaspar selected from the group consisting of lagic acid, glutamic acid, polyglutamic acid, and salts thereof; 14. The method of claim 13, wherein the method is selected.

15. Claim 13, wherein the amino acid is aspartic acid or a salt thereof. How to put it on.

16. The above amino acids may be present in an aqueous medium at about 100 ppm to about 5.0 ppm under conditions of use. Claim 13, wherein the amino acid is present in an amount sufficient to provide an amino acid concentration of greater than or equal to % by weight. Method described.

17. The amino acids may contain from about 11,000 pp to about 3.3 ppm in the aqueous medium under conditions of use. Claim 16, wherein the amino acid is present in an amount sufficient to provide an amino acid concentration of greater than or equal to % by weight. Method described.

18. The base, alkali metal hydroxide, alkali metal carbonate, alkali earth metal hydroxides, ammonium hydroxides and hydrocarbylamines, The method according to claim 13.

19. The method according to claim 13, wherein the base is an alkali metal hydroxide. .

20. The alkali metal hydroxide, sodium hydroxide and potassium hydroxide 20. The method of claim 19, wherein the method is selected from the group consisting of:

21, the pH in the aqueous medium under the conditions of use is at least 8.9. The method described in Section 3.

22. The pH in the aqueous medium under conditions of use is from about 8.9 to about 14. The method described in Section 1.

23. The pH in the aqueous medium is from about 9.9 to about 12 when measured at room temperature. The method according to paragraph 13.

24. The pH in the aqueous medium is about 10 to about 11 when measured at room temperature. Mutualism as described in Section 23.

25. The corrosion rate of ferrous metals compared to the corrosion rate in the absence of amino acids, 14. The method of claim 13, wherein the reduction is about 100 to about 1000 times.

26. The method of claim 13, wherein the aqueous medium is substantially quiescent.

27. The method of claim 13, wherein the aqueous medium is in a dynamic flow state.

28. The aqueous medium under conditions of use is at a temperature of about 25°C to about 90°C. The method according to paragraph 13.

29. The method of claim 28, wherein the temperature is about 30<0>C.

30. The method of claim 28, wherein the temperature is about 90<0>C. A international search report tm++am+fist Lla+i<sa+, cabas 綽OPt'iT/I+! ;o r+tr+Ai FΩ international investigation report

Claims (30)

[Claims] 1. In a composition for inhibiting corrosion of ferrous metals in the presence of an aqueous medium, (a) Formula: ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R1 is H, ▲numerical formula, chemical formula, table, etc.▼ or H2N-(-CH 2-)■-;, R2 is HO-, ▲numerical formula, chemical formula, table, etc.▼, or represents HOOC-(-CH2-)■-NH-; R3 represents H or -COOH; x and y each independently represent an integer from 1 to 3, and n is an amount of repeating arrangement of aminoacyl units effective to inhibit corrosion of ferrous metals. Show the number. ) and the amino acids indicated by (b) an amount effective to provide the amino acid in a sufficiently ionized form under the conditions of use; A corrosion inhibiting composition comprising a base. 2. The amino acid is glycine, polyglycine, aspartic acid, polyaspara Selected from the group consisting of gic acid, glutamic acid, polyglutamic acid, and salts thereof The composition according to claim 1, wherein the composition is 3. The set according to claim 1, wherein the amino acid is aspartic acid and its salts. A product. 4. The amino acid is present in an aqueous medium at about 100 ppm to about 5.0 weight by weight under conditions of use. % or more of the amino acid concentration. Composition. 5. The amino acid is present in an aqueous medium at about 1000 ppm to about 3.3 ppm under conditions of use. % of the amino acid concentration. A product. 6. The base is an alkali metal hydroxide, an alkali metal carbonate, an alkaline earth metal hydroxides, ammonium hydroxides, and hydrocarbylamines, A composition according to claim 1. 7. 7. The composition of claim 6, wherein the base is an alkali metal hydroxide. 8. The alkali metal hydroxide is selected from sodium hydroxide and potassium hydroxide. 8. The composition of claim 7, wherein the composition is selected from the group consisting of: 9. Claim 1, wherein under the conditions of use the pH in the aqueous medium is at least 8.9. Compositions as described. 10. Claim 9, wherein the pH in the aqueous medium under conditions of use is from about 8.9 to about 14. Compositions as described in Section. 11. 5. The pH of the aqueous medium is from about 9.9 to about 12 when measured at room temperature. The composition according to item 1. 12. Claim 1, wherein the pH in the aqueous medium is from about 10 to about 11 when measured at room temperature. Composition according to item 1. 13. In a method of inhibiting corrosion of ferrous metal in the presence of an aqueous medium, the aqueous medium all over your body, (a) Formula: ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R1 is H, ▲numerical formula, chemical formula, table, etc.▼, or H2N-(-C Indicates H2-)■-, R2 is HO-, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, or HOOC-(-CH 2-)■-NH- shows, R3 represents H or -COOH, x and y each independently represent an integer from 1 to 3, and n is an amount of repeating arrangement of aminoacyl units effective to inhibit corrosion of ferrous metals. Show the number. ) and the amino acids indicated by (b) an amount effective to provide the amino acid in a sufficiently ionized form under the conditions of use; A method comprising adding a base. 14. The above amino acids include glycine, polyglycine, aspartic acid, polyaspartic acid, selected from the group consisting of lagic acid, glutamic acid, polyglutamic acid, and salts thereof; 14. The method of claim 13, wherein the method is selected. 15. Claim 13, wherein the amino acid is aspartic acid and a salt thereof. How to put it on. 16. The amino acid is present in an aqueous medium at about 100 ppm to about 5.0 weight by weight under conditions of use. 14. The amino acid concentration of claim 13 is present in an amount sufficient to provide an amino acid concentration of greater than or equal to %. How to put it on. 17. The amino acid is present in the aqueous medium at about 1000 ppm to about 3.3 ppm under conditions of use. Claim 16, wherein the amino acid is present in an amount sufficient to provide an amino acid concentration of greater than or equal to % by weight. Method described. 18. The base is an alkali metal hydroxide, an alkali metal carbonate, an alkali earth metal hydroxides, ammonium hydroxides and hydrocarbylamines, The method according to claim 13. 19. 14. The method of claim 13, wherein the base is an alkali metal hydroxide. . 20. The alkali metal hydroxide may be sodium hydroxide or potassium hydroxide. 20. The method of claim 19, wherein the method is selected from the group consisting of: 21. Claim 1, wherein under the conditions of use the pH in the aqueous medium is at least 8.9. The method described in Section 3. 22. Claim 2, wherein the pH in the aqueous medium under conditions of use is from about 8.9 to about 14. The method described in Section 1. 23. 5. The pH of the aqueous medium is from about 9.9 to about 12 when measured at room temperature. The method according to paragraph 13. 24. Claim 1, wherein the pH in the aqueous medium is from about 10 to about 11 when measured at room temperature. Composition according to item 23. 25. The corrosion rate of ferrous metals compared to the corrosion rate in the absence of amino acids 14. The method of claim 13, wherein the reduction is by a factor of about 100 to about 1000. 26. 14. The method of claim 13, wherein the aqueous medium is substantially quiescent. 27. 14. The method of claim 13, wherein the aqueous medium is in a dynamic flow state. 28. Claim 1, wherein the aqueous medium under conditions of use is at a temperature of about 25°C to about 90°C. The method described in Section 3. 29. 30. The method of claim 29, wherein the temperature is about 30<0>C. 30. 30. The method of claim 29, wherein the temperature is about 90<0>C.