MXPA98000363A - Acids of decapar inhibits containing chloride ions and z - Google Patents

Abstract

Inhibitors containing a triazine ring, which have been extensively disclosed in the prior art as excellent inhibitors for hydrocarbon acid-based stripping compositions, have been found to be most effective during prolonged use when stripping compositions can dissolve significant amounts of zinc ions, because the inhibitor is precipitated as a solid in the presence of both zinc and chloride ions. Other nitrogen-containing stripping inhibitors are exempt from this difficulty and function effectively even in the presence of zinc. Hexamethylene combinations and tetramine are particularly effective

Description

"INHIBITED DECAPARING ACIDS CONTAINING CHLORIDE AND ZINC IONS" BACKGROUND OF THE INVENTION FIELD OF THE INVENTION This invention relates to the treatment of metal surfaces with aqueous acids to remove the scale or oxide layer and similar surface materials, a process commonly known in the art as "pickling" and with aqueous liquid stripping compositions used in these. processes, which contain both chloride and zinc ions and an inhibitor.

DECLARATIONS OF THE RELATED TECHNIQUE Strong mineral acids such as hydrochloric and sulfuric acids, together with an inhibiting component that considerably reduces the rate of dissolution of the clean metal surface from the regime that would prevail in the same type of acid solution without the inhibitor, is commonly used as stripping compositions. Advantageous inhibitors reduce the rate of dissolution of the clean metal as much as possible while reducing the rate of dissolution of the flake or oxide layer of the surface and similar contamination materials as little as possible. A common quantitative datum to classify the inhibitors used in the art, and in this description presented below, involves measuring the corrosion rate of the metal to be pickled in a solution containing the type and concentration of acid to be used for pickling, measure the corrosion rate in a solution that is otherwise the same except that the inhibitor to be used is added, and then disclose the results as the percentage of "protection" of the inhibitor. The percentage of protection is defined by the following equation: P = 100 [l- (Rj./Ru)] where P = protection percentage, R_ = corrosion rate of the metal in the inhibited solution, and Ru = corrosion rate of the metal in the non-inhibited solution that is expressed in the same units as R-1. A very wide variety of inhibitors for stripping compositions are known in the art. A useful review is provided by G. Trabanelli and V. Carassiti, "Mechanism and Phenomenology of Organic Inhibitors," in Corrosion Science and Technology, Volume 1 (Plenum Press, New York, 1970). Triazine inhibitors are among those most highly recommended in the prior art for aqueous solutions of hydrochloric and / or sulfuric acids, the most frequently used basic pickling compositions.

DESCRIPTION OF THE INVENTION GENERAL PRINCIPLES OF DESCRIPTION Except in the claims and working examples, or where expressly indicated otherwise, all numerical quantities in this description indicating the material quantities or conditions of the reaction, and / or use, must be understood as modified by the word "approximately" when describing the broader scope of the invention. Practice within stated numerical limits, however, is generally preferred. Likewise, unless otherwise expressly stated, the percentage "parts of" and relationship values are by weight; the term "polymer" includes "oligomer", "copolymer", "terpolymer" and the like, the description of a group or class of materials as appropriate or preferred for a given object in relation to the invention implies that mixtures of any two or more of the group members or classes are equally appropriate or preferred; the description of the electrically neutral constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, and does not necessarily prevent the chemical interactions between the constituents of a mixture once it has been mixed; the specification of materials in ionic form means that a soluble salt or acid containing the ions is actually supplied in an amount sufficient to provide the stated amount of the aforementioned ionic material and further implies the presence, in the composition containing a constituent specified in ionic form, of sufficient counterions to produce electrical neutrality for the composition as a whole, any of the counterions therefore, implicitly specified, are preferably selected from among other constituents explicitly specified in ionic form, to the greatest extent possible; otherwise, these counterions can be freely selected except to avoid counter-actions that act per udicially for the objects of the invention; and the terms "solution", "soluble" and the like should be understood as including not only true equilibrium solutions but also dispersions that show no visually detectable trend toward phase separation over an observation period of at least 1000. hours.

COMPENDIUM AND OBJECT OF THE INVENTION It has been found that zinc ions, triazine inhibitors and chloride ions are mutually incompatible constituents in aqueous solutions, resulting in a precipitated material. The case is not the same for any two of these three components in the absence of third, nor is it the case for the combination of zinc, triazine inhibitors and sulfate ions. The unexpected discovery is of practical importance because, although the zinciferous surfaces are usually not stripped with stripping compositions based on hydrochloric acid, the steel surfaces before galvanization are often decapitated with these stripping compositions. In many cases, the conveyor equipment for the steel objects to be galvanized includes chains or other elements that have the form of a continuous band, and therefore, are exposed to both the stripping composition used and the galvanization step. and subsequently they return to the zone of stripping with zinc on their surfaces. Any zinc material present that comes into contact with the liquid stripping composition usually dissolves rapidly because the stripping inhibitors that are most effective in inhibiting the dissolution of the steel often do not inhibit zinc dissolution very effectively. When the triazine inhibited with solutions of stripping of hydrochloric acid or other triazine-inhibited stripping solutions contain considerable amounts of chloride ions, and are used in contact with the zinciferous surfaces, the inhibiting effect has been noticed to decrease, or even disappear. entirely, with prolonged use. This is undesirable because the excessive dissolution of the ferrous metal surfaces exposed to the stripping composition then occurs rapidly. Investigation of this operation led to the observation of a material precipitated in the stripping compositions, sometimes not observed under the same conditions when only ferrous surfaces not containing zinc are stripped. A principal object of this invention is to provide a well-inhibited chloride-containing stripping composition which can be used on ferrous and zinciferous surfaces without losing their inhibitory character as rapidly as triazine-inhibited hydrochloric acid solutions when used. It has been found that inhibitors containing nitrogen, excluding those containing a triazine ring in their molecules, are satisfactory for this purpose.

A stripping composition according to the invention therefore comprises preferably essentially or especially preferably consists of water and: (A) chloride anions; (B) zinc cations (C) an inhibitor that is selected from the group consisting of nitrogen-containing organic compounds that do not include a triazine ring; and (D) acid, and optionally, (E) iron cations. A process according to the invention comprises contacting a metal workpiece to be etched with a working stripping solution according to the invention, as described above.

DETAILED DESCRIPTION OF THE INVENTION, INCLUDING PREFERRED MODALITIES The stripping compositions according to the invention preferably contain chloride ions in a concentration that is at least, preferably increased in the order provided, of 0.01 percent, 0.02 percent, 0.05 percent, 0.1 percent, 0.2 percent, 0.5 percent, 1.0 percent, 2.0 percent, 3.0 percent, 4.0 percent, 5.0 percent, 6.0 percent, 7.0 percent, 8.0 percent, 9.0 percent, 10.0 percent, 11.0 percent percent, 12.0 percent, 13.0 percent, 14.0 percent, 15.0 percent, 16.0 percent, 17.0 percent, 18.0 percent, 19.0 percent, 0 20.0 percent and independently due mainly to reasons of worker's economy and safety and comfort, preferably, is not greater than, preferably increased in the order of 50 percent, 40 percent, 35 percent, 30 percent, or 25 percent. The preferred chloride ion source is hydrochloric acid, because it supplies both chloride and acid, both of which are needed. Therefore, stoichiometric equivalents such as hydrochloric acid of the above-mentioned amounts of chloride ions are preferred. However, other acids such as sulfuric acid could also be used together with another source of chloride. The concentration of the acid present is preferably high enough to 1 No more than 35 percent aqueous hydrochloric acid chloride can be achieved, except under pressure greater than normal atmospheric pressure due to equilibrium with gaseous hydrogen chloride. produce a practically useful pickling regime; and these concentrations can easily be determined by those skilled in the art. Independently, the stripping compositions according to the invention preferably contain zinc ions in a concentration that is at least, preferably increased in the order of 0.0001 percent, 0.0002 percent, 0.0005 percent, 0.001 percent, 0.002 percent, 0.005 percent, 0.008 percent, 0.010 percent, 0.020 percent, 0.030 percent, 0.035 percent, 0.040 percent, 0.045 percent, or 0.048 percent. Also independently, the stripping compositions according to the invention preferably contain nitrogen-containing inhibitory molecules, excluding those having molecular structures including a triazine ring, in a concentration that is at least, preferably increased in the order provided by 0.0001 percent, 0.0002 percent, 0.0005 percent, 0.001 percent, 0.002 percent, 0.005 percent, 0.008 percent, 0.010 percent, 0.020 percent, 0.030 percent or 0.035 percent and independently due mainly to reasons of economy, preferably not greater than, preferably increased in the proportionate order of 5 percent, 3 percent, 2 percent, 1 percent, 0.5 percent, 0.2 percent, 0.1 percent, 0.08 percent, 0.060 percent, 0.050 percent, 0.045 percent, or 0.040 percent. Independently, the nitrogenous inhibitory molecules are preferably selected from the group consisting of alkyl pyridines, hexamethylene tetramine, abiethyl, hydroabiethyl and dihydroabiethyl amines and keto-substituted derivatives thereof, more preferably ketonyl rosin amines, as described in US Pat. No. 2, 975, 125 of March 14, 1961, issued to Saukaitis et al., all the disclosure of which to the extent that it describes ketotylated abietil, hydroabiethyl and dihydroabiethyl amines and is not incompatible with no explicit statement hereof, it is hereby incorporated by reference, and all amines including both at least one alkyl group and at least one aryl group attached to a single nitrogen atom. More preferably, the inhibitors contain polyalkyleneamines of alkylaryl and tetramine of hexamethylene in a ratio that is preferably at least, preferably increased in the order of 0.10: 1.0, 0.15: 1.0, 0.20: 1.0, 0.25: 1.0, 0.30. : 1.0, 0.33: 1.0, 0.35: 1.0 or 0.37: 1.0 and independently preferably is not greater than with increased preference in the proportioned order of 1.5: 1.0; 1.0: 1.0; 0.9: 1.0; 0.8: 1.0; 0.7: 1.0; 0.6: 1.0; 0.55: 1.0; 0.50: 1.0; 0.45: 1.0; 0.42: 1.0; 0.40: 1.0 or 0.39: 1.0. A process according to the invention comprises contacting a workpiece of metal to be etched with a working stripping solution according to the invention, as described above, preferably, a temperature which is, within the increased preference in the order provided by at least 16 ° C, 30 ° C or 38 ° C and, if the scale or oxide layer to be removed is relatively thick, a fast pickling is desired and the adequate protection of the works against the tendency of firing vapors the solution of pickling at higher temperatures, more preferably at least, preferably increased in the order of 52 ° C, 60 ° C, 66 ° C, 70 ° C, 74 ° C, 78 ° C or 81 ° C, and independently of preference is, preferably increased in the order provided, not greater than 93 ° C, 88 ° C or 83 ° C, for a sufficient period of time to remove flake or oxide layer and other coatings d and oxide from the surface of the work piece. Independently, the contact time for most preferably pickling applications is at least, preferably increased in the order of 1, 5, 10, 15, 20 or 25 minutes, and preferably independently is not greater than , preferably increased in the proportioned order of 60, 55, 50, 45, 40 or 35 minutes, although the time will naturally vary considerably as a function of the amount of surface contamination type to be removed. The contact between the work piece and the work stripping solution is usually by immersion, but any process for establishing the required contact can be used, many of which are known per se in the art. The practice and benefits of the invention can also be appreciated by taking into account the following non-limiting examples and comparison examples. LABORATORY DEMONSTRATION OF THE INCOMPATIBILITY OF ZINC, CHLORIDE AND TRIAZINES Attempts were made to prepare solutions with the constituents shown in Table 1, with results also shown in the inhibitor RODINE® 51, shown in Table 1 containing considerable amounts of triazines, while RODINE® 1150 which is the inhibitor also shown in Table 1, does not contain triazines, but contains alkylaryl polyalkyleneamines and hexamethylene tetramine in a ratio of about 0.38: 1.0.

Table 1 Ingredient Amount of the Ingredient in the Composition Tested Number Water of the key lOOmL lOOmL lOOmL lOOmL 32% HCl in water lOOmL lOOmL lOOmL lOOmL Ions of Faith + 2 0.05 ^ none 0.05 * 0.05% Ions of Zn + 2 none 0.05% 0.05% 0.05% RODINE® 51 0.2 v% 0.2 v% 0.2 v% 0.2 v ?.

RODINE® 1150 none none none 0.2 vs Result: solution precipitate precipitate solution Abbreviations for Table 1 'mL "=" milliliters ";" v% "=" percentage in volume " Attempts were made to complete the tested compositions 2 and 3, as shown in Table 1 without added precipitation RODIDE® 51 the inhibitor, only for the HCL solution initially, then mixing this solution with another one elaborated by adding zinc and iron, or zinc only to water. The precipitation occurred immediately when the two solutions were mixed. In another attempt, the inhibitor was mixed with water, zinc and iron and formed a crystalline solution, but precipitation occurred as soon as hydrochloric acid was added to this mixture. RESULTS OF LARGE SCALE OPERATIONS A sample of the rinse water from a commercial galavanization plant was obtained. This rinse water was used in the plant to make pickling compositions containing about 10 percent of the HCl. This rinse water containing iron and zinc cations at levels of at least about 0.03 percent each, in addition, the stripping compositions inhibited with RODINE® 51 the inhibitor in this operation, used stripping steel to prepare the same for galvanization, initially provided satisfactory operation when processed with fresh tap water, but soon ceased to be satisfactory as additional amounts of rinse water containing zinc were added, together with the additional concentrated hydrochloric acid to replenish the losses of performance of the stripping compositions. The compositions shown in Table 2 below used some of the aforementioned practical rinse water containing small amounts of iron and zinc, were tested in order to determine if apparent precipitation occurred.

Table 2 Ingredient Amount of Ingredient in Proposed Composition Number 7 Water rinse > lOOmL lOOmL lOOmL none Key water none none none none 32% HCl in water lOOmL lOOmL none none 98-100% of ti2- or none none lOOmL lOOmL Ions of Fe + 2 none none none 0.05% Ions of Zn + 2 none none none 0.05% RODINE® 51 0.2 v% none 0.2 v% 0.2 v * RODINE® 1150 none 0.2 v% none none Result: precipitate solution precipitate solution Abbreviations for Table 2 'mL' = "milliliters"; "v%" = "percentage by volume" Even the relatively small amount of hydrochloric acid in the rinse water caused a precipitate in Composition 7 Tested, the zinc content and iron alone did not result in any precipitation in otherwise the Composition 8 proved similar, Characteristically, even when the rinse water contained all the hydrochloric acid, zinc and iron and was crystalline without evidence of a precipitate, as soon as the triazine-containing inhibitor in Composition 5 Precipitation was tested This did not happen when the other triazine-free inhibitor was used in Composition 6.

Claims (15)

R E I V I N D I C A C I O N E S:

1. An inhibited decanter composition comprising water, and: (A) chloride anions; (B) zinc cations; (C) an inhibitor that is selected from the group consisting of nitrogen-containing organic compounds, which do not include a triazine ring; and (D) an amount of acid sufficient to produce a practically useful stripping rate in the steel.

2. An inhibited stripping composition according to claim 1, comprising from 1.0 percent to about 50 percent chloride ions, at least about 0.0002 percent zinc ions and from about 0.001 percent to about 5 percent. percent inhibitors that are selected from the group consisting of (i) alkyl pyridines, (ii) hexamethylene tetramines, (iii) abiethyl, hydroabiethyl and dihydroabiethyl amines and keto-substituted derivatives thereof, and (iv) all the other amines including both of at least the alkyl group and at least one aryl group attached to a single nitrogen atom, but not including any triazine ring.

3. An inhibited decanter composition according to claim 2, comprising from about 2.0 percent to about 40 percent chloride ions, at least about 0.0005 percent zinc ions, and from about 0.002 percent to about 3 percent of the inhibitor component (C).

4. An inhibited stripping composition according to claim 3, comprising from about 4.0 percent to about 40 percent chloride ions, at least about 0.001 percent zinc ions, and about 0.005 percent percent about 2 percent of the inhibitor component (C).

5. An inhibited decanter composition according to claim 4, comprising from about 6.0 percent to about 35 percent chloride ions derived from hydrochloric acid, at least about 0.002 percent zinc ions, and from about 0.008 percent to about 1 percent of the inhibitor component (C).

6. An inhibited stripping composition according to claim 5, comprising from about 8.0 percent to about 35 percent chloride ions derived from hydrochloric acid, at least about 0.005 percent zinc ions, and about 0.010 percent to about 0.5 percent of the inhibitor component (C).

7. An inhibited stripping composition according to claim 6, comprising from about 10.0 percent to about 30 percent chloride ions derived from hydrochloric acid, at least about 0.010 percent zinc ions and about 0.010 percent. percent to about 0.2 percent of inhibitors that are selected from the group consisting of (i) alkyl pyridines, (ii) hexamethylene tetramine, (iii) acetylated rosin amines and (iv) all other amines including both minus one alkyl group, at least one aryl group attached to a single nitrogen atom, but not including any triazine ring.

8. An inhibited decanter composition according to claim 7, wherein: the component (A) is present in a concentration of about 16.0 percent to about 30 percent derived from hydrochloric acid, the component (B) is present in a concentration of at least about 0.030 percent, component (C) is present in a total concentration of about 0.020 percent to about 0.01 percent and consists essentially of alkylaryl polyalkylene (Cl) amines and (C.2) hexamethylene tetramine in a ratio of (Cl): (C.2) which is from about 0.15: 1.0 to about 0.9: 1.0.

9. An inhibited stripping composition according to claim 8, wherein: component (A) is present in a concentration of about 16.0 percent to about 30 percent derived from hydrochloric acid, component (B) is present in a concentration of at least approximately 0.040 percent; and component (C) is present in a total concentration of about 0.030 percent to about 0.060 percent and consists essentially of alkylaryl polyalkylene (Cl) amines and (C.2) hexamethylene tetramine in a ratio of (Cl) : (C.2) which is from about 0.30: 1.0 to about 0.50: 1.0.

10. An inhibited pickling composition according to claim 9, wherein: the component (A) is present in a concentration of about 20.0 percent to about 25 percent derived from hydrochloric acid, the component (B) is present in a concentration of at least about 0.048 percent; Component (C) is present in a total concentration of about 0.035 percent to about 0.040 percent and consists essentially of (Cl) polyalkylene alkylaryl amines and (C.2) hexamethylene tetramine in a ratio of (Cl): (C.2) which is from about 0.35: 1.0 to about 0.40: 1.0.

11. A process comprising contacting a metal workpiece to be pickled with an inhibited pickling composition according to any of claims 1 to 10, for a period of time sufficient to remove the flake or oxide layer. , and other oxides from the surface of the work piece.

12. A process according to claim 11, wherein the stripping composition inhibited during its contact with the workpiece has a temperature of about 30 ° C to about 93 ° C, and is kept in contact with the workpiece. , for a time of about 1 to about 60 minutes. A process according to claim 12, wherein the stripping composition inhibited during its contact with the workpiece has a temperature of about 38 ° C to about 83 ° C, and is kept in contact with the workpiece , for a time of about 5 to about 55 minutes. A process according to claim 13, wherein the stripping composition inhibited during its contact with the workpiece has a temperature of about 52 ° C to about 83 ° C, and is kept in contact with the workpiece , for a time of about 10 to about 40 minutes. 15. A process according to claim 12, wherein the stripping composition inhibited during its contact with the workpiece has a temperature from about 60 ° C to about 83 ° C, and is kept in contact with the workpiece. , for a time of about 15 to about 35 minutes.