CS244376B1 - Compound metal corrosion inhibitor for closed aqueous and aqueous alcoholic systems, in particular aluminum and aluminum alloy parts - Google Patents

Abstract

The solution belongs to the field of metal corrosion protection and solves the problem of reducing corrosion of metal, especially aluminum parts of closed water and water-alcoholic heat exchange systems. It achieves this by formulating a mixed corrosion inhibitor, which contains in defined proportions benzoates, borates, nitrites, phosphates and alkali metal silicates in a mixture of β 1, 2, 3 benzotriazole and ζ-caprolactam.

Description

The present invention relates to a mixed metal corrosion inhibitor for a

closed water and aqueous alcoholic systems, in particular parts of aluminum and its alloys. It is intended for protection of cooling and heating systems with circulating water or aqueous alcoholic solution, for example cooling and heating circuits of motor vehicles. Their parts are made of various metals which are subject to corrosion in the presence of a cooling or heating aqueous medium. The type and degree of corrosion attack depends on the composition of the heat transfer medium, temperature and flow rate. In particular, aluminum and its alloys are subject to intense corrosion at higher flow rates, in particular above 0.5 m.s. Distilled water and condensate also have a corrosive effect. To reduce the risk of corrosion, corrosion inhibitors - corrosion inhibitors - are added to the heat transfer medium.

Chromates, nitrites, phosphates, silicates, borates, benzoates, monoethanolamine, triethanolamine, mercaptobenzotriazole, benztriazole and other compounds, either alone or in various mixtures, are known and used as corrosion inhibitors in aqueous solutions. However, the known inhibitors are poorly effective against corrosion, especially in aluminum, at higher flow rates.

It has now been found that this drawback largely removes the mixed metal corrosion inhibitor for closed water and aqueous alcoholic systems, particularly with aluminum and aluminum alloy parts according to the invention. Its essence is that it contains from 10 to 30 wt. % alkali metal benzoate, for example sodium benzoate, from 10 to 30 wt. % alkali borate

2,244,376 metal, for example potassium tetraborate, from 5 to 15 wt. % alkali metal nitrite, for example sodium nitrite, from 20 to 50 wt. an alkali metal phosphate, for example potassium phosphate, of from 1 to 15 wt. % alkali metal silicate, for example potassium metasilicate, from 0.1 to 5 wt. % Of 1,2,3 benzotriazole and from 0.001 to 0.5 wt. % < -caprolactam.

The inhibitor is dosed in an aqueous or aqueous alcoholic medium of cooling systems in an amount of 0.10 to 20 g per liter, the pH of the treated medium being 7.5 to 9.

The mixed corrosion inhibitor according to the invention is distinguished in particular by an increased efficiency at flow rates of an aqueous medium above 0.5 m.s.

The invention and its effects are described in more detail below by way of examples of a possible specific embodiment thereof.

Example 1

1000 liters of demineralized water are introduced into the storage tank and 6510 g of mixed inhibitor containing 1000 g of sodium benzoate, i.e. 25.7 wt. %, 1900 g sodium tetraborate · 10 HgO, ie 25.7 wt. %, 500 g of sodium nitrite, i.e. 12.8 wt. %, 2500 g disodium phosphate · 12

H _0, i.e. 25.7 wt. % as anhydrous, 10 g of ε-caprolactam, i.

^d i

0.26 wt. %, 100 g of 1,2,3-benzotriazole, i.e. 2.4 wt. % and 500 g of sodium metasilicate. 5 H 2 O, i.e. 7.39 wt. %.

After mixing and dissolution of all components, the pH of the aqueous solution is adjusted to 8-8.5 with 85% phosphoric acid.

The potency of the mixed corrosion inhibitor of Example 1 was evaluated on a circulating test apparatus at a water flow rate of 1.5 m / s and a temperature of 70 ° C. Compared to untreated water and water treated with the inhibitor of the invention, the following aluminum corrosion rates g / m @ 2 d were found after a 14-day test:

3 244 376 condensate corrosion rate of aluminum without treatment 0.653 with treatment according to example 1 0.004

Corrosion inhibition against other tested metallic materials - steel, cast iron, brass - was 97-99%.

Example 2

In a storage tank containing 2000 liters of demineralised water and ethanol in a ratio of 1: 1, 30 kg of a mixed inhibitor containing 3 kg of potassium benzoate are dissolved with stirring. ie 10 wt. %, 3 kg of potassium tetraborate, i.e. 10 wt. %

4.5 kg of potassium nitrite, i.e. 15 wt. %, 4.5 kg of potassium metasilicate, i.e. 15 wt. %, 1.5 kg of 1,2,3-benzotriazole, i.e. 5 wt. %, 0.15 kg of N-caprolactam, i.e. 0.5 wt. % and 13.35 kg of tricalcium phosphate, i.e. 44.5 wt. %.

After dissolution of the components, the pH is adjusted to 8.3 with 85% phosphoric acid. The potency of the mixed corrosion inhibitor of Example 2 was evaluated on the circulatory apparatus at a flow rate of 1.5 m / s. While on the circulation apparatus in water without inhibitor, the corrosion rate of aluminum reached 0.653 o g / md, in water with the mixed inhibitor according to the invention was

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corrosion rate of aluminum only 0.006 g / m .d. The potency of this mixed inhibitor against the other metallic materials tested was 98%.

The invention is intended to provide corrosion protection and the necessary service life of closed cooling and heating systems, the parts of which are made of various metals, in particular aluminum and its alloys. In particular, it can be used for cooling circuits of motor vehicles, locomotives, diesel engines, occasionally used heating systems of residential buildings and primary circuits of solar systems where water ✓ or an aqueous alcohol solution is used as a cooling medium.

Claims (1)

SUBJECT OF THE INVENTION 244 376 Mixed metal corrosion inhibitor for closed water and aqueous alcoholic systems, in particular with parts of aluminum and its alloys, characterized in that it contains from 10 to 30 wt. % alkali metal benzoate, for example sodium benzoate, from 10 to 30 wt. % alkali metal borate, for example potassium tetraborate, from 5 to 15 wt. % of an alkali metal nitrite, for example sodium nitrite, from 20 to 50 wt. % alkali metal phosphate, for example potassium phosphate, from 1 to 15 wt. % of an alkali metal silicate, for example potassium metasilicate, from 0.1 to 5 wt. % Of 1,2,3-benzotriazole and from 0.001 to 0.5 wt. % £ -caprolactam.