JPS6048593B2 - Method for forming a corrosion-resistant coating and aqueous treatment solution used in the method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a treatment for imparting increased corrosion resistance to metal substrates, particularly on aluminum plus used in surface condensers and heat exchangers using seawater as cooling water. , relates to providing coatings that reduce corrosion failure of such devices.

Seawater is used as a coolant in many heat exchangers and condensers, and while it has the advantage of being easily available in many cases where the use of fresh water is not possible, it is relatively corrosive. It has the disadvantage of having ''Condenser that uses seawater as cooling water (Marinec Ondens)
ers)'' is a term generally used herein to refer to a surface heat exchanger, which has a true condenser and is used to handle estuarine waters of varying salinity. The seawater it contains is used as a coolant.

The invention is applicable to all conventional designs of seawater-cooled condensers, but in particular to cooling a series of tubes within an external vessel (shell) through which the liquid to be cooled or condensed flows. Suitable for ``tube shell'' type where agent (seawater) is flowing.

Heat exchange takes place through the tube walls. Marine steam turbine condensers are usually of this type. In an effort to maximize the cooling power of marine condensers, designs were typically made using high coolant flow rates of up to 300 m/s. Coolant flow. The flow is, at least in part, turbulent, so that its actual velocity may be several times greater than said flow velocity, and in part it may exceed 10 m/s. Aluminum Plus is in contact with seawater while being used with clean seawater that is circulated at a moderate speed. The surface forms a thin protective coating over a period of several weeks. The properties of this protective coating are not known with certainty, but it is likely to be hydrotalcite or a similar substance and can be described as a mixture of basic oxycarbonates of zinc, magnesium and aluminum. . The coating may also contain minor proportions of other metals. The mechanism by which this coating provides corrosion resistance is unknown, but our research has led us to believe that it acts to buffer the substrate against corrosion. This is enhanced by the low galvanic potential between the metal substrate and the coating.
However, since the film is formed slowly,
After initial service, or after re-commissioning after repair or maintenance, there is a period during which seawater-cooled condensers are susceptible to corrosion, which can lead to premature failure, especially at high flow velocities. This problem is further aggravated by the fact that the water used to service seawater cooling condensers becomes heavily contaminated with sulphides, especially during the maintenance of internal bays and ports, for example.
The sulfide reacts with the substrate to form copper sulfide, which mechanically interferes with the formation of the protective coating or damages the coating and introduces copper into this coating in relatively high concentrations. . It has been found that the presence of copper in a naturally produced protective coating (naturally occurring coating) reduces the corrosion resistance of the coating. For example, even if a complete naturally occurring corrosion-resistant coating were formed, it would be mechanically damaged by the high impact velocities of the coolant.

This problem has been addressed by incorporating Fe(11) into the coolant, which deposits on the condenser surface to form a coating that is also resistant to mechanical damage due to the high impact velocities of the coolant. Because of its relatively short lifetime, this Fe(■)-containing coating is required to be periodically incorporated into the coolant, typically once.

This iron is normally added to the coolant supply as ferrous sulfate which is oxidized to Fe(■) with dissolved oxygen. As a practical matter, corrosion failure of the aluminum-plus components in seawater cooled condensers occurs less frequently when higher quality alloys and construction are used.

However, individual failures are very costly, especially if those failures fall outside of the scheduled maintenance schedule. Improving the corrosion resistance of Aluminum Plus has been the subject of research to date. Treatment with sodium dimethyldithiocarbamate was therefore proposed.
Although the protection afforded by this is qualitatively satisfactory, it must be monitored by periodic reprocessing if necessary. Cupric aluminate coatings have also been proposed, but our current work shows that these coatings promote corrosion in some situations. The present invention is based on the discovery that a corrosion-resistant coating can be deposited on aluminum plas by treatment with an oxidizing solution.

This coating has a low copper content and is very similar in properties to naturally occurring coatings. Furthermore, while in contact with seawater, the coating transforms into a coarse material that is substantially the same in composition as the naturally occurring coating.
The present invention therefore provides corrosion resistance on the surface of the aluminum plus substrate. There is provided a method for forming a film, the method comprising: a pH of 4;
~9, H. O. Calculate the inorganic peroxide as 0.2
The substrate surface is brought into contact with an aqueous treatment solution containing a strong complexing agent for copper dissolved in a concentration of 5 to 30 g/l and a concentration of at least 0.05 equivalent/l, thereby forming a corrosion-resistant coating on the substrate surface. It consists of forming This relatively simple solution can form a protective coating on Aluminum Plus, but
The pH of the solution tends to increase, retarding the formation of the desired film.

This effect is particularly pronounced when the ratio of the surface area to be treated to the volume of the treatment liquid is relatively high, such as when treating tube-shell capacitors. Therefore, the solution has a pH of
It is highly desirable to include a laxative to maintain the PH at or near a predetermined operating PH. Therefore, the present invention further includes a barless peroxide containing H. O. Measured as 0.25-30
g/l concentration of at least 0.0 strong complexing agent for copper
An aqueous treatment solution containing a laxative dissolved at a concentration of 5 equivalents/l and at least 0.015 molar concentration effective to maintain the pH of the solution in the range 4 to 9 is brought into contact with the substrate, thereby forming a corrosion-resistant coating. A method of forming a corrosion-resistant coating on the surface of an aluminum plus substrate is provided. In practice, the desired protective coating is formed on the aluminum plus surface of the condenser using seawater as cooling water in situ in the assembled unit.

Therefore, the present invention includes a method for treating the aluminum plus heat exchange surface of a condenser using seawater as cooling water in order to increase resistance to corrosion by seawater. The process consists of circulating a treatment solution through the coolant circulation path of the condenser to form a corrosion-resistant coating on the aluminum plus surface. The substrate to which the present invention can be applied is aluminum plus. Aluminum Plus is an alloy of copper, zinc and aluminum, and a typical example of Aluminum Plus used in a condenser that uses seawater as cooling water is British Standard BS2.
87l/1972 (Part 3) and international standards 1. S.O.
426/11973(E), which is an alloy detailed in 426/11973(E). S. 287l is 76-78% copper, All. 8-2
．． 3%, AsO. O2~006%, impurities max. 0.3%
, the name CZIIO, which includes the remainder of Zn, is specified as aluminum plus. 1. called CuZn2OAl2. S. O.
The alloys have similar compositions. The inclusion of trace amounts of arsenic is a known means of preventing rapid dezincification of such alloys upon contact with seawater. This arsenic can be replaced by an equal amount of antimony, 1. S. O. 426 mentions this possibility. The presence of arsenic (or antimony) in the aluminum plus substrate is not critical to the formation of the corrosion-resistant coating of the present invention, however, it requires that known means of preventing dezincing be used. The presence of a high concentration of copper in the coating is due to the presence of a high concentration of copper in the coating, which is facilitated by peroxides which depolarize the reaction, and the subsequent precipitation of hydroxides, mainly aluminum and zinc, forming a protective coating. As mentioned, copper is undesirable because it tends to promote failure of the coating.Since the majority of the substrate is copper, a method is needed to prevent copper precipitation in the coating.In the present invention,
We accomplish this by including a strong complexing agent for the copper in the processing solution. This strong complexing agent binds to the copper, keeping it in solution and preventing copper precipitation into the coating. Although a small amount of copper may be captured in the coating, for example by occlusion from solution, this is less than the amount that could be present in the coating in the absence of the strong complexing agent. The complexing agent used in the present invention satisfies the following requirements.

1. They complex strongly enough with copper, especially Cu(■), in aqueous solution to keep the copper in solution in the PH range used in this invention; 2. They complex strongly with aluminum. do not.

Preferably, they do not form any complexes with aluminum; 3. They are stable to peroxides, i.e. they are not oxidized by peroxides under the conditions of the invention; 4. Do not otherwise interfere with the formation of a satisfactory film; and 5. as described below.
If metals such as magnesium are included in the processing solution, the complexing agent should not form a strong complex with such metals for inclusion in the coating.

Preferably, the strong complexing agent is also strongly complexed with zinc, although this is not essential.

Among the strong complexing agents that can be used in the present invention are glycine, citrate, tartrate and other similar amino and oxycarboxylic acids, polyamines including diamines such as ethylenecyamine and the trade name Miran ( ) There are polyamine surfactants available in 1.

Glycine is a preferred complexing agent. Examples of ligands that strongly complex or combine with copper but are not strong complexing agents useful in the present invention include gluconate, which complexes with A1 (■), and insoluble copper. There are polycarboxylic acids that tend to form salts, and ammonium ions that, for reasons still unclear, have poor corrosion resistance in the films formed.
The amount of complexing agent used depends on the individual circumstances. However, the use of concentrations lower than 0.05 eq/l rapidly loses its ability to prevent precipitation of copper in solution;
It was found that the resulting coatings were either too thin to be of practical use, or contained so much copper that the coatings were not corrosion resistant. In the normal practice of the invention, the concentration of the complexing agent will be between 0.01 and 1 eq/e, particularly preferably between 0.1 and 1 eq/l. Generally, the optimum concentration is between 0.1 and 0.
5 equivalents/l, but it is somewhat lower by using different complexing agents. change. The weight concentration depends on the molecular weight and complexing agent function of the materials used. Glycine is bidentate in its complex formation with Cu(■), so its preferred concentration range is 2-20 g/e), optimally 2-10 g/e).
e) In particular about 5 g/l. Before! The use of concentrations higher than the upper limit of the stated range only increases costs without producing any further beneficial effects. Note that the equivalent of the complexing agent is H.

This corresponds to the amount of Cu eluted by O2. For complexing agents with two or more COOH groups? In this case, since the dissociation coefficients are not the same, not all COOH groups react with Cu゛ at the same time, but assuming that all COOH groups react with Cu゛, the equivalent amounts are as follows.

4 The treatment solution contains an inorganic peroxide as an essential component.

The term ``inorganic peroxide'' refers to the PH used in the present invention.
hydrogen peroxide or peroxide ions (or
(charged intermediates) and alkali and alkaline earth metal peroxides. Preferred alkali metal peroxides are the peroxides of sodium and potassium, which give strongly alkaline aqueous solutions and therefore require appropriate adjustment of the pH. Alkaline earth metal peroxides such as calcium and magnesium peroxides may be used, but in the pH range used they are relatively water insoluble and therefore acidic pre-solutions are required. Hydrogen peroxide is a preferred source of peroxide in solution as it is relatively cheap and readily available in the UK in aqueous solution, particularly at 30% Wt/VOIH.

O. Aqueous solutions are convenient. H. O. When an aqueous solution is not available, the use of metal peroxidants is recommended because H is known to decompose fairly rapidly during storage. O. It may have the technical advantage of having a relatively long life in the solid state compared to water. The concentration of inorganic peroxide used is H.

O. It is calculated as 0.25-30g/l. 0.25
Concentrations below g/l do not give satisfactory coatings.

This is believed to be because the peroxide is used up so quickly that there is not enough time to form the desired coating thickness. H. At concentrations of 0.5 to 1 g/l as O2, the reaction is slower than normally desired. 30g/. At concentrations greater than e, oxidative attack on the substrate surface proceeds rapidly and any coating formed is affected by oxygen (Cu.

Satisfactory coatings are not formed because f is destroyed by the release of f (generated by the decomposition of peroxide which acts as a catalyst). The satisfactory result is H.

O. obtained in a concentration range of 1 to 15 g/l, and 15 g
The use of concentrations higher than /l' has no particular advantage, is more expensive, and is prone to large losses due to catalytic decomposition. Lower concentrations, e.g. 1.0-1.5 g/l, can be used to reduce the cost of the solution if long processing times are not inconvenient, but technically the optimum concentration range is H. O. 1.5 to 10 g/l), especially about 5 g/l. The pH of the treatment solution is in the range of 4-9.

At a pH lower than 4, A1 (■) dissolves and a satisfactory coating cannot be reliably obtained.

As the pH increases, the oxidation rate on the substrate surface decreases,
Therefore limiting the rate of film formation. At pH higher than 9,
In particular, since the pH in the surface film of the solution tends to be higher than in the bulk of the solution, the rate of film formation decreases and the aluminum oxide is redissolved as aluminate.

When the treatment solution intentionally does not contain added magnesium or calcium, the solution pH is usually in the range of 4.5 to 5.5, and when Mg (■) or Ca (Π) is added, the pH of the solution is usually in the range of 4.5 to 5.5.
is usually slightly higher, typically between 7.5 and 8.5.

As mentioned above, if there is no buffer, it is easy to rise,
It is therefore highly desirable to include a buffer in the solution to stabilize the pH which reduces the rate of film formation. The buffer used in the present invention satisfies the following required properties. 1. Effective as a buffer at pH within the range used in the present invention; 2. Stable against oxidation by peroxides; 3. Not forming strong complexes with [A]; 4. Insoluble copper salts. Do not precipitate; 5 Do not otherwise interfere with film formation; and 6 Do not precipitate the added metal, if any, from the solution.

Suitable buffers include acetate (congeners of acetate can also be used, but are very expensive and become increasingly less soluble as the molecular weight of the copper salt increases), phosphates, carbonates, and bicarbonates. There are salts and citrates.

(Although acetate is generally preferred for technical reasons, especially at an operational pH of about 5, carbonates and/or bicarbonates are effective non-fouling, especially at higher pHs in the above range). 8 is particularly suitable. If phosphoric acid is used, then care must be taken to avoid precipitation of phosphoric acid copper, for example by using relatively high concentrations of complexing agent (for copper). Although salts are relatively expensive, they have the advantage of acting as buffers and complexing agents for strong copper.The concentration of buffers used is
Depends on the PH that is to be maintained.

However, the buffering effect is 0. Very small at concentrations smaller than river moles. Typically the concentration is between 0.05 and 2 molar.

As an example, for acetate as buffering agent, the concentration used should normally not be lower than 1 g/l. Normally,(
(as HAc) at least 2 g/l. Concentrations above about 100 g/l (as HAc) offer little additional benefit and are only more expensive. PH=5
For the operation, the treatment solution was 4 g of sodium acetate
/l and 1.8 g/l acetic acid. Since the processing solution is used fairly close to neutrality, it is usually best to add a buffer to the solution as a conjugate acid or conjugate base component in the required proportions, rather than adding one or the other to adjust with a strong acid or base. It would be the most convenient. For pH ranges of 7.5 to 9, bicarbonate is most useful as it forms the acid component of the CO2 buffer dissolved in solution.

For pH greater than 8, additional hydroxide needs to be added.

Typically, a pH of about 8 is between 0.5 and 0.5 for sodium bicarbonate.
This can be achieved by adding 10 g/l. As mentioned earlier, NH
．． ．． , is a satisfactory corrosion-resistant coating. It is not used as a buffering agent in the present invention because it interferes with the formation of .

Although it is generally desirable to keep the composition of the treatment solution as simple as possible, there are two additional components that may be included as active ingredients in the solution.

The first step is the surfactant. This is useful for wetting the substrate; the oxygen released upon catalytic decomposition produces bubbles and the presence of the surfactant aids in the removal of these bubbles, thus preventing logging of the substrate. The amount used is typically about 1
0ppm) The practical maximum value is 100ppm, which is 5. As previously mentioned, substituted imidazoline surfactants sold under the trade name MiranOl can be used as strong complexing agents for copper and are therefore included in very high concentrations, in this case. There is no need to add a separate surfactant. A particularly useful and effective surfactant is sodium lauryl sulfate. The second of the two possible further components mentioned above is an alkaline earth metal, which can be included in solution as an aqueous salt.
Especially magnesium and, less preferably, calcium.

This possibility was briefly discussed above. A particular advantage of including magnesium is that it is incorporated into the deposited coating when a solution with a pH of about 8 is used. This appears to have a beneficial effect on corrosion resistance, making the initially formed coating more similar to the naturally occurring coating. Magnesium is contained as sulfate, nitrate or acetate. Calcium is less preferred than magnesium because it is less effective in enhancing the corrosion resistance of the coating and makes sulfates and carbonates practically unusable in solution. If such a material is included, its concentration is typically MgSO.
5-50g/l) especially 10-30g/l
It is l. It turned out that, in addition to the substances that are described as desirable, certain other substances have harmful effects, the absence of which is desirable.

Ammonia has been mentioned above as an impediment to the formation of suitable corrosion-resistant coatings. The reason for this is not clear, but
This appears to be due to the incorporation of ammonium ions into the coating. Additionally, when magnesium is contained in the solution, NH.
Or NH. The presence of f promotes the precipitation of Mg(■)-containing materials from the bulk of the solution. Other major exclusions are:
A halide ion, especially chloride.

Although the reason is completely unknown, the presence of a significant amount of chloride
Promotes the formation of incomplete coatings and rapidly causes pinhole corrosion under the coating. The maximum permissible concentration of halides, particularly chlorides, is about 500 ppm, preferably less than 200 ppm, optimally less than 100 ppm. Most UK green water is less than 100 PpmCl- and therefore can be used to prepare the solutions of this invention. However, when the feed water is more brackish, it may also be necessary to deionize or distill it to top up a satisfactory solution water. Other halides, other than chloride, are less harmful than halides, but are usually limited to low or zero concentrations. Aluminum salts are not added to the processing solution because they precipitate the hydrated alumina and make the solution more acidic than desired.

Similarly copper, zinc salts are not added as they may deplete the strong complexing agents. As is clear, sulfide is a corrosion promoter, so it is not added, although it will rapidly oxidize to sulfate in solution and deplete the peroxide. The aluminum plus surface treatment according to the invention is conveniently carried out at room temperature, which in the UK is usually in the range 15-25°C.

At higher temperatures, the reaction proceeds more rapidly and even violently, preventing satisfactory film formation. Although temperatures up to 35°C are acceptable, it is desirable to operate below 30°C if possible.

This is because at temperatures higher than 35° C., the substrate becomes susceptible to rapid pitting. As mentioned above, the decomposition of peroxide produces oxygen gas, which is kept during processing to aid in the removal of oxygen bubbles and to prevent processing solution stagnation due to possible excessive pH fluctuations. Stirring is preferred.

When long tubes are processed, such as in tube-shell condensers, the flow rate through the tubes is between 1 and 5 c.
m/sec, typically about 2 cm/sec, is satisfactory. When processing condensers, this agitation is carried out using a low power circulation pump between the outlet and inlet boxes of the condenser unit. The desired coating is formed many times faster than the natural coating, but much slower than conversion coating on more reactive substrates, such as chromate coatings on Al substrates.

In this invention, the treatment time is typically at least 1 hour, but may be up to 24 hours as appropriate. The optimal treatment time for a solution in terms of reactivity is typically 2 to 6 hours, but when cost is taken into consideration, a dilute solution may be used and a long treatment time may be required. in most applications at least 1 pm) and preferably at least 2 pm)
It is desirable to provide a minimum film thickness of μm. The optimal reaction system described above typically yields 0.5-1 μm in 1 hour.
) A film of 1.5 to 2.5 μm is formed in 3 to 6 hours.

In the operation of condensers using seawater as cooling water treated according to the present invention, ion exchange between the coating and the seawater coolant results in a coating that traps Mg(■), which eventually leads to the formation of a naturally occurring coating and a chemical one. seems to be the same.

For naturally occurring coatings, the advantageous properties at high flow rates are
It can be enhanced by regular iron incorporation into the inlet coolant. The results of our tests indicate that the coatings produced according to the invention have a low resistance to corrosion by contaminated seawater, reducing the risk of damage during subsequent operation in clean seawater. Shown. The following examples are illustrative of the invention.

The Galpani potential is shown below as the potential between a sample and a saturated calomel electrode during a test in seawater.

The impact test was performed using J, Inst, Met, 195O, vO.
177, p. 33l (MayJ
etTest). The aluminum frass used was B. S. 287l/1972, CZ ■ Metallurgy. Example 1 An aqueous solution having the following composition was prepared.

Sodium acetate 5g/l・ Glacial acetic acid 0.8 cd/l Glycine 5g/1 30%w/v hydrogen peroxide solution IOH/l The pH of the above solution is 4.9.

An aluminum plastic tube was placed in the slowly stirred solution.
Soaked for 3 hours at 5°C. At the end of this soaking time the solution became a deep blue color. The tube was cleaned and dried. Upon inspection, a white powdery coating was observed on the tube surface. The thickness of this coating was measured to be approximately 2.5 μm. Coating on one tube with 10% H. When the solution obtained by dissolving SO in an aqueous solution was analyzed by atomic absorption spectrometry, the film was found to be
The content was about 15% A1, about 9% Zn, and about 3.5% Cu. Also, the galvanic potential of other treated tubes is -25
0rnV, which was found to rise to -225mV over 5 days. A second set of tubes was treated in a similar solution (PH=5.0) except that glycine was omitted.

The formed film was colored gold and had a thickness of less than 1 μm. The composition of the coating is approximately 11% A1 and approximately 26% Cu.
It was hot. The Calvany potential of one of these tubes was -220 mV and rose to -150 mV over 5 days. In addition, the untreated tube had a voltage of -250 mV, which increased to -225 mV within 5 days.

Example 2 Fu An aqueous solution with the following composition was prepared: Glycine 5g/1 30%w/VH.

O. Water 10/1 pH was adjusted to 5.0.

This solution is similar to the solution of Example 1 except for the buffer.

The aluminum plastic tube is placed in a slowly stirred solution for 25 minutes.
°C) Soaked for 3 hours. After cleaning and drying, the tube was inspected and a white film with a measured thickness of 0.9 μm was observed on the surface. The solution was modified by adding 4 g/l of sodium acetate and 0.8 crit/l of glacial acetic acid.

The pH was adjusted to 5.0. A second tube similar to that described above was immersed in this modified solution and after 3 hours a coating approximately 2.7 μm thick was formed on the second tube.

Example 3 An aqueous solution having the following structure was prepared.

Sodium bicarbonate 5g/l Glycine 5g/1 30/w/VH.

O. Aqueous solution 10d/l magnesium sulfate 20g/1 The pH was adjusted to 8.0 by adding sodium carbonate.

The aluminum plastic tube was immersed in the gently stirred solution at 25° C. for 3 hours. After washing and drying, 1.5
A white film with a thickness measured in μm was observed on the surface. Samples analyzed as described in Example 1 showed that this coating A1 was about 13.5% Zn about 13.9% Cu.
It was shown to contain about 2.5% and about 0.5% Mg. Example 4 An aqueous solution having the following composition was prepared.

Sodium bicarbonate 5g/l Glycine 5g/1 30%w/VH.

O. An aqueous solution of 10 ml of CaSO, 142 mg/ml was immersed in the slowly stirred solution for 3 hours at 25°C.

After washing and drying, a white film with a thickness of about 1.4 μm was observed. Samples analyzed in the same manner as in Example 1 were
Cul. 9%, Zn8.9%, and AIIO. 8%). Panels exposed to the same solution as above except for the potassium sulfate had a 1.7 μm thick coating containing 2.9% Cu, 8.5% Znl and 2% All.

EXAMPLE 5 Three sets of Aluminum Plus having a wall thickness of 1.2- were processed as follows.

A. Treatment (for control) B. Treatment according to the present invention described in Example 1 C. Treatment according to the present invention described in Example 3. Each treated sample was placed at room temperature ( Corrosion resistance is tested by soaking for 24 hours at a temperature of about 20° C., and three sets of samples are prepared from the tubes for impact testing.

An impact test (mage test) was carried out using recirculating seawater supplemented with 3% air at a jet speed of 10 m/s for a period of 4 weeks.

The results are listed in Table 1 below. These results are
One false measurement (ROq
ue)''. Includes results (sample 2 treatment A). After completing the test, one of the jets was blocked, although it is impossible (in retrospect) to confirm this unequivocally.
It seems to correspond to ``false measurement value'' results. We know from previous implementations of this test that ``false readings'' result 2 sometimes occur. This indicates that deficiencies in the equipment in use are unpredictable and increases the difficulty in planning maintenance schedules to accommodate such deficiencies. *1:
00 means that the test sample was perforated by the end of the test, but the time to perforation was not measured.

Claims (1)

[Claims] 1. The surface of an aluminum brass substrate has a pH of 4 to 9 and an inorganic peroxide of 0.25 to 30/ as measured as H_2O_2.
l concentration, and a strong complexing agent for copper at least 0.1.
A method for forming a corrosion-resistant coating on the surface of an aluminum brass substrate by contacting with an aqueous treatment solution containing dissolved therein at a concentration of 0.05 equivalents/l to form a corrosion-resistant coating on the surface of the substrate. 2 The surface of the aluminum brass base was heated with inorganic peroxide in H_2O.
_2 concentration of 0.25 to 30 g/l, a strong complexing agent for copper at a concentration of at least 0.05 equivalent/l, measured as _2;
and contacting with an aqueous treatment solution containing dissolved therein a buffering agent effective to maintain the pH of the solution between 4 and 9 at a concentration of at least 0.015 molar to form a corrosion-resistant coating on the surface of the substrate. A method of forming a corrosion-resistant coating on the surface of an aluminum brass substrate. 3 When the pH of the aqueous treatment solution is 4.5-6, the solution contains 1-15 g/l of H_2O_2 and 2-1 g/l of glycine.
3. The method according to claim 2, wherein the acetate is 1 to 100 g/l, calculated as acetic acid. 4 The pH of the aqueous treatment solution is 7.5-9, and the solution contains 1-15 g/l of H_2O_2 and 2-15 g/l of glycine.
10 g/l and bicarbonate and/or carbonate from 0.05
2. A method according to claim 2, comprising 2m01/l. 5 The aqueous treatment solution is further calculated as MgSO_4.
5. The method according to claim 4, comprising 5 to 50 g/l of g(II). 6 The aluminum brass base is the heat exchanger surface of a condenser that uses seawater as cooling water, and the aqueous treatment solution is circulated through the coolant circulation passage of the condenser that uses seawater as cooling water to form a corrosion-resistant film on the aluminum brass surface. A method according to any one of claims 1 to 5. 7 pH is 4 to 9 and 1 to 15 g of H_2O_2 is contained in it.
/l, glycine 2-10g/l, and buffering agent 0.
An aqueous treatment solution for aluminum brass substrates for forming a corrosion-resistant coating on the surface of aluminum brass substrates, containing 05 to 2 m01/l dissolved therein. 8. A solution according to claim 7, wherein the pH is 4.5 to 6 and the buffering agent is acetate in a concentration of 1 to 100 g/l, calculated as acetic acid. 9. The solution according to claim 7, wherein the pH is 7.5 to 8.5 and the buffering agent is bicarbonate and/or carbonate. 10 In addition, Mg(
8. The solution according to claim 7, containing 10 to 50 g/l of II).