CS241087B2 - A method for producing corrosion inhibitors - Google Patents

Abstract

The subject of the invention is a method for producing a corrosion inhibitor based on organic phosphates of the general formula I R, L í .ťl Π) where the individual symbols have the meaning given in the definition with an optional content of not more than 10% zinc phosphate, based on the amount of organic phosphate, suitable as an additive to water, characterized in that phosphoric acid with a concentration of 5 to 85% is reacted with cyclohexylamine or dlcyclohexylamine. The obtained inhibitors are suitable for devices with cold or hot water circulation

Description

-Patent holder BORSODI VEGYI KOMBINÁT, KAZINCBARCIKA (MLR) (54) Method of producing corrosion inhibitors

2

The subject of the invention is a method for producing a corrosion inhibitor based on organic phosphates of the general formula I

R, L ^í .ťl

Π) where the individual symbols have the meaning given in the definition with an optional content of not more than 10% zinc phosphate, based on the amount of organic phosphate, suitable as an additive to water, characterized in that phosphoric acid with a concentration of 5 to 85% is reacted with cyclohexylamine or dicyclohexylamine.

The obtained inhibitors are suitable for devices with cold or hot water circulation.

The invention relates to a method for producing corrosion inhibitors based on organic phosphates of the general formula I

R.

Η<,-ηΡΟ _Η (I) where

R 1 represents a hydrogen atom or a cyclohexyl group,

R2 represents a cyclohexyl group and n has a value of 0.5 to 3, and zinc phosphate.

The additives produced by the method according to the invention can be used for warm, hot and cold water circulation to reduce corrosion of the respective equipment.

It is known that the corrosion of metals in aqueous solutions in most cases occurs as an electrochemical process, the speed of which depends on the speed of two reactions that take place on the surface of metals and influence each other. This is the anodic reaction, during which metal ions leave the lattice and enter the solution, and the cathodic reaction, in which the depolarizer absorbs the electrons released in the first reaction.

It is also known that, compared to some previously used methods of corrosion protection, especially compared to the use of some substances that are resistant to corrosion, it is more advantageous, simpler and cheaper to use protective coatings and methods that reduce corrosion.

The corrosion process must be closed in order for it to take place at all. This means that chemicals that, when added to water, inhibit the 'anode reaction, also inhibit corrosion, .. which also applies to agents that inhibit _{the x} rate of the cathodic reaction. It is therefore clear that it is possible to distinguish inhibitors that fundamentally inhibit the anodic reaction or the cathodic reaction. The third group of inhibitors forms organic films that protect the metal and inhibit both reactions.

Among the inhibitors of the anodic reaction, the most effective are chromites and orthophosphates. The use of chromium salts is limited due to environmental protection requirements, the use of orthophosphate is limited because calcium phosphate can be deposited, which slows down heat transfer.

In the case of pure anodic reaction inhibitors, the corrosion rate also depends on the inhibitor concentration. If its concentration falls below a certain value, the corrosion rate is not reduced by the inhibitor, but increased.

In the case of cathodic reaction inhibitors, for example, when polyphosphonate or zinc is used, these problems do not occur, but their effectiveness in inhibiting corrosion is much lower.

Organic film-forming agents are usually from the group of amines with a long carbon chain and form a film on the metal surface and thus a barrier between water and metal, so that corrosion is slowed down. Film-forming agents have the disadvantage that a small crack in the film is enough and the effect on corrosion slowing down is reduced to practically zero.

In order to increase corrosion inhibition, combinations of inhibitors of various types have recently been used, especially in the form of mixtures with a synergistic effect.

The corrosion inhibitors produced by the method according to the invention do not have the disadvantages of the above-mentioned types of inhibitors. They can be obtained from readily available compounds in a simple and inexpensive manner. Their corrosion inhibition efficiency is equal to or exceeds the efficiency of known, commonly used inhibitors.

The inhibitors produced by the method according to the invention can be used in devices in which both cold and hot water circulate, and thus high corrosion inhibition can be achieved.

By the method according to the invention, it is possible to obtain organic phosphates of general formula I by a simple chemical reaction by adding cyclohexylamine or dicyclohexylamine to 5 to 85% phosphoric acid with constant stirring and cooling.

Depending on the concentration of phosphoric acid, the organophosphorus compounds of the general formula I are obtained in pure form or in the form of an aqueous solution. Particularly effective inhibitors can be obtained by adding up to 10% zinc phosphate to the organic phosphates of the general formula I. Zinc can also be added by first dissolving zinc oxide in phosphoric acid and then adding cyclohexylamine or dicyclohexylamine to the resulting solution.

Unlike known inhibitors, the inhibitors produced by the method according to the invention contain cyclohexylamine phosphate or dicyclohexylamine phosphate. The use of these compounds against corrosion has not yet been known, nor is their combination with zinc phosphate.

The corrosion inhibitors produced by the method according to the invention have the following advantages as water additives:

— these substances slow down corrosion in all three of the above-mentioned ways. First, as inhibitors of the anodic reaction (phosphate), as inhibitors of the cathodic reaction (zinc) and also as film-forming substances (cyclohexylamine or dicyclohexylamine) and for this reason cause almost complete inhibition of corrosion, — the said substances reduce the corrosion rate even at higher water temperatures, — they can be produced in a simple way in a common industrial chemical plant (autoclave), / — due to their simple production they are cheaper than substances with the same effect that have been used until now, — the compounds are neutral or almost neutral in nature and for this reason they hardly affect the pH of the circulating water, — the substances do not contain heavy salts, which are undesirable with regard to environmental pollution, — in. compared to compositions containing phosphate and having similar efficacy, compositions produced by the method according to the invention contain a much lower concentration of phosphate in water, —- compared to compositions containing zinc and having similar efficacy, compositions produced by the method according to the invention contain a much lower concentration of zinc in water, — unlike known compositions containing phosphorus, calcium phosphate deposition is almost non-existent or occurs only to a small extent, — any possible contamination of water with copper ions does not reduce the efficacy of inhibitors produced by the method according to the invention.

The invention will be illustrated by the following examples.

I

Example 1

Into an enamelled autoclave, equipped with a stirrer and a double jacket, are placed: 474 litres of water, free of ions. Then 23.4 litres of phosphoric acid with a concentration of 85% are added. With constant stirring, 58 g of zinc oxide are dissolved in the acid. With constant stirring and cooling with water, 86.2 kg of dicyclohexylamine are added to this solution at a rate of 90 kg per hour. After the addition is complete, the mixture is stirred for another 10 minutes and then placed in storage containers, preferably made of plastic.

The corrosion inhibitor thus obtained has the following properties: pH: 7 to 8?

specific gravity: 1.04 g/cm ³ at 20 °C composition:

zinc 70 to 90 mg/kg phosphate 52 to 58. g/kg dicyclohexylamine 140 to 150- g/kg

Example 2

In a 100 ml beaker, dissolve 0.01 g of zinc oxide in 56.7 g of 8.5% phosphoric acid. In a 2 litre beaker, dissolve 40.8 g of cyclohexylamine in 903 g of distilled water. Then, the solution of zinc oxide in phosphoric acid is slowly added to the amine solution with constant stirring over a period of 10 minutes: The resulting product has the following properties:

color;

pH:

specific gravity: composition:

zinc phosphate cyclohexylamine colorless or slightly yellow 4 to 5

1.03' g/cm ³ at 20'°C' to 9 mg/liter to 50 g/liter to 44' g/liter

Example 3

0.30 mg of zinc oxide is dissolved in 1.97 g of 85% phosphoric acid. This solution is added, with vigorous stirring, to 4.5 g of dicyclohexylaminium;

The resulting product thus obtained has the following composition:

pH composition appearance:

zinc phosphate dicyclohexylamine water up to 8'at the concentration of aqueous.

solution 20% white crystalline substance.

0.0035 to 0.0040% up to 27% up to 71% up to 6%

Example 4

612 liters of deionized water are placed in an enameled autoclave, equipped with a stirrer and a double jacket with a volume of 1 m ³ . Then 47.8 liters of phosphoric acid with a concentration of 85% are added. While cooling with water and stirring continuously, 99 liters of dicyclohexylamine are added. The resulting product is then filled into storage containers.

The resulting product thus obtained has the following properties:

color:

pH specific gravity: composition:

zinc phosphate dicyclohexylamine colorless or slightly yellow 3 to 4

1.05 g/cm ³ at 20 °C up to 13 mg/kg up to 90 g/kg

110 to 120 g/kg of corrosion inhibitor. Comparative experiments were carried out according to the method of Kemmer, Frank N.: The NALCO Water Handbook, McGraw-Hill, Inc., 1979, and Betz: Nadbook of Industrial Water Conditioning, 1076 by measuring the values achieved on the samples in mm/year and also by evaluating the relative inhibitory efficiency (corrosion value in %, based on the control sample). In the case of known inhibitors, the concentration stated by the manufacturer was used.

hours 90 °C every 24 hours continuously 7.5 to 8.5 to 100 mg/liter 500 to 600 ,uS 40 to 60 mg/liter 0.1 to 0.2 mg/liter 140 to 160 mg/liter 20 to 30 mg/liter 3 to 5 mg/liter

The inhibitory efficacy of the corrosion inhibitors produced by the method according to the invention was demonstrated in the following experiments:

Attempt 1

The effectiveness of the inhibitor produced by the method according to Example 1 (hereinafter X-102) and the inhibitor produced by the method according to Example 3 (hereinafter X-100) was compared with the effectiveness of the known, commonly supplied Experimental conditions:

duration of the experiment water temperature removal of any sludge aeration PH

Properties of the water used: total hardness (in GaCCb) conductivity alkalinity (in CaCO3) total iron sulfates chlorides silica

The results are shown in the following Table I. It is clear from this table that the corrosion inhibitors produced by the process of the invention achieve or exceed the effectiveness of the best corrosion inhibitors known to date.

Attempt 2

The composition prepared by the method of Example 4 (hereinafter referred to as X-1001) was used continuously, as was its modified form with ten times the zinc content (hereinafter referred to as X-1021). The results were compared with known compositions. The experimental parameters and water quality corresponded to the conditions given in Experiment 1. The results are also given in Table 1 below. It is clear that the corrosion inhibitors prepared by the method of the invention achieve or exceed the effectiveness of known compositions when added to water.

Experiment 3 performed by the method according to Example 2 (hereinafter X— —103) for pretreatment and for continuous treatment by the method according to Example

1. The experimental parameters and water quality were the same as in experiment 1. From the results shown in Table I, it is clear that the X-103 agent provides better corrosion protection than the commercially available agent.

Experiment 4 The effectiveness of the composition X-102 in Example 1 in the pre-treatment and the composition X-100 from Example 3 continuously was compared with the effectiveness of the known composition, which had the best effectiveness in the preliminary experiments. It was a combination of I + II + III (the meaning of these symbols is given under Table IJ. The experiment was carried out at a lower water temperature. The results are given in the following Table II. It is clear that the additive produced by the method according to the invention slows down corrosion at least as much as the comparative compounds.

In this experiment, a product manufactured by 241087 was used.

Table I

Comparative effectiveness of various substances as corrosion inhibitors when added to water

·’. attempt number precautionary measure concentration mg/liter concentrated agent for protection trace mg/liter corrosion rate mm/year inhibitor efficiency in % 1 __ _ . _ 2.203 0 2 I II 1000 200 III 150 0.069 97 3 IV 200 IV 150 0.726 67 4 in VI 200 100 V+VI 100 0.194 92 5 VII 200 VII 150 1.90 14 6 VIII 100 VIII 30 1.76 20 7 X—102 5000 X—100 150 0.068 97 8 X—1021 5000 X—1001 150 0.032 99 9 X—103 2000 X—103 300 0.212 90 Table II Comparative the effectiveness of various substances such as· inhibitor 1 corrosion when added into the water attempt means concentration medium- final- temperature speed efficiency number for preliminary protection mg/liter blanket for protection trace water mg/liter °C corrosion mm/year inhibitor in % 1 —. — — — 30 0.814 0 2 I II 1000 200 III 150 30 0.021 97 3 X—102 5000 X—100 150 30 0.021 97 4 — — — — 60 1,021 0 5 I II 1000 200 III 150 60 0.024 98 6 X—102 5000 X—100 150 60 0.024 98

Explanations to the tables:

I polyphosphate, zinc salt [3% zinc), copper inhibitor

II sodium polyacrylate copolymer

III polyphosphonate, zinc salt, copper inhibitor, phosphate

IV inhibitor mixture, consisting of organic and inorganic components, zinc content 34 mg/liter, copper 10 mg/liter, phosphate 20%

V zinc phosphate inhibitor, zinc content 13%, phosphate content 17%

VI organic inhibitor

VII phosphate inhibitor mixture, phosphate content 7-%

VIII zinc, organic phosphates and phosphonic acids, zinc content 7.3 %, phosphate content 10 %

Claims (6)

Subject A process for the production of an organic phosphate corrosion inhibitor of the general formula I NH, (1) wherein R1 represents a hydrogen atom or a cyclohexyl group, R2 is cyclohexyl and n has a value of 0.5 to 3, with an optional content of not more than 10% of zinc phosphate, based on the amount of organic phosphate, suitable as an additive dc of the water invention, characterized in that S5% with cyclohexylamine or dicyclohexylamine. 2. The process of claim 1 wherein R1 is hydrogen. 3. The process of claim 1 wherein R1 is cyclohexyl. 4. The process of claim 1 wherein one reactant is added continuously to the other. 5. The process according to claim 1, characterized in that zinc phosphate or a zinc compound formed with phosphoric acid of not more than 10% is added to the reaction mixture before, during or after the reaction. 6. Process according to claims 1, 4 and 5, characterized in that the reaction is carried out without solvent or in the presence of an inert solvent, preferably water.