RU2415201C1 - Agent for removal of corrosion products off surface of metals - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention refers to chemical treatment of metals and can be used at chemical processing metal items for removal of oxides and hydroxides of iron of various origin, and also for preparing surface of items before following process application of varnish-and-paint coating. The agent contains 25-35 wt % of phosphoric acid, 1-5 wt % 1,3,5,8-tetra-methyl-2-vinyl-4-ethyl-6, γ-cyclopenthenon-10 -methyl-propionyl-7-phytyl-propionyl-chlorine, 8-14 wt % starch, water - the rest.

EFFECT: fast and efficient removal of metal oxides and hydroxides of various origin at room temperature, protection of cleaned surface from over pickling; and additionally, surface of treated items is phosphated, which increases service life of applied varnish-and-paint coating.

1 tbl, 4 ex

Description

The invention relates to the chemical treatment of metals and can be used in the chemical treatment of metal products to remove iron oxides (dross) and iron hydroxides (rust) of various origins, as well as for preparing metal surfaces for subsequent technological operations of applying coatings.

Known means for removing scale and rust from the surface of steel products, including solutions of inorganic acids: sulfuric (20-25%), hydrochloric, and in some cases, mixtures thereof (French Patent No. 2683832, C23F 1/28, 1991) .

Known means allows you to remove corrosion products from the surface of the metal.

The disadvantages of the known funds are:

1. Dissolution of the base metal, which can lead to surface etching, uneven removal, increased micro roughness;

2. Deterioration of the mechanical properties of the metal due to sorption of hydrogen liberated by the metal, which leads to an increase in brittleness, a decrease in viscosity and a deterioration in the elastic characteristics of the product material;

3. Environmental pollution generated during the processing of toxic vapors of hydrogen chloride, and sulfuric acid "mists" formed in the air of the working area, which requires additional costs for creating systems to neutralize harmful fumes.

Also known is a tool for removing scale and rust from the surface of steel products, including surface treatment with solutions of concentrated sulfuric and hydrochloric acids containing special additives - the so-called corrosion inhibitors (Japanese Patent No. 5-24996, C23G 1/06, 1993). This tool allows you to protect the surface of the processed products from over-etching due to the action of the inhibitor - the adsorption of inhibitor particles on the metal surface. However, this known tool does not eliminate the disadvantages of the previous tool in relation to environmental pollution due to the use of the same inorganic acids. In addition, the adsorption nature of the inhibitory effect of additives affects the state of the metal surface, which leads to a decrease in the strength of the applied coatings.

A means is known for removing solid fine scale of iron formed in steam generating plants which are made of austenitic stainless steel and have parts of low alloy steels containing molybdenum. Surface treatment is carried out with a composition comprising at least more than one type of such organic acids as citric, glycolic, gluconic, malic, and thioglycolic acid with the addition of a mixture containing at least more than one type of compounds such as hydrazine, L-ascorbic acid, erisorbic acid and an acid corrosion inhibitor (Japanese Patent No. 5-14027, C23G 1/08, 1993). The processing of products by the specified composition is as follows. An acidic mixed aqueous solution is introduced into the equipment being washed at normal or elevated pressure at a temperature of 100 ° C; the scale is removed when dissolved. To achieve effective washing, 0.2-2.0% of thioglycolic acid is sufficient, the role of which is supposedly reduced to a strong chelating effect, which contributes to the dissolution of scale. The concentration of organic acids is 2-3%. Exposure to free carboxylic acid groups may favor dissolution of scale. An organic amine in an amount of 0.5% is used as an acid corrosion inhibitor. However, partial decomposition of thioglycolic acid leads to the formation of hydrogen sulfide, which reacts with molybdenum contained in parts of the washing systems made of low alloy steels, as a result of which insoluble molybdenum sulfide precipitates on the washed surface. The release of hydrogen sulfide is also the cause of granular corrosion of austenitic stainless steel. The problem of the decomposition of thioglycolic acid in a known agent is solved by reducing the iron ions (+3), which are responsible for the decomposition and oxidation of thioglycolic acid, to iron ions (+2), introducing 0.1- 0.3%.

However, the known tool has the following disadvantages.

1. Limited use, as it applies only to the process of removing hard, fine scale from austenitic stainless steel and low-alloy steel containing molybdenum. However, the problem associated with the removal of solid oxide scale of iron oxide is relevant not only for the operation of boilers and steam generators. The removal of oxides, as well as iron hydroxides from the surface of the ferrous metal is the most important operation of surface preparation before coating. In addition, in the rolling processes at high temperature and heat treatment, a thick, heterogeneous oxide film (scale) is formed.

2. The decomposition of one of the fundamental components (thioglycolic acid) of the mixture used. In this regard, there is a need for additional input into the system of reducing agents that prevent the destruction of thioglycolic acid, which is associated with additional costs.

3. High processing temperatures (100 ° C).

4. The fact that a corrosion inhibitor is introduced into the system indicates that the acid mixed solution used, in the absence of an inhibitor, does not solve the problem of protecting the surface of the steels from over-etching.

The closest in technical essence, selected by us for the prototype, is a metal etching agent containing a mixture of maleic and sulfomaleic acids and additionally comprising monoalkyl esters of maleic and sulfomaleic acids at 50-60 ° C in the bath for 2-11 minutes ( RF patent 2119553, C23G 1/08, 1998).

The specified known tool allows you to remove scale and rust from the surface of steel products.

However, the known tool has several disadvantages.

1. The need to place the product in the bath.

2. The etching temperature is high - 50-60 ° C.

In this regard, the urgency of the task of removing the oxide film extends not only to austenitic stainless steel, but also to carbon alloy steels.

The objective of the present invention is to provide high quality machined surfaces, eliminating metal loss during etching, as well as simplifying the use of the tool during etching.

This object is achieved in that the means for removing corrosion products from the surface of steel products includes an aqueous acid solution, moreover, the agent contains phosphoric acid as an aqueous acid solution and additionally contains 1,3,5,8-tetramethyl-2-vinyl-4- ethyl-6, γ-cyclopentenone-10-methylpropionyl-7-wickylpropionylchlorin and starch, in the following ratio, wt.%:

phosphoric acid 25-35% starch 8-14% 1,3,5,8-tetramethyl-2-vinyl-4-ethyl-6, γ-cyclopentenone-10-methylpropionyl-7-fitylpropionylchlorin 1-5% water Rest

The product is not immersed in the bath, but a paste is applied to its surface, while the removal of metal is 0.2 microns.

Surface treatment is carried out at room temperature for 1 hour.

The essential features indicated in the claims are not found in other known means for removing iron oxides and hydroxides from the surface of steel products.

Surface treatment by the proposed method is as follows.

The paste of the proposed product is applied and aged for 1 hour. Rust removal control - visual. After processing, the paste is washed with a rag or washed off with water. If necessary, processing is repeated.

Partial hydrolysis products of starch play the role of a complexing agent. The role of the complexing agent is played by 1,3,5,8-tetramethyl-2-vinyl-4-ethyl-6, γ-cyclopentenone-10-methylpropionyl-7-fitylpropionylchlorin. The paste allows you to remove products of atmospheric corrosion that has occurred over decades.

When implementing the proposed tool, along with the removal of oxides, hydroxides of iron, simultaneous protection against etching occurs, which allows not to introduce an acid corrosion inhibitor into the system. In addition, the surface of the processed products is phosphated, thereby increasing the service life of the paintwork.

The proposed tool has the following advantages.

1. Removal of oxides and hydroxides of iron of various origin from the surface of metals is carried out quickly, efficiently at room temperature.

2. Provides protection of the cleaned surface from over-etching, which reduces metal loss. The removal of metal is 0.2 microns, which allows you to process the surface of the membranes. A corrosion inhibitor is also excluded.

3. The metal surface is phosphated, which increases the service life of the paintwork.

4. The proposed tool has a 4th hazard class, which allows it to be used in everyday life, and the products of removing corrosion can be disposed of as household waste, because they undergo biological destruction.

5. The proposed tool is a gel that allows you to process vertical, ceiling surfaces and surfaces with a negative slope.

The proposed tool is illustrated by the following examples, the data of which are listed in table 1.

Example 1

phosphoric acid twenty% starch 8% 1,3,5,8-tetramethyl-2-vinyl-4-ethyl-6, γ-cyclopentenone-10-methylpropionyl-7-fitylpropionylchlorin one% water Rest.

When the content of phosphoric acid is less than 20%, the effectiveness of the paste is reduced and the rust is not corroded.

Example 2

phosphoric acid 40% starch 13% 1,3,5,8-tetramethyl-2-vinyl-4-ethyl-6, γ-cyclopentenone-10-methylpropionyl-7-fitylpropionylchlorin 3% water Rest

With a phosphoric acid content of more than 35%, the paste liquefies too quickly.

Example 3

phosphoric acid 25% starch 7% 1,3,5,8-tetramethyl-2-vinyl-4-ethyl-6, γ-cyclopentenone-10-methylpropionyl-7-fitylpropionylchlorin 2% water Rest.

When the starch content is less than 8%, the paste does not hold on vertical surfaces, and on surfaces with a negative slope, the paste drips onto the worker.

Example 4

phosphoric acid 35% starch 12% 1,3,5,8-tetramethyl-2-vinyl-4-ethyl-6, γ-cyclopentenone-10-methylpropionyl-7-fitylpropionylchlorin 2.5% water Rest

The composition well etches the surface without draining from it. The composition is optimal.

Claims (1)

A tool for removing corrosion products from the surface of metals, including an aqueous acid solution, characterized in that it contains phosphoric acid as an aqueous acid solution and further comprises 1,3,5,8-tetra-methyl-2-vinyl-4-ethyl- 6, γ-cyclopentenone-10-methylpropionyl-7-fitylpropionylchlorin and starch in the following ratio, wt.%:
phosphoric acid 25-35 1,3,5,8-tetramethyl-2-vinyl-4-ethyl-6, γ-cyclopentenone- 10-methylpropionyl-7-fitylpropionylchlorin 1-5 starch 8-14 water rest