AU592367B2

AU592367B2 - Boiler corrosion inhibitor compositions and method

Info

Publication number: AU592367B2
Application number: AU62734/86A
Authority: AU
Inventors: Lois J. Neil; Dennis J. Sepelak; Rabindra K. Sinha; John D. Zupanovich
Original assignee: Calgon Corp
Current assignee: Calgon Corp
Priority date: 1985-09-17
Filing date: 1986-09-16
Publication date: 1990-01-11
Anticipated expiration: 2006-09-16
Also published as: EP0215655B1; AU6273486A; EP0215655A1; JP2617453B2; JPS62116788A; CA1294420C; DE3668190D1

Description

FORM 10 592367 SPRUSON FERGUSON COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: C41 1a Class Int. Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: This document ccntailS the amendments made under Sectinn 49 and is correct Ic printing.

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A Ar tC ttf I C tr D e I I' Name of Applicant: Address of Applicant: Actual Inventor(s): Address for Service: CALGON CORPORATION Route 60-Campbell's Run Road, Roi.inson Township, Pennsylvania, United States of America JOHN D. ZUPANOVICH, LOIS J. NEIL, DENNIS J.

SEPELAK and RABINDRA K. SINHA Spruson Ferguson, Patent Attorneys, Level 33 St Martins Tower, 31 Market Street, Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: 1 "VSfe BOILER CORROSION INHIBITOR COMPOSITIONS AND METHOD" The following statement is full description of this invention, including the best method of performing it known to us I/JS/0011U 2

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C-1414Y TITLE OF THE INVENTION Ik V:

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ABSTRACT OF THE INVENTION A method for inhibiting corrosion due to dissolved oxygen wherein a trihydroxybenezene compound, hexahydroxybenezene or levadopa, alone or in combination with conventional oxygen scavengers, is added to boiler water to prevent corrosion by reducing dissolved oxygen levels in boiler feedwater.

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C-1414Y TITLE OF THE INVENTION NUVEt" BOILER CORROSION INHIBITOR COMPOSITIONS AND

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e c. c c BACKGROUND OF THE INVENTION -I il:- This invention relates to a method for inhibiting corrosion in boiler feedwater systems and boilers due to dissolved oxygen comprising adding to boiler feedwater an effective amount of at least one compound selected from the group consisting of trihydroxybenzene compounds, hexahydroxybenzene and levadopa, alone or in combination with conventional C

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2 C-1414Y boiler corrosion inhibitors such as hydroquinone, methoxypropylamine, cyclohexylamine, diethylethanolamine, morpholine, diethyl hydroxylamine, dimethyl amino-2-propanol, 2-amino 2-methylpropanol, carbohydrazide, erythorbic acid, and salts of erythorbic acid; in combination with catalysts such as cobalt; or in combination with scale/deposit inhibitors such as chelants; dispersants, sequestrants, polyelectrolytes and organic or inorganic phosphates.

Protection of boiler feedwater systems is becoming an increasingly important aspect of plant operation.

The presence of dissolved oxygen in boiler feed water is a primary cause of waterside corrosion. In these energy-conscious times, an increase in the quality of boiler feedwater results in cost savings for the total boiler system.

Historically, the action of dissolved gases such 20 as oxygen and carbon dioxide have been two of the main factors that lead to feedwater system and boiler corrosion. In order to understand the role of dissolved gases in corrosion, one must understand the electrochemical nature of corrosion. Under most 25 conditions, there is a tendency for iron to dissolve in water, and two electrons are released for each iron atom that dissolves. These electrons transfer to hydrogen ions present in the water, and the ions are reduced to elemental gaseous hydrogen. All action ceases at this point if the hydrogen remains on the surface of the metal since a protective coating forms with the passage of electrons. However, any agent which increases the number of hydrogen ions present in Q 4 9 4 4 44 6. 4 4 S 4 t C 444 C c e c 4*! t. e 16 -3 C-1414Y the water, or which will cause the removal of the protective film, serves to increase the rate of corrosion.

The presence of oxygen in boiler feedwater causes a two-fold reaction to occur. Some molecules ot oxygen combine with displaced hydrogen, thereby exposing the metal to fresh attack. Other oxygen molecules combine with iron ions to form insoluble iron oxide compounds.

The first product of corrosion may be ferric oxide, which is only loosely adherent and aggravates corrosion by blocking off areas to oxygen access.

These areas become anionic and iron oxide couples are set up. The iron under the oxide deposit then dissolves, and pitting develops.

With respect to oxygen, the severity of attack will depend on the concentration of dissolved oxygen in the water, water pH and temperature. As water temperature increases, corrosion in feed lines, .i :heaters, boilers, steam and return lines made of iron and steel increases.

S. The inventors have discovered a new improved $method for control of corrosion in boiler feedwater systems and boilers.

A major approach to reducing oxygen in boiler feedwater is mechanical deaeration. Efficient CCk mechanical deaeration can reduce dissolved oxygen to ECt? as low as 5-10 ppb in industrial plants and 2-3 ppb in utility operations. However, even with this trace 4 C-1414Y amount of oxygen, some corrosion may occur in boilers. Removal of the last traces of oxygen from boiler feedwater is generally accomplished by the addition of chemicals that react with oxygen and which are hereinafter referred to as oxygen scavengers.

Several oxygen scavengers are known in the art.

Widely used oxygen scavengers include, but are not limited to, sodium sulfite, hydrazine, diethylhyaroxylamine, carbohydrazide and hydroquinone. U.S. Patent 3,551,349 discloses the use of quinones, particularly hydroquinone, as catalysts for the hydrazine-oxygen reaction. U.S. Patent 4,095,090 discloses the use of hydrazine compounas, a catalytic organometallic complex, and preferably a quinone compound for deoxygenating feedwater. U.S.

Patent 3,808,138 discloses the use of cobalt maleic acid hydrazide with hyarazine for oxygen removal.

U.S. Patent 3,962,113 discloses the use of organic hydrazine such as monoalkyl hydrazine, dialkyl 20 hydrazine and trialkyl hyarazine as oxygen scavengers.

Disadvantages of hydrazine and related compounds include toxicity and suspected carcinogenic effects.

Hydrazine is toxic if inhaled, ana is also an irritant 25 to the eyes and skin.

Carbohydrazide, a derivative of hydrazine, decomposes to form hydrazine and carbon dioxide at temperatures above 360 F. U.S. Patent 4,269,717 30 discloses the use of carbohydrazide as an oxygen scavenger and metal passivator.

U.S. Patents 4,278,635 and 4,282,111 disclose the 4 *444 44 04 4 4 4 444 .4 4 9 44 9 4 9 4', *i4.

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use of hydroquinone, among other dihydroxy, diamino and amino hydroxy benzenes, as oxygen scavengers.

U.S. Patents 4,279,767 and 4,487,708 disclose the use of hydroquinone and "mu-amines", which are defined as amines which are compatible with hydroquinone.

Methoxypropylamine is a preferred mu-amine.

U.S. Patent 4,363,.734 discloses the use of catalyzed 1,3-dihydroxy acetone as an oxygen scavenger. U.S.

Patent 4,419,327 discloses the use of amine or ammonia neutralized erythorbates as oxygen scavengers.

Adoitionally, aiethylhyoroxylamine (DEHA) has been used as an oxygen scavenger, and U.S. Patent 4,192,844 discloses the use of methoxypropylamine and hydrazine as a corrosion inhibiting composition. European Patent number 0054345 discloses the use of amino-phenol compounds or acid addition salts thereof as oxygen scavengers.

UK patent application 2138796A discloses the use 20 of trivalent phenols, preferably pyrogallol, to improve the activity of hydrazine-trivalent cobalt compositions.

DETAILED DESCRIPTION OF THE INVENTION In instant invention is directed to a method for controlling corrosion in boilers and boiler feedwater systems comprising adding to boiler feedwater containing dissolved oxygen an effective amount of at least one compound selected from the group conisting of trihydroxy benzene compounds hexahydroxybenzene (benzenehexol) and levodopa, and, optionally a second oxygen scavenger or neutralizing amine selected from 4 4 4.

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S i z- r 7 6 the group consisting of hydroquinone, methoxypropylamine, cyclohexylamine, diethylethanolamine, morpholine, diethyl hydroxylamine, dimethyl amino-2propanol, carbohydrazide, 2-amino 2-methylpropanol, erythorbic acid, and salts of erythorbic acid.

According to a first embodiment of the present invention there is provided a hydrazine-free method of inhibiting corrosion in boiler comprising adding to boiler feedwater containing oxygen an effective amount of a compound selected from the group consisting of trihydroxybenzene compounds, hexahydroxybenzene, levodopa, salts of levodopa and homologues of levodopa.

According to a second embodiment of the present invention there is provided a hydrazine-free corrosion inhibiting composition comprising: a compound selected from the group consisting of trihydroxy benzene compounds, hexahydroxybenzene, levodopa, salts of levodopa and homologues of levodopa and a compound selected from the group consisting of S*.o hydroquinone, methoxypropylamine, cyclohexylamine, diethylethanolamine, morpholine, diethyl hydroxylamine, dimethyl amino-2-propanol, 2-amino 2-methylpropanol, carbohydrazide, erythorbic acid, and salts of erythorbic acid, wherein the weight ratio of to is from 1:99 to 99:1.

Any trihydroxy benzene compound can be used. Examples include 1,2,3-trihydroxy benzene (pyrogallol), 1,2,4-trihydroxy benzene (benzene triol), and 1,3,5-trihydroxy benzene (phloroglucinol). The preferred trihydroxy benzene compounds are pyrogallol and benzene triol, with the most preferred compound being pyrogallol.

S Optionally, the trihydroxy benzene compounds may be used in combination with each other or with other known corrosion inhibitors, including but not limited to filming amines and neutralizing amines.

sl e d Preferred compounds for use with trihydroxy benzene compounds are S" J selected from the group consisting of: hydroquinone, carbohydrazide, diethylhydroxylamine, erythorbic acid, and salts of erythorbic acid, especially scdium erythorbate. The most preferred compounds are hydroquinone and diethylhydroxylamine. Though trlhydroxy benzene compounds can be combined with hydrazlne, such a combination is not preferred because.

of the toxic qualities of hydrazine.

The trihydroxy benzene compounds of the instant invention may be used at any effective dosage. As used herein, the term "effective amount" is that j, JLH/598y ro 20 C-1414Y EXAMPLES 40-42

I

7 C-1414Y amount which inhibits corrosion in the system being treated. The preferred dosage is from about 0.1 to about 1,000 parts per million in the feedwater being treated, more preferably from about 1 to about 100 parts per million. The preferred mol ratio of trihydroxybenzene:dissolved 02 ranges from 0.01:1.0 to 100.1, with the most.preferred mol ratio ranging from 0.1:1 to 20:1.

When used in combination with the second corrosion inhibitor, the weight ratio of the trihydroxy benzene compound to the second compound should be from 1:99 to 99:1, by weight, preferably 1:50 to 50:1 and most preferably 10:1 to 1:10. At least about 0.1 ppm to about 1,000 ppm of the composition should be added.

The preferred dosage is 1 to 100 ppm of the composition.

Approximately 0.66 mole of hexahydroxybenzene is required for every mole of oxygen in the water being treated. By contrast, approximately 2 moles of hydroquinone, a commonly used oxygen scavenger, are required per mole of oxygen. Additionally, the kinetic properties of hexahydroxybenzene are more favorable than those of hydroquinone, and 25 hexahydroxybenzene has better passivating properties.

Optionally, hexahydroxybenzene may be used in combination with other known corrosion inhibitors.

Preferred compounds for use with hexahydroxybenzene are selected from the group consisting of: hydroquinone, methoxypropylamine, cyclohexylamine, diethylethanolamine, morpholine, diethyl hydroxylamine, dimethyl amino-2-propanol, I t I I S 5 S~ S s S it (i is SI C ilcC C

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c~e rcC c C n 8 C-1414Y 2-amino-2-methylpropanol, carbohydrazide, and erythorbic acid. Though hexahydroxybenzene can be combined with hydrazine, such a combination is not preferred because of the toxic qualities of hydrazine.

As used herein, the term "effective amount" is that amount of hexahydroxybenzene which inhibits corrosion when added to boiler feedwater. Preferably, hexahydroxybenzene may be used at dosages of from about 0.1 to about 1,000 parts per million (weight basis) in the feedwater being treated, more preferably from about 1 to about 100 parts per million (weight basis). The preferred mol ratio of hexahydroxybenzene:dissolved 02 ranges from 0.01:1.0 to 100:1, with the more preferred mol ratio ranging from 0.1:1 to 20:1.

When used in combination with a second oxygen scavenger, the ratio of the hexahydroxybenzene to the 20 second oxygen scavenger should be from 1:99 to 99:1, by weight, preferably 1:50 to 50:1 and most preferably 10:1 to 1:10. At least about 0.1 ppm to about 1,000 ppm of the composition should be added. The preferred dosage is 1 to 100 ppm of such a composition.

Levodopa, i.e. 2-amino-3-(3,4 dihydroxyphenyl) propanoic acid, may be represented as follows: *tr t f *C e I i l t It It It Itc I. I I q C

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-7 9 C-1414Y The levodopa compositions of the instant invention may be used at any effective dosage. Dosages of from about 0.1 to about 1,000 parts per million in the feedwater being treated are preferred, with dosages of from about 1 to about 10G parts per million being most preferred. The preferred male ratio of levodopa:0 2 ranges from 0.01:1.0 to 100:1, with the most preferred mole ratio ranging from 0.1:1 to 20:1.

Any salt of levodopa, or homologue of levodopa, can be used. Dopamine 3,4-dihydroxyphenethyl amine) is considered to be a homologue of levodopa.

Optionally, levodopa may be used in combination with other known corrosion inhibitors. When used in combination with a second corrosion inhibitor, the ratio of levodopa to the second corrosion inhibitor should be from 1:99 to 99:1, by weight, preferably 1:50 to 50:1 and most preferably 10:1 to 1:10. At 20 least 0.1 ppm to about 1,000 ppm of such a composition should be added. The preferred dosage is 1 to 100 ppm of such a composition.

The compositions of this invention may be fed to 25 the boiler feedwater by any means known in the art.

Thus, the instant compositions may be pumped into boiler feedwater tanks or lines, or added by some other suitable means. Though for convenience purposes it is recommended levodopa and the second corrosion inhibitor, if used, be added as a composition, they may be added separately without departing from the spirit or scope of this invention.

II lt t t t t t t t t C C 10 C-1414Y The compositions of this invention may be fed to the boiler feedwater by any means known in the art.

Thus, the instant compositions may be pumped into boiler feedwater tanks or lines, or added by some other suitable means. Though for convenience purposes it is recommended that the trihydroxy benzene compound, hexahydroxybenzene or levodopa and the second corrosion inhibitor, if used, be added as a composition, they may be added separately without departing from the spirit or scope of this invention.

EXAMPLES

The following examples further illustrate the invention. They should not be construed as in any way limiting the invention.

EXAMPLES 1-11 20 Examples 1-11 show the oxygen scavenging on ao "capability of pyrogallol. Pyrogallol, at the "concentration indicated in Table I, was added to a simulated boiler feedwater at a pH of 9.0 and at the temperature shown. Percent oxygen removal values after, 2, 4, 6, 8 and 10 minutes are shown in Table I below.

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a a a a a TABLE I Ex. Dosage Mol. Ratio Weight Ratio Temperature 02 Removal v. Time No. (ppm) Pyrogallol:0 2 Pyrogallol:0 2 (Degree C) 2 min. 4 min. 6 min. 8 min. 10 min.

1 40 1.1:1 4.5:1 20 7.4 12.5 15.3 16.5 17.6 2 20 .64:1 2.5:1 29 69.3 80.7 83.8 84.8 84.8 3 10 .32:1 1.3:1 33 51.6 55.0 55.4 54.6 54.2 4 5 .17:1 .65:1 31 25.0 26.2 28.2 28.2 26.2 20 .94:1 3.6:1 51.3 61.8 70.2 73.4 74.5 75.2 6 10 .4:1 1.6:1 50 43.6 51.2 54.9 54.5 55.0 7' 20 .8:1 3.1:1 50 44.2 54.3 55.3 57.8 58.6 8 20 .9:1 3.8:1 48.7 47.6 57.0 60.7 62.3 63.5 9 10 .53:1 2.1:1 57.2 38.0 46.4 50.4 51.9 51.9 5 .24:1 .94:1 49.8 30.8 31.7 30.8 34.9 35.9 11 20 .94:1 3.7:1 48.5 40.0 48.8 52.6 54.7 55.7 JLH-/59 8 y

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12 C-1414Y EXAMPLES 12-14 Examples 12-14 show the oxygen scavenging capability of l,2,4-trihydroxybenzene (benzene.

triol). Benzene triol was added'to simulated boiler feedwater at ph 9, and at the temperatures and dosages shown. Percent oxygen removal values after 2, 4, 6, 8 and 10 minutes are shown in Table II, below.

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4, 4, *C C C C C C C C 4, 4~ *4 C C C C C CC S F, F, C C C C C CC C C C C C o 44 4. C C C C C C C C C C S C C Th4,O C a em C CbS S TABLE II Ex. Dosage Mol. Ratio Weight Ratio Temperature 0~ Removal v. Tirie No. (ppm) Benzene Trial Benzene Trial (Degrees C) 2 min. 4 min. 6 min. 8 min 10 min.

12 65 4:1 15.1:1 54 95.6 98.3 98.0 99.5 97.7 13 20 1.1:1 4.2:1 48.3 54.8 64.2 65.9 65.7 66.6 14 10 0.5:1 2:1 50 38.2 38.2 38.5 37.6 37.9 JLH/598y -14- EXAMPLES 15-32 These examples compare the oxygen capabilities of several well-known ox C-1414Y scavenging rgen scavengers those of compositions comprising pyrogallol and a second conventional oxygen scavenger. Results are shown in Table III, below.

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Resorcinol 25 .79:1 2.7:1 22.5 0. 1.3 1.9 2.4 2.7 16 Diethylhydroxyamine 25 1.1:1 2.8:1 22.5 2.7 5.6 8.4 9.9 12.5 38.2 1.5:1 4.1:1 19.0 1.3 2.3 4.0 4.4 5.3 38.2 1.7:1 4.6:1 31.3 36.4 58.7 71.1 78.9 83.3 34 1.46:1 4.1:1 33.0 42.1 62.4 73.7 79.6 82.4 34 2.4:1 6.8:1 48.4 61.9 85.3 93.4 95.6 96.1 17 .76:1 2.1:1 31.0 18.5 31.3 38.7 43.4 46.2 34 2:1 5.7:1 51.0 14.1 27.8 38.6 47.3 54.5 34 2.2:1 6.1:1 51.0 20.2 36.3 48.1 56.2 62.2 17 Hydroquinone 25 .88:1 3:1 22.7 22.5 39.0 47.3 52.2 54.9 .32:1 1.1:1 21 31.4 32.5 32.1 31.5 31.4 .21:1 .64:1 32 15.0 17.7 16.4 15.4 15.7 .34:1 1.3:1 30 33.8 34.9 34.6 34.6 33.3 .72:1 2.5:1 30 63.6 68.5 68.5 67.6 66.7 18 Hydrazine 9.5 1:1 1.1:1 21 1.1 1.1 1.1 2.2 2.2 19 Sodium Sulfite 78.4 2.2:1 8.9:1 21 1.3 6.2 11.8 16.2 21.2 2-Methyl Resorcinol 40 .1:1 4.5:1 20 0.26 21 Catechol 40 1.3:1 4.5:1 20 1.9 .69:1 2.4:1 31 10 19.6 25.6 31.0 33.8 22 Carbohydrazide 10 .4:1 1.1:1 22 0.85 1.6:1 4.5:1 22 0.83 23 p-Methylamine 40 43.1 4.5:1 22 0.54 Phenol Sulfate 24 Tartaric Acid 40 1.1:1 4.6:1 22 0.73 Dimethyl Amino-2- 45.6 1.5:1 4.9:1 22 0.0 Propanol 39.6 1.9:1 6.3:1 36.7 0.0 26 Sulfurous Acid 20 1.6:1 4.1:1 51 0.0 27 Thioglycolic Acid 40 3.1:1 8.9:1 51 JLH/598y ii 02 Doag 0l Rai Wegh Rai Teprtr 0O Reoalv0Tm 28 Dity Amn 39. 30.3@00*.93 28 Diethyl Amino 39.2 4.7:1 30.3 0.93 Ethanol Pyrogallol/Diethyl- 20/34 33 86.1 92.9 94.3 94.4 94.0 Hydroxylamine 10/17 31 56.7 60.2 61.5 61.3 61.3 20/34 48.3 99.6 99.6 99.6 99.6 99.6 10/17 51.8 86.8 91.6 94.1 94.9 95.3 5/8.5 49 42.4 5e 2 55.2 59.1 62.8 31 Cobalt/Pyrogallol .6/20 32.6 83.3 83.5 82.2 80.5 78.9 32 Hydroquinone! 100/10 50 98.8 99.0 98.8 98.7 98.5 Pyrogallol 50/.5 50 99.4 99.5 99.4 99.4 99.3 10/.1 50 44.9 50.9 55.0 56.9 57.7 20/.2 50 98 98.8 98.5 98 97.7 7.5/.075 49.1 33.7 38.9 43.0 46.9 20/.1 50.3 95.6 98.2 98.1 97.5 96.8 *Examples 15 through 29 are Comparison Examples.

JLH/598y i ~3 -i 17 C-1414Y EXAMPLE 33 9 9 9 99 94 9 9 99 I It I Cf C Cr

II

Although the traditional method of measuring the effectiveness of oxygen scavengers as boiler water corrosion inhibitors has been to measure the relative speed with which they react with dissolved oxygen, such results can be misleading. This is true because, in operating systems, oxygen is an intermediary in the corrosion reaction and the first product of corrosion is ferric oxide. Oxygen alone would not necessarily be detrimental were it not for this corrosion reaction. The primary function of an oxygen scavenger may therefore be to reduce ferric ions to their original state. Under such conditions, it is the iron 15 specie itself that is the primary "oxygen scavenger"' the dosing agent functions primarily as a reducing agent for ferric ions.

Accordingly, a test procedure was used to measure the relative effectiveness of boiler corrosion inhibitors with respect to their ability to reduce ferric ions. This procedure compared the time required for equal molar concentrations of reducing agents to reduce a constant ferric concentration to a specified level. Thus, the reducing agents being tested were reacted with a ferric standard in a test cell. The sensing head of a Brinkman Colorimeter Model PC/800, set at 520 nanometers, was placed in the cells. The drop in ferric ion concentration was continuously recorded using a Brinkman Servogor Model 210 set at 12 cm/minute. Using the data obtained, curves showing time in minutes on the ordinate versus percent absorbance on the abscissa were developed.

The negative slopes of these curves are indirectly 16;

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1 ;L i ji- 18 C-1414Y proportional to the relative effectiveness of their respective reducing agents. The most effective inhibitor evaluated was pyrogallol, which had an inverse slope of 10.0. The least effective inhibitor was sodium sulfite, which had an inverse slope of 1.2. These results are shown in Table IV, below.

TABLE IV Relative Effectiveness Negative Slope of Reduction Rate* t r *E C x c' *c C CC Hydroquinone Pyrogallol Hydroquinone/Pyrogallol Erythorbic Acid Hydrazine Sodium Sulfite 2.7 10.0 3.3 6.7 1.8 1.2 20 *All compounds evaluated were at 0.18x10-3.g-moles/l.

+Hydroquinone/pyrogallol composition was 95:5 wt:wt% hydroquinone:pyrogallol.

EXAMPLES 34-39

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i: \i a t C c EC C Examples 34-39 show the oxygen scavenging capability of hexahydroxybenzene. Hexahydroxybenzene, at the concentration indicated in Table V, was added to a simulated boiler feedwater at a pH of 9.0 and at the temperature shown. Percent oxygen removal values after 2, 4, 6, 8 and 10 minutes are shown in Table V below.

ii '9 .9 .9.9.9 19 ~9.9 .91~ 0 .9 .9 4 .9 .9 .9 .9 .9 99 .9 .9 #9 .9 .9 ~9fl .9 .9 a .9 .94* 0.9.9 .9 .9 0 .9 .9 .9 .9 .9 .9 .9 TABLE V Ex. Dosage Hol. Ratio Weight Ratio Temperature 02 Removal v. Time No. (ppm) Hexahydroxy- Hexahydroxy- (Degrees C) 2 min. 4 min. 6 min. 8 min. 10 min.

Benzene:0 2 Benzene:0 2 34 20 .85:1 4.8:1 52.5 99.9 99.9 99.9 99.9 99.3* 20 .4:1 2.1:1 48.7 53.9 53.9 52.0 51.2 50.8 36 89 2.3:1 12.8:1 28.0 99.8 37 20 .5:1 2.8:1 30.8 66.8 67.4 67.2 38 20 .6:1 3.8:1 51,3 98.9 39 10 .29:1 1.5:1 48 46.4 46.5 45.6 45.2 45.5 Percent removal vs. time values decrease slightly due to leakage of 02 from the atmosphere into the reaction vessel.

JLH/598y i '-1 1~ 20 C-1414Y EXAMPLES 40-42 Examples 40-42 show the oxygen scavenging capability of levodopa. Levodopa, at the concentration indicated in Table VI, was added to a simulated boiler feedwater at a pH of 9.0 and at the temperature shown. Percent oxygen removal values after 2, 4, 6, 8 and 10 minutes are shown in Table VI, below.

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100 4.25:1 26.8:1 52.4 48.4 86.2 98.8 41 100 3:1 18.2:1 54.7 58.7 92.7 99.3 99.5 99.5 42 50 1.7:1 10.5:1 51.3 19.8 43.1 68.3 85.5 95.5 JLH/598y

Claims

1. A hydrazine-free method of inhibiting corrosion in boiler comprising adding to boiler feedwater containing oxygen an effective amount of a compound selected from the group consisting of trihydroxybenzene compounds, hexahydroxybenzene, levodopa, salts of levodopa and homologues of levodopa.

2. The method of Claim 1, which further comprises adding a second corrosion inhibitor selected from the group consisting of: hydroquinone, methoxypropylamine, cyclohexylamine, diethylethanolamine, morpholine, diethyl hydroxylamine, dimethyl amino-2-propanol, 2-amino 2-methylpropanol, carbohydrazide, erythorbic acid, and salts of erythorbic acid.

3. The method of Claim 1, wherein said compound is added at a dosage of from 0.1 ppm to 1,000 ppm.

4. The method of Claim 1, wherein said compound is added at a dosage of from 1 to 100 ppm.

5. The method of any one of Claims 1 to 4, wherein said trihydroxy benzene compound is selected from the group consisting of pyrogallol and benzene triol.

6. The method of any one of Claims 1 to 4, wherein said homologue is dopamine.

7. A hydrazine-free corrosion inhibiting composition comprising: a compound selected from the group consisting of trihydroxy benzene compounds, hexahydroxybenzene, levodopa, salts of levodopa and homologues of levodopa and a compound selected from the group consisting of hydroquinone, methoxypropylamine, cyclohexylamine, diethylethanolamine, morpholine, diethyl hydroxylamine, dimethyl amino-2-propanol, 2-amino 2-methylpropanol, carbohydrazide, erythorbic acid, and salts of erythorbic acid, wherein the weight ratio of to is from 1:99 to 99:1.

8. The composition of Claim 7, wherein said compound is selected from the group consisting of hydroquinone, carbohydrazide, diethylhydroxyl- amine, erythorbic acid, and salts of erythorbic acid.

9. The composition of Claim 7 or Claim 8, wherein said trihydroxy benzene compound is selected from the group consisting of pyrogallol and benzene triol.

The composition of Claim 7 or Claim 8, wherein said homologue is dopamine.

11. A hydrazine-free method of inhibiting corrosion in a boiler substantially as herein described with reference to any one of Examples 1 JLH/598y I f a -:ii C''r C 4 C Cc nrYI Ii 23 to 14, 30 to 32 or 34 to 42.

12. A hydrazine-free corrosion inhibiting composition substantially as herein described with reference to Example 30 or Example 32. DATED this EIGHTEENTH day of OCTOBER 1989 Cal gon Corporation Patent Attorneys for the Applicant SPRUSON FERGUSON 0#t* B 0 0409 9 0a 09 a .0.Qe. *4B I, S t 'Sc, C (0