COMPOSITIONS OF ACID INHIBITOR FOR CLEANING AND / OR DECAPPING METAL
FIELD OF THE INVENTION This invention relates to acid inhibitor concentrates and solutions prepared thereof which are useful for pickling and acid cleaning metal surfaces. BACKGROUND OF THE INVENTION It is known to use certain compounds or mixtures of compounds in acidic solutions which are used to clean or strip metal surfaces to remove unwanted oxides, flake or other undesirable corrosion products therefrom. These compounds reduce the tendency of the acid cleaning solution to corrode the metal surface without interfering with the cleaning operation performed by the solution. Compounds that function in this manner are generally referred to as "acid inhibitors". In the absence of acid inhibitors, an acid metal cleaning or pickling solution can cause significant base metal loss and also damage to the metal surface as a result of excessive exposure to hydrogen. Corrosion of metal surfaces by acidic cleaning solutions is caused by acids
present in the solution. The acids generally used in such cleaning or metal pickling solutions are so-called "non-oxidizing" acids. Included in this category are inorganic (mineral) acids such as hydrochloric acid, phosphoric acid, sulfamic acid, sulfonic acid and sulfuric acid and organic acids such as acetic acid, citric acid, formic acid, glycolic acid and oxalic acid. The acid component of the cleaning solution is effective when removing unwanted deposits from metal surfaces, but unfortunately it also tends to attack and corrode the base metal. This corrosion is obviously very undesirable. To counteract the corrosive effects of the acid, acid inhibitors are added to the cleaning solution. An effective inhibitor must be dispersed through the pickling solution in low concentrations, must suppress the evolution of hydrogen, and must not leave excessive blight or residual film on the surface of the metal. It must also maintain effectiveness through an acid scale and iron concentrations and temperatures, with such effectiveness being long lasting so that the metal pickling or cleaning solution does not need to be discarded or
replenish frequently. Many types of acid inhibitor compositions are known in the art, with several being commercially available. However, in many cases these formulations contain undesirably high concentrations of certain substances such as formaldehyde or acetylenic alcohols which are toxic and / or flammable and are thus subject to strict regulation due to environmental, health and safety interests. Furthermore, it is desirable due to cost and convenience reasons to sell said acid inhibitor compositions in the form of concentrates which are diluted and combined with aqueous acidic solutions to prepare a metal pickling or cleaning solution. Alternatively, these concentrates are used to replenish metal working metal pickling or cleaning solutions that have been depleted or no longer have the desired degree of effectiveness with respect to acid inhibition. The acid inhibitor concentrates should remain stable for extended periods of time so that they can be stored safely until they are combined with aqueous acid to form or replenish a metal pickling or cleaning solution. That is, the concentrate must remain a homogeneous solution (eg, without phase separation or precipitation of
solids) and should not deteriorate or degrade in effectiveness to a significant degree. In addition, the prepared solutions of said concentrates must meet the strict requirements of the client regarding cost and performance (eg, inhibition of metal engraving), both immediately and over time (e.g., as the iron levels in the solution increase during continuous use of the solution). Additional improvements in the field of acid inhibitor concentrates and metal cleaning and pickling solutions, therefore, would be desirable. BRIEF SUMMARY OF THE INVENTION The present invention provides an acid inhibitor concentrate comprising water, at least one polyamino-aldehyde resin and at least one compound selected from the group consisting of acetylenic alcohols, ethoxylated fatty amines, salts of ethoxylated fatty amine. and aldehyde release compounds. These concentrates form useful cleaning and metal pickling solutions when combined with aqueous acid. These solutions, when placed in contact with a metal surface such as steel, aluminum alloy, or zinc surface, are effective at removing scale and other deposits from the surface.
metal surface while exhibiting a reduced tendency for aqueous acid to attack or etch the metal itself. The metal cleaning and pickling solutions of the present invention, compared to solutions prepared using conventional types of acid inhibitors, exhibit particularly good protection against etching of base metal when the solution contains high levels of iron and is maintained at a high level. relatively high temperature over a prolonged period of time. DETAILED DESCRIPTION OF CERTAIN MODALITIES OF THE INVENTION The acid inhibitor concentrates of the present invention may contain one or more polyamino-aldehyde resins. These resins can be described as the reaction products of polyamine and aldehyde compounds and preferably are sufficiently soluble in water at 25 degrees C so as to allow their incorporation into the concentrates levels of at least about 1% by weight. Although acid-base inhibitor concentrates based on unmodified polyamines (ie, polyamines that have not been reacted with aldehyde) also exhibit some degree of inhibitory effects of acid attack, modifying the polyamines with aldehyde has been found to provide improvement significant in the operation. The
improvement is particularly pronounced, for example, when a substrate containing iron is contacted with a solution containing HC1 at elevated temperatures and / or in the presence of dissolved iron and when a substrate containing aluminum is contacted with a solution which contains HC1 at elevated temperatures. The polyamino-aldehyde resins can be in cationic, salt and / or quaternized form so as to increase their water solubility and / or effectiveness to the desired degree. Water miscible organic solvents such as glycol ethers, glycols, ketones, alcohols, esters and the like can also be used to solubilize the polyamino-aldehyde resin (and other organic components) in the concentrate, but the preferred concentrates in accordance with the present invention they do not contain or essentially do not contain (e.g., less than 1% by weight) volatile organic solvents. Preferably, the components of the acid inhibitor concentrate are selected so that the closed cup release point of the concentrate is greater than 80 degrees C (alternatively, greater than 100 degrees C). Polyamine compounds suitable as starting materials for the polyamino-aldehyde resin can generally be described as organic compounds
containing two or more (e.g., three, four, five or six or more) nitrogen atoms per molecule and preferably are soluble in water. For example, the polyamine compound can be prepared by polymerization or oligomerization of one or more monomers containing nitrogen or by condensation of two or more nitrogen-containing substances. This polymerization, oligomerization or condensation may involve other molecules in addition to monomers containing nitrogen or nitrogen-containing substances. For example, compounds that do not contain nitrogen can be used as comonomers and / or as polymerization initiators. Generally speaking, it is desirable that the polyamine compound contains a plurality of nitrogen atoms (e.g., three or more or four or more or five or more nitrogen atoms) in the structure of a polymer chain containing units or covalently linked repeat fractions. For example, the ratio of nitrogen atoms to carbon atoms preferably can be at least about 0.2, more preferably at least about 0.4. It will generally be preferred that the nitrogen atoms are present in the form of amine groups, which may be secondary, tertiary or quaternary primary in
structure. The number average molecular weight of the polyamine is not believed to be particularly critical and may be, for example, as low as 200, 400, 600, 800, 1000 or 2000 daltons or as high as 2,000,000, 1,000,000, 750,000, 500,000, 250,000 or 100,000 daltons. Polyalkylene polyamines (sometimes also referred to as polyalkyleneimines or polyalkyleneimines) represent a particularly desirable type of polyamine compound for use in preparing the polyamino-aldehyde resin. These materials are well known in the art and are described, for example, in U.S. Patent Nos. 2,182,306; 3,033,746, 2,208,095; 2,806,839; 2,553,696; and 3,251,778, each of which is incorporated herein by reference in its entirety. The polyalkylene polyamines that can be used as starting materials for the polyamino-aldehyde resins used in the acid inhibitor concentrates contemplated by the present invention include the oligomeric and polymeric materials that can be prepared by reacting ammonia or other nitrogen-containing compounds with dihalides. of alkylene (.gr., ethylene dichloride) or by ring opening polymerization of substituted or unsubstituted 1, 2-alkylene imines (e.g., ethylene imine). The polyalkylene polyamine may be linear or
branched in structure and may contain some crosslinking. The nitrogen atoms present in the polyalkylene polyamine may be primary, secondary, tertiary and / or quaternary (ie, ammonium). The polyethylene polyamines can be obtained from commercial sources such as BASF, which entails certain polyethylene polyamines under the trademarks "Polymin" and "Lupasol". Suitable polyethylene polyamines include oligomers and polymers comprised of repeat units having the structure (-CH2CH2NH-), even though other types of repeating units may also be present. Suitable polyalkylene polyamines also include copolymers of different imines as well as copolymers of imines with non-imine monomers. The polyalkylene polyamine may be spiked or derivatized before being reacted with the aldehyde to form the polyamino-ldehyde resin used as a component of the acid inhibitor concentrates and metal cleaning and stripping solutions of the present invention. As used herein, the term "polyalkylene polyamine" includes all these modified or derived substances. For example, the polyalkylene polyamine can be alkoxylated 8 v. G., Ethoxylated, propoxylated) by reacting with an oxide of
alkylene such as ethylene oxide and / or propylene oxide. The polyalkylene polyamine can also be acylated, alkylated and / or olefininated. These derivations are described in greater detail in U.S. Patent Nos. 3301,783 and 3,251,778, each incorporated herein by reference in its entirety. The salts of the polyalkylene polyamine or other polyamine can also be used, with said salts being formed generally by adding an acid to an aqueous solution of the polyamine compound. Other suitable polyamine compounds may include, for example, polyvinylamines, polyallylamines, polyvinylguanidines, and the like. In one embodiment of the invention, the polyamine compound is quaternized (before reaction with aldehyde) in a known manner, such as, for example, by reaction thereof with one or more quaternization agents. Suitable quaternization agents for reaction with the polyamine compound include lower (C1-C10) alkyl or alkenyl halides such as methyl chloride, methyl bromide, or methyl iodide; ethyl chloride, ethyl bromide, or ethyl iodide; or alpha chloroglycerol; dialkyl sulfates such as sulphate of
dimethyl, diethyl sulfate, dipropyl sulfates, or di-butyl sulfates; aralkyl halides such as benzyl chloride (an especially preferred quaternization agent); lower alkyl esters of dearlyl sulfonates such as methyl sulfonate toluene and methyl sulfonatb benzene; alkylhalo esters such as ethylchloroacetate; alkylene halohydrins such as ethylene chlorohydrin or alkylene oxides such as ethylene oxide or propylene oxide; alpha haloacetic acid derivatives, for example, alpha chloro ethyl acetate, alpha chloroacetamide, alpha chloro sodium acetate; haloketones such as chloroacetone; lactones, for example, propiolactone and sulfonates such as propane sultone. It will be appreciated by those skilled in the art that quaternization reactions do not easily go to completion and usually a degree of substitution of less than 100% (e.g., up to 40%, up to 60% or up to 80%) is achieved and can be achieved. be very effective for purposes of the present invention. In this way, it should be understood that it is possible that only a fraction of the nitrogen atoms in a quaternized polyamine compound can in fact be quaternized. Particularly preferred polyamine compounds suitable for use in preparing the resins of
polyamino-aldehyde include those substances classified as CAS 68603-67-8 ("Amines, polyethylenepoly, reaction products with benzyl chloride"). Quaternized polyamine compounds suitable for use in the present invention are also available from commercial sources, including, for example, CHE QÜAT SP-1060 and CHEMQUAT SP-2060 (available from C &; F Chemicals, Inc. of Exton, Pennsylvania). The aldehyde (aldehydes) reacted with the polyamine compound or compounds to form the polyamino-aldehyde resin can be selected from the group of organic compounds containing one or more aldehyde functional groups (-CHO) (or equivalents or precursors) of them) per molecule. The aldehyde can be aliphatic, aromatic or araliphatic in character. Exemplary suitable aldehydes include formaldehyde, C2-C6 aliphatic aldehydes (including dihaldethiides), benzaldehyde, glutaraldehyde, acetaldehyde, paraformaldehyde, glyoxal, furfural, methylglyoxal, malondialdehyde, succindialdehyde, and the like, with glyoxal being particularly preferred. The term "aldehyde" as used herein includes not only compounds containing one or more -CHO groups per molecule, but all equivalents and derivatives
related, precorders or forms thereof including groups capable of forming aldehyde groups in situ). For example, in 40% aqueous solution, glyoxal exists mainly in the form of a hydrated monomer, together with a dioxolane dimer and two debis (dioxolane) trimers. As will be explained later herein, aqueous glyoxal solutions can be conveniently used in the preparation of the polyamino-aldehyde resins which can be a component of the acid inhibitor concentrates and metal cleaning and stripping solutions of the present invention. invention. The reaction of the aldehydes and polyamine compounds to obtain the polyamino-aldehyde resins used in the acid inhibitor concentrates of the present invention can be carried out under any suitable conditions known in the art to react said types of substances. However, it will generally be desirable to use effective conditions to provide resins having a relatively high degree of water solubility. That is, it is preferred that the resin produced be capable of being dissolved in water at 25 degrees C at concentrations of at least 5% by weight, alternatively at least 10% by weight or at least 20%
in weigh. One method for preparing the resins is to combine the aqueous solutions of the aldehydes and the polyamine compounds in the desired ratio at room temperature. The exothermic reaction of these components will generally take place, with the reaction generally being substantially complete within about 1 hour. If desired, catalysts and / or heating could be used to accelerate the reaction rate. In certain embodiments of the invention, the polyamine compound is not reacted with any other type of compound other than the aldehydes. For example, the polyamine compound is not reacted with a ketone or reacted with a fatty acid, but with the aldehyde alone. Particularly preferred polyamine-aldehyde resins suitable paraffin in the present invention include those substances classified as CAS 78330-33-3 ("Amines, polyethylenepoly-, benzyl-quaternized chloride, polymers with glyoxal"). These substances can also be obtained from commercial sources, such as the resin sold under the tradename "Chemquat JL-1060" by C &F Chemicals Inc., k of Oxton, Pennsylvania, as well as the resin sold under the trade name "Corrosion. Inhibitor CES-90"by
Consulting Engineering Services, LLC, of Spartanburg, South Carolina. Typically, the acid inhibitor concentrates of the present invention contain from about 0.5 to about 15% by weight (e.g., from about 1 to about 10% by weight) of polyamino-aldehyde resin. As those skilled in the art will appreciate, however, the resin concentration can be varied as needed or desired, depending, among other factors, on the degree to which the concentrate will be diluted with aqueous acid to form a cleaning or pickling solution. of metal as well as the desired concentration of resin in the cleaning solution or metal pickling. In addition to water and at least one polyamino-aldehyde resin, the acid-inhibitor concentrates of the present invention may contain at least one aldehyde-releasing compound and / or at least one ethoxylated fatty amine and / or at least one salt thereof. ethoxylated fatty amine and / or at least one acetylenic alcohol. In one embodiment of the invention, however, the concentrate and prepopulated metal pickling and cleaning solution thereof are free of acetylenic alcohol. The aldehyde release compound is a
compound that liberates an aldehyde when formulated into an aqueous acid-containing metal stripping or cleaning solution having a relatively low pH (e.g., less than about 4 or less than about 3) and used for stripping and / or cleaning metal surfaces that have scale or other unwanted material deposited thereon. Preferably, the aldehyde that is released in this way or formed in situ is formaldehyde. The aldehyde releasing compound is preferably soluble in water. Illustrative examples of these aldehyde-releasing compounds include, but are not limited to, Schiff bases, formal, acetaldehyde dialkyl, trioxane, polyoxymethylenes, paraformaldehyde, paraldehyde, ammonia condensation products or primary amines with aldehydes, and the like . Preferably, the aldehyde release compound has a high water solubility and low volatility. Compounds which are condensation products of ammonia or primary amines such as methylamine with formaldehyde are preferred, condensation products of ammonia with formaldehyde are more preferred, and hexamethylenetetramine (also sometimes referred to as hexamine, methenamine, urotropin, or urotropin) in particular it is more preferred. The salts of said compounds are also
can use. Typically, the acid inhibitor concentrates of the present invention may contain from about 1 to about 405 wt.%, From about 5 to about 40 wt.%) Of aldehyde-releasing compound. As those skilled in the art will appreciate, however, the concentration of aldehyde release compound can be varied as needed or desired depending, among other factors, on the degree to which the concentrate will be diluted with aqueous acid to form a cleaning solution. or metal pickling as well as the desired concentration of aldehyde release compound in the metal cleaning or pickling solution. In certain desirable embodiments of the invention, the weight ratio of aldehyde release compound to polyamino-aldehyde resin in the concentrate (and in metal cleaning and pickling solutions prepared from the concentrate) is within the scale of about 0.5. : 1 to around 20: 1 (e.g., around 1: 1 to around 10: 1). Acetylenic alcohols suitable for purposes of the present invention include those organic compounds which contain both at least
a -OH group as at least one triple carbon-carbon bond per molecule. Preferred acetylenic alcohols are water soluble and include C3-C10 acertillenic alcohols such as, for example, l-propyn-3-ol, l-butyn-3-ol, l-pnetinh-3-ol, l-heptinh-3 -ol, l-octnyl-3-1, l-nonyl-3-ol,
1-decin-3-ol, 1-ethynylcyclohexanol, methylbutinol, 2-butyn-1,4-diol (a particularly preferred acetylenic alcohol),
2-methyl-3-butin-2-ol, 2,5-dimethyl-3-hexyl-2,5-diol, benzylbutynol, alpha-ethynyl-benzyl alcohol, 5-decin-4,7-dil, 4- ethyl-l-octin-3-ol, 2-propyn-l-ol (propargyl alcohol), and the like and mixtures thereof. The alkoxylated derivatives of these acetylenic alcohols 8v.gr., acetylenic alcohols which have been reacted with 1-20 equivalents of one or more epoxides such as ethylene oxide and / or propylene oxide, such as ethoxylated propargyl alcohols) are also can use. Typically, the acid inhibitor concentrates of the present invention may contain from about 0.5 to about 15% by weight (e.g., from about 1 to about 10% by weight) of acetylenic alcohol. As those skilled in the art will appreciate, however, the concentration of acetylenic alcohol can be varied as needed or desired, depending, among other factors,
of the degree to which the concentrate will be diluted with aqueous acid to form a metal cleaning or pickling solution as well as the desired concentration of acetylenic alcohol in the cleaning solution or metal pickling. As previously mentioned, however, in certain embodiments of the invention the acid inhibitor concentrate and the solution prepared therefrom do not contain any acetylenic alcohol. To optimize the effectiveness and stability of the acid inhibitor concentrates of the present invention, it may be desirable to adjust the pH of the concentrate solution by adding effective amounts of acids or bases. For example, the concentrate can be formulated with one or more acids selected from the group consisting of hydrochloric acid, phosphoric acid, acetic acid, hydroxyacetic acid or other inorganic or organic acids. It will be understood by those skilled in the art that typically at least a portion of the added acid or base will be combined with other substances used in the concentrate formulation to form salts, even if some free acid or base may also be present in solution. In one embodiment of the invention, the acid inhibitor concentrate includes one or more wetting agents, which generally help to improve the functioning of the
cleaning and pickling solutions prepared from the concentrate. These wetting agents are typically surfactants, including in particular nonionic and cationic surfactants. The moisturizing agent, if desired, can be selected so as to impart foaming properties to the metal cleaning and pickling solutions prepared from the acid inhibitor concentrates of the present invention. In one embodiment of the invention, however, one or more wetting agents are selected so that the resulting solution is essentially non-foaming (ie, it does not exhibit a substantial propensity to foam when the solution is being used to treat metal substrates) .. The ethoxylated fatty amines and salts thereof represent a clusse of especially preferred wetting agents, since at least some members of this class appear to impart improvements in synergistic operation to the acid inhibitor concentrates and acid solutions prepared therefrom. In particular, it has been unexpectedly discovered that pickling or cleaning solutions containing at least certain ethoxylated fatty amines or salts thereof are particularly effective in inhibiting the loss of base metal (i.e., reducing the rate of chemical attack) when the solutions contain
relatively high concentrations of iron salts, especially when the solution is being used at a relatively high temperature. That is, the presence of said ethoxylated fatty amines or salts thereof tends to reduce the tendency of the pickling or cleaning solution to attack the base metal more aggressively since the solution is used repeatedly and accumulates higher levels of iron salts . Illustrative ethoxylated fatty amines include amines substituted with one or more linear C6-C22 as well as branched aliphatic groups (including alkyl groups as well as alkylene groups containing one or more carbon-carbon double bonds per alkylene group) that have been reacted ( ethoxylated) with from about 2 to about 20 moles of ethylene oxide per mole of amine as well as salts thereof (e.g., carboxylate salts such as acetate salts). The ethoxylated fatty amine may be based on a diamine (e.g., a compound containing two nitrogen atoms per molecule, at least one of which is substituted with one or more saturated and / or unsaturated C6-C22 alkyl groups) ). Specific examples of useful ethoxylated fatty amines include ethoxylated coconut amines, ethoxylated bait amines, ethoxylated hydrogenated bait amines, ethoxylated dodecylamines,
ethoxylated octadecyl amines, ethoxylated soy amines, ethoxylated oleyl amines, ethoxylated stearic amines, ethoxylated N-bait diamines, ethoxylated N-oleyl diamines, and salts thereof (e.g., carboxylate salts such as acetate salts). Ethoxylated coconut amines containing an average of about 8 to about 16 (e.g., from about 10 to about 14) moles of ethylene oxide reacted per mole of coconut amine, ethoxylated bait amines which contain an average of about 6 to about 14 (e.g., about 8 to about 12) moles of ethylene oxide reacted per mole of bait amine as well as salts of said ethoxylated coconut amines or amines of Ethoxylated baits are particularly preferred. These wetting agents are readily available as commercial products, including surfactants sold under the tradename "Chemeen" by Chemex, Inc., surfactants sold under the tradename "Varonic" by Goldschmidt Chemical Corporation, as well as surfactants sold under the trade names "Ethomeen" and "Ethoduomeen" by Akzo Nobel. Other types of wetting agents that may also be used include, for example, ethoxylated nonylphenols, ethoxylated alcohols, ethoxylated fatty acids, fluorosurfactants and the like.
similar. In one embodiment of the invention, however, the concentrate and the metal cleaning and pickling solution are free of fluorosurfactant. Suitable ethoxylated fatty amines can have the formula: RN- (CH2CH2) mH I (CH2CH20) mH wherein R is a straight or branched chain, saturated or unsaturated aliphatic group having from 6 to 22 carbon atoms, n and m are the same or different and each preferably are at least I and n + m is from 2 to 20. Mixtures of these compounds can also be used. Typically, the acid inhibitor concentrates of the present invention contain from about 0.1 to about 5% by weight (e.g., from about 0.5 to about 3% by weight) of wetting agent (in particular, amine) ethoxylated fat). As those skilled in the art will appreciate, however, the concentration of wetting agent can be varied as needed or desired, depending, among other factors, on the degree to which the concentrate will be diluted with aqueous acid to form a cleaning solution or pickling as well as the desired concentration of wetting agent in the solution
cleaning or metal pickling. In certain desirable embodiments of the invention, the weight ratio of wetting agent to polyamino-aldehyde resin in the concentrate (and in metal cleaning and pickling solutions prepared from the concentrate) is from about 0.05: 1 to about 3: 1 (v.gr., about 0.1 to about 2: 1). In other desirable embodiments of the invention, the weight ratio of wetting agent to aldehyde release compound in the concentrate (and in the metal cleaning and pickling solutions prepared from the concentrate) is from about 0.005: 1 to about 2. : 2 8v.gr., around 0.02 to around 0.5: 1). To increase the water solubility of the polyamino-aldehyde resin in the concentrate, it may be desirable to acidify the concentrate by adding an acid such as hydrochloric acid (at least a portion of the added acid can form salts with the amine groups of the polyamino resin -aldehyde). However, a highly acidic solution may tend to accelerate the decomposition of the aldehyde-releasing compound to an unacceptable extent (thus releasing the aldehyde prematurely, ie before the time when the concentrate is used to make a cleaning solution. or pickling combined with aqueous acid).
If the aldehyde liberation compound releases formaldehyde (a regulated substantial), for example, this may mean that the concentrate has to be handled especially in order to avoid accumulation of unacceptably high concentrations of formaldehyde. Due to this reason, it may be desirable to pack the concentrate as a two-part system or equipment, wherein one part comprises an aqueous solution of the aldehyde-releasing compound and, optionally, a wetting agent (said solution having a pH that is moderately alkaline). , eg, about 9 to about 10) and the second part comprises an acidified aqueous solution comprising the polyamino-aldehyde resin 8 that is, the aldehyde-releasing compound and the polyamino-aldehyde resin are kept separate until shortly before use, when the two parts of the concentrate are combined and diluted with aqueous acid to prepare the cleaning solution or metal pickling). The second part may optionally contain a wetting agent. If it is desired to maintain the formaldehyde level of less than 0.1% by weight in an acid inhibitor concentrate according to the present invention, it will generally be preferred to adjust the pH so that it is higher than
about 7. The acid inhibitor concentrates of the present invention will find use in preparing acid cleaning and pickling solutions which are effective for cleaning unwanted metal oxide flake metal surfaces and other undesirable corrosion products. Examples of these cleaning solutions are those containing mineral and / or organic acids such as, for example, hydrochloric acid, phosphoric acid, hydrofluoric acid, sulfamic acid, sulfonic acid, sulfuric acid, acetic acid, citric acid, formic acid, glycolic acid , oxalic acid and mixtures thereof. The concentration of acid in the metal cleaning or pickling solution can be adjusted as needed in order to achieve the desired level of cleaning activity. For example, when hydrochloric acid is used as the acid, typically the HC1 content of the solution is kept within the range of about 1 to about 30% (e.g., about 5 to about 20%). on a weight basis7volume. Typically, the acids selected and the concentration of said acids in the metal cleaning or pickling solution are effective to provide a highly acidic solution, e.g., a solution having a pH
less than about 3, less than about 2, or less than about 1. The acid inhibitor concentrates described herein can be used with particularly good advantage in applications involving stripping with hydrochloric acid from ti9ra line. , continuous and batch of ferrous surfaces, that is, in applications where the iron tends to accumulate in the cleaning solution. Various types of steel can be effectively cleaned of scale and the like by treatment with solutions containing HC1 prepared from the present acid inhibitor concentrates, for example, However, acid inhibitor concentrates are also useful in other types of solutions. cleaning and pickling, such as those, for example, that are used to clean surfaces of aluminum, or aluminum alloy or surfaces of zinc or zinc alloys. In general, the acid inhibitor concentrates of the present invention are incorporated into acid cleaning solutions in any effective amount to reduce the tendency of the acid to attack and corrode without significantly interfering with the cleaning operation performed by the acid. The optimal amount of inhibitor concentrate
The acid to be combined with an aqueous acidic solution will vary depending on a number of factors, including the particular active components present in the concentrate (e.g., the particular polyamino-aldehyde resin)., the particular aldehyde release compound, the particular wetting agent, etc.), the type of acid concentration, the metal tio being treated, as well as the treatment conditions (e.g., contact time, temperature ). Typically, however, a part by volume of the acid inhibitor concentrates of the present invention is diluted with about 50 to about 50,000 parts by volume of aqueous acid. That is, the acid inhibitor concentrate is typically combined with an aqueous acid solution at a concentration of about 0.001 to about 2% (e.g., about 0.005 to about 0.5) on a volume / volume basis . If the metal cleaning or pickling solution is to be used at a relatively high temperature, the amount of concentrate present in the solution will generally be higher than if the solution is to come into contact with metal surfaces at relatively low temperatures. The concentrate can first be combined with a relatively acidic solution
concentrate (e.g., 37% concentrated HC1) and the resulting mixture is then diluted with water to provide the working solution that will be used to clean and / or remove a metal surface. Said mixture can also be conveniently used to replenish an existing solution wherein the acid concentration and / or the concentrations of acid inhibiting substances have fallen below the desired levels. Alternatively, the concentrate can be combined directly with an aqueous solution having the desired acid concentration for the purposes of the cleaning and pickling solution. In certain embodiments, metal cleaning or pickling solutions may contain concentration of components at the following scales: Polyamino-aldehyde resin 0.5-500 ppm (e.g., 1-200 ppm) 0-1000 aldehyde release compound ppm (e.g., 5-500 ppm)
Wetting agent 0-200 ppm (e.g., 0.5-100 ppm)
Acetylenic alcohol 0-700 ppm (e.g., 5-300 ppm) The concentration shown above varies based on the amounts of the individual components as charged initially to the solution. Certain of the components, in particular the release compound of
aldehyde, it is believed that they undergo chemical reaction or transformation once the solution has been formed and / or once the solution is put to use for cleaning and / or pickling metal surfaces. For example, without wishing to be bound by theory, it is believed that the aldehyde-releasing compound decomposes to form aldehydes and other decomposition products after having been combined with aqueous acid to form the metal pickling or cleaning solution, since these solutions are typically highly acidic and the aldehyde release compound is known to be unstable at low pH (e.g., where the pH is less than 3). Generally speaking, the cleaning and pickling solutions containing the acid inhibitor concentrates of the present invention can be used to treat any of a variety of metals. Examples of metal surfaces include both pure metals and alloys such as, for example, aluminum (including aluminum alloys), magnesium, zinc, titanium, iron, copper, steel (including, for example, cold rolled steel, steel laminated into hot, galvanized steel, alloy steel, carbon steel), bronze, stainless steel, brass and the like. For example, him
The substrate to be contacted with the solution may be comprised of at least 50 weight percent aluminum, zinc or iron. The substrate that comprises the metal surface to be treated in accordance with the present invention can take any form, including, for example, wire, wire mesh, sheets, strips, panels, protectors, vehicle components, housings, decks , furniture components, aircraft components, device components, profiles, molded parts, pipes, racks, tool components, bolts, nuts, screws, springs or the like. The metal substrate may contain only one type. of metal or different types of metal attached or held together in some way. The substrate to be treated in accordance with the process of the present invention may contain metal portions in combination with portions that are non-metallic, such as plastic, resin, glass or ceramic portions. The metal cleaning or pickling solutions prepared from the acid inhibitor concentrates of the present invention exhibit good consistent inhibition of metal attack even when the solution is operated at relatively high temperatures for a prolonged period of time and / or contains a level iron loading
high. For example, the solution can be maintained at ambient temperatures (ie, around 20 degrees C) to around 100 degrees C. The surface of metal with scale or other material deposited or adhered therein to be cleaned and / or pickling is contacted with the solution for a time and at an effective temperature to remove the desired amount of flake or other material from the metal surface, leaving the surface cleaned and / or descaled and / or pickled with reduced loss (etching) of the metal itself as compared to contacting the same type of solution that does not contain an acid inhibitor concentrate in accordance with the present invention. The solution can be brought into contact with the metal surface using any suitable or known method such as, for example, dipping (dipping), brushing, spraying, roller coating, rubbing and the like. Once the solution has been in contact with the metal surface for the desired period of time, the substrate having the metal surface can be removed from contact with the volume of the solution (for example, by removing the substrate from an anchor). or tub containing the solution). The residual solution adhering to the metal surface can be allowed to drain off the surface or
be removed by other means such as rubbing. The metal surface can be rinsed with water or another solution to remove any remaining solution and / or to neutralize any residual acid and / or to prevent "flash rust" from the newly exposed metal surface. The metal pickling or cleaning solutions of the present invention are capable of producing easy-to-rinse metal surfaces by exhibiting the "water lamination" phenomena that clean, not dirty, typically high-energy metal surfaces. The "water lamination" exhibited by the rinsed metal surfaces processed in accordance with the present invention distinguishes the present invention from many acid inhibitor technologies known in the prior art, which tend to produce a highly hydrophobic "water dripping surface". "(ie, a metal surface on which water forms separate separate beads). "Water beads" on cleaned or pickled metal surfaces indicate that thin organic films have remained on the surface after the rinsing step; said residual films may adversely affect and / or further complicate processing under the metal-containing article.
The end uses of the compositions of the present invention include, but are not limited to, chemical and electrolytic pickling operations, acid immersion process, plant washing procedures, metal surface cleaning of industrial equipment 8v.gr., cleaning of industrial boilers, heat exchangers and condensers), and oil well acidification operations. EXAMPLES Example 1. To prepare a polyamino-aldehyde resin for use in formulating an acid inhibitor concentrate according to the present invention, 100 parts by weight of an aqueous solution of CHEMQUAT SP-1060 (a polyethylene polyamine quaternized with benzyl chloride 60% solids) is combined with 30 parts by weight of a 40% glyoxal aqueous solution. An exothermic reaction is observed, producing a dark colored solution exhibiting strong absorption at 1640 cm "1 in the FTIR spectrum Example 2. To prepare an acid inhibitor concentrate according to the present invention, the following are combined components and are mixed (preferably in the following order of addition) to provide a homogeneous solution:
Deionized water 65.05% by weight
Hexamethylenetetramine 16.0% by weight
CHEMEEN C-12G ethoxylated coconut amine 1.75% by weight
Hydrochloric acid (20 degrees baume) 9.75% by weight Acetic acid (56%) 0.45% by weight
CES-901 Corrosion Inhibitor 8 - *% by weight
1 supplied by Consulting Engineering Services, LLC; reported to contain 59-61% polyethylenepolyamine polymers quaternized with benzyl chloride with glyoxal (CAS 78330-33-3), less than 4% tetraethylenepentamine, less than 1% triethylene tetramine, and 39-41% water. To prepare the metal cleaning or pickling solutions according to the present reference, 1 part by volume of the described acid inhibitor concentrate arrives, for example, can be combined with from 200 to 20,000 parts by volume of an aqueous solution containing 10% weight / volume of HC1. Other acids as well as other concentrations of HC1 (e.g., about 0.5 to about 20% weight / volume) can also be used. The effectiveness of the pickling or cleaning solutions of the present invention in reducing the amount of loss of base metal when the solutions are used for
Treat metal surfaces is demonstrated in the following examples. EXAMPLE 3 The solution was prepared by combining 0.1710 g of QUEMQUAT SP-1060 quaternized polyethylenepolyamine with 2 L of 10% aqueous hydrochloric acid at 7 volume. Solution B was prepared by combining 0.222 g of the polyamino-aldehyde resin of Example 1 with 2 L of 10% w / v aqueous hydrochloric acid. Solution C was prepared by first preparing a mixture of 130 parts by weight of the polyamino-aldehyde resin of Example 1 with 20 parts by weight of CHEMEEN G-12G ethoxylated fatty amine and then combining 0.257 g of this mixture with 2 L of acid hydrochloric acid at 10% weight / volume. Coupons of cold rolled steel (alloy 1008) measuring 0.813 mm x 5.08 cm x 10.16 cm (0.032 x 2 x 4 inches9) were rubbed with fresh isopropyl alcohol, dried and weighed (to the nearest 0.1 mg). Test panels 82 by test9 were suspended on plastic coated hooks through 6.35 mm (1/4") drilled holes and placed for 30 minutes in each of Solutions A, B and C, solutions were maintained at 82 ° C (180 ° F), were agitated with a magnetic stir bar
(flow rate of solution to panels of 0.914-1.524 m (3-5 ft / second), they were covered with water-cooled watch glasses.) After the exposure, the panels were rinsed immediately in a bath of fresh flowing water, they were moistened with isopropyl alcohol and then wiped firmly / dried with fresh clean soft paper before weighing again: the test panels exhibited the following amount of base metal loss: Solution A: 0.035 kg / cm2 / hour (0.5040 lb / ft2 / hr) Solution B: 0.0206 kg / cmVhora (0.2935 lg / ft2 / hr) Solution C: 0.019 kg / cm2 / hour (0.2773 lb / ft2 / hr) These results show that the reaction product of polyethylenepolyamine Quaternized and glyoxal (Solution B) was much more effective in inhibiting loss of base metal than unreacted quaternized polyethylenepolyamine (Solution A) and that the presence of an ethoxylated fatty amine (Solution C) also provides additional inhibition enhancement. Example 4 Solutions A-1, B-1, and C-1 were prepared by adding 0.69 g of hexamethylenetetramine to each of Solutions A, B, and C, respectively, in Example 3. After the same test protocol above
described in Example 3, cold rolled steel coupons exposed to Solutions Al, Bl, and Cl exhibited the following amount of base metal loss: Al Solution: 0.011 kg / cm2 / hour (0.1606 lb / ft2 / hr) Solution Bl: 0.008 kg / cm2 / nora (0.1220 lb / ft2 / hr) Cl solution: 0.005 kg / cm2 / hour (0.0824 lb / ft2 / hr) These results demonstrate that the hexamethylenetetramine present further improves the effectiveness of the resin of quaternized-glyoxal polyethylene-polyamine by inhibiting loss of base metal in the pickling or metal cleaning solution containing non-oxidising acid (compare Solution Bl with Solution B and Solution Cl with Solution C). Solutions B2 and C2 were prepared by adding 0.24 g of 1,4-butyndiol to each of Solutions B-1 and Cl, respectively. Following the same test protocol described above, cold rolled steel coupons exposed to Solutions B-2 and C-2 exhibited the following amount of base metal loss: Solution B-2: 0.0049 kg / cm2 / hour (0.0710) lb / ft2 / hr) Solution C-2: 0.0034 kg / cm2 / hour (0.0494 lb / ft2 / hr) These examples demonstrate the benefits of including
an acetylenic alcohol in the acid inhibitor compositions of the present invention. Example 5 The effectiveness of the acid inhibitor concentrates of the present invention in inhibiting loss of base metal during cleaning of an aluminum-containing substrate is demonstrated by the following examples: Two baths were prepared as follows: Bath 1: 19.0 mL from HC1 to 375 diluted in 181 g deionized water Baño 2: 20 mL of an inhibitor / acid mixture (the mixture being prepared from 13.4 g of deionized water, 72.6 mL of 37% HCl, and 0.475 g of a acid inhibitor concentrate according to Example 2) diluted in 180 g of deionized water. Each bath was placed in a glass beaker at room temperature. The aluminum panels (aluminum alloy 3003; 5.08 x 10.16 x 0.635 cm (2"x 4" x 0.025") were cleaned with SCOTCH-BRITE pads and water, then rubbed with isopropanol, rubbed to dry and then weighed (to the nearest 0.0001 g.) The panels were then placed on each of the pointed vessels so that about two thirds of each panel was submerged
in the bathroom. The submerged panel in Bath 1 exhibited significantly more gas evolution than the submerged panel in Bath 2. After 6 minutes of immersion, the weight of the panel in Bath 1 had decreased by 0.0066 g, while the panel weight in the Bath 2 had decreased by 0.0006 g (91% inhibition). Before weighing, the panels were rinsed and then rubbed with isopropanol. After an additional 60 minutes of immersion, the weight loss of the panel in Bath 1 (which was hazy and gray and had reached a temperature of 36 degrees C due to the exothermic created by dissolving the metal) was 1.4436 g and the weight loss of the panel in Bath 2 (which was clear and 17 BC (67 degrees F) of temperature) was 0.0137 g (99.05% inhibition). The panel that had been submerged in Bath 1 had a significant amount of ash on its surface, while the panel that had been submerged in Bath 2 had very little ash on its surface. Example 6. To demonstrate the effectiveness of the inventive compositions in inhibiting the etching of a variety of aluminum alloy surfaces by hydrochloric acid, the following solutions of
proof. Control: 2.0% (w / v) hydrochloric acid. Invention: The acid inhibitor concentrate of Example 2 was diluted to 0.05% (v7v) in 2.0% (w / v) hydrochloric acid. Test panels of various aluminum alloys measuring 5.08 by 10.16 cm (2"by 4") (two for each test) were cleaned using a SCOTCH-BRITE pad and water, then dried and weighed to 0 mg precision. The panels were then placed in 2 liters of the stirred test solutions (freshly prepared for each test and maintained at the temperatures shown in Table 1) during the times shown in Table 1. The panels were then cleaned, dried and the metal loss in kg / cm / day (lbsw / ft2 / day) was calculated and compared with the control to determine the percentage of inhibition achieved. The results shown in Table 1 demonstrate that the bath in accordance with the invention generally exhibited a much higher degree of acid attack inhibition compared to control through a scale of temperatures typically encountered during metal cleaning operations, regardless of which type of aluminum alloy substrate was used. Table 1
Substrate% of% of Inhibition Inhibition Inhibition 38 ° C 49 ° C 60 ° C Alloy of Al 1100 82.0 72.3 43.9
Al Alloy 2024 91.8 95.0 95.8 T3 Alloy Al 3003 90.5 91.1 69.9
Alloy of 5052 85.5 82.1 73.3
Alloy of Al 6061 96.3 98.3 96.8
Alloy 7075 81.0 57.8 63.6 T6 Contact Time 60/240 30/90 15/60 in Minutes (Control / invention)
Example 7 To demonstrate the effectiveness of the inventive compositions in inhibiting chemical attack of pure zinc metal surfaces by phosphoric acid, the following test solutions were prepared. Control: 5.0% (w / v) phosphoric acid Invention: the acid inhibitor concentrate of Example 2
it was diluted to 0.05% (v / v) in 5.0% (w / v) of phosphoric acid (1.06 g / 2 L). Test panels of pure zinc metal measuring 5.08 cm x 5.08 cm (2"by 2") (two for each test) were cleaned using a SCOTCH-BRITE pad and water, then dried and weighed to 0.1 mg accuracy. The panels were subsequently suspended in 2 liters of the stirred test solutions (freshly prepared for each test) maintained at the temperatures shown in Table 2 by the times also shown in Table 2. The panels were then cleaned and dried and the Average metal loss in kg / m2 / day (lbs / ft2 / day) was calculated and compared with the control to determine the% inhibition achieved. The results shown in Table 2 demonstrate that the bath according to the invention exhibited an exceptionally high degree of acid attack inhibition compared to the control. Test Solution%% of & of Inhibition. Inhibition, Inhibition, 38 ° C 49 ° C 60 ° X Invention 95.6 95.1 91.9
Contact Time 60/180 30/90 15/60 in Minutes
(Control / Invention
Example 8 This example illustrates the effectiveness of compositions in accordance with the present invention in inhibiting the acid attack of aluminum surfaces, particularly when said compositions contain both an aldehyde-releasing compound and an ethoxylated fatty amine. The following baths were prepared: Invention A - 0.0742 g of CES-90 (supplied by Consulting Engineering Services, LLC, reported to contain 59-61% polyethylenepolyamine polymers quaternized with benzyl chloride with glyoxal (CAS 78330-33-3) , less than 4% tetraethylenepentamine, less than 1% triethylenetetramine, and 39-41% water) and6 0.1696 g H 2 MT in 2.0 ligers (w / v) of HC1. Invention B - 0.0186 g of CHEMEEN C-12G ethoxylated coconut amine was added to the bath of Invention A after said bath had been used (some acid consumed). Two 5.08 x 10.16 cm (2"x 4") panels of 3003 aluminum alloy (recently cleaned using a SCOTCH-BRITE pad) were placed in each shaking bath,
maintained at the temperature indicated in Table 3. After contact times identical to those listed in Table 1, the amount of metal loss and% inhibition calculated as compared to a control was determined (2.0% w / v HCF1). , without inhibitor). The results obtained (Table 3) show that the use of a quaternized polyethylenepolyamine which has been reacted with aldehyde (glyoxal) provides effective inhibition of acid attack, particularly at elevated temperatures and when used in combination with both H AT and a fatty amine ethoxylated. Table 3 Temperature, Invention A,% of Invention B,% of ° C Inhibition against Inhibition against Control Control 38 89.3 92.3 49 87.6 90.6 60 63.0 79.9