DE2941419A1 - USE OF ACID PHOSPHORIC ACID ESTERS OR THEIR SALTS AS AN AGENT TO PREVENT CORROSION OF METALS - Google Patents

Abstract

1. Use of acid phosphoric acid esters or their salts as agents inhibiting the corrosion of metals, characterised in that, in order to inhibit the corrosion of metals caused by inorganic and/or organic acids or their aqueous solutions, use is made of that agent which has been obtained by subjecting phosphorus(V)oxide to reaction with a mixture consisting of a monohydric alcohol and an alkane polyol having 2 to 12 carbon atoms and 2 to 6 hydroxyl groups while respecting a molar ratio of phosphorus(V)oxide to monohydric alcohol to alkane polyol of 1 : 2 : 4/n, n standing for the number of hydroxyl groups in the alkane polyol molecule, or while using a stoichiometric excess of the alcoholic component, and mixing or kneading the reaction components at a temperature between about 0 degree C and 120 degrees C with exclusion of moisture and in the presence of an inert gas, within a period of about 1 to 6 hours.

Description

HOECHST AKTIENGESELLSCHAFT HOE 79 / H

Use of acidic phosphoric acid esters or their salts as agents for preventing corrosion of metals

The inhibition of corrosion of metals includes Processes of a reduction in corrosion by one or more substances, the agent causing the corrosion be added to reduce corrosion or already contained in it from the outset in whole or in part could be. The substances that reduce the corrosion of metals in this way are called corrosion inhibitors.

Iron, steel or other ferrous metals, but also light metals such as aluminum or aluminum Alloys are more or less corroded by inorganic or organic acids. the Corrosiveness of these acids or their aqueous solutions with respect to metals can be reduced by means of suitable inhibitors can be reduced or completely eliminated, for example by applying protective films to the metal surfaces or top layers are formed. The applied films or layers do not have an inhibiting effect, but only those substances from which such deposits in the corrosive agent, for example organic adsorptives, Chromates, phosphates, nitrites and others can arise.

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It is also known that alkali and amine salts of straight-chain aliphatic, saturated or unsaturated Carboxylic acids in aqueous medium can be used as effective corrosion protection agents for metals. This forms a coherent, firmly adhering film that makes the metal surface more aggressive before attack Protects liquids. Salts of aliphatic carboxylic acids or ring-substituted arylsulfonamide carboxylic acids are also used and their salts are known as corrosion inhibitors.

However, these connections have disadvantages. For example, the effectiveness of fatty amine salts is as Corrosion protection agent strongly from the surrounding liquid medium, the corrosion conditions and the type of metals. Plus, they often own the undesirable property of foaming. Therefore, their use is always limited to certain metals and areas of application limited.

As from the European patent application 0 002 530 A1 is known, acidic esters of phosphoric acids and alkoxylated aliphatic alcohols have recently been used used as a corrosion protection agent for metals

25 places.

It is also known that phosphoric acid esters of ethoxylated alcohols or alkylphenols or ethoxylated and propoxylated fatty alcohols or alkylphenols have corrosion-reducing properties.

However, the aforementioned phosphoric acid esters can only be used in a few, special areas of application due to their more or less strong foaming tendency can be used. By adding defoaming agents, both

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for example silicone defoamers, the foam formed can be partially or completely removed, however Then the usability of the phosphoric acid ester becomes even more extensive due to the side effects of the defoamers limited.

Finally, it should be mentioned that the protective effect of the well-known corrosion inhibitors in aqueous, acidic solutions or acids towards metals strongly depend on the concentration and the temperature and the pH of the solution.

The present invention is intended to overcome the disadvantages of the known corrosion inhibitors.

The invention relates to the use of acidic phosphoric acid esters or their salts as an agent for preventing the corrosion of metals and consists in using the agent which is caused by inorganic and / or organic acids or their aqueous solutions to prevent the corrosion of metals Reaction of phosphorus V oxide with a mixture consisting of a monohydric alcohol and an alkane polyol with 2 to 12 carbon atoms and 2 to 6 hydroxyl groups, while maintaining a molar ratio of phosphorus V oxide to monohydric alcohol to alkane polyol of 1 to 2 to / n, where η denotes the number of hydroxyl groups in the alkane polyol molecule or a stoichiometric excess of the alcoholic components, as well as mixing or kneading the reaction components at a temperature between about ⁰ ° C. and 120 ^° C. with exclusion of moisture and in the presence of an inert gas was obtained over the course of about 1-6 hours.

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The corrosion protection brought about by the agents according to the invention extends in particular to steel, stainless steel, copper, aluminum, aluminum / magnesium / Silicon alloys or on aluminum / zinc / magnesium alloys, being the acid causing corrosion orthophosphoric acid, formic acid, hydrogen chloride acid, sulfuric acid, amidosulfuric acid or nitric acid.

According to a preferred embodiment of the invention, the monohydric alcohol is an aliphatic alcohol with 1 to 22 carbon atoms or the reaction product of an aliphatic alcohol with 1-22 carbon atoms or one Phenol with 6-18 carbon atoms with 2-20 moles of ethylene oxide, such as. B. methanol, ethanol, isopropanol, n-butanol, Isotridecyl alcohol, stearyl alcohol, oleyl alcohol, a technical mixture of aliphatic alcohols, 2-chloroethanol, 2,3-dibromopropanol-1, 3-methoxybutanol-1 or 2-phenylpropanol-1 and the ethylene oxide adduct of methylglycol, ethylglycol, butylglycol or butyldiglycol or the adduct of 4 moles of ethylene oxide and 1 mole of lauryl alcohol, of 8 moles of ethylene oxide and 1 mole of stearyl alcohol, from 6 moles of ethylene oxide and 1 mole of phenol or from 8 moles of ethylene oxide and 1 mole of nonylphenol.

On the other hand, the alkane polyol component is preferably included in the preparation of the acidic phosphoric acid ester following connections:

Ethylene glycol, 1,2-propanediol, 1,3-propanediol »1,3-butanediol, 1,4-butanediol, diethylene glycol, polyethylene glycol, neopentyl glycol, dibromoneopentyl glycol, glycerine, Trimethylolpropane, mannitol or pentaerythritol.

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The preparation of the agents suitable according to the invention can in principle be carried out according to the methods of the German Offenlegungsschriften No. 26 45 211 and 27 39 916. As already stated in these laid-open documents, the implementation can of phosphorus V-oxide with the monohydric alcohol and an alkanediol while maintaining a molar ratio of 1: 2: 2. Replaces the alkanediol an alkanetetrol, the molar ratio is preferably 1: 2: 1.

According to a further preferred embodiment of the invention, the inorganic and / or organic acids can or their aqueous solutions, the agent dissolved or suspended in a ratio of acid to inhibitor such as 100: 0.5 to 1: 1 included.

Compared to the known corrosion inhibitors, the acidic phosphoric acid esters according to the invention have the advantage that they are absolutely foam-free when mixed with inorganic and / or organic acids or their aqueous solutions and regardless of the concentration used and the pH of the acids or their aqueous solutions, corrosion-reducing works.

This effect was not to be expected, since the protective effect of known corrosion inhibitors, such as those used, for example in the European patent application no. 0 002 530 A1, is only limited to a limited pH range extends, and, moreover, these inhibitors, referred to as low-foam, are not completely free from foam formation.

The following examples are intended to explain the invention in greater detail without, however, restricting it in detail.

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example 1

There were solutions of water, orthophosphoric acid and the reaction product of P ^ O ^ q with n-butanol 5 and ethylene glycol in a molar ratio of 1: 2: 2, as described in Example 1 of DE-OS 2 645 211, manufactured as a corrosion inhibitor in the following proportions:

a) 10 parts of orthophosphoric acid, 0 parts of inhibitor and 90 parts by weight of water

b) 9 parts of orthophosphoric acid, 1 part of inhibitor and 90 parts by weight of water

c) 8 parts of orthophosphoric acid, 2 parts of inhibitor and 90 parts by weight of water

d) 7 parts of orthophosphoric acid, 3 parts of inhibitor and 90 parts by weight of water

e) 6 parts of orthophosphoric acid, 4 parts of inhibitor and 90 parts by weight of water

f) 5 parts of orthophosphoric acid, 5 parts of inhibitor and 90 parts by weight of water

and brought into contact with the following metals or metal alloys in the form of test sheets: 25th

I stainless steel, material no. 1.4571 II steel, material no. ST 37-2 (sandblasted) III copper, pure

IV Aluminum, pure V Aluminum alloy Al Mg Si 1 VI aluminum alloy Al Zn Mg

by placing the sample panels in the solutions labeled a - f over a period of 24 hours 35 were immersed at 20 ° C. The sample panels were then rinsed with water, dried and

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10

the weight difference in g / m / day is determined by weighing. The results obtained are shown in Table 1.

Table 1 Differences in weight of the sample panels
I II III W V 63.5 1.6 14.6 17.8 (g / m ² / day)
VI aqueous
solutions
according to 0 17.2 1.2 3.7 6.0 26.4 a) 0 16.1 1.1 3.2 4.3 10.8 b) 0 13.5 1.1 2.4 3.8 6.9 c) 0 10.5 1.1 2.0 3.7 6.5 d) 0 10.3 1.1 1.6 3.4 5.7 e) 0 4.6 f)

With solutions of orthophosphoric acid and water in the following proportions, the same was as above Test conditions a comparative test was carried out.

2ο Table 2

Water difference in weight of the sample panels

(g / m2 / day)

I II III IV

10 TIe: 90 TIe O 63.5 1.6 14.6 9 TIe: 91 TIe O 76.5 1.6 14.4 8th TIe: 92 TIe O 116.6 1.6 14.1 7th TIe: 93 TIe O 98.3 1.6 12.1 6th TIe: 94 TIe O 97.9 1.6 11.7 5 TIe: 95 TIe O 56.5 1.5 10.8

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The test results according to Table 1 in comparison to Table 2 show that the reaction product of PaO-J ₀ with n-butanol and ethylene glycol in a molar ratio of 1: 2: 2 despite the strongly acidic character of the solution (pH value of 1% igen aqueous solution 1.7) has corrosion-reducing properties towards metals and metal alloys.

Example 2

The procedure was analogous to Example 1, except that aqueous solutions were used in the Mengai ratios according to Table 3 produced and the corrosion removal according to the test conditions specified in Example 1 determined on steel sheets ST 37-2 · For comparison, aqueous orthophosphoric acid was used without the addition of an inhibitor checked (Table 4).

Table 3

Test solutions
H ₃ PO ₄ : inhibitor TIe: 1 Tl: 90 : H ₂ O 9 Tie: 2 Tie: 80 Tie 18th Tie: 3 Tie: 70 Tie 27 Tie: 4th Tie: 60 Tie 36 Tie: 5 Tie: 50 Tie 45 Tie: 6th Tie: 40 Tie 54 Tie: 7th Tie: 30th Tie 63 Tie: 8th Tie: 20th Tie 72 Tie: 9 Tie: 10 Tie 81 Tie

Corrosion removal in g / m / day steel ST 37-2 (sandblasted)

9 Tie: 1 Tl: 9o Tie 13.1

15.1 18.1 30.9 32.6

54 Tie: 6 Tie: 40 Tie 35.4

37.0 40.4 45.2 90 Tie: 10 Tie: 0 Tie 50.0

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Tabel 4th PO ₄ : H ₂ 0 Tie Tie: 91 Tie Test solutions Tie: 82 Tie H ₂ ] Tie: 73 Tie 9 Tie: 64 Tie 18th Tie: 55 Tie 27 Tie: 46 Tie 36 Tie: 37 Tie 45 Tie: 28 Tie 54 Tie: 19th 63 72 81

Corrosion removal in g / m / day steel ST 37-2 (sandblasted)

46.9 60.4

74.9

115.5 45 Tie: 55 Tie 135.1

165.8 187.6

218.7

237.2 90 Tie: 10 Tie 255.1

The effect of the corrosion inhibitor is based on the corrosion removal values in Table 3 in comparison to Table 4 can be seen clearly. 2o

Example 3

The procedure was analogous to Example 1, but the aqueous solutions instead of phosphoric acid one of the contained the following acids:

- A) formic acid

B) hydrochloric acid

3o C) sulfuric acid

D) amidosulfuric acid

The aqueous solutions were in the proportions shown in Table 5 against metals and metal alloys with the designations I to VI tested for corrosion analogously to Example 1.

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Tabel

Corrosion agent
(Parts by weight)

Corrosion inhibitor (parts by weight)

H ₂ O

(Parts by weight)

Difference in weight of the test panels (g / m / day) I II III IV V VI

10 TIe A. 0 TIe 90 TIe 0 0.9 48.8 0.5 1.1 1.6 9 TIe A. 1 Tl 90 TIe 0 0.9 11, 8 0.2 0.5 1.1 8th TIe A. 2 TIe 90 TIe 0 0.8 10.4 0.1 0.4 1.1 7th TIe A. 3 TIe 90 TIe 0 0.7 9.4 0.1 0.3 1.0 6th TIe A. 4th TIe 90 TIe 0 0.7 9.2 0.1 0.3 0.8 5 TIe A. 5 TIe 90 TIe 0 0.7 8.8 0.1 0.2 0.6 10 TIe B. 0 TIe 90 TIe 8.5 75.2 5.7 244 148 248 9 TIe B. 1 Tl 90 TIe 5.0 17.6 5.6 26.8 133 246 8th TIe B. 2 TIe 90 TIe 3.4 16.5 5.2 13.6 123 240 7th TIe B. 3 TIe 90 TIe 2.8 15.5 5.1 3.4 63.8 226 6th TIe B. 4th TIe 90 TIe 0.0 13.1 4.8 1.6 11.5 79.6 5 TIe B. 5 TIe 90 TIe 0.0 11.8 4.7 1.5 2.3 14.8

Table 5 (continued)

Corrosion agent (parts by weight)

Corrosion inhibitor (parts by weight)

H ₂ O

(Parts by weight)

Difference in weight of the test panels (g / m / day) I II III IV V VI

10 TIe C. 0 TIe 90 TIe 0.2 113 1.8 3.3 3.4 4.3 9 TIe C. 1 Tl 90 TIe 0.1 21.7 1.1 1.7 2.9 3.8 8th TIe C. 2 TIe 90 TIe 0.05 12.7 1.0 . 0.7 1.5 3.0 7th TIe C. 3 TIe 90 TIe 0.0 10.3 0.9 0.4 0.9 0.9 6th TIe C. 4th TIe 90 TIe 0.0 10.0 0.9 0.4 0.9 0.8 5 TIe C. 5 TIe 90 TIe 0.0 9.7 0.9 0.3 0.8 0.8 10 TIe D. 0 TIe 90 TIe 0.0 165 2.0 1.2 2.0 2.4 9 TIe D. 1 Tl 90 TIe 0.0 5.9 1.1 0.1 0.2 0.5 8th TIe D. 2 TIe 90 TIe 0.0 4.4 1.1 0.1 0.2 0.4 7th TIe D. 3 TIe 90 TIe 0.0 4.3 1.1 0.1 0.1 0.3 6th TIe D. 4th TIe 90 TIe 0.0 4.2 1.1 0.1 0.1 0.3 5 TIe D. 5 TIe 90 TIe 0.0 4.2 1.1 0.1 0.1 0.3

15 29ΑΗΊ9

Table 5 shows that the corrosion inhibitor according to Example 1 both in aqueous solutions as inorganic organic acids also have a corrosion-inhibiting effect on metals.

Example 4

The reaction product of PiO ₁₀ , n-butanol and ethylene-Ίο glycol according to Example 1 was processed with further mixture components to form a cleaning agent with the following composition.

10% by weight of orthophosphoric acid monomethyl ester

15 5 parts by weight of amidosulfuric acid

5% by weight sulfuric acid (98 %)

5% by weight of the reaction product according to Example 1 as a corrosion inhibitor

1% by weight of a polycondensation product from propylene oxide and ethylene oxide with 20% by weight ethylene oxide

(Genapol PF 20 ' ^R ', Hoechst Aktiengesellschaft, Frankfurt / Main)

2 % by weight of an alkylaryl polyglycol ether (solvent GX 5 ' ^R ,

Hoechst Aktiengesellschaft, Frankfürt / Main) 72% by weight of water, perfume, dye

10 wt ^ ige aqueous solutions of the cleaning agent were with aluminum or aluminum alloys according to the test conditions brought into contact according to Example 1.

The test results are shown in Table 6.

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Table 6 Corrosion removal Al Mg Si (g / m ² /Day) Cleaning Al purest 1.0 1 Al Zn Mg 1 middle 0.5 2.7 1.1 with inhibitor
additive 2.6 2.8 without inhibi
gate addition Example 5

The reaction product of P ₄ O ₁₀ with ethanol and ethylene glycol in a molar ratio of 1: 2: 2 was dissolved with the inorganic and organic acids mentioned in Table 7 in a quantitative ratio of 6 parts acid: 4 parts urea decomposition product: 90 parts water and the corrosivity of the solution according to the test conditions according to Example 1 against metals and metal alloys with the designations I to IV analogously to Example 1.

Table 7 25

Difference in weight of the sample panels (g / m ² / day)

acid I. II III IV 3o H ₂ SO ₄ 0 68.8 1.1 2.1 H ₃ PO ₄ 0 52.0 1.1 6.0 35 HCl 0 20.0 3.8 190.3 Formic acid 0 46.1 1.1 0.6 Amidosulfuric acid 0 52.1 1.4 0.7

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Example 6

The procedure was analogous to Example k , but the reaction _{product of P ^ O 10} ^with ethanol and ethylene glycol according to Example 5 was used as the corrosion inhibitor.

The corrosiveness of the aqueous solutions prepared from the cleaning agent to metals was analogous to the example 1 tested. The result is shown in Table 8. 1o

Table 8

10% strength by weight aqueous corrosion removal (g / m / day) cleaning agent solution Al pure Al Mg Si 1 Al Zn Mg

with inhibitor 1, 7th 1, 8th 1, 9 without inhibitor 2, 6th 2, 7th 2, 8th

The reaction product was prepared according to the

Process of DE-OS 27 39 916, example 1.

25 Example 7

The reaction product according to Example 1 was treated with nitric acid (65%) in the proportions shown in Table 9 mixed and according to the test conditions according to Example 1 for metals and metal alloys with the designation I tested to VI. The test results are shown in Table 9.

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Claims (9)

HOECHST AKTIENGESELLSCHAFT HOE 79 / H 038 Use of acidic phosphoric acid esters or their salts as agents for preventing the corrosion of metals 1 ο patent claims Λΐ Use of acidic phosphoric acid esters or their salts as agents for preventing the corrosion of metals, characterized in that the agent is used to prevent the corrosion of metals caused by inorganic and / or organic acids or their aqueous solutions by reacting phosphorus V oxide with a mixture consisting of a monohydric alcohol and an alkane polyol with 2 to 12 carbon atoms and 2 to 6 hydroxyl groups, while maintaining a molar ratio of phosphorus V oxide to monohydric alcohol to alkane polyol of 1 to 2 to / n, where η is the number of hydroxyl groups in the alkane polyol molecule or a stoichiometric excess of the alcoholic components and mixing or kneading of the reaction components at a temperature between about ⁰ ° C. and 120 ^° C. with exclusion of moisture and in the presence of an inert gas was obtained over the course of about 1-6 hours. 2. Use according to claim 1, characterized in that the metal is steel, stainless steel, copper, aluminum, an aluminum / magnesium / silicon alloy or an aluminum / zinc / magnesium alloy. 130017/0331 3. Use according to claim 1 or 2, characterized in that the acid is orthophosphoric acid, formic acid, hydrochloric acid, sulfuric acid, amidosulfuric acid or nitric acid. 4. Use according to claims 1-3, characterized in that the monohydric alcohol is an aliphatic alcohol with 1-22 carbon atoms or the reaction product of an aliphatic alcohol with 1-22 carbon atoms or a phenol with 6-18 carbon atoms with 2-20 moles of ethylene oxide. 5. Use according to claim 4, characterized in that the monohydric alcohol is methanol, ethanol, isopropanol, n-butanol, isobutanol, cyclohexanol, 2-ethylhexanol, lauryl alcohol, isotridecyl alcohol, stearyl alcohol, oleyl alcohol, a technical mixture of aliphatic alcohols, 2-chloroethanol, 2,3-dibromopropanol-1, 3-methoxybutanol-1 or 2-phenylpropanol-1. 6. Use according to claim 4, characterized in that the monohydric alcohol is an adduct of ethylene oxide and methyl glycol or ethyl glycol, butyl glycol or butyl diglycol or an adduct of 4 moles of ethylene oxide and 1 mole of lauryl alcohol, from 8 moles of ethylene oxide and 1 mole of stearyl alcohol, from 6 Moles of ethylene oxide and 1 mole of phenol or from 8 moles of ethylene oxide and 1 mole of nonylphenol. 7. Use according to claims 1-6, characterized in that the alkane polyol is ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, diethylene glycol, polyethylene glycol, neopentyl glycol, dibromoneopentyl glycol, glycerol , Trimethylolpropane, mannitol or pentaerythritol. 130017/0331 8. Use according to claims 1-7, characterized in that the molar ratio of phosphorus V-oxide to monohydric alcohol to alkanediol is 1: 2: 2. 9. Use according to claims 1-8, characterized in that the molar ratio of phosphorus V-oxide to monohydric alcohol to alkanetetrol is 1: 2: 1. 1o. Use according to claims 1-9 , characterized in that the inorganic and / or organic acids or their aqueous solutions contain the agent dissolved or suspended in a ratio of acid to inhibitor such as 100: 0.5 to 1: 1. 130017/0331