US3400022A - Method for the protection of internal surfaces of the tubes for high-temperature, high-pressure boilers from corrosion - Google Patents
Method for the protection of internal surfaces of the tubes for high-temperature, high-pressure boilers from corrosion Download PDFInfo
- Publication number
- US3400022A US3400022A US635630A US63563067A US3400022A US 3400022 A US3400022 A US 3400022A US 635630 A US635630 A US 635630A US 63563067 A US63563067 A US 63563067A US 3400022 A US3400022 A US 3400022A
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- US
- United States
- Prior art keywords
- corrosion
- tubes
- solution
- treatment
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000005260 corrosion Methods 0.000 title description 34
- 230000007797 corrosion Effects 0.000 title description 27
- 238000000034 method Methods 0.000 title description 10
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 57
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 48
- 239000000243 solution Substances 0.000 description 23
- 235000011121 sodium hydroxide Nutrition 0.000 description 16
- 239000012670 alkaline solution Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
- 239000002253 acid Substances 0.000 description 4
- 230000007547 defect Effects 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 238000005554 pickling Methods 0.000 description 3
- 230000001681 protective effect Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000001464 adherent effect Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000007689 inspection Methods 0.000 description 2
- 235000014413 iron hydroxide Nutrition 0.000 description 2
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 2
- 238000006386 neutralization reaction Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 235000017550 sodium carbonate Nutrition 0.000 description 1
- 229940001593 sodium carbonate Drugs 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 239000001488 sodium phosphate Substances 0.000 description 1
- 229910000162 sodium phosphate Inorganic materials 0.000 description 1
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
- C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
- C23F11/18—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids using inorganic inhibitors
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/60—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using alkaline aqueous solutions with pH greater than 8
- C23C22/62—Treatment of iron or alloys based thereon
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
Definitions
- Such a treatment is resorted to because the existence of said adherent substances on the internal surface of the boiler is the principal cause of the above-mentioned corrosion. Since the metallic surface is very susceptible to corrosion after such adherent matters have been removed by pickling, some additional anti-corrosion treatment must be carried out.
- the simplest method for this latter treatment is to pass an alkaline solution of sodium phosphate, caustic soda, or their mixture with sodiumcarbonate through the metal tubes so as to neutralize the remaining acid liquid and form an anti-corrosion film on the surface of the metal tubes.
- iron hydroxide will be formed on the internal walls of the'tubes in a steel boiler according to the following formula Next, since the boiler is to be heated to approximately 300 C., the iron hydroxide will decompose in accordance with the following chemical reaction whereby an anti-corrosion film of Fe O forms on the interior surface of the iron tube.
- An essential object of this invention is to provide a method of protecting the boiler tubes from corrosion without the accompaniment of the above-mentioned various difiiculties.
- the lithium hydroxide solution to be used as a treatment solution in this invention is contained in conventional alkaline solutions which have been in use heretofore.
- no study whatsoever has been made of this lithium hydroxide solution, and consequently the remarkable effect derived from said substance has not yet been generally known.
- the cause of this remarkable effect i.e., the excellent anti-corrosion effect, has not yet been clarified sufficiently, but it is considered that, first of all, the Fe O film obtained by the treatment with lithium hydroxide solution is free from said defects, differing from the Fe O film formed by caustic soda solution.
- the fact that the film formed by the use of lithium hydroxide has an excellent anti-corrosion property has been confirmed by a large number of experimental data.
- Corrosion rate Conditions (mg/dm. month) 1. In the case of subjecting to corrosion with l N NaOH at 300 C. (after 200 hrs.) 2. In the case of subjecting to corrosion with l N LiOH at 300 C. (after 200 hrs.) 3. In the case of subjecting to corrosion with 1 N NaOH at 300 C. after treatment with 1 N LiOH at 300 C. for 200 hrs. (after 200 hrs.) 4. In the case of subjecting to corrosion with 5 N NaOH at 300 C. after treatment with 1 N LiOH at 300 C. for 200 hrs. (after 200 hrs.) 5. In the case of subjecting to corrosion with 1 N LiOH at 300 C. after treatment with 1 N NaOH at 300 C. for 200 hrs.
- the essential point of this invention is to treat first with LiOH solution. If it is uneconomical to carry out the treatment with LiOH alone, the treatment can be carried out first with LiOH solution by the treatment with NaOH, thus the film of Fe O formed on the surface of a steel tube is rendered thicker, whereby the corrosion rate decreases.
- the drawing clearly shows, when the concentration of the alkaline solution is low, the difference in the corrosion rate between the LiOH and NaOH is not particularly large. However, the drawing also clearly shows that an LiOH solution of as low as 0.1 normality has a better anticorrosive effect than a corresponding NaOH solution.
- concentration is near 2 N, :the difference between the two solutions is the slightest, but beyond that concentration, the difference in the corrosion rate grows rapidly, the effect of LiOH becoming substantially steady whereas the corrosion rate steeply increases when using NaOH.
- the method of preventing corrosion according to this invention has a remarkably excellent anti-corrosion effect in comparison with conventional methods and can be used most advantageously, particularly when the water of a boiler, as in the case of a high-temperature, high-pressure boiler, has a tendency to become an alkaline solution of high concentration.
- a method of protecting the internal wall of evaporative tubes used in a high-temperature, high-pressure boilers which consists essentially of passing "an aqueous solution of lithium hydroxide at least once through said tubes in the course of neutralization of acid liquids and formation of an anti-corrosion film on the internal surface f said tubes, said solution containing a sufficient number of lithium ions to produce an Fe O protective film which is free from defects.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Inorganic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
- Preventing Corrosion Or Incrustation Of Metals (AREA)
Description
Sept. 3. 1968 OSAMU ASAI 3,400,022
METHOD FOR THE PROTECTION OF INTERNAL SURFACES OF THE TUBES FOR HIGH-TEMPERATURE, HIGH-PRESSURE BOILERS FROM CORROSION Filed Feb. 17, 1967 CAUSTIC SODA LITHUM HYDROXIDE 8 TEMPERATURE 300 C CORROSION RATE (mq/dmZ PER MONTH) CONCENTRATION (N) United States Patent 3 Claims. 01. 148-614) ABSTRACT OF THE DISCLOSURE A method for the protection of the internal surfaces of tubes in high-temperature, high-pressure boilers from corrosion by passing through these tubes a lithium hydroxide solution after pickling. The LiOH wash promotes formation of a heavy iron oxide film which substantially decreases the corrosion rate of the tubes.
This application is a continuation-in-part of my application Ser. No. 307,193, filed Sept. 6, 1963, now abandoned.
In an evaporative tube of a boiler being used at a new modernized thermal power plant, it sometimes happens that the boiler water is concentrated in the portion adjacent to the tube surface thereby becoming a highly concentrated alkaline solution which often causes severe corrosion on the tube surface because of the prevailing high temperature and high pressure. As a method of preventing such corrosion as described above, mill-scale, red rust and other corrosion products formed on the internal surface of a boiler have heretofore been removed by a washing treatment commonly known as so-called pickling at the time of inspection prior to commencement of the operation after the erection of the boiler as well as at the time of annual periodic inspections. Such a treatment is resorted to because the existence of said adherent substances on the internal surface of the boiler is the principal cause of the above-mentioned corrosion. Since the metallic surface is very susceptible to corrosion after such adherent matters have been removed by pickling, some additional anti-corrosion treatment must be carried out. The simplest method for this latter treatment is to pass an alkaline solution of sodium phosphate, caustic soda, or their mixture with sodiumcarbonate through the metal tubes so as to neutralize the remaining acid liquid and form an anti-corrosion film on the surface of the metal tubes.
By the use of said alkaline solution, iron hydroxide will be formed on the internal walls of the'tubes in a steel boiler according to the following formula Next, since the boiler is to be heated to approximately 300 C., the iron hydroxide will decompose in accordance with the following chemical reaction whereby an anti-corrosion film of Fe O forms on the interior surface of the iron tube.
However, although this kind of liquid can neutralize the acid liquid, it has been impossible to form a metallic oxidized film which is truly protective against corrosion on the surface of the metal tube.
3,400,022 Patented Sept. 3, 1968 As a result of various studies, the inventor has come to the conclusion that, in the formation of a film by use of said alkaline solution, the above-mentioned inability of forming a truly protective film is probably due to the chemical weakness of the film against the alkaline solution, and to the fact that the formed film has many defects such as the formation of extremely small pin-holes, cracks and crystal defects. As a result of studies based on said conclusion, this invention has been developed. An essential object of this invention is to provide a method of protecting the boiler tubes from corrosion without the accompaniment of the above-mentioned various difiiculties.
Said object and other objects of this invention have been attained by passing a lithium hydroxide solution through the metal tubes at least once during the course of neutralization of acid liquid and the formation of anticorrosion film on the interior surface of tubes.
The lithium hydroxide solution to be used as a treatment solution in this invention is contained in conventional alkaline solutions which have been in use heretofore. However, no study whatsoever has been made of this lithium hydroxide solution, and consequently the remarkable effect derived from said substance has not yet been generally known. The cause of this remarkable effect, i.e., the excellent anti-corrosion effect, has not yet been clarified sufficiently, but it is considered that, first of all, the Fe O film obtained by the treatment with lithium hydroxide solution is free from said defects, differing from the Fe O film formed by caustic soda solution. In any case, the fact that the film formed by the use of lithium hydroxide has an excellent anti-corrosion property has been confirmed by a large number of experimental data.
The following is an example of such data:
Corrosion rate Conditions: (mg/dm. month) 1. In the case of subjecting to corrosion with l N NaOH at 300 C. (after 200 hrs.) 2. In the case of subjecting to corrosion with l N LiOH at 300 C. (after 200 hrs.) 3. In the case of subjecting to corrosion with 1 N NaOH at 300 C. after treatment with 1 N LiOH at 300 C. for 200 hrs. (after 200 hrs.) 4. In the case of subjecting to corrosion with 5 N NaOH at 300 C. after treatment with 1 N LiOH at 300 C. for 200 hrs. (after 200 hrs.) 5. In the case of subjecting to corrosion with 1 N LiOH at 300 C. after treatment with 1 N NaOH at 300 C. for 200 hrs. (after 200 hrs.) 400 It is clear from the above table that in the case of treatment with only NaOH solution the corosion rate is very large, whereas in the case of treatment with LiOH solution, as shown in the case 2, the corrosion rate becomes less than half of that of the case 1.
An even more noteworthy fact is that, as will be clear from the columns 2, and 4, in the case of pretreatment with LiOH solution, the succeeding treatment with NaOH solution brings about the same result in the corrosion rate as in the case of treatment with LiOH alone. Furthermore, the corrosion rate in the case of treating first with an NaOH solution and then with a LiOH solution is almost the same as when only NaOH issued in the treatment.
The essential point of this invention, therefore, is to treat first with LiOH solution. If it is uneconomical to carry out the treatment with LiOH alone, the treatment can be carried out first with LiOH solution by the treatment with NaOH, thus the film of Fe O formed on the surface of a steel tube is rendered thicker, whereby the corrosion rate decreases.
The advantages and other features of this invention will become more apparent by the following description of the relationship between corrosion rates and the concentration of alkali solution, taken in connection with the accompanying drawing, in which a graph with curves indicating the said relationship is shown.
As the drawing clearly shows, when the concentration of the alkaline solution is low, the difference in the corrosion rate between the LiOH and NaOH is not particularly large. However, the drawing also clearly shows that an LiOH solution of as low as 0.1 normality has a better anticorrosive effect than a corresponding NaOH solution. When the concentration is near 2 N, :the difference between the two solutions is the slightest, but beyond that concentration, the difference in the corrosion rate grows rapidly, the effect of LiOH becoming substantially steady whereas the corrosion rate steeply increases when using NaOH.
Thus, the method of preventing corrosion according to this invention has a remarkably excellent anti-corrosion effect in comparison with conventional methods and can be used most advantageously, particularly when the water of a boiler, as in the case of a high-temperature, high-pressure boiler, has a tendency to become an alkaline solution of high concentration.
I claim as my invention:
1. A method of protecting the internal wall of evaporative tubes used in a high-temperature, high-pressure boilers which consists essentially of passing "an aqueous solution of lithium hydroxide at least once through said tubes in the course of neutralization of acid liquids and formation of an anti-corrosion film on the internal surface f said tubes, said solution containing a sufficient number of lithium ions to produce an Fe O protective film which is free from defects.
2. The method as defined in claim 1, wherein the passing of said lithium hydroxide solution is followed by passing a substantially 1 to 2 normal sodium hydroxide solution.
3. The method as defined in claim 1, wherein said solution of lithium hydroxide is in the range of from 0.1 to 8 normal.
References Cited UNITED STATES PATENTS 3,173,404 3/2965 Bloom et a1. 2127 X RALPH s. KENDALL, Primary Examiner.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3851862 | 1962-09-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3400022A true US3400022A (en) | 1968-09-03 |
Family
ID=12527476
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US635630A Expired - Lifetime US3400022A (en) | 1962-09-10 | 1967-02-17 | Method for the protection of internal surfaces of the tubes for high-temperature, high-pressure boilers from corrosion |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US3400022A (en) |
| CH (1) | CH425397A (en) |
| DE (1) | DE1278802B (en) |
| GB (1) | GB1021325A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4364900A (en) * | 1977-06-09 | 1982-12-21 | Atomic Energy Of Canada Limited | Deposit suppression in the core of water-cooled nuclear reactors |
| US4532045A (en) * | 1982-07-07 | 1985-07-30 | Waterscience, Inc. | Bleed-off elimination system and method |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3971628A (en) * | 1971-03-09 | 1976-07-27 | Aminkemi Ab | Method for inhibiting rust formation on iron-containing articles |
| DE4117624A1 (en) * | 1991-05-29 | 1992-12-03 | Siemens Ag | METHOD FOR PASSIVATING A COMPONENT SURFACE |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3173404A (en) * | 1963-08-16 | 1965-03-16 | Mortimer C Bloom | Protective film formation in high pressure steam generators |
-
1963
- 1963-09-03 CH CH1091363A patent/CH425397A/en unknown
- 1963-09-09 DE DEK50778A patent/DE1278802B/en active Pending
- 1963-09-10 GB GB35686/63A patent/GB1021325A/en not_active Expired
-
1967
- 1967-02-17 US US635630A patent/US3400022A/en not_active Expired - Lifetime
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3173404A (en) * | 1963-08-16 | 1965-03-16 | Mortimer C Bloom | Protective film formation in high pressure steam generators |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4364900A (en) * | 1977-06-09 | 1982-12-21 | Atomic Energy Of Canada Limited | Deposit suppression in the core of water-cooled nuclear reactors |
| US4532045A (en) * | 1982-07-07 | 1985-07-30 | Waterscience, Inc. | Bleed-off elimination system and method |
Also Published As
| Publication number | Publication date |
|---|---|
| DE1278802B (en) | 1968-09-26 |
| CH425397A (en) | 1966-11-30 |
| GB1021325A (en) | 1966-03-02 |
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