CS199171B1 - Corrosion inhibitor especially of steel - Google Patents

Description

The invention relates to a corrosion inhibitor of metals, in particular steel, which is effective in a neutral and weak alkaline or weakly acidic environment.

Inhibitors occupy an important place in the set of agents used to prevent corrosion of metals exposed to the atmosphere, water and industrial liquid and gaseous environments.

dím. However, from a wide range of metal inhibitors for a wide variety of environments, there is not yet enough choice for neutral and weakly acidic and weakly alkaline environments. It is known that salts, in particular calcium, lead and strontium, azelaic, suberepelargonic acids act as inhibitors of steel corrosion, especially in a neutral and weakly acidic environment. These salts cannot be prepared from pure acids due to their high cost. However, it is possible to prepare a mixture of these acids by oxidative cleavage of natural and synthetic double-bonded substances and from this mixture further calcium, lead, strontium or other salts which inhibit steel corrosion.

These prior art inhibitors are improved by the corrosion inhibitor of metals, in particular steel, according to the invention. It is based on the fact that it is a salt of the product obtained by reacting unsaturated organic acids with nitric acid at a concentration above 55% by weight, at a temperature of 50 ° C. Suitably, the unsaturated organic acid is composed of an acid having 16 to 20 carbon atoms and 1 and 3 double bonds per molecule, e.g. oleic acid. The inhibitor is preferably a salt formed by the reaction of said product with oxide

19? 171 alkaline earth metal, e.g. calcium salt, or a salt formed by reacting said product with a soluble salt of an organic or inorganic acid, such as lead acetate.

If it is used for the oxidation of unsaturated organic acids, such as oleic acid, nitric acid, then the mixture obtained contains, in addition to the substances and azelaic and pelargonic acids, also a non-definable mixture of substances with nitrogen nitro compounds. By converting this mixture into the form of calcium, lead, strontium, ammonium, or ammonium. with other salts, a product is obtained which acts on metals, especially steel, as an effective corrosion inhibitor. Thus, the effect of known inhibitors of this kind is further enhanced. . <

. 'V' ''

The invention and its effects are described in more detail below by way of examples.

Example 1

100 wt.% Was charged to a reactor equipped with a stirrer with heating and cooling. parts, oleic acid. While stirring, 180 wt. parts of concentrated nitric acid at a bath temperature of 85 ° C for 30 min. Then, the reaction mixture was stirred for another 4 hours at 90 ° C. After cooling, 300 wt. parts of water. The reaction product was dissolved in 80 wt. parts of ammonia and .150 wt. parts of water. A suspension of 24 wt. parts of calcium oxide in 50 wt. parts of water. After stirring for 3 hours, the precipitate was aspirated through a frit and dried at 60 ° C. 110 wt. parts of calcium salts. Product nitrogen 3.91%, water solubility 600 mg / l,

Inhibitory activity of the following calcium salts:

Environment Inhibitor concentration in mg / l Corrosion loss of steel in g / cnr.day water i 0, 909.1 O ” ⁷ saturated solution 600 5,8.10 “ ⁷ 5x ripens. solution ’120 o.io ' ⁷ 10x ripens. solution 60 χ 572.10 ^-7

Saturated inhibitor solution, i.e. at a concentration of 600 mg / L, reduces the corrosion rate of steel 156 times. At 120 mg / l, the corrosion rate of steel is 91 times lower than in water.

Example 2 '\.

The reaction / oleic acid with nitric acid was carried out analogously to Example 1. The reaction product was dissolved in 80 wt. parts of ammonia and 200 wt. 100 parts by weight of water and 100 wt. - dissolved in 200% by weight of lead acetate; parts of water. The precipitate was aspirated through a frit and dried at room temperature. 131 wt. parts of lead salt. The solubility of this salt in water is 131 mg / L.

Inhibitory activity of lead salt:

Environment Inhibitor concentration in mg / l Corrosion loss of steel in g / cm .day water 0 909.10 ' ⁷ saturated solution 131 0 Dilute 5 times 26 0 10 times diluted solution. 13 577.10 ” ⁷

Saturated a. 5-fold diluted inhibitor solution, ie at 131 and 26 mg / l, completely suppresses steel corrosion and at 13 mg / l reduces corrosion rate by 1.5 times.

Claims (4)

SUBJECT OF THE INVENTION Corrosion inhibitor of metals, in particular steel, characterized in that it is a salt of the product obtained by reacting unsaturated organic acids with nitric acid having a concentration above 55% by weight. above 50 ° C, 2. The corrosion inhibitor of claim 1, wherein the unsaturated organic acid is an acid having from 16 to 20 carbon atoms per molecule and from 1 to 3 double bonds, such as oleic acid. 3. The corrosion inhibitor of claim 1, wherein said corrosion inhibitor is a salt obtained by reacting said product with an alkaline earth metal oxide, such as calcium oxide. '· 4. The corrosion inhibitor of claim 1, wherein said inhibitor is a salt obtained by reacting said product with a soluble salt of an organic or inorganic acid such as lead acetate.