RU2588615C1 - Inhibitor for corrosion protection of reaction equipment - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to protection from corrosion of equipment made from stainless steel and iron-chromium-nickel alloys. Disclosed is a inhibitor which contains a phosphorus-containing acid and ions of metals of VI and X groups of periodic table of elements. Weight ratio of metal ions of VI group to ions of metals of X group and phosphorus-containing acid in inhibitor is equal to (0.01-0.5):(0.003-0.04):1, respectively.

EFFECT: invention provides reduced corrosion of stainless steel and iron-chromium-nickel alloys in aqueous media at high temperatures.

3 cl, 1 tbl

Description

The invention relates to the field of protection against corrosion of metals in aqueous media and can be used, in particular, to protect equipment from stainless steels and iron-chromium-nickel alloys from phosphoric acid corrosion.

A known inhibitor of metal corrosion in acidic environments is a BA-6 inhibitor. The BA-6 inhibitor is a product of the condensation of benzylamine with urotropine [Altsybeeva A.I., Levin S.Z. Metal corrosion inhibitors. - L .: Chemistry, 1968, p. 29].

The disadvantage of this inhibitor is the lack of protective effect for high alloy steels, as well as an insufficient degree of protection at elevated temperatures.

Known inhibitor for the protection of steel in acidic environments, which is hexamethylenetetramine (HMTA) [Altsybeeva A.I., Levin S.Z. Metal corrosion inhibitors. - L .: Chemistry, 1968, p. 28].

The disadvantages of this inhibitor are a weak protective effect at elevated temperatures for stainless steels, a high protective concentration. In addition, HMTA reduces the catalytic activity of acids (when using the latter as catalysts) due to their neutralization, which leads to the formation of formaldehyde, which is toxic.

Known metal corrosion inhibitor in environments containing phosphoric acid, including hexamethylene tetraamine and hydroxyethylidene diphosphonic acid with a molar ratio of hexamethylenetetramine and hydroxyethylidene diphosphonic acid equal to (1-30): (1-3) [RU 2094531, published 10.27.1997].

The disadvantages of this acid corrosion inhibitor is a weak protective effect at elevated temperatures for high alloy steels, and the reverse effect of increased corrosion due to inaccurate dosage is also possible. Also, at temperatures above 110-130 ° C and low speeds of circulation water, favorable conditions are created for the chemical destruction of the inhibitor, which leads to a sharp decrease in its effectiveness and, as a consequence, to an increase in corrosion.

Known corrosion inhibitor for carbon steels in acidic and neutral oxygen-containing aqueous solutions with a content in its composition, parts by weight: ammonia 0.50-1.00, morpholine 5.00-20.00, low boiling amines, including N- ethylmorpholine 1.50-54.50, high-boiling amines, including 2,2'-β- (di) N-morpholino-diethyl ether 5.00-15.00, ethylene glycol 1.00-3.00, diethylene glycol 30 , 00-60.00, cobalt sulfate 3.00-6.00, salt, including a metal anion of variable valency 15.00-5.00 and antioxidant 6.00-30.00 with a certain ratio of components [RU 2097445, published 27.11 .1997].

The disadvantage of this acid corrosion inhibitor is a weak protective effect for stainless alloys during phosphoric acid corrosion.

Known corrosion inhibitor for protecting equipment from nitric acid corrosion, which contains, by weight. %: aliphatic nitrogen-containing compound 10-80, thiourea 80-10, copper (II) salt 0.1-10 [RU 2259423, published on 27.08.2005].

The disadvantage of this inhibitor is the low protective effect against phosphoric acid corrosion at elevated temperatures.

The closest analogue is a corrosion inhibitor - phosphoric acid. Phosphoric acid is used as an inhibitor in formic acid for austenitic and carbon ferritic stainless steels at a concentration of 0.001-3% [Altsybeeva AI, Levin S.Z. Metal corrosion inhibitors. - L .: Chemistry, 1968, p. 81-82].

The disadvantage of this inhibitor is the lack of a protective effect against phosphoric acid corrosion at elevated temperatures.

The technical result of the invention is to increase the protective effect of a corrosion inhibitor for stainless steels and iron-chromium-nickel alloys in aqueous media containing phosphoric acid at elevated temperatures, reducing the corrosion rate of equipment.

The technical result is achieved by using an inhibitor for corrosion protection of reaction equipment made of stainless steel and alloys based on an aqueous acid solution, while the inhibitor contains metal ions of the VI and X groups of the Periodic Table of the Periodic Table of Elements of the metal ions of the VI group metals: metal ions of the X group: acid equal to (0.01-0.5) :( 0.003-0.04): 1, respectively.

Preferably, phosphorus-containing acid, or mixtures of phosphorus-containing acids, for example, ortho-, pyro-, meta-, polyphosphoric acids, or hydroxyethylidene diphosphonic acid are used as the acid in the inhibitor.

As metal ions of group VI and X of the Periodic Table of the Elements, the inhibitor contains chromium and nickel ions. Preferably, the inhibitor contains chromium and nickel cations.

The high protective effect of the proposed inhibitor for stainless steels and alloys in acidic environments at elevated temperatures is based on a synergistic effect.

Separately, the components of the claimed inhibitor do not adequately protect stainless steels in acidic environments at elevated temperatures. A high degree of protection is achieved by sharing the components at the stated concentrations.

The use of the claimed inhibitor composition allows to increase the protective effect for stainless steels and iron-chromium-nickel alloys in environments containing inorganic acid at elevated temperatures.

The anticorrosive effectiveness of the inhibitor was determined according to GOST R 9.905-2007.

For the implementation of the claimed invention, the compositions of the corrosion inhibitor of stainless metals were prepared, differing from each other in the content of components. The inhibitor compositions are shown in the table.

Inhibitors with formulations 1-9 are tested in the laboratory. For testing take alloy Incoloy 825 (sample). Tests are carried out in accordance with GOST 9.908-85. The essence of the method is to determine the linear rate of metal corrosion. The test time is not less than 100 hours, temperature 165 ° C. The tests are carried out in an air thermostat with the ability to maintain temperature with an accuracy of 0.1 ° C. A sample is placed in a glass ampoule with the prepared composition. As a corrosive medium, a 7% aqueous solution of phosphoric acid with a pH of 1.15 was used with the addition of an inhibitor with a dosage of 25 g / l. The ampoule is sealed to eliminate environmental influences and placed in a thermostat in a protective casing. Before testing, each sample undergoes processing to give it a flat shape; cracks and irregularities are removed (GOST 9.905-82). Before testing, each sample is weighed with an accuracy of 0.0001 g; geometric dimensions are determined with an accuracy of 0.02 mm. After testing, the samples are removed from the ampoules, they are inspected. If corrosion products are present on the surface of the samples, they are removed in accordance with GOST R 9.907-2007. Samples are wiped with an organic solvent (acetone, ethanol) and placed in a desiccator over calcium chloride for 24 hours. Then the samples are reweighed. Processing of the results is carried out in accordance with GOST 9.908-85.

The test results are presented in the table.

From the data given in the table, it is seen that the proposed inhibitor during testing shows high efficiency in corrosion protection of stainless steels. In the case of using the substances included in the inhibitor, the protective effect is not sufficient to protect stainless steels individually.

Claims (3)

1. An inhibitor for corrosion protection of reaction equipment made of stainless steel and Fe-Cr-Ni alloys, characterized in that it contains an aqueous solution of phosphoric acid and metal ions of groups 6 and 10 of the Periodic system of elements D.I. Mendeleev at a mass ratio of metal ions of group 6: metal ions of group 10: phosphorus acid, equal to (0.01-0.5) :( 0.003-0.04): 1, respectively. 2. The inhibitor according to claim 1, characterized in that as a phosphorus-containing acid it contains an inorganic or organic acid or a mixture thereof. 3. The inhibitor according to claim 1, characterized in that, as metal ions of groups 6 and 10, it preferably contains chromium and nickel ions.