CA1191677A - Sulfite-erythorbic acid corrosion inhibitors - Google Patents
Sulfite-erythorbic acid corrosion inhibitorsInfo
- Publication number
- CA1191677A CA1191677A CA000424794A CA424794A CA1191677A CA 1191677 A CA1191677 A CA 1191677A CA 000424794 A CA000424794 A CA 000424794A CA 424794 A CA424794 A CA 424794A CA 1191677 A CA1191677 A CA 1191677A
- Authority
- CA
- Canada
- Prior art keywords
- ppm
- sulfite
- acid
- hydrazine
- boiler
- 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
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
- C02F5/08—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents
- C02F5/10—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances
- C02F5/105—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances combined with inorganic substances
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Inorganic Chemistry (AREA)
- Metallurgy (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Preventing Corrosion Or Incrustation Of Metals (AREA)
Abstract
ABSTRACT OF THE INVENTION
An improved method for inhibiting corrosion and scale in boiler waters which contain dissolved oxygen which comprises maintaining within the said waters at least 5 ppm of soluble sulfite ion residual and at least 2 moles of an acid which may be either erythorbic or ascorbic acid per mole of dissolved oxygen.
An improved method for inhibiting corrosion and scale in boiler waters which contain dissolved oxygen which comprises maintaining within the said waters at least 5 ppm of soluble sulfite ion residual and at least 2 moles of an acid which may be either erythorbic or ascorbic acid per mole of dissolved oxygen.
Description
~g~6~7 INTRC)DUCTION
There are two major parameters involved in inhibiting corrosion in preboiler and boiler svstems. Corrosion is minimized by no-t only oxygen removal but, also, by the forma-tion oE protective Eilms. Of the two major oxygen scavengers, sulfite ion is no-t only the most effective reducing agent, but also it is much more cost effective. It has serious drawbacks, however, the major one is its contribution to dissolved solids content (a critical parameter) in boilers. In addition, it does not promote protective films by reducing ferric and cupric ions.
Hydrazine, the other major oxygen scavenger, is a less effective reducing agent and costs much more. Therefore, it must have additional advantages. These are that it does not add solids because i-ts decomposition and reaction products are volatile, but it also can interact with soluble ferric, cupric salts and oxides to produce lower valence state oxides which form protective films inhibiting further corrosion. This is the most important parameter for hydrazine since protective films can be formed in the presence of low levels (<10 ppb) oxygen (hydrazine is known as a passive film former).
It is also known that erythorbie acid and, also ascorbie acid passivate metal in seale boiler studies even under conditions in which oxygen is known to still be present.
In fact, erythorbic acid is much more effective in this role than either hydrazine or sulfite. It is also known that it reacts better with oxygen than hydrazine but it is less effective than sulfite.
There are several facts about ascorbic/erythorbic aeid that indicate its potential xole as a passivating agent. The literature reports its abili-ty to reduce cupric to cuprous and ferric to ferrous ions. Both of these reactions are key in this role. Passivation tests in a laboratory scale boiler sho~7 that erythorbic acid is better than hydrazine or sulfite in passivating ability.
¦ Sulfite gives better results than hydrazine in oxygen scavenging because of its oxygen control at 600 psig (~490F).
SulEite does not significantl~ decompose in the boiler whereas ¦hydrazine does. Hydrazine's reported decomposition temperature is ¦400F. ln addition, this material is volatile Therefore, sul-¦fite, which is non-volatile, maintains a reducing atmosphere in ¦the ~oiler and keeps oxy~en concentration at a minimum.
¦ Many industrial plants presently use a combination of ¦sodium sulfite and hydrazine to inhibit corrosion in the preboiler and boiler systems. This application technology is based on the use of sulfite as an oxygen scavenger and hydrazine as a passive film enhancer.
Hydrazine is a toxic material and m~y present a health problem when it is handled by non-chemically tra~ned operat~rs.
For this reason, i~s use as a commerical che~i~l is becoming limited.
THE INVENTION
An improved method for inhibiting corrosion and scale in boiler waters which contain dissolved oxygen which comprises maintaining within the said waters at least 5 ppm of soluble S03 -residual and at least 2 moles of an acid which may be either ery-thorbic or ascorbic acid per mole of dissolved oxygen.
The sulfite ion-is most conveniently furnished by utilizing the well known oxygen scavenger, sodium sulfite. ~inile other water-soluble sulfites may be used, the sodiu~ salt is preferred. The dosage level of sulfite ion, S03=r that should ¦ b aintained in the boiler i~ at least 5 ppm with amo~nts - a-ranging between 10 - 50 ppm being preferred, with 20 - 40 ppm be-ing most preferred. I
The acids used in the invention are either erythorbic acid or ascorbic acid. The most preferred is erythorbic acid. It is used at a dosage level of at leas-t 2 molesper mole of dissolved oxygen present in the boiler waters. Amounts in excess of 2 moles may be used, but no particular advantage is gained.
An interesting fact which has previously been discovered is that both erythorbic and ascorbic acid to be effective must be utilized in boiler waters having pH's greater than 7 and, pre-ferably, greater than 8.5, and most preferably pH's greater than ~Ø
To evaluate the invention and to show prior art compari-sons, the followiny test method was used.
Test Method The ability of several oxygen scavengers to passivate heat transfer surfaces was investigated in experimental research boilers. The test covered a 48 hour period and test conditions were 600 psi, 10 c~cles of concentration and 110,000 BTU/ft2/hr.
The feedwater contained 4 ppm Ca (as CaCO3), 2 ppm Mg ~as CaCO3), and 1 ppm silica (as SiO2). In addition, feedwaters contained various amine compounds such as morpholine, cyclohexylamine, and diethyl amino ethanol at concentrations of about 50 ppm each. -These amine compounds normally are present in boiler feedwaters, so as to provide corrosion protection for the overhead condensate system within the boiler unit. Their presence or absence is not anticipated to effect positively or negatively the oxygen scavenger /
metal passivating activities of the compounds of this invention.
The feedwater was passed through.a deaerator prior to introduction into the experimental boiler system. Final oxygen levels before treatment with the compounds of this invention were less than .
-3~
50 ppb (parts per billion)~ Sufficient NTA1 was in the feedwater to provide a 5 ppm residual in the boiler.
Three oxygen scavengexs: hydrazine, sulfite, and ery-thorbic acid, and combinations thereof, were examined during these tests~ Hydrazine was fed at 2 ppm, erythorbic acid at 2 ppm active equivalents (i.e., 2 moles EA/l mole hydrazine/l mole 2) 1 and sulfite sufficient to provide 30 ppm residual in the boiler water. A comparison of the firerods from these tests show that erythorbic acid produces a passivated surface superior to that ob- !
tained with either sulfite or hydrazine. A dark, thin, magnetite I
layer resulted from treatment with erythorbic acid. On the other ;
hand, both sulfite and hydrazine produced a magnetite layer that had various degrees of discoloration due to the presence of reddis~
iron oxides that had not been completely converted to Fe304.
Various combinations of the above mentioned oxygen scavengers were evaluated in the scale boilers under conditions previously described. As can be seen from the Table, the combina-tion of erythorbic acid plus sulfite is an excellent corrosion inhibition system. This test ranking surpasses all other tests conducted in the boiler for passivation potential. This film was uniform, black, ~ery thin, and difficult to scrape off.
The combination of hydrazine and sulfite was also testedl and rated against either the single components mentioned above or¦
combinations thereof. Hydrazine and sulfite combination formula-tions, tested in the same manner, gave results which rated suh-stantially below the combination of erythorbic acid and sulfite and even rated measurably below erythorbic acid itself. The data is presented in the following Table.
lNitrilotriacetic acid, sodium salt TABLE
Cbnditions of Test Rating System -All feedwaters contained 4 ppm Ca 4 poor (as CaC03), 2 ppm Mg (as CaC03), and 4 - 6 acceptable 1 ppm Silica - Chelate treated to pror 6 - 7 gocd vide 5 ppm residual ~T~ in the boiler 7 - 8 very good water tested at 600 psig, 110,000 8 - 9 superior BTU/ft2/hr. and 10 concentratians. 9 -10 excellent All feedwaters also cont~ined 50 ppm each of morpholine, cyclohexylamune, and die~hylan~noethanol.
Test No. Rating 1 S03 residual at 20-40 ppm; EA at 10 equivalent dosage to 2 ppm hydrazine where EA require~ 2 Mbles/l Mole 2 and hydrazine required 1 Mble/l Mole 02-
There are two major parameters involved in inhibiting corrosion in preboiler and boiler svstems. Corrosion is minimized by no-t only oxygen removal but, also, by the forma-tion oE protective Eilms. Of the two major oxygen scavengers, sulfite ion is no-t only the most effective reducing agent, but also it is much more cost effective. It has serious drawbacks, however, the major one is its contribution to dissolved solids content (a critical parameter) in boilers. In addition, it does not promote protective films by reducing ferric and cupric ions.
Hydrazine, the other major oxygen scavenger, is a less effective reducing agent and costs much more. Therefore, it must have additional advantages. These are that it does not add solids because i-ts decomposition and reaction products are volatile, but it also can interact with soluble ferric, cupric salts and oxides to produce lower valence state oxides which form protective films inhibiting further corrosion. This is the most important parameter for hydrazine since protective films can be formed in the presence of low levels (<10 ppb) oxygen (hydrazine is known as a passive film former).
It is also known that erythorbie acid and, also ascorbie acid passivate metal in seale boiler studies even under conditions in which oxygen is known to still be present.
In fact, erythorbic acid is much more effective in this role than either hydrazine or sulfite. It is also known that it reacts better with oxygen than hydrazine but it is less effective than sulfite.
There are several facts about ascorbic/erythorbic aeid that indicate its potential xole as a passivating agent. The literature reports its abili-ty to reduce cupric to cuprous and ferric to ferrous ions. Both of these reactions are key in this role. Passivation tests in a laboratory scale boiler sho~7 that erythorbic acid is better than hydrazine or sulfite in passivating ability.
¦ Sulfite gives better results than hydrazine in oxygen scavenging because of its oxygen control at 600 psig (~490F).
SulEite does not significantl~ decompose in the boiler whereas ¦hydrazine does. Hydrazine's reported decomposition temperature is ¦400F. ln addition, this material is volatile Therefore, sul-¦fite, which is non-volatile, maintains a reducing atmosphere in ¦the ~oiler and keeps oxy~en concentration at a minimum.
¦ Many industrial plants presently use a combination of ¦sodium sulfite and hydrazine to inhibit corrosion in the preboiler and boiler systems. This application technology is based on the use of sulfite as an oxygen scavenger and hydrazine as a passive film enhancer.
Hydrazine is a toxic material and m~y present a health problem when it is handled by non-chemically tra~ned operat~rs.
For this reason, i~s use as a commerical che~i~l is becoming limited.
THE INVENTION
An improved method for inhibiting corrosion and scale in boiler waters which contain dissolved oxygen which comprises maintaining within the said waters at least 5 ppm of soluble S03 -residual and at least 2 moles of an acid which may be either ery-thorbic or ascorbic acid per mole of dissolved oxygen.
The sulfite ion-is most conveniently furnished by utilizing the well known oxygen scavenger, sodium sulfite. ~inile other water-soluble sulfites may be used, the sodiu~ salt is preferred. The dosage level of sulfite ion, S03=r that should ¦ b aintained in the boiler i~ at least 5 ppm with amo~nts - a-ranging between 10 - 50 ppm being preferred, with 20 - 40 ppm be-ing most preferred. I
The acids used in the invention are either erythorbic acid or ascorbic acid. The most preferred is erythorbic acid. It is used at a dosage level of at leas-t 2 molesper mole of dissolved oxygen present in the boiler waters. Amounts in excess of 2 moles may be used, but no particular advantage is gained.
An interesting fact which has previously been discovered is that both erythorbic and ascorbic acid to be effective must be utilized in boiler waters having pH's greater than 7 and, pre-ferably, greater than 8.5, and most preferably pH's greater than ~Ø
To evaluate the invention and to show prior art compari-sons, the followiny test method was used.
Test Method The ability of several oxygen scavengers to passivate heat transfer surfaces was investigated in experimental research boilers. The test covered a 48 hour period and test conditions were 600 psi, 10 c~cles of concentration and 110,000 BTU/ft2/hr.
The feedwater contained 4 ppm Ca (as CaCO3), 2 ppm Mg ~as CaCO3), and 1 ppm silica (as SiO2). In addition, feedwaters contained various amine compounds such as morpholine, cyclohexylamine, and diethyl amino ethanol at concentrations of about 50 ppm each. -These amine compounds normally are present in boiler feedwaters, so as to provide corrosion protection for the overhead condensate system within the boiler unit. Their presence or absence is not anticipated to effect positively or negatively the oxygen scavenger /
metal passivating activities of the compounds of this invention.
The feedwater was passed through.a deaerator prior to introduction into the experimental boiler system. Final oxygen levels before treatment with the compounds of this invention were less than .
-3~
50 ppb (parts per billion)~ Sufficient NTA1 was in the feedwater to provide a 5 ppm residual in the boiler.
Three oxygen scavengexs: hydrazine, sulfite, and ery-thorbic acid, and combinations thereof, were examined during these tests~ Hydrazine was fed at 2 ppm, erythorbic acid at 2 ppm active equivalents (i.e., 2 moles EA/l mole hydrazine/l mole 2) 1 and sulfite sufficient to provide 30 ppm residual in the boiler water. A comparison of the firerods from these tests show that erythorbic acid produces a passivated surface superior to that ob- !
tained with either sulfite or hydrazine. A dark, thin, magnetite I
layer resulted from treatment with erythorbic acid. On the other ;
hand, both sulfite and hydrazine produced a magnetite layer that had various degrees of discoloration due to the presence of reddis~
iron oxides that had not been completely converted to Fe304.
Various combinations of the above mentioned oxygen scavengers were evaluated in the scale boilers under conditions previously described. As can be seen from the Table, the combina-tion of erythorbic acid plus sulfite is an excellent corrosion inhibition system. This test ranking surpasses all other tests conducted in the boiler for passivation potential. This film was uniform, black, ~ery thin, and difficult to scrape off.
The combination of hydrazine and sulfite was also testedl and rated against either the single components mentioned above or¦
combinations thereof. Hydrazine and sulfite combination formula-tions, tested in the same manner, gave results which rated suh-stantially below the combination of erythorbic acid and sulfite and even rated measurably below erythorbic acid itself. The data is presented in the following Table.
lNitrilotriacetic acid, sodium salt TABLE
Cbnditions of Test Rating System -All feedwaters contained 4 ppm Ca 4 poor (as CaC03), 2 ppm Mg (as CaC03), and 4 - 6 acceptable 1 ppm Silica - Chelate treated to pror 6 - 7 gocd vide 5 ppm residual ~T~ in the boiler 7 - 8 very good water tested at 600 psig, 110,000 8 - 9 superior BTU/ft2/hr. and 10 concentratians. 9 -10 excellent All feedwaters also cont~ined 50 ppm each of morpholine, cyclohexylamune, and die~hylan~noethanol.
Test No. Rating 1 S03 residual at 20-40 ppm; EA at 10 equivalent dosage to 2 ppm hydrazine where EA require~ 2 Mbles/l Mole 2 and hydrazine required 1 Mble/l Mole 02-
2 Same as akove but no S03-. 9
3 S03 residual 20-40 ppm. 7.5 - 8.0
4 Hydrazine at 2 ppm. 7 Hydrazine at 2 ppm; Sulfite 8.5 residual at 20-40 p~m.
6 No oxygen scavenger 0
6 No oxygen scavenger 0
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An improved method for inhibiting corrosion and scale in boiler waters which contain dissolved oxygen which comprises maintaining within the said waters at a pH of at least 7, at least 5 ppm of soluble SO3= residual and at least 2 moles of an acid which may be either erythorbic or ascorbic acid per mole of dissolved oxygen.
2. The method of claim 1 where the level of SO3= is between 20 - 40 ppm.
3. The method of claim 2 where the acid is erythorbic acid.
4. The method of claim 2 where the acid is ascorbic acid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US36457982A | 1982-04-01 | 1982-04-01 | |
| US364,579 | 1994-12-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1191677A true CA1191677A (en) | 1985-08-13 |
Family
ID=23435143
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000424794A Expired CA1191677A (en) | 1982-04-01 | 1983-03-29 | Sulfite-erythorbic acid corrosion inhibitors |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS58181874A (en) |
| CA (1) | CA1191677A (en) |
| GB (1) | GB2117369B (en) |
| HK (1) | HK99085A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4539122A (en) * | 1984-02-21 | 1985-09-03 | Halliburton Company | Corrosion inhibitor for heavy brines |
| JPS61117289A (en) * | 1984-11-12 | 1986-06-04 | Shimadaya Honten:Kk | Method for preventing corrosion of aluminum vessel containing set food |
| DE3872849T2 (en) * | 1987-12-16 | 1992-12-03 | Diversey Corp | ALL COMPOSITION FOR THE TREATMENT OF BOILER WATER. |
| US4851130A (en) * | 1988-11-30 | 1989-07-25 | Pfizer Inc. | Oxygen removal with carbon catalyzed erythorbate or ascorbate |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5141578A (en) * | 1974-10-04 | 1976-04-07 | Konishiroku Photo Ind |
-
1983
- 1983-03-14 GB GB08307006A patent/GB2117369B/en not_active Expired
- 1983-03-29 CA CA000424794A patent/CA1191677A/en not_active Expired
- 1983-03-30 JP JP5283683A patent/JPS58181874A/en active Pending
-
1985
- 1985-12-05 HK HK99085A patent/HK99085A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| JPS58181874A (en) | 1983-10-24 |
| GB8307006D0 (en) | 1983-04-20 |
| GB2117369B (en) | 1985-02-27 |
| GB2117369A (en) | 1983-10-12 |
| HK99085A (en) | 1985-12-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |