RU2230135C1 - Inhibitor for protecting building steel against corrosion-mechanical disru ption in hydrogen sulfide-containing mineralized medium - Google Patents

Abstract

FIELD: metallurgy, anticorrosive agents. SUBSTANCE: invention relates to the protection of metals against corrosion-mechanical disruption in hydrogen sulfide-containing mineralized media. Inhibitor comprises the following components, vol. %: complex 1,2,4-bis-triazolylmethane-ZnCl₂, 7-12; butanol, 40-50; water, the balance. Invention provides reducing price of an anticorrosive agent, enhancing its effectiveness and exposed assortment of inhibitors. EFFECT: valuable properties of inhibitor. 3 tbl

Description

The invention relates to the protection of metals from corrosion-mechanical destruction (CMR) in hydrogen sulfide-containing mineralized environments.

Among the closest inhibitors according to their purpose, it is known, for example, the use of the 5-methyl-5-acetyl-1,3-dioxane complex as an inhibitor of KMP of low alloy steels in hydrogen sulfide-containing media [RF patent No. 2082714 from 06.27.97].

The disadvantage of this inhibitor is the complexity of its production in comparison with the proposed inhibitor.

The claimed inhibitor is similar in composition (prototype) to a sulfide metal corrosion inhibitor, including, vol.%: A complex based on a nitrogen-containing compound of the formula 1,2,4-bistriazolylmethane-NiCl ₂ - 5-15; butanol - 45-60 and water - the rest is up to 100 [RF patent No. 2176686 dated 10.12.01]. This inhibitor is obtained under normal conditions by mixing the components in the specified ratio.

The disadvantages of the prototype are:

1) scarcity of raw materials;

2) insufficient protective ability in the NACE environment.

The objective of the invention is:

1) development of a highly effective CMR inhibitor of steel equipment for oil gathering systems and reservoir pressure maintenance;

2) reduction in the cost of corrosion inhibitors;

3) expanding the range of inhibitors.

The problem is solved in that the CMR inhibitor of structural steels in hydrogen sulfide-containing mineralized media, including a complex based on a nitrogen-containing compound, butanol and water, according to the invention as a nitrogen-containing complex contains a complex of 1,2,4-bistriazolylmethane-ZnCl _{2 of the} form

in the following ratio of components, about. %:

Complex 1,2,4-bistriazolylmethane-ZnCl ₂ 7-12

Butanol 40-50

Water Else

The proposed inhibitor is obtained under normal conditions by mixing the components of the specified ratio.

There are no data on the use of this solution for corrosion protection in the literature.

Determination of the inhibitory effectiveness of the compounds was carried out on samples of steel 20, widely used in the construction of gas and oil pipelines.

A NACE type test electrolyte (50 g / l NaCl, 5 g / l CH ₃ COOH, 3.4 g / l H ₂ S) was used as a model corrosion medium (CS).

The effectiveness of protection against general corrosion (OK) was evaluated according to polarization curves as follows [RD 39-141-96 “Inhibitors of corrosion and mechanical destruction of metals”, Ufa, 1996, hereinafter referred to as RD].

By extrapolating the tafel sections of the anodic and cathodic polarization curves to the value of the corrosion potential, we obtained the value of the corrosion current in CS. Comparing the course of the polarization curves in the inhibited and non-inhibited CS, the values of the corrosion current densities in the inhibited (i) and non-inhibited (i ₀ ) CS were obtained.

The degree of protection against OK was determined by the formula

The measurement data are shown in table 1.

Next, we tested steel 20 samples on an MP-5-8B tensile testing machine in air, in a NACE model medium, and in the same medium with an inhibitor added. A sealed cell was used to test the samples in the CS. The strain rate of the metal was 7.2 · 10 ^-8 m / s, which corresponds to the dynamics of the development of deformations in the metal of the existing oil and gas equipment.

Then, the effect of the inhibitor on the relative narrowing of the ψ samples was determined during a tensile test in uninhibited and inhibited CS. The parameter ψ characterizes the ductility margin of steel [RD], which sharply decreases during corrosion in hydrogen sulfide-containing media, and thus indicates the degree of hydrogenation of the metal, which is one of the main causes of CMR under these conditions.

Table 2 shows the results of this test series.

The degree of protection of the steel inhibitor in this case was determined by the formula

where Ψ _k , Ψ _and and Ψ _в are the relative narrowing of the samples destroyed in non-inhibited, inhibited corrosive environments and in air, respectively.

The degree of protection of the steel as an inhibitor under the conditions of corrosion-fatigue (KU) loading, consisting in the effect on the steel of total cyclic alternating stresses characteristic of gas and oil pipelines, was determined as follows [RD].

Flat steel samples were subjected to cantilever bending with a span of elastoplastic deformation of 0.74% at a frequency of a symmetrical loading cycle of 0.6 Hz, which corresponds to the actual operating conditions of oil and gas equipment. Loading was carried out in air, as well as in a sealed overhead cell in the KS and in the KS with the addition of an inhibitor. The number of cycles was determined until complete destruction of the samples.

The degree of protection of the Z metal inhibitor from KU was calculated by the formula

where N _in , N _to and N _and are the fatigue life of the samples in cycles to failure when tested in air, in uninhibited and inhibited CS, respectively.

Table 3 shows the results of this series of measurements.

From the data given in table. 1-3, it follows that the developed KMP inhibitor of building steels SPM-2 has a high degree of protection against both OK and SR and KU in the considered KS. The inhibitor may find application in the oil industry for corrosion protection of oil recovery systems equipment and reservoir pressure maintenance. Using the proposed composition of the inhibitor will increase the degree of protection compared with the prototype and, thereby, significantly increase the effectiveness of the protection of equipment from OK and CMR.

Claims (1)

An inhibitor for protecting building steels from corrosion and mechanical damage in hydrogen sulfide-containing mineralized environments, including a complex based on a nitrogen-containing compound, butanol and water, characterized in that as a complex based on a nitrogen-containing compound, it contains a complex of 1,2,4-bistriazolylmethane-ZnCl ₂ kind of

 in the following ratio of components, vol.%: Complex 1,2,4-bistriazolylmethane-ZnCl ₂ 7-12 Butanol 40-50 Water Else

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