CS213153B1 - Corrosion inhibitor for waterborne heat transfer media - Google Patents

Abstract

The invention belongs to the field of corrosion protection and solves the anti-corrosion treatment of a heat exchange medium based on aqueous solutions of alkanolamines and amino acids, and their salts, intended especially for the operation of solar systems. The heat exchange medium is treated according to the invention so that 0.5 to 5 g of alkali metal silicates or alkaline earth metals, 0.05 to 0.5 S of 85% phosphoric acid or their salts with monovalent cations, 0.5 to 5 g of aromatic thiazoles are added to 1 kg of the medium. These components can be added to the medium individually or in the form of a preparation consisting of 50 to 50 wt. of alkali metal silicates or alkaline earth metals, 5 to 15 wt. % of 85% phosphoric acid or their salts with monovalent cations, 20 to 40 wt. aromatic acids or their salts and 0.5 to 5 g of aromatic thiazoles.

Description

The present invention relates to a corrosion inhibitor for water-borne heat transfer media. It is designed for water-dilutable media mainly based on alkanolamines and amino acids and their salts.

Heat transferring, eg solar systems, are commonly made of several kinds of metals, especially aluminum alloys and non-ferrous metals. These metals are degraded by corrosion due to the aggressiveness of the used heat transfer medium based on alkanolamines, amino acids and their salts. The corrosion rate of aluminum in this environment is in the order of tens of mm / year. These materials would be practically unusable for the production of heat-carrying parts of solar system equipment for the above-mentioned reasons.

Adverse aggressive action of heat transfer media based on alkanolamines and amino acids can be prevented by the addition of metal corrosion inhibitors, ie corrosion inhibitors. Known metal corrosion inhibitors for the environment and the alkaline reaction, such as thioureas, sulfonates, tartrates, tannins, boric acid, have a specific effect on individual metals; however, only parts made of a particular metal material are always protected, while parts of the device made of a different type of metal are not protected by this ihnibitor.

These drawbacks of the prior art are largely eliminated by the corrosion inhibitor for the water-borne heat transfer media of the invention, which comprises 30 to > 0% by weight. alkali metal and alkaline earth metal silicates, e.g. sodium silicate, 5 to 1% by weight of 8% by weight phosphoric acid or salts thereof with monovalent cations, e.g. aromatic acids or their salts, e.g. % sodium salicylate and 20 to 40 wt. aromatic thiazoles such as 2-mercapto-6-methylbenzothiazole.

The effect of the invention lies in the overall protection of solar systems against the aggressive action of the types of heat transfer medium used, which results in corrosion degradation of the metal components of these systems. In addition, the composition according to the invention is characterized by a synergistic anticorrosive effect.

The effects of the invention have been demonstrated by tests, the results of which are given in the exemplary embodiments of the invention.

Example 1

2 g of waterglass, 0.5 g of 85% phosphoric acid, 1 g of sodium benzoate and 1 g of 2-mercaptobenzothiazole were successively added to 1 kg of heat transfer medium of 250 g of trlethanolamine, 100 g of tetrasodium ethylenediaminetetraootic acid and 650 g of water. and the mixture was mixed. This treatment provided 100% copper corrosion inhibitory activity, 82% brass activity, 99.9% aluminum activity and 50% cast iron activity.

Example 2

The corrosion inhibitor was prepared by mechanical mixing and homogenization of 45 wt. sodium silicate, 22 wt. % sodium benzoate, 22 wt. 2-mercaptobenzothiazole and 12% sodium hydrogen phosphate. Tablets weighing from this mixture were made

4.5 g. In order to achieve satisfactory inhibitory activity, an additive of 10 tablets per 10 kg of heat-bearing medite was used.

Example 3

The corrosion inhibitor was prepared by mechanical mixing and homogenization of 30 wt. % of water glass, 20 wt. % salicylic acid, 15 wt. sodium hexametaphosphate and 35%

2-mercaptobenzothiazole. Tablets weighing 10 g were made from the mixture thus prepared. Five of these tablets added to 10 kg of heat carrier medium provided sufficient protection against the corrosion of the solar system.

The invention is applicable in all areas where heat transfer systems with aqueous alkanolamine and amino acid solutions and salts thereof are used.

Claims (2)

corrosion inhibitor for water-borne heat transfer media, characterized in that it contains 30 to 50 wt. % alkali metal and alkaline earth metal silicates, 5 to 15 wt. 85% by weight of phosphoric acid or its salts with monovalent cations, 20 to 40%. wt. % aromatic acids or their salts, e.g. sodium benzoate, and 20 to 40 wt. aromatic thiazoles, e.g. 2-mercaptobenzothiazole.