FR2501709A1 - PROCESS AND COMPOSITION FOR PREVENTING CORROSION IN AQUEOUS SYSTEMS - Google Patents

Abstract

THE INVENTION RELATES TO A METHOD AND COMPOSITION FOR PREVENTING CORROSION IN AQUEOUS SYSTEMS; TO PREVENT CORROSION, THE 5-AMINO-TRIAZOLE-1, 2, 4-3-CARBOXYLIC ACID OR ONE OF ITS SALTS IS ADDED TO THE SYSTEM, POSSIBLY ALSO A ZINC SALT AND OR AN ORGANIC PHOSPHATE OR PHOSPHONATE AND OR A POLYMER; AN INHIBITORING COMPOSITION CONTAINING 5-AMINO-TRIAZOLE-1, 2, 4-CARBOXYL-3 ACID OR ONE OF ITS SALTS AND ONE OR MORE OF THE ABOVE COMPOUNDS IS ALSO DESCRIBED.

Description

250 1 7 0 9

  The present invention relates to a method and a

  composition for preventing corrosion in aqueous systems.

  It has been known for some time to use certain arylenetriazoles to prevent corrosion in aqueous systems, particularly systems in contact with a ferrous metal. Equal-

  certain organic phosphonates, polymers of low molecular weight

  Zinc salts and salts have some corrosion inhibiting properties but are not effective enough to be used alone. The invention is based on the discovery that a type

  triazole is effective in protecting iron

  For corrosion resistance, this triazole is 5-amino-1,2-triazole-3-carboxylic acid having the formula:

N N

lH2N .. 2N COORH I -N

  The invention relates to a method for avoiding the cor-

  erosion in an aqueous system which comprises adding to the aqueous system 5-amino-1,2-triazole-3-carboxylic acid. In general, the concentration of triazole is 0.5 to 20 and in particular

from 1 to 10 mg / l.

  This particular triazole not only ensures

  inhibition of the higher corrosion for example that of the benso-

  triazole, but furthermore it has been found that the combination of this triazole with zinc salts, organic phosphates and phosphonates and low molecular weight polymers, typically either a zinc salt and an organic phosphonate, or an organic phosphonate and a low molecular weight polymer provides synergistic effects. In other words, it is possible to obtain results which are greater than what is possible to predict the addition of the results obtained with the individual ingredients. The invention therefore also relates to a composition suitable for addition to aqueous media, which comprises 5-amino-1,2-triazole-3-carboxylic acid and at least one selected compound.

  among a zinc salt, an organic phosphate, an organic phosphonate

  and a low molecular weight polymer. It is of course

  possible to incorporate the ingredients individually into the system.

250 1 7 0 9

  Typical phosphonates that can be used in the invention include those of the general formula: R1

H20 3P-C-PO3H2 II

X

  in which R 1 represents a hydrogen atom or a lower alkyl radical (that is to say having 1 to 6 and in particular 1 to 4 carbon atoms) and X represents a hydrogen atom, a lower alkyl radical or a hydroxy radical; or having the general formula: R2 c

/ CHPO3H2

3 N III

R3 'CHPO3H2

  R3 / 2 R in which each of R2 represents independently

  a hydrogen atom or a lower alkyl radical, and R3 represents

feeling: R2

R2 CO3H2

  or 32 -C'H-PO3H2 or - - N / x \ CHPO3H2 where x is an integer from 1 to 6, or

R2

P03H2

CRPO3H

CHR 2 3 2

I R2

PO 3H2

  o y is an integer of 1 to 3; or having the general formula: R4 I

H203P C _COOH IV

i

CH 2 COOH

  in which R4 represents a hydrogen atom, an alkyl radical 6

R R

  or -CH-CH-COOH where R represents a hydrogen atom, an alkyl radical or a carboxy radical and R6 represents a hydrogen atom

or an alkyl radical.

  Preferred phosphonates are hydroxyethyl

  denediaphosphonic acid (HEDPA), that is to say the compound of formula (II) in which R 1 represents a methyl radical and X represents a hydroxyl radical; and nitrilo tris-methylenephosphonic acid, that is to say the compound of formula (III) in which R 2 represents a hydrogen atom and R represents

R2

-CHPO3H2

  The concentration of phosphonate in the system is appreciably

  from 1 to 50 and in particular from 2 to 10 mg / l.

  The polymers which can be used in the invention are vinyl adducts having a molecular weight of the order of 500 to 100,000, having units corresponding to the general formula: Y iR7

Z Y

  in which R represents a hydrogen atom or a lower alkyl radical, Y represents -COOH, and Z represents an atom

  of hydrogen or -COOH, or Y and Z together represent -CO-O-CO-.

250 1 7 0 9

  Preferred polymers are polymethacrylic acids, i.e.

  those where R represents a methyl radical, Y represents -COOH and Z represents a hydrogen atom, in particular having a weight

  molecular weight of about 5,000, and polyacrylic acids, that is,

  say those where R7 and Z both represent a hydrogen atom and Y represents -COOH, having in particular a molecular weight

  approximately 1,000. The polymer concentration is appro-

  from 1 to 50 and preferably from 2 to 10 mg / l.

  The 5-amino-triazole-1,2,4-carazole acid can be prepared.

  Box-3 by dehydration of oxalylaminoguanidine

(HOOC-CONH.NH-CNH2)

NH

  (see, for example, Ann 1898, 303, 52) or by heating the diazo-

  ethyl acetate and potassium hydroxide (see eg Ber 1907, 40, 815, 1194). This latter method also forms a

  certain amount of 4-amino-1,4-triazole-3,5-dicarboxylic acid.

  The typical zinc salts that can be used are chloride, sulfate, nitrate and acetate. Typically the zinc salts may be present in the range of from 0.5 to 20 and

especially from 1 to 10 mg Zn / l.

  Although the formulas for phosphonates and poly-

  have been presented in the form of free acids, it is obvious that they can also be used in the form of organic or inorganic salts, in particular an alkali metal salt,

  preferred, such as sodium or potassium, a salt of

  monium or a lower amine or other metal salt. Triazole can not only form salts as above but also form amine salts with mineral acids; we can

use it in these forms.

  Note that one can incorporate other low-toxicity materials conventionally used in the treatment of water, such as mineral silicate, phosphate or polyphosphate and

lignin derivatives.

  The invention is illustrated by the nonlimited examples

following.

Examples 1 to 4

Effect on mild steel.

  Mild steel samples are immersed in aerated water and allowed to stand at 18 ° C for 5 days. The samples are cleaned and weighed before and after the test and, based on the observed weight loss, the average rate of corrosion expressed in millimeters per year is calculated. The water used in these tests is Widnes mains water with a total hardness of 140 mg / l, an M alkalinity of 100 mg / l and a

from Langelier of -0.5.

Examples 5 to 12

  Effect in melenRe with zinc and phosphonate.

  Suspended mild steel samples are placed in a stirred water tank maintained at 60C with agitation

  such that the air entrainment keeps the water saturated with oxygen.

  The water lost by evaporation is replaced by water contained in a raised tank by means of a constant level syphon to keep the volume in the reservoir constant. The water used in the tests is Widnes mains water which, as a result

  Evaporation during the test is concentrated or triplicate.

  In each test treatment, a triple concentration of normal is used for 24 hours to passivate the steel; it is then diluted to normal concentration for the remainder of the test. Each test is carried out for three days

at least.

  Example No. I concentration (mg / l) Corrosion rate (mm / year)

_ _ 0.46

2 25 0.40

3 50 0.38

4 100 0.33

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  In these examples, the zinc salt is chloride

  of zinc and phosphonate is nitrilo tris-methylene phosphorus

  sound. In Examples 9 and 12, 5 mg / l is also used

of a lignin sulphonate.

  Examples 13 to 20 Effect Mixed with a Phosphonate and a Polymer A laboratory test apparatus is used in which a pump circulates water from a reservoir maintained at a temperature of 40 ° C through a tube assembly. glass containing the samples of metal studied to return it to the tank by drawing air in order to maintain the water

  saturated with oxygen as is the case in a cooling circuit

  open drainage. Cooling water losses are

  thought from a raised container by means of a float maintaining a constant volume in the system, the water used being Widnes mains water which during the test is

  concentrated to double as a result of evaporation.

  In each test treatment, one uses a

  Triple center of normal for 24 hours to passivate the steel then dilute to normal concentration for the rest

  of the test. Each test is carried out for at least three days.

Additives (mg / 1)

Example n ', Speed of cor-

  Zinc salt Phosphonate Triazole I erosion (mm / year) (in Zn)

- - - 2.68

6 10 - - 2.04

7 - 10 - 1.57

8 - - 10 1.50

9 5 4.25 - 0.83

10 - 2 0.56

i l- 10 2 0.91

12 5 4.25 2 0.076

  In these examples the phosphonate is a 1/1 mixture

  hydroxyethylidenediphosphonic acid and nitrilo trice

  methylene phosphonic acid, and the polymer is polymdthalic acid.

  crylic having a molecular weight of 5,000, all these compounds being present in the form of their potassium salt. In Examples 16 and 20, 3 mg / l of orthophosphate is also used.

of potassium.

  Examples 21 and 22 Comparison with benzotriazole These examples are carried out under the conditions described for Examples 5 to 12 (Example 21) and for Examples 13 to 20 (Example 22). i

Additives (mg / l) Speed of cor-

Example n, ...

  ExemPhoploae n * erosion (mm / yr) Phosphonate Polymer Triazole I erosion (year)

13 '- - 0.97

14 7 - - 0.83

3 _ 0.59

16 7 3 - 0.46

17 7 - 5 0.65

18 - 3 5 0.37

19 - - 10 0.33

7 3 5 0.058

I _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _

  O tu to No -,. M 0 4> Additives mg / l Example n Triazole I Benzotriazole Corrosion rate Phosphonate Polymer Zinc salt (mm / year) (in Zn)

12 4.25 - 5 2 - 0.076

21 4.25 - 5 - 2 0.15

7 3 - 5 - 0.058

22 7 3 - 5 0.066

250 1 7 0 9

  In Examples 12 and 21, the phosphonate is nitrilo trismethylene phosphonic acid, the zinc salt is chloride

  zinc and the compositions also contain 5 mg / l of a lignin-

  sulfonate. In Examples 20 and 22 the phosphonate is a 1: 1 mixture of hydroxyethylidenediphosphonic acid and nitrilo-tris- methylenephosphonic acid, the polymer is a polymethacrylic acid having a molecular weight of 5,000, all of these compounds being present

  in the form of their potassium salt, and the compositions contain

  are also 3 mg / l of potassium orthophosphonate.

  These examples show that although triazole I has

  in themselves corrosion inhibition properties, these are

  grow when a zinc salt, phosphonate or polymer is added and increase strongly when a zinc salt and a phosphonate or phosphonate and a polymer are incorporated, which

  shows synergy. Its performance is clearly superior

than those of benzotriazole.

  Naturally, various modifications may be made by those skilled in the art to the devices or processes which have just been described as non-limiting examples.

  without departing from the scope of the invention.

250 1 7 0 9

Claims (10)

  1. Method for removing corrosion in a system   aqueous solution, characterized by the addition to the 5-amino-triazole   1,2,4-carboxylic acid or a salt thereof.   2. Method according to claim 1, characterized by   adding said triazole to the system so as to obtain a concentration of from 0.5 to 20 mg / l.   3. Method according to claim 2, characterized in that   that the concentration of said triazole is 1 to 10 mg / l.   4. Method according to any one of claims 1   at 3, characterized in that one or more components selected from a zinc salt, a phosphate, are also added to the system.   or organic phosphonate and a polymer.   5. Method according to claim 4, characterized in that   that a zinc salt and an organic phosphonate are added.   6. Process according to claim 4, characterized in that   that an organic phosphonate and a polymer are added.   7. Composition, characterized in that it comprises amino-5-triazole-1,2,4-carboxylic acid-3 or a salt thereof and one or more components selected from a zinc salt, a phosphate   or organic phosphonate and a polymer.   8. Composition according to Claim 7, characterized   in that it comprises a zinc salt and an organic phosphonate.   9. Composition according to Claim 7, characterized   in that it comprises an organic phosphonate and a polymer.   10. Composition according to any one of the claims   7 to 9, characterized in that the phosphonate is hydroxy-acid   ethylidenediphosphonic acid or nitrilo tris-methylenephosphonic acid   the polymer is polyacrylic acid or poly-   methacrylic acid and zinc salt is chloride, sulfate, nitrate or zinc acetate.