CS242438B1 - Mixed Metal Corrosion Inhibitor for Closed Circulatory Systems - Google Patents

Abstract

The device solves the composition of a metal corrosion inhibitor suitable for the protection of metal components of water temperature circuits with air access. It is intended mainly for spring water with a reduced salt content as a medium. It has a high inhibitory effect even at the water-steam interface and in the steam space of heat exchange systems. It contains phosphate and hydrogen phosphate ions, nitrite, silicate and a complexing or sequestering agent for calcium ions in defined concentrations.

Description

(54)

BARTONlCEK ROBERT ing.CSc. * GERMAN JITKA ing. CSc., PRAGUE

Mixed metal corrosion inhibitor for closed • circulatory systems

The device solves the composition of metal corrosion inhibitor suitable for protection of metal parts of water tempering circuits with access of air. It is intended especially spring water with reduced salt content as a medium. It has a high inhibitory effect on the water-steam interface and in the steam space of heat exchange systems. It contains phosphate and hydrogen phosphate ions, nitrite, silicate and a complexing or sequestering agent of calcium ions at specified concentrations.

242 438

- 4,242,438

The invention relates to a mixed metal corrosion inhibitor pjfo closed water circulation systems of air, operating in the temperature range from 5 to 250 ^c C, intended for the control of corrosion of metals, which are constructed from a water tempering systems. These are in particular steel, cast iron, copper, aluminum, zinc and their alloys, which are subject to corrosion in the environment of the tempering aqueous medium, the intensity and form of which depend in particular on the composition of the aquatic environment, its flow, temperature, connection with other material and system design. Corrosion causes the system to leak, reducing component strength, thereby shortening component life and operational reliability. The resulting deposits worsen the heat transfer coefficients of the heat exchange surface and increase the hydraulic resistance.

Various simple and mixed corrosion inhibitors are known and used to reduce the corrosion effect of the circulatory system's tempering environment - water, possibly softened, demineralized, distilled or with the addition of antifreeze. Among the one-component inhibitors, for example, chromates, nitrites, phosphates, silicates, borates, benzoates of various, especially alkali metals, ethanolamines, benztriazole, mercaptobenztriazole and other substances are known. These substances are also combined in different ways. These known inhibitors have some drawbacks, in particular they are not equally effective on all metals in multi-metal systems, do not have sufficient slip corrosion inhibitory activity, are unable to reduce corrosion in the vapor space of the system, and favor the deposition of calcium carbonate layers from aqueous solutions .

242 438

The known corrosion inhibitors are improved by a mixed metal corrosion inhibitor for closed water circulating systems with air access, operating in the temperature range from 5 to 250 ° C, according to the invention, characterized in that it contains from 10 to 35% by weight. % of phosphate ions in the form of a tertiary salt of an alkali metal phosphoric acid, a C 2 -C 8 alkylamine or a C 2 -C 6 alkanolamine, for example trisodium phosphate, triisopropylamine phosphate or triethanolamine phosphate, from 1 to 15 wt. % of hydrogen phosphate ions in the form of a secondary salt of phosphoric acid with an alkali metal, an alkylamine having 2 to 8 carbon atoms in the chain, for example disodium hydrogen phosphate, diisobutylamine hydrogen phosphate or diethanolamine hydrogen phosphate, from 15 to 40 wt. % of nitrite ions, for example in the form of sodium or potassium nitrite, from 1 to 25 wt. % of silicate ions in the form of an alkali metal salt of silicic acid, for example sodium metasilicate, and from 0.2 to 10 wt. a calcium ion complexing or sequestering agent, for example sodium diamine tetraacetic acid. The pH of the inhibitor solution should be between 9 and 12.

The mixed corrosion inhibitor according to the invention has a high efficiency, in particular in low salt water, with a reduced content of calcium and magnesium ions. Particularly important is its corrosion-inhibiting effect on the water-vapor interface and in the steam space, while limiting the formation of insoluble calcium carbonate layers in calcium-containing waters. Its main area of application is water tempering circuits in the rubber and plastics industries, where the equipment is first heated and cooled in the next phase by the water circuit. It can also be used in other areas, for example in the cooling circuits of motor vehicles.

The inhibitor is dosed in water or aqueous solutions in an amount of 0.5 to 10 g / ^l , as a powder or concentrated

- 3,242,438 aqueous solution. The pH of the conditioned medium is 9.0 to 12.0 and is checked in a conventional manner. The inhibitor content in the environment is controlled by the phosphate ion content.

The invention, its applications and effects are explained in more detail in the following examples of a possible specific embodiment thereof.

Example 1

900 g of inhibitor mixture containing 34 wt.% Was added to a cooling water circuit with reduced calcium and magnesium ions with a volume of 1000 liters, at temperatures ranging from 30 to 40 ° C. % trisodium phosphate, 9.5 wt. % diethanolamine hydrogen phosphate, 44 wt. % potassium nitrite, 9 wt. % sodium metasilicate and 3.5 wt. sodium diamine tetraacetic acid. After stirring, the pH of the aqueous solution was 11.0. The inhibitory corrosion efficiency of the mixture was 98% for steel, 95% for cast iron, 100% for chromium stainless steel and 95% for aluminum.

Example 2

A 1250 g mixed inhibitor was added to a model heating circuit, at temperatures of 150-180 ° C, filled with demineralized water of 500 L. The inhibitor mixture contained 44.3 wt. % triisopropylaminophosphate, 11.2 wt. % dicalcium phosphate, 32 wt. % sodium nitrite, 0.5 wt. % sodium diamintetraacetic acid and 12 wt. sodium metasilicate. The stirred water had a pH of 9.1. Inhibitory corrosion efficiency was 95% for steel, IDO% for stainless steel and Ms77Al 96 for brass

Example 3

To a 100-liter laboratory temperature circuit filled with water with reduced calcium and magnesium content

242 438 ions and with a chloride ion content of 35 mg / l were added 150 g of a mixed inhibitor of 34 wt. % trisodium phosphate, 8 wt. disodium hydrogen phosphate, 30 wt.% sodium nitrite, 15 wt. % sodium metasilicate and 3 wt. sodium diamine tetraacetic acid. In a solution having a pH of 9.8 and a temperature ranging from 30 to 160 ° C, inhibitory efficacy was achieved for steel 96%, cast iron 97%, silumin 95%, copper 96% and brass Ms63 98%.

The invention is intended to provide corrosion protection and the required service life and operational reliability in closed circulating temperature circuits, cooling or heating circuits, the components of which are made of various metallic materials. In particular, it can be used for tempering circuits in the chemical, rubber, plastics and food industries, as well as in refrigeration (motor vehicle circles and wherever water is used as a heat-medium).

Claims (1)

SUBJECT OF THE INVENTION 242 438 Mixed metal corrosion inhibitor for closed air circulating systems with air access, operating in the temperature range from 5 to 250 ° C, characterized in that it contains from 10 to 35% by weight. % of phosphate ions in the form of a tertiary salt of phosphoric acid with an alkali metal, C 2 -C 8 alkylamine in the chain or an alkanolamine of 2 to 6 carbon atoms in the chain, for example trisodium phosphate, triisopropylamine phosphate or triethanolamine phosphate; % of hydrogen phosphate ions in the form of a secondary salt of phosphoric acid with an alkali metal, an alkylamine of 2 to 8 carbon atoms in the chain, for example disodium hydrogen phosphate, diisobutylamine hydrogen phosphate or diethanolamine hydrogen phosphate, from 15 to 40 wt. % of nitrite ions, for example in the form of sodium or potassium nitrite, from 1 to 25 wt. % of silicate ions in the form of an alkali metal salt of silicic acid, for example sodium metasilicate, and from 0.2 to 10 wt. a calcium ion complexing or sequestering agent, for example sodium diamintetraacetic acid.