CS227447B1 - Agent with dispersion-sequestrative and corrosion-inhibitive effects - Google Patents

Description

The invention relates to a dispersant composition sekvestračníin and inhibit corrosion effects intended for the cooling ^of me dia, pH 6.5 α »9th

Aqueous coolants cause corrosion of metallic materials in metal heat exchangers, the components of which are made, for example, of steel, brass and aluminum. Chlorides, sulphates, deposits of biomass and its metabolic products and undissolved particles contained in cooling water accelerate the corrosion process, while uniform corrosion is often accompanied by uneven corrosion, such as pitting, which leads to perforation of the metal tube of the exchanger.

Deposits on the metal surface are not only corrosive, but also cause a deterioration in heat transfer, especially in power systems, so that their presence in the aqueous medium and their deposition on the metal surface is undesirable.

Cooling waters with a pH of 6.5 and 9 are so far treated by means of a dispersing sequestering agent, i.e., agents preventing the deposition of insoluble substances such as calcium salts and their settling. As dispersing sequestering agents, for example, organosulfonic acids and their salts, polyacrylates, cellulose and its derivatives and lignins are known. Cooling waters are treated with corrosion inhibitors such as zinc chromates to reduce corrosion

227 447 salts, molybdates, silicates, aromatic triazoles, salts of aromatic thiazoles with amino alcohols and ferrous sulphate. Compositions with inhibitory corrosion properties, however, do not limit the deposition and deposition of particles on the metal surface, and conversely, the compositions with sequestering and dispersing effect do not inhibit, but instead stimulate metal corrosion. A corrosion inhibitor of metals, in particular steel, copper and its alloys, is known which also has a sequestering and dispersing effect which contains, in particular, a major component of the mercaptobenzothiazole salt with alkanolamines or alkali metals, phosphoric acid salts with alkanolamines and surfactants. This product is intended in particular to protect steel and brass components in cooling systems with an aqueous cooling medium.

However, it does not have sufficient efficiency for aluminum cooling components.

The drawbacks of the prior art in this field are largely overcome by the dispersing sequestering and corrosion inhibiting composition according to the invention, which comprises from 20 to 50 wt. % of phosphoric acid or its alkali metal salts, for example dinatrihydrogen phosphate, from 20 to 50 wt. % C3-C8 organic hydroxides or their alkali metal salts, e.g. citric acid, from 5 to 30 wt. % of C6 - C24 carboxylic acid alkanolamides, e.g. lauric monoethanolamide, and from 5 to 30 wt. % surfactants. Surfactants which may be used are, for example, a copolymer of ethylene oxide with propylene oxide, alkylaryl polyglylcol ether phosphates and alkyl polyglycol ethers and mixtures thereof.

On the one hand, the composition according to the invention has a sequestering effect, i.e. it limits the excretion of water-insoluble compounds due to the strong cation binding to the soluble complexes. The undesirable sedimentation of other solid impurities on the metal surface is hampered by the dispersing ability of the composition.

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Due to the dispersing sequestering effect of the composition, its inhibitory corrosion effect can also be applied to the entire metal surface and thus prevent both uniform and uneven corrosion of the metals. By the action of reactive phosphate, hydroxyl and amide groups, a synergistic effect is achieved which is higher than the sum of the effect of the individuals.

A composition with a dispersing sequestering and inhibitory activity _in 3 spirits effect is dosed in a concentration of 5 c & 100 g / m of aqueous medium of μΗ - 6, δ.Λ ^ν 9.

The invention and its effects are explained in more detail by way of a description of the following examples.

Example 1

15 kg of phosphoric acid, 15 kg of citric acid, 10 kg of coconut fat diethanolamides and 10 kg of lauryl polyglycol ether phosphate were dosed into 1000 µl of cooling water at pH = 7.2, which flows in a system comprising steel of class 11 and aluminum. Deposit formation was reduced by 71%, steel corrosion decreased by 92% and aluminum corrosion by 35%.

Example 2

8 kg of disodium hydrogen phosphate, 8 kg of tartaric acid, 1 kg of oleic acid monoethanolamide and 3 kg of ethylene oxide-propylene oxide copolymer in a ratio of 1: 1 were dosed into 2000 cooling water of pH = 6.9 flowing in a system containing Cu70Zn29Al type brass and aluminum. . Brass corrosion decreased by 91% and deposit formation from undissolved salts decreased by 80%, aluminum corrosion decreased by 86 5to ·.

Example 3 227 447

4 Kg of phosphoric acid, 4 kg of sodium gluconate, 6 Kg of stearic acid monoethanolamide and 6 kg of nonylphenol polyglycol-L-phosphate were metered into 4000 m of cooling water at pH -7.9, which flowed through a system comprising class 11 structural steel and brass type Gu 77Zn21A12. Steel corrosion decreased by 39%, brass corrosion by 95% and deposit formation decreased by 9G%.

Example 4

45 kg of trisodium phosphate, 20 kg of gallic acid, 10 kg of palmitic acid aethanolamide and 25 kg of octyl polyglycol ether were dosed into 10C0 m of cooling water at pH = 8.9 flowing in a system comprising structural steel class 11 equipment. The corrosion of the steel was reduced by 98% and the formation of calcium salt deposits was reduced by 33%.

Example 5

100 kg of phosphoric acid, 40 kg of sodium citrate, 20 kg of tall oil diethylamides, 20 kg of copolymer were dosed into 5000 m of cooling water at pH = 7.8 flowing in a system comprising class 11 structural steel equipment and brass type Cu77Zn2lA12As. ethylene oxide with propylene oxide in a ratio of 1: 2 and 20 kg of nonylphenol polyglycol ether phosphate. Steel corrosion was reduced by 91%, brass corrosion by 94% and deposits of predominantly calcium salts decreased by 89%.

The dispersing sequestering and inhibitory corrosion effects of the ingredients in the process equipment were determined using control samples located at various locations in the cooling systems. The dispersing effect was determined by determining the amount of deposits on the surface of the metal specimens, the sequestering effect by detecting the possibility of using increased water concentration and inhibiting corrosion

227 447 effect gravimetrically and electrochemically by determining the corrosion rate of control metal samples.

The invention is intended for cooling systems in the power, chemical, metallurgical and food industries where water is used as a cooling medium.

Claims (1)

SUBJECT OF THE INVENTION 227 447 Composition with sequestering and dispersing effect _of inhibiting corrosion, characterized in that it comprises from 20 to 50 wt. % of phosphoric acid or its alkali metal salts, for example disodium hydrogen phosphate, from 20 to 50 wt. % of C 3 -C 8 organic hydroxides or their alkali metal salts, for example citric acid or sodium citrate, from 5 to 30 wt. C6 -C24 alkanolamides of carboxylic acids, for example lauric monoethanolamide, and from 5 to 30 wt. % surfactants, for example ethylene oxide-propylene oxide copolymer.