Rust accelerator

Abstract

The invention relates to a rust accelerator that is present as a one-component rust accelerator or as a two-component rust accelerator, comprising as component (a) one or more aliphatic carboxylic acids or carboxylic acid esters in a total amount of 0.5 to 6 parts by weight, as component (b) one or more alkali halides or ammonium chloride in a total amount of 0.002 to 0.5 parts by weight, and as component (c) at least one hydrogen peroxide compound in an amount of 2.0 to 150 parts by weight. The invention also relates to a process for the oxidation of iron-containing metals using the rust accelerator according to the invention.

Description

The invention relates to a rust accelerator which is present as a one-component rust accelerator or as a two-component rust accelerator. The invention further relates to a method for oxidizing ferrous metals with the aid of such a rust accelerator.Objects, installations, sculptures or architectural elements of oxidisable metals, especially ferrous metals, which are exposed to weathering, receive a unique, often very attractive surface through the effects of water and oxygen from the environment. However, this weathered surface only forms during months or even years.Rust accelerators in the form of aqueous solutions which promote oxidation of the ferrous metals are known. When the aqueous solution is applied to the articles to be rusted, the oxidation of metallic iron to red-brown iron(III) oxide begins immediately.Known products based on copper compounds such as copper sulfate are very efficient in their action and bring about the formation of a pronounced deep red brown rust patina within 24 hours. However, these rust accelerators do not meet present-day environmental protection requirements, since copper sulfate is declared to be very toxic to aquatic organisms in accordance with the GHS (global harmonised system for grading and identifying chemicals) hazardous substance identification from Regulation (EG) No. 1272 / 2008 (CLP). Such a rust accelerator must be handled very carefully, since introduction into the environment is absolutely to be avoided. This fact makes the use of copper-containing products problematic, especially in the outdoor sector and especially for end consumers inexperienced in handling chemicals.Attempts have already been made to produce products which are more environmentally friendly and accelerate the process of rust by the action of reactive oxygen. Thus, an aqueous solution of hydrogen peroxide and catalytic amounts of sodium chloride is known. However, a disadvantage of these products is that a rust patina is formed only after several days to weeks.Proceeding from the described prior art, the object of the present invention is to provide a rust accelerator which avoids the disadvantages mentioned above.The object is achieved according to the invention by a rust accelerator which is present as a one-component rust accelerator (first aspect) or as a two-component rust accelerator (second aspect), comprising as constituent (a) one or more aliphatic carboxylic acids or carboxylic esters in a total amount of from 0.5 to 6 parts by weight, as constituent (b) one or more alkali halides or ammonium chloride in a total amount of from 0.002 to 0.5 parts by weight, and as constituent (c) at least one hydrogen peroxide compound in an amount of from 2 to 150 parts by weight, in each case based on the sum of constituents (a) to (c).Herein, the amounts of the components are given in parts by weight. The proportions in the relevant mixtures are thereby also determined.The rust accelerator of the present invention preferably contains water as component (d) in an amount of 50.0 to 97.0 parts by weight.As constituent (a), use is made according to the invention of one or more aliphatic carboxylic acids or carboxylic esters. In principle, the use of any desired aliphatic carboxylic acids having any desired number of carbon atoms is possible, provided that they are soluble in this amount in an aqueous composition generally used for use. It is thus also possible to use dicarboxylic acids and hydroxycarboxylic acids. Suitable carboxylic esters are, in particular, ethyl acetate and methyl acetate.Preferred carboxylic acids have 1 to 10 carbon atoms, particularly preferably 2 to 8 carbon atoms, further preferably 2 to 6 carbon atoms. These carboxylic acids are, in particular, acetic acid, propionic acid, butyric acid (butanoic acid), isobutyric acid (2-methylpropanoic acid), valeric acid (pentanoic acid), caproic acid (hexanoic acid), isovaleric acid (3-methylbutanoic acid), heptanoic acid (enanthic acid), caprylic acid (octanoic acid), citric acid and formic acid. Tartaric acid and lactic acid are also suitable in principle, for example. A particularly preferred carboxylic acid is acetic acid, alone or in combination with other carboxylic acids. Acetic acid is particularly preferred as constituent (a) according to the invention.As component (b), sodium chloride and / or potassium chloride is preferably used.A rust accelerator is preferred wherein at least one hydrogen peroxide compound of the component (c) is hydrogen peroxide and / or a hydrogen peroxide adduct, preferably a hydrogen peroxide adduct.Here, it is again preferred that it comprises one or more hydrogen peroxide adducts from the group of carbamide peroxide, sodium percarbonate and potassium percarbonate.Carbamide peroxide in the context of the present invention is understood to mean the adduct of urea and hydrogen peroxide with the empirical formula CH 4 N 2 O x H 2 O 2. Carbamide peroxide is alternatively also referred to as a hydrogen peroxide-urea adduct and is registered under CAS number 124-43-6. Commercial carbamide peroxide contains about 35% by weight hydrogen peroxide.Sodium percarbonate is understood in the sense of the present invention to mean the adduct of sodium carbonate and hydrogen peroxide with the empirical formula Na 2 CO 3 x 1.5 H 2 O 2 and the alternative name hydrogen peroxide-sodium carbonate adduct. Potassium percarbonate is understood in the sense of the present invention to mean the adduct of potassium carbonate and hydrogen peroxide with the empirical formula K 2 CO 3 x 1.5 H 2 O 2 and the alternative name hydrogen peroxide-potassium carbonate adduct. A particularly preferred hydrogen peroxide adduct is carbamide peroxide.In a particularly preferred embodiment, the rust accelerator comprises, as constituent (c), hydrogen peroxide adducts in a total amount of from 3 to 6 parts by weight.In the second aspect of the invention, the rust accelerator is configured as a two-component rust accelerator comprising components (A) and (B), (A) a composition comprising, as constituent (a), one or more carboxylic acids (a) or carboxylic esters in a total amount of from 0.5 to 6 parts by weight, and, as constituent (b), one or more alkali halides or ammonium chloride in a total amount of from 0.002 to 0.5 parts by weight and, if appropriate, water as constituent (d), and (B) as constituent (c), one or more hydrogen peroxide adducts in a total amount of from 2 to 150 parts by weight and, if appropriate, water as constituent (d).In this rust accelerator, component (d) is preferably contained in component (A) but not in component (B).Components (A) and (B) can be present in the rust accelerator as an aqueous liquid or as a powder. Component (B) is preferably present in the form of a powder. Component (A) is preferably present as an aqueous composition.The rust accelerator of the invention preferably contains one or more aliphatic carboxylic acids as constituent (a). These are used in a total amount of from 0.5 to 6 parts by weight, preferably in a total amount of from 0.5 to 4 parts by weight, in particular from 0.5 to 2.5 parts by weight.The rust accelerator of the present invention preferably contains as the component (b) one or more alkali halides in a total amount of 0.002 to 0.5 part by weight, more preferably in a total amount of 0.05 to 0.4 part by weight, particularly in a total amount of 0.1 to 0.35 part by weight. The alkali halides are, in particular, sodium chloride and potassium chloride. A particularly preferred alkali halide is sodium chloride.The rust accelerator of the invention comprises, as constituent (c), for example in a component (B), one or more hydrogen peroxide adducts in a total amount of from 3 to 150 parts by weight, preferably in a total amount of from 3 to 6 parts by weight. The hydrogen peroxide adducts are generally carbamide peroxide, sodium percarbonate and potassium percarbonate.It is particularly preferred according to the invention that the rust accelerator, preferably in component (A), contains 1.2 to 2 parts by weight of acetic acid as constituent (a) and 0.1 to 0.5 parts by weight of sodium chloride as constituent (b), and contains 4.5 to 6 parts by weight of carbamide peroxide as constituent (c), preferably in component (B).The 2-component rust accelerator of this aspect of the invention is activated by mixing components (A), (B) and, if they do not already contain water, generally with water, and is immediately ready for use.It has surprisingly been found that with the activated 2-component rust accelerator a deep red brown iron(III) oxide patina can be produced on oxidisable metal surfaces which contain iron within a short time, sometimes in a few hours, but frequently also in a few seconds.The 2-component rust accelerator of this aspect of the present invention has an advantage that it is made of components which contain no toxic components or form upon mixing the components and which can therefore be used without any special precautions. Furthermore, the configuration as a 2-component system is advantageous since the components of the rust accelerator can be stored and transported separately.The 2-component rust accelerator may contain conventional additives, in particular solvents, colorants, thickeners, surfactants, binders, fragrances, pH regulators, preservatives, stabilizers, foam stabilizers, dispersants and / or fillers. Suitable fillers increase the volume of the activator without affecting its chemical properties and are known to those skilled in the art. These substances can be added to the individual constituents or components and / or to the overall mixture.As component (d), water is taken. The use of water is required especially in the case of a content of hydrogen peroxide adducts. In addition, the use of a mono- or polyhydric alcohol, in particular ethanol or isopropanol, is also possible. The use of alcohols may be particularly useful in order to improve the solubility of carboxylic acids in the aqueous composition. Thus, according to the invention, it is also possible to use fire-like gum which, in addition to acetic acid, generally has a maximum ethanol content of 0.2% by weight.An aqueous composition of the rust accelerator obtained by using constituent (d), in particular of the 2-component rust accelerator, can in principle be formulated as a solution or gel, wherein, in the case of the formulation as a gel, the aqueous composition contains one or more thickeners, preferably from the group of xanthan, alginate and carboxymethylcellulose.Furthermore, the aqueous composition of the 2-component rust accelerator may contain anionic, cationic, zwitterionic (amphoteric) and nonionic surfactants.The 2-component rust accelerator is preferably composed so that the activated rust accelerator obtained by mixing component (A) and component (B) has an alkaline pH. The 2-component rust accelerator preferably has a pH of 8 to 13, particularly preferably of 9 to 12, in each case measured at 20° C. It may also be useful to influence the pH of the 2-component rust accelerator by pH regulators. Suitable pH regulators are known to the skilled worker. If the pH regulator or regulators are present in component (B), these are generally solid at room temperature (20° C.). The amounts used of the pH regulator or regulators are selected by the skilled worker depending on the pH which is to be adjusted in the activated 2-component rust accelerator.The rust accelerator of the present invention may be provided in a container, a bottle, a bag or a can.In the case of the configuration of the grate accelerator as a 2-component grate accelerator, the dimensions of the container for one of the two components are advantageously chosen such that the container is only partially filled and permits further filling with the other component.The container is filled in particular such that the two components come into contact with one another only by an action of a user. The activated 2-component rust accelerator is prepared by adding the other component and shaking the container, for example.In one embodiment, component (A) may be provided in a screw-capped bottle and component (B) may be contained in a container in the screw-capped lid, with a wall of the container closing the neck of the bottle. Component (B) can be added by tightening the screw cap, in which, for example, the bottle neck pierces the wall of the container. After activation of the 2-component rust accelerator, the screw cap can be replaced by a manually operable spray attachment.In a fourth aspect, the invention relates to a process for oxidizing ferrous metals, comprising the steps of (I) preparing a rust accelerator described above by mixing components (a) to (c), (II) applying the rust accelerator from step (I) containing the additional component (d), water, to a surface of the ferrous metal, (III) allowing the rust accelerator to act.The exposure time at room temperature (20° C.) is preferably from 45 minutes to 8 hours, particularly preferably from 1 hour to 6 hours.The exposure in step (III) is generally carried out until a desired oxidation state is reached.After the oxidation degree at which a desired rust patina has formed is reached, residues of the 2-component rust accelerator can be removed from the metal. This is advantageously done by rinsing with water.The rust accelerator according to the invention, in particular if it is designed as a 2-component rust accelerator, can be used for the accelerated oxidation of ferrous metals and metal alloys such as iron, steel, cast iron and core steel. In a preferred embodiment of the method according to the invention, the ferrous metal is steel or core steel.In a fourth aspect of the process according to the invention, the process for oxidizing ferrous metals comprises the steps of (I) preparing an activated 2-component rust accelerator by mixing the components (A) and (B) WHICH HAVE BEEN PHYSICALLY SEPARATED BEFOREHAND, (II) applying the 2-component rust accelerator from step (I) as an aqueous composition to an oxidisable metal surface, (III) allowing the 2-component rust accelerator to act.The application of the 2-component rust accelerator can be effected in each case by spraying, brushing, rolling or dipping.In a preferred embodiment of these processes according to the invention, these comprise the further step(IV) Rinsing of the rust accelerator from the surface of the ferrous metal.ExamplesThe following examples are intended to illustrate the invention using a two component rust accelerator ("2-component rust accelerator").Example 1Component (A)Unless otherwise indicated, the amounts are based on parts by weight. All quantities stated add up to a maximum of 100 parts by weight.Acetic acid1,67Sodium chloride0,30WaterAD 100 AD 100 AD 100 AD 100 AD 100 AD 100 AD 100 AD 100 AD 100 AD 100 ADAn aqueous composition according to Example 1 is prepared by mixing acetic acid, sodium chloride and water in any order. It has proven useful to use aqueous solutions of acetic acid and sodium chloride. It has also proved to be useful to mix a 5% solution of acetic acid, a 0.9% saline solution and distilled water in equal parts. The mixing is carried out by methods known to the skilled worker, for example with the aid of a stirring system.Component (B)5.33 parts by weight of carbamide peroxide containing 35 wt% of hydrogen peroxide is provided for 100 parts by weight of component (A) prepared.ApplicationComponent (A) is mixed with component (B). The activated 2-component rust accelerator obtained in this manner contains about 1.86 parts by weight of hydrogen peroxide and has a pH of about 8.A steel sheet is coated, if appropriate after removal of an existing scale layer, with the 2-component rust accelerator according to Example 1. The surface is coated by spraying on the 2-component rust accelerator. After one hour, the sheet shows a pronounced rust patina.Application of the 2-component rust accelerator to the surface by brush application or by sponge application resulted in comparable results to spray application.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Cited Non-Patent LiteratureRegulation (EC) No. 1272 / 2008

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Claims

A rust accelerator which is present as a one-component rust accelerator or as a two-component rust accelerator, comprising as constituent (a) one or more aliphatic carboxylic acids or carboxylic esters in a total amount of from 0.5 to 6 parts by weight, as constituent (b) one or more alkali halides or ammonium chloride in a total amount of from 0.002 to 0.5 parts by weight and as constituent (c) at least one hydrogen peroxide compound in an amount of from 2.0 to 150 parts by weight.The rust accelerator according to claim 1, characterized in that it contains water as component (d) in an amount of 50.0 to 97.0 parts by weight.The rust accelerator according to claim 1 or 2, characterized in that the at least one hydrogen peroxide compound is hydrogen peroxide and / or a hydrogen peroxide adduct, preferably a hydrogen peroxide adduct.The rust accelerator according to claim 3, characterized in that it comprises one or more hydrogen peroxide adducts from the group of carbamide peroxide, sodium percarbonate and potassium percarbonate.Rust accelerator according to one of Claims 1 to 4, characterized in that it comprises, as constituent (a), one or more carboxylic acids from the group consisting of acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, isovaleric acid, heptanoic acid, caprylic acid, citric acid and formic acid.Rust accelerator according to one of Claims 1 to 5, characterized in that sodium chloride and / or potassium chloride is used as constituent (b).The rust accelerator according to any of claims 1 to 6, characterized in that it is configured as a two-component rust accelerator comprising components (A) and (B), (A) a composition comprising, as constituent (a), one or more carboxylic acids (a) or carboxylic esters in a total amount of from 0.5 to 6 parts by weight, and, as constituent (b), one or more alkali halides or ammonium chloride in a total amount of from 0.002 to 0.5 parts by weight, and also, optionally, as constituent (d), water, (B) as constituent (c), one or more hydrogen peroxide adducts in a total amount of from 2 to 150 parts by weight, and, optionally, as constituent (d), water.The rust accelerator according to claim 7, wherein component (d) is contained in component (A) but not in component (B).The rust accelerator according to claim 7 or 8, characterized in that component (B) is present in the form of a powder.The rust accelerator according to any one of claims 7 to 9, characterized in that component (A) contains the constituent (a) in a total amount of 0.5 to 2.5 parts by weight.The rust accelerator according to any one of claims 7 to 10, characterized in that component (A) contains the constituent (b) in a total amount of 0.002 to 0.35 parts by weight.The rust accelerator according to any of claims 7 to 11, wherein component (c) is hydrogen peroxide adducts in a total amount of 3 to 6 parts by weight.Rust accelerator according to one of Claims 7 to 12, characterized in that component (A) contains 1.5 to 2 parts by weight of acetic acid as constituent (a) and 0.1 to 0.5 parts by weight of sodium chloride as constituent (b), and component (B) contains 4.5 to 6 parts by weight of carbamide peroxide as constituent (c).A process for oxidizing ferrous metals, comprising the steps of (I) preparing a rust accelerator according to any one of claims 1 to 13 by mixing components (a) to (c), (II) applying the rust accelerator from step (I), to which component (d), water, has been added, to a surface of the ferrous metal, and (III) allowing the rust accelerator to act.A process for oxidizing ferrous metals, comprising the steps of (I) preparing a rust accelerator described above by mixing the components (a) to (c), (II) applying the rust accelerator containing the additional component (d), water, from step (I) to a surface of the ferrous metal, (III) allowing the rust accelerator to act.Method according to claim 14 or 15, characterized in that the method comprises the further step (IV) of rinsing the rust accelerator from the surface of the ferrous metal.Method according to one of Claims 14 to 16, characterized in that the ferrous metal is steel or core steel.