CS259294B1 - Composition for alkaline treatment of circulating cooling water - Google Patents

Abstract

The solution belongs to the field of metal corrosion protection and concerns corrosion protection of steel and other metals in heat exchange systems, including stabilization of Ca + + Mg with an aqueous cooling medium. The composition contains 1 to 20 wt. % hydroxyethanediphosphonic acid, 0.1 to 5 wt. % 1,2,3-benzotriazole or tolyltriazole, 1 to 15 wt. % aqueous solution of sodium, ammonium or sodium ammonium salt of acrylate polymer or copolymer, 1 to 10 wt. % Ν,Ν-dimethylformamide, 1 to 10 wt. % sodium or potassium hydroxide and 40 to 80 wt. % water. The composition is continuously maintained in aqueous heat exchange media with a concentration of 20 to 100 g per 1 m3.

Description

The invention relates to a composition with corrosion-inhibiting, dispersing-sequestering effect for progressive alkaline treatment of the heat exchange environment of steel systems also containing materials of copper, aluminum, zinc and their alloys in circulating cooling circuits.

The effect of the water heat exchange environment on steel systems causes corrosion of steel and other metals. Corrosion occurs evenly, but due to the formation of deposits of insoluble substances such as insoluble salts, mainly calcium carbonate, dust, silt, sand, corrosion products, biomass, it becomes uneven, most often in the form of pitting corrosion, but it also worsens the hydraulic resistance of water flow in pipes and thus increases additional resistance on heat exchange surfaces.

In order to prevent the corrosive effect of aqueous heat exchange media on steel systems, corrosion inhibitors based on chromates, nitrites, silicates, phosphates, molybdenites and zinc salts are added to these media. These agents are capable of suppressing steel corrosion to varying degrees (but not Cu, Al and Zn and their alloys), they do not suppress the growth of deposit layers and therefore cannot prevent the increase in hydraulic and thermal resistances and thus the appearance of uneven forms of corrosion. In addition, some known corrosion inhibitors are also harmful to health, for example chromates, nitrites and at the same time do not suppress steel corrosion safely unless their required minimum concentration in the aqueous medium is maintained. Therefore, to suppress deposits, additives with a dispersing effect are used, such as cellulose and its derivatives, polyacrylates, polyacrylamides and the latest synthetic polymers such as copolymer of ethylene oxide and propylene oxide and others.

To suppress the formation of solid deposits, sequestering agents are known, which prevent the formation of non-stoichiometric complexes and the formation of insoluble salts and their layers on the surface of steels. The inhibitors of these deposits include primarily polyphosphates, natural polymers such as lignin and tannin.

The polyphosphate programs that have been most commonly used to date have the disadvantage that in systems with longer residence times, high operating temperatures and higher pH values, the reversion (retragradation) of polyphosphate to orthophosphate occurs, resulting in sticky deposits of calcium orthophosphate.

The shortcomings of the known state of the art in this field are to a certain extent eliminated by the composition for progressive alkaline treatment of circulating cooling waters with corrosion-inhibiting, dispersing-sequestering effect for water circulating cooling circuits according to the invention, which consists of:

From 1 to 20% by weight of hydroxyethanediphosphonic acid,

0.1 to 5 % by weight of 1,2,3-benzotriazole or tolyltriazole, up to 15 % by weight of an aqueous solution of sodium, ammonium or sodium ammonium salt of an acrylate polymer or acrylate copolymer, up to 10 % by weight of N,N-dimethylformamide, up to 10 % by weight of sodium or potassium hydroxide and up to 80 % by weight of water (distilled, condensate or hard tap water).

The composition mentioned is added to the aqueous heat exchange medium in a concentration of 20 to 100 g m ^-3 .

This composition, as a multi-component mixture of synthetic organic corrosion inhibitors including specific control agents for deposits, provides double corrosion control. At the anode, this is provided by the action of an azole inhibitor (1,2,3-benzotriazole or tolyltriazole — specific corrosion inhibitors for Cu, Al, Zn and their alloys) and at the cathode, it is provided by the action of a phosphonate — hydroxyethanediphosphonic acid, where the phosphonate part of the inhibitor, in addition to acting as a cathodic corrosion inhibitor, also has a strong chelating component that ensures the stability of Ca + Mg at high temperatures (200—250 °C), long retention times (100 hours) and high pH values (pH — 10.5—11), where the phosphonate under the given conditions is quite stable.

This provides the possibility of higher thickening and also helps to remove iron oxides from the cooling system, together with an anionic dispersant (sodium, ammonium or sodium ammonium salt of an acrylate polymer or copolymer).

The composition provides scale control, allowing the cooling water treatment system to operate in neutral and alkaline ranges while providing selective scale control of calcium carbonate (by modifying the crystal lattice structure).

It is not affected by chlorine or process impurities such as hydrogen sulfide or hydrocarbons.

The composition has self-passivating properties without the need for hardening ions. It can also be used in systems where calcium concentrations are insufficient for proper phosphate film formation.

The above-mentioned method of operation using the above-mentioned composition at higher concentrations ensures a relatively large reduction in costs for chemical treatment of circulating cooling waters, saving of additional water and saving of energy necessary for pumping the water heat exchange medium and for its cooling.

The invention and its effectiveness are explained in more detail by means of the description in the given examples of embodiments.

Example 1

Repair using a composition in the amount of 50 mg.l- ¹ of cooling water with a composition of 8% by weight of hydroxyethanediphosphonic acid, 0.5% by weight of benzotriazole, 15% by weight of sodium ammonium salt of acrylate-acrylonitrile copolymer, 3% by weight of N,N-dimethylformamide, 6% by weight of sodium hydroxide and the rest of the aqueous condensate, reduced steel corrosion by 97.5% and the formation of deposits arising from impurities, calcium and magnesium salts by 98.2%.

The composition obtained according to the recipe in Example 1 is a clear, yellowish to light brown liquid with a pronounced corrosion inhibitory effect and good stabilization of Ca + Mg in water. It does not contain phosphates or heavy metals. Its effectiveness in comparison with foreign equivalents is shown in Table 1.

Table 1

Corrosion inhibition and Ca stabilization values

Mg

Composition applied conc. (mg.l- ¹ )

Corrosion rate of steel without additives with additives

compositions (gm- ² . ti ^-1 ) inhibitory deposits efficiency (%) (gm-^.h-') compositions (gm- ² .!!- ¹ )

Kurizet S 113K 50 0.383 0.028 90.0 0.044 Drewgard 187+ 50 0.390 0.080 79.0 0.101 Butrol 305 50 0.335 0.037 94.8 0.025 Composition according to example 1 50 0.439 0.011 97.5 0.013

The invention is intended for use in steel systems in general and also in steel systems containing Cu, Al and Zn alloys in heat exchange environments in the chemical, food, pharmaceutical, metallurgical industries, but mainly in energy engineering.

Claims (1)

2S9294 is described by way of example in the foregoing Examples. Example 1 Correction using a composition at 50 mg. i-1 cooling water of 8% by weight. of hydroxyethane diphosphonic acid, 0.5p. wt. % benztriazole, 15 wt. % sodium ammonium salt of acrylate-acrylonitrile copolymer, 3 wt. Ν, Ν-dimethylformamide, 6 washes. wt. sodium hydroxide · and condensate water, reduced the corrosion of the steel by 97.5p. and the formation of 98.2% non-impurity, calcium and magnesium salts. The composition obtained according to the formulation of Example 1 is a clear, yellowish to light-brown liquid with a marked corrosion-inhibiting activity and good stabilizing Ca + Mg water. It does not contain phosphates or heavy metals. Its efficiency compared to foreign ones. equivalents are shown in Table 1. Table 1 Ca Mg inhibition and stabilization values Appl. (mg. I'1) Corrosion rate of steel without addition of composition (gm-2.h 1) inhibition deposits effective (%) (gm-2. 1) Kurizet S 113K 50 0.383 0.028 90.0 0.044 Drewgard 187+ 50 0.390 0.080 79.0 0.101 Butrol 305 50 0.335 0.037 94.8 0.025 Composition according to Example 1 50 0.439 0.011 97.5 0.013 in general, as well as in steel containing Cu, Al and Zn alloys in heat exchange environments in chemical, food, pharmaceutical, metallurgical, but mainly epergetics. water, characterized in that it comprises from 1 to 20% by weight of hydroxyethanediphosphonic acid, from 0.1 to 5% by weight of 1,2,3-benztriazole, or from tolyltriazole, from 1 to 15% by weight of aqueous sodium ammonium solution; the sodium ammonium salt of an acrylate polymer, or an acrylate copolymer, 1 to 10% by weight of N, N-dimethylformamide, 1 % to 10% by weight of sodium hydroxide and potassium hydroxide and from 40 to 80% by weight; water.