CS253367B1 - Mixed evaporation inhibitor of metal corrosion - Google Patents

Abstract

The solution relates to a mixed evaporative corrosion inhibitor for metals and their alloys. The aim of the solution is an effective evaporative corrosion inhibitor for metals and their alloys based on salts of benzoic acid and salts of dialkylphosphoric acid, the essence of which lies in the fact that it contains 0.1 to 50 parts by weight of salts of benzoic acid with ammonium hydroxide and/or organic amines, individually or in a mixture, 0.1 to 80 parts by weight of salts of dialkylphosphoric acid with ammonium hydroxide and/or organic amines, individually or in a mixture, or 0.001 to 5 parts by weight of 1, 2, 3-benzotriazole and/or its derivatives, individually or in a mixture.

Description

The invention relates to a mixed evaporative corrosion inhibitor for metals and their alloys in approximately neutral aqueous environments, especially under atmospheric conditions.

The effect of corrosion, occurring in an approximately neutral aqueous environment, especially in atmospheric conditions, is very unfavorable for metal products, because corrosion products are formed on their surface, which degrade them functionally and visually. To reduce or completely eliminate these negative phenomena, a number of methods and means of temporary protection are used for products, of which the use of metal corrosion inhibitors of the evaporation type is of great importance.

The majority of known evaporation inhibitors are characterized by high inhibitory efficiency, but their use on an industrial scale is limited due to their hygienic problems.

This type includes evaporation inhibitors based on the anion of nitrous acid and chromic acid, in particular dicyclohexylamine nitrite, diisopropylamine nitrite and cyclohexylamine chromene. Also amine salts of 3,5-dinitrobenzoic acid having significant hygienic limitations.

Among the health-safe evaporation inhibitors, octadecylamine, 1,2,3-benzotriazole and its alkyl or hydroxy derivatives, ammonium benzoate and a number of mixed types are known, but they are characterized by relatively low protective efficacy, low volatility, especially at low temperatures or in the absence of moisture, and in some cases poor solubility.

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The above-mentioned shortcomings of the current state of the art in this area are largely eliminated by a mixed evaporative corrosion inhibitor for metals and their alloys based on a mixture of benzoic acid salts and dialkylphosphoric acid salts according to the invention, the essence of which lies in the fact that the inhibitor contains 50 to 0.1 parts by weight of benzoic acid salts with ammonium hydroxide and/or organic amines, individually or in a mixture, 0.1 to 80 parts by weight of dialkylphosphoric acid salts with ammonium hydroxide and/or organic amines, individually or in a mixture, or 0.001 to 5 parts by weight of 1,2,3-benzotriazole and/or its derivatives, individually or in a mixture.

According to the invention, dialkylphosphoric acid is understood to mean an acid of the general formula where R1 and _R2 are alkyls with carbon numbers up to C10, in particular dimethylphosphoric acid, which is formed as a distillation residue in the production of dimethyl phosphide.

According to the invention, organic amines are understood to mean alkanolamines, in particular 2-aminoethanol H ₂ N-CH ₂ -CH ₂ -OH, and also cyclic primary and/or secondary amines, in particular morpholine, piperidine and cyclohexylamine.

1,2,3-Benzotriazole and its derivatives, especially methyl-, 1-hydroxy- and tolyl-, are suitable according to the invention both as chemically pure and as technical products, individually or in mixtures.

The corrosion inhibitor according to the invention exhibits very good inhibitory activity against corrosion of iron, nickel, copper, aluminum and their alloys, is well soluble and volatile even at low temperatures. It is preferably applied in the form of an aqueous or alcoholic solution, or as an impregnation of packaging material, in the form of a powder, aerosol or dispersion. The solution and/or dispersion can be applied to metal products by dipping, dipping and spraying.

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The invention, its effects and uses are further explained in more detail with specific examples of its composition and use.

Table 1 lists five examples of mixed inhibitor compositions according to the invention.

Inhibitor components parts by weight of components for example

1 2 3 4 5 ammonium benzoate 20 15 10 — 2-aminoethanol benzoate 20 15 20 10 40 2,2-iminodiethanol benzoate «* 15 - 20 - ammonium dimethylphosphite 30 10 - - <· 5 morpholine dimethylphosphite 25 - - 40 30 piperidine ethyl methyl phosphite — 30 50 40 1,2,3-benzotriazole 1 0.1 - 3 0.5 1-hydroxy-1,2,3-benzotriazole - 0.9 5 2 2

By electrochemical measurement of the corrosion system for the monitored metals and an approximately neutral aqueous environment c (Na _o S0.) =

- 0.01 mol . 1 a high inhibition coefficient was found for all the examples of inhibitor compositions given. The inhibition coefficient, which is expressed as the ratio of the average reduced corrosion rate in the presence of the inhibitor to the average unreduced corrosion rate in an approximately neutral aqueous environment, ranged from 0.85 to 0.98 for all the examples of inhibitor compositions for corrosion of iron, copper, aluminum and their alloys.

- 4 Example 1

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A mixture containing 45 parts by weight of 2-aminoethanol benzoate and 35 parts by weight of piperidine dimethylphosphite was dissolved in water to a 3% solution. Steel samples 11 373 (ČSN 41 1373) were placed in this solution for 60 s. After evaporation of the solvent, their inhibitory efficiency until the first corrosion attack was determined according to Annex 02 of ČSN 03 8205/ST SEV 992-78 and the results were compared with unprotected samples. The inhibited samples remained free of corrosion products after 10 test cycles, while the formation of corrosion was recorded on the unprotected samples already during the first cycle.

Example 2

A mixture containing 15 parts by weight of morpholine benzoate, 20 parts by weight of morpholine dimethylphosphite and 3 parts by weight of 1,2,3-benzotriazole was dissolved in a mixture of water - dimethylketone 1 : 1 to an 8% solution. Samples of steel 11 373 and copper 99.85 were immersed in this solution for 120 s. The samples were tested in a similar manner as in example 1. ₃ and a similar effect was found. The steel samples were free of corrosion products after 8 cycles and the copper samples after 15 cycles, whereas on the unprotected samples the formation of corrosion products in steel and local darkening in copper was recorded after the first cycle.

Example 3

A mixture of 25 parts by weight of cyclohexylamine benzoate, 35 parts by weight of ammonium methylethylphosphite and 2 parts by weight of a mixture of 1,2,3-benzotriazole and 1-hydroxy-1,2,3-benzotriazole in a weight ratio of 3 : 1 was dissolved in water to a 0.3% solution. Samples of steel 11 373, copper 99.85 (ČSN 42 3003) and aluminum 99.5 (ČSN 42 4105) were immersed in this solution to verify the contact effect of the inhibitor.

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While no corrosion attack was detected in samples immersed in a mixed inhibitor solution after 80 days, corrosion attack was detected in samples immersed in water without an inhibitor in steel and copper after the 1st cycle, and in aluminum after the 3rd cycle.

Claims (1)

Mixed metal corrosion inhibitor based on a mixture of benzoic acid salts and dialkyl phosphoric acid salts, characterized in that it contains 0.1 to 50 parts by weight of ammonium benzoate, monoethanolamine benzoate, diethanolamine benzoate, triethanolamine benzoate, morpholine benzoate, piperidine benzoate and / or benzoate cyclohexylamine, singly or in admixture, from 0.1 to 80 parts by weight of a dialkylphosphoric acid salt of the formula wherein R ₁ and R 6 are alkyls having a carbon number of up to C 1, preferably methyl and A is ammonium hydroxide, monoethanolamine, diethanolamine, triethanolamine, morpholine piperidine and / or cyclohexylamine, singly or in admixture, optionally from 0.001 to 5 parts by weight of 1,2,3-benzotriazole, 1-methyl-1,2,3-benzotriazole, 1-tolyl-1,2,3 -benzotriazole and / or 1-hydroxy-1,2,3-benzotriazole, singly or in admixture.