WO1998030652A1

WO1998030652A1 - Acid deoxidizing/etching composition and process suitable for vertical aluminum surfaces

Info

Publication number: WO1998030652A1
Application number: PCT/US1997/000006
Authority: WO
Inventors: Scott J. Beleck
Original assignee: Henkel Corporation
Priority date: 1997-01-09
Filing date: 1997-01-09
Publication date: 1998-07-16
Also published as: CA2248568A1

Abstract

A thixotropic aqueous liquid composition suitable for deoxidizing and etching aluminum substrates, even if they are vertical to local gravity and not immersed in any container, contains fluoride ions, an acid with an ionization constant greater than that of HF, a viscosity increasing agent that preferably is a modified xanthan gum, and both anionic and nonionic surfactants. Preferably the composition also contains a colorant, so that the thickness of the coating applied to a substrate may be visually estimated.

Description

ACID DEOXIDIZING/ETCHING COMPOSITION AND PROCESS SUITABLE OR VERTICAL ALUMINUM SURFACES

Field of the Invention

This invention relates to an improved composition and process for etching and/or deoxidizing aluminum and aluminum alloy surfaces that may be at any angle to the local gravitational force of the earth and are not immersed in the composition. (Hereinafter, unless the context requires otherwise, the simple term "aluminum" is to be understood as including alloys containing at least 50 % by weight of aluminum.) As a result, the compositions must have sufficient viscosity at low shear rates to resist flowing off the surfaces to which they are applied under the influence of the gravitational force of the earth. Discussion of Related Art

Common chemical and mechanical treatments of aluminum often leave the surface with an oxide coating that must be removed before subsequent surface finishing steps can be satisfactorily completed. This process is generally known in the art as "deoxidizing" or, if the oxide coating is dark colored, alternatively as "desmutting". In order to assure full removal of the undesired oxide coating, the surface is often etched, i.e., some fraction, preferably a small one, of the metal of the surface itself is removed, along with the oxide layer on it.

For aluminum objects of sufficiently small size, a deoxidizing/etching process is normally accomplished by immersing the objects in a relatively low viscosity aqueous liquid, traditionally an aqueous acid solution including hexavalent chromium. This method is generally effective, but it can not be practically applied to large aircraft, rail cars, and the like which are too large to immerse in any available container. For such substrates a composition that will cling for a sufficient time to the entire surface to be deoxidized/etched, even if all or part of the surface is vertical to the local gravitational force of the earth, is needed.

DESCRIPTION OF THE INVENTION Objects of the Invention

A major object of the invention is to provide a new type of flow resistant deoxi- dizing/etching composition that is improved with respect to available prior art counterparts in at least one of the following desiderata: (1) an etching rate of 2.5±0.5 micrometres per hour of exposure (hereinafter usually abbreviated as "μm/hr") on all parts of an aluminum surface to which it is applied; (2) minimal etch of titanium or ferriferous sur- faces, which are often adjacent to aluminum surfaces desired to be deoxidized and difficult to protect completely against some exposure to the composition applied to deoxidize neighboring aluminum parts of a composite structure; (3) easy visual detection of the presence of the composition on a large aluminum structure being treated with it; (4) facile removal of the composition when its desired action is complete by an at least predom- inantly aqueous rinsing liquid; (5) effective removal of any moderate amounts of organic contaminants that may be on the aluminum surface to be deoxidized; (6) facile wetting of and/or spreading over aluminum surfaces to be treated with the composition; (7) uniformity of visual appearance of the substrate surface after treatment with the composition; and (8) minimal pollution from the compositions. Other objects will be ap- parent from the description below. General Principles of Description

Except in the claims and the specific examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word "about" in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred, however. Also, unless expressly stated or necessarily implied by the context to the contrary: percent, "parts of, and ratio values are by weight; the term "polymer" includes "oligomer", "copolymer", "terpolymer", and the like; the first definition or description of the meaning of a word, phrase, acronym, abbreviation or the like applies to all subsequent uses of the same word, phrase, acronym, abbreviation or the like and applies, mutatis mutandis, to normal grammatical variations thereof; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; specifications in chemical terms of materials in compositions refer to the materials at the time of addition to any composition so specified, and do not necessarily exclude the possibility of reaction between such materials and other materials already present in the composition at the time of addition of the specified materials; specification of materials in ionic form implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole; and any counterions thus implicitly specified preferably are selected from among other constituents explicitly specified in ionic form, to the extent possible; oth- erwise such counterions may be freely selected, except for avoiding counterions that act adversely to the objects of the invention. Summary of the Invention

It has been discovered that the above stated object of the invention can be achieved with a viscous liquid composition that comprises, preferably consists essentially of, or more preferably consists of, water and:

(A) an amount of a source of dissolved fluoride ions;

(B) an amount of a source of an acid with a larger ionization constant than hydrofluoric acid;

(C) an amount of a viscosity increasing agent that is not part of any of the previously recited components;

(D) an amount of anionic surfactant that is not part of any of the previously recited components;

(E) an amount of nonionic surfactant that is not part of any of the previously recited components; and, optionally, one or more of the following: (F) a hydrotroping agent that is not part of any of the previously recited components; (G) a coloring agent that is not part of any of the previously recited components; (H) a biocidal agent that is not part of any of the previously recited components; and (J) an oxidizing agent that is not part of any of the previously recited components. Another embodiment of the invention is a process comprising, preferably consist ing essentially of, or more preferably consisting of, at least steps of:

(I) forming on an aluminum substrate surface to be deoxidized/etched a coating of a viscous liquid composition according to the invention as described above;

(II) maintaining in place the coating formed in step (I) for a time sufficient to deoxidize/etch the aluminum substrate surface; and (III) subsequently removing the coating of viscous liquid composition formed in step (I) from further contact with the aluminum substrate surface. Other steps, including those conventional per se, may be included in a process according to the invention along with these necessary steps.

Other embodiments of the invention include substrates prepared by a process according to the invention as described above, the use of such substrates in any application to which aluminum articles are adapted, and the like. Detailed Description of the Invention. Including Preferred Embodiments

For various reasons, it is often preferred that compositions according to the invention be substantially free from various constituents that can cause practical difficulties when present. More particularly, with increasing preference in the order given and with independent preference for each noted component, compositions according to the inven- tion preferably contain no more than 4.0, 2.2, 0.90, 0.50, 0.20, 0.12, 0.070, 0.030, 0.010, 0.0050, 0.0020, 0.0010, 0.00050, 0.00020, or 0.00010 grams of constituent per kilogram of total composition (hereinafter usually abbreviated as "g/kg") of any of the following: metal cations with a valence of 2 or higher; chloride, bromide, or iodide ions (which can cause pitting corrosive attack on aluminum); any anions containing a metallic element in a valence state of +3 or more; organic peroxides; halate or perhalate anions; and any organic molecules containing at least two but not more than twelve moieties selected from the group consisting of hydroxyl, amino, phosphino, carboxyl, and carboxylate moieties, wherein any two of said at least two but not more than twelve moieties are separated from each other by exactly 2 or 3 other atoms within the organic molecule, so that a chelate complex can readily be formed between the organic molecules and metal ions.

Fluoride ions component (A) is preferably supplied by one or more substances selected from hydrofluoric acid and all of its water soluble salts, including fully and partially neutralized salts, and the stoichiometric equivalent as fluoride of all of these dissolved materials present in the composition is to be considered as part of component (A), irrespective of the actual extent of ionization existing in the composition. Inasmuch as "free fluoride" is needed to achieve the levels of etching speed desired, complex fluoride anions such as fluoborate, fluotitanate, fluosilicate, and fluozirconate are not considered part of component (A) if present in a composition according to the invention and preferably, at least for reasons of economy, are not present at all. Ammonium and alkali metal fluorides and/or bifluorides are preferred and ammonium fluoride and/or bifluoride is most preferred. Irrespective of the source, the amount of fluoride ions present in a working composition according to the invention preferably is at least, with increasing preference in the order given, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, 14.0, 16.0, 17.0, or 18.0 grams per kilogram of total composition (hereinafter usually abbreviated as "g/kg") and independently pref- erably is not more than, with increasing preference in the order given, 60, 50, 40, 35, 30, 28, 26, 24, 22, 20.0, or 19.0 g/kg.

Component (B) of strong acid is, primarily for reasons of economy, preferably selected from inexpensive strong mineral acids such as sulfuric, hydrochloric, and nitric acids, with sulfuric most preferred. Irrespective of the source, the amount of acid from component (B) in a working composition according to the invention preferably is such as to provide at least, with increasing preference in the order given, 0.080, 0.15, 0.30, 0.40, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, or 0.78 moles of ionized hydrogen atoms per kilogram of total composition (hereinafter usually abbreviated as "mH/kg") and independently preferably to provide not more than, with increasing preference in the order given, 6.0, 5.0, 4.0, 3.0, 2.5, 2.0, 1.5, 1.2, 1.0, or 0.80 mH/kg. In calculating these amounts of hydrogen ions for known chemical compositions, all of the hydrogen atoms of any acid present that ionize with a larger ionization constant than hydrofluoric acid are assumed to be completely ionized. Thus, for example, both hydrogen atoms of each dissolved H₂SO₄ molecule are assumed to be ionized, because the second ionization constant of sulfuric acid is 0.012 while that for HF is only 0.00072. For H₃PO₄, however, only its first ionization constant is greater than that for HF, so that only one hydrogen would be assumed to ionize from this molecule.

Independently of their separate amounts, the amount of ionized hydrogen ions in mH/kg preferably has a ratio to the amount of fluoride in g/kg that is at least, with in- creasing preference in the order given, 0.0040:1.0, 0.0060: 1.0, 0.0080:1.0, 0.0100:1.0,

0.015:1.0, 0.020:1.0, 0.025:1.0, 0.030:1.0, 0.035:1.0, 0.038:1.0, 0.040:1.0, or 0.042:1.0 and independently preferably is not more than 0.40:1.0, 0.30:1.0, 0.20:1.0, 0.15:1.0,

0.10:1.0, 0.090:1.0, 0.080:1.0, 0.070:1.0, 0.060:1.0, 0.055:1.0, 0.050:1.0, or 0.045:1.0.

A working liquid substrate coating composition according to this invention pref- erably is highly thixotropic, i.e., it preferably has a relatively high viscosity when beginning to be disturbed from a motionless state, but becomes relatively low in viscosity when subjected to stronger forces, so that it may readily be applied by convenient meth- ods such as spraying, dipping, brushing, and the like to a substrate to be protected, to form a coating that will remain in place against the influence of natural gravity without becoming thinned to an undesirable degree. The thixotropy may conveniently be measured by means of a well known type of instrument, a Brookfield viscometer, using spindle # 4. The viscosity at 25 °C of a viscous liquid working composition according to the invention measured in this way, when measured at 0.5 revolution per minute (hereinafter usually abbreviated as "rpm") preferably is at least, with increasing preference in the order given, 100, 200, 300, 400, 500, 600, 650, 700, 750, 800, 850, 870, 890, or 910 poises (hereinafter usually abbreviated as "ps"); independently preferably is, when measured at 2.5 rpm, at least, with increasing preference in the order given, 25, 50, 75, 100, 150, 200, 250, 300, 350, 370, 390, or 400 ps; and also independently preferably is, when measured at 20 rpm, not more than, with increasing preference in the order given, 400, 350, 300, 250, 210, 170, 130, 105, 100, 95, 90, or 86 ps.

A wide variety of natural and synthetic materials, such as natural gums and other polysaccharides, various synthetic polymers, and finely divided inorganic solids such as certain clays and silica sols, are known in the art for achieving thixotropy and may be used in a composition according to the invention. The most preferred material for component (C) is xanthan gum, preferably a type of this gum which has been modified from its natural state to result in smoother flow properties at low shear rates, as described in more detail in connection with the working examples according to the invention below. For any viscosity modifying component, the amount preferably should be selected to achieve preferable values of viscosities at various measuring speeds as already specified above. For the preferred modified xanthan gum as noted above, along with other preferred types and amounts of components (A) and (B), the concentration of the modified xanthan gum in a viscous liquid working composition according to the invention preferably is at least, with increasing preference in the order given, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0, 20.0, 21.0, or 22.0 g/kg and independently preferably is not more than, with increasing preference in the order given, 150, 125, 100, 80, 60, 50, 40, 30, 25.0, or 22.5 g/kg. A wide variety of commercially available and other known materials are suitable for component (D) of anionic surfactants. Examples include sulfonic acids, partial esters of sulfuric and phosphoric acids, and the like, and salts of all of these acids, in each instance selected from molecules that contain a hydrophobic moiety containing from 8 to 22, more preferably from 10 to 20, or still more preferably from 12 to 18, carbon atoms and not more than, with increasing preference in the order given, 5, 3, 2, 1, or 0 atoms other than carbon, hydrogen, and halogen atoms. Largely for reasons of economy, sulfonic acids, partial esters of sulfuric acid, and salts of both these types of are preferred. Linear alkylbenzene sulfonic acids and their corresponding sulfonates are most preferred for component (D). The amount of component (D) in a working composition according to the invention preferably is at least, with increasing preference in the order given, 2, 4,

6, 8, 10, 1 1.0, 12.0, 13.0, 14.0, 15.0, or 15.8 g/kg and independently preferably is not more than, with increasing preference in the order given, 75, 60, 50, 40, 35, 30, 25, 23,

21, 19, 18.0, 17.0, 16.5 or 16.2 g/kg.

As with component (D), a wide variety of commercially available and other known surfactants are suitable for component (E) of non-ionic surfactant. Preferred molecules for component (E) conform to the general chemical formula (I): R'O(CH₂CH₂O)_y(CH₂CHCH₃O)_zH (I) where R¹ is a moiety selected from the group consisting of saturated-and-unsaturated straight-and-branched-chain-aliphatic-monovalent-hydrocarbon-moiety-substituent - bearing phenyl moieties in which the aromatic ring of the phenyl moiety is directly bonded to the oxygen atom appearing immediately after the R¹ symbol in formula (II); y is a positive integer; and z is zero, one, or two. More preferably, independently for each preference stated, z is 1 or 0, most preferably zero; the aliphatic monovalent hydrocarbon moiety substituent in R¹ has at least, with increasing preference in the order given, 5, 6,

7, 8, or 9 carbon atoms and independently preferably has not more than, with increasing preference in the order given, 12, 11, 10, or 9 carbon atoms; the aliphatic monovalent hydrocarbon moiety substituent in R¹ is straight chain rather than branched; and the average value of y is at least, with increasing preference in the order given, 3, 4, 5, 6, 7, or 8 and independently preferably is not more than, with increasing preference in the order given, 16, 15, 14, 13, 12, 11, 10, or 9.

Independently of its specific chemical composition, the amount of component (E) in a composition according to the invention preferably is such that it has a ratio to the amount of component (D), measured in the same units, in the same composition that is at least, with increasing preference in the order given, 0.015:1.0, 0.030:1.0, 0.045:1.0, 0.060:1.0, 0.075:1.0, 0.090:1.0, 0.100:1.0, 0.110: 1.0, 0.115: 1.0, 0.120:1.0, or 0.123:1.0 and independently preferably is not more than, with increasing preference in the order given, 2.0:1.0, 1.5:1.0, 1.0:1.0, 0.50:1.0, 0.40:1.0, 0.30:1.0, 0.25:1.0, 0.20:1.0, 0.18:1.0, 0.16: 1.0, 0.150:1.0, 0.140:1.0, or 0.130:1.0. The presence of optional hydrotroping agent component (F) is generally preferred in concentrates according to the invention. Conventional hydrotroping agents such as the salts of alkyl benzene sulfonic acids, particularly of cumene sulfonic acid, are suitable for compositions according to this invention and are generally preferred for reasons of economy. However, if very low tolerances for residual sulfur on the deoxidized surface are prescribed, at least one of two other types of hydrotropes are then preferred: (i) organic phosphate esters and (ii) alkyl and alkenyl substituted cyclic acid anhydrides, particularly the anhydrides of C_4.6 terminal dicarboxylic acids substituted with alkyl or alkenyl groups having 6 to 20 carbon atoms. Particularly preferred examples of this type of hydrotrope are octenyl and nonenyl succinic anhydrides. The amount of hydrotroping agent, when it is used at all, is preferably such as to have a ratio to the amount of component (E), measured in the same units, that is at least, with increasing preference in the order given, 2: 1.0, 4: 1.0, 6: 1.0, or 8: 1.0 and independently, primarily for reasons of economy, preferably is not more than, with increasing preference in the order given, 25:1.0, 20:1.0, 15:1.0, 13:1.0, 11 :1.0, or 9: 1.0, with the higher ratios within this range generally preferred for very highly concentrated compositions according to this invention and lower ratios, including omission of any hydrotroping agent at all, often satisfactory for working compositions.

Optional colorant component (G) is often preferred in a composition according to this invention, to serve as a visual indicator of the thickness of the coating applied to a substrate surface with a complicated shape and thereby make it easier to achieve the usual goal of an approximately equally thick coating over the entire surface to be deoxidized/etched. Numerous conventional dyes and/or pigments, as known to those skilled in the art, may be used for component (G).

Optional biocidal component (H) is not normally needed, but may be preferably present in a liquid composition according to the invention in an amount effective to repress the biodegradation of any of the components of the composition, when the composition is used in an environment in which acid-tolerant microorganisms are prevalent. Optional oxidizing agent component (J) is not normally needed, but may be useful to accelerate the etching process on some substrates. Hydrogen peroxide is preferred when this component is used; it also has some biocidal activity and may be used for that purpose as part of component (H). In preparing the compositions according to this invention, it is preferable to add the viscosity increasing agent to water before adding any of the other ingredients. If this is not done, long term viscosity instability may be experienced.

Preferably a substrate to be deoxidized and/or etched in a process according to this invention should be cleaned to remove most gross soils before being exposed to a composition according to this invention as described above.

A process according to the invention is normally performed at ambient temperature, if for no other reason than that maintaining a different temperature would be a considerable practical difficulty in view of the large size of the substrates usually treated. A contact time from 1 to 20 minutes, or more preferably from 8 to 12 minutes, is normally preferred in a process according to this invention.

The invention may be further appreciated by consideration of the following examples and comparison examples. Materials Used

BRIJ™ 35 surfactant was obtained commercially from ICI Americas, Inc. and is reported by its supplier to consist of ethoxylates of lauryl alcohol with an average of 23 moles of ethylene oxide per mole of lauryl alcohol.

CAB-O-SIL™ M5 dispersion of finely divided silica in water was obtained commercially from Cabot Corp. and is recommended as a viscosity increasing agent

CALSOFT™ LAS 99 surfactant was supplied by Van Waters and Rogers, Kirkland, Washington and is reported by its supplier to be linear alkyl benzene sulfonate. KELZAN™ AR xanthan gum powder was commercially obtained from the Kelco division of Merck & Co., Inc. and is reported by its supplier to contain 86 - 92 % solids of xanthan gum (which is constituted of polymers of β-l,4-linked D-glucose units) that has been modified to give lower viscosity at low shear rates than unmodified natural xan- than gum. For example, a solution of 0.3 % of each of potassium chloride and KELZAN™ AR in water has a viscosity of about 800 centipoises (hereinafter usually abbreviated as "cps") at a shear rate of 0.1 reciprocal seconds (hereinafter usually abbre- viated as "sec^"'"), whereas an otherwise identical solution of natural xanthan gum has a viscosity of almost 10,000 cps. At a shear rate of 10 sec^"1, the viscosities of these solutions are about 100 and 500 cps respectively.

NAXONATE™ SC hydrotroping agent was obtained commercially from Ruet- gers-Nease Chemical Co., Inc., Ross, Ohio and was reported by its supplier to be 93 % sodium cumene sulfonate.

TRITON™ N-101 surfactant was commercially supplied by Van Waters and Rogers, Kirkland, Washington and was reported by its supplier to be a nonionic surfactant consisting of ethoxylated nonylphenol molecules with residues from an average of 9.5 molecules of ethylene oxide per molecule of surfactant;

UNISPERSE™ Blue colorant was obtained commercially from Ciba-Geigy as a paste. It is reported by its supplier to contain about 50 % of copper phthalocyanine blue pigment in dispersion.

VEEGUM™ T was obtained commercially from R. T. Vanderbilt Co., Norwalk, Connecticut and is reported by its supplier to be hydrated magnesium aluminosilicate smectite clay. It is recommended as a viscosity increasing agent. Working Coating Compositions and Processes Therewith

Example and comparison example working compositions are set forth in Table 1 below. Blank cells in the table indicate that none of the material was added to the com- position, or that the property value that would properly appear in the cell was not measured. The viscosities reported in Table 1 were measured with a Brookfield viscosimeter using spindle # 4. The balance of each composition not shown in Table 1 was water.

In the lower part of Table 1 , etch rates and times of exposure that achieved satisfactory deoxidizing/etching with some of the working compositions are also shown.

TABLE 1

Abbreviation in Table 1 : "RPM" means "Revolutions per Minute'

This table is continued on the next page. TABLE 1 continued

The coatings were formed for these examples simply by immersing the test panels in the composition and then withdrawing them after a few seconds, with no deliberate aid or hindrance to drainage of the composition from the panel surface. The coated panel was then held with its highest area surfaces vertical for the contact time indicated in the Table. The viscous liquid coating over the panel surfaces was then rinsed away with water. Panels had been weighed before applying the working composition and were weighed again after this rinsing and subsequent drying to determine the mass loss, which was converted to an etch rate by the usual mathematical calculations (i.e., dividing the total mass loss for the panel by the area of the panel to determine loss per unit area, then dividing the loss per unit area by the density of the panel to determine the thickness of metal corresponding to the mass loss.)

Some of the panels treated, instead of being dried to determine etch rates, were treated after rinsing with a commercially available composition (ALODINE® 1000 Chromate Conversion Coating Liquid, available from the Parker Amchem Division of Henkel Corp., Madison Heights, Michigan) to produce a conventional chromate conversion coating on the panel surfaces. The coatings produced are fully as good in properties as those produced by using the same treatment on otherwise identical panels that had been deoxidized/etched by a conventional high quality, low viscosity liquid composition for use by immersion of the substrates being treated.

Claims

1. A liquid composition of matter suitable either as such or after dilution with additional water to form a viscous liquid layer, over at least a portion of a surface of an aluminum substrate to be deoxidized and etched in a location within one mile of Earth, said viscous liquid layer having the property that it will not, in response to Earth's gravitational force, fall away from contact with any initially covered portion of said aluminum substrate during a period of time sufficient to deoxidize and etch said initially covered portion of said aluminum substrate, irrespective of whatever angle may exist between any part of said initially covered portion of said aluminum substrate and any part of Earth's surface, said liquid composition comprising water and:

(A) an amount of a source of dissolved fluoride ions;

(D) an amount of anionic surfactant that is not part of any of the previously recited components; and

(E) an amount of nonionic surfactant that is not part of any of the previously recited components.

2. A composition according to claim 1 , wherein: the amount of fluoride ions is from about 2.0 to about 60 g/kg; the amount of ionized hydrogen atoms is from about 0.080 to about 6.0 mH/kg and has a ratio to the amount of fluoride ions in g/kg that is from about 0.0040:1.0 to about 0.40:1.0; the viscosity of the composition, measured at 25 ┬░C with a Brookfield viscosimeter using spindle # 4, is at least about 100 poises at 0.5 rpm and is not more than about 400 poises at 20 rpm; the amount of anionic surfactant is from about 2 to about 75 g/kg; and the amount of nonionic surfactant has a ratio to the amount of anionic surfactant that is from about 0.015:1.0 to about 2.0:1.0.

3. A composition according to claim 2, wherein: the amount of fluoride ions is from about 4.0 to about 50 g/kg; the amount of ionized hydrogen atoms is from about 0.15 to about 5.0 mH/kg and has a ratio to the amount of fluoride ions in g/kg that is from about

0.0060:1.0 to about 0.30: 1.0; the viscosity of the composition, measured at 25 ┬░C with a Brookfield viscosimeter using spindle # 4, is at least about 200 poises at 0.5 rpm and is not more than about 350 poises at 20 rpm; the amount of anionic surfactant is from about 4 to about 60 g/kg; and the amount of nonionic surfactant has a ratio to the amount of anionic surfactant that is from about 0.030: 1.0 to about 1.0: 1.0. ╬┤ 4. A composition according to claim 3, wherein: the amount of fluoride ions is from about 6.0 to about 40 g/kg; the amount of ionized hydrogen atoms is from about 0.30 to about 4.0 mH/kg and has a ratio to the amount of fluoride ions in g/kg that is from about 0.0100:1.0 to about 0.20:1.0; the viscosity of the composition, measured at 25 ┬░C with a Brookfield viscosimeter using spindle # 4, is at least about 300 poises at 0.5 rpm and o is not more than about 300 poises at 20 rpm; the amount of anionic surfactant is from about 6 to about 40 g/kg; and the amount of nonionic surfactant has a ratio to the amount of anionic surfactant that is from about 0.045:1.0 to about 0.50: 1.0.

5. A composition according to claim 4, wherein: component (A) is selected from the group consisting of ammonium and alkali metal fluorides and acid fluorides; component s (D) is selected from the group consisting of sulfonic acids, partial esters of sulfuric acid, and salts of both of these types of acids; and component (E) is selected from the group of molecules conforming to general chemical formula (I):

R¹O(CH₂CH₂O)_y(CH₂CHCH₃O)_zH (I), where R¹ is a moiety selected from the group consisting of saturated-and-unsaturated 0 straight-and-branched-chain-aliphatic-monovalent-hydrocarbon-moiety-substituent - bearing phenyl moieties in which the aromatic ring of the phenyl moiety is directly bonded to the oxygen atom appearing immediately after the R¹ symbol in formula (I); y is a positive integer; and z is zero, one, or two.

6. A composition according to claim 5, wherein: the amount of fluoride ions is from 5 about 8.0 to about 35 g/kg; the amount of ionized hydrogen atoms is from about 0.40 to about 2.5 mH/kg and has a ratio to the amount of fluoride ions in g/kg that is from about 0.020:1.0 to about 0.10:1.0; the viscosity of the composition, measured at 25 ┬░C with a Brookfield viscosimeter using spindle # 4, is at least about 400 poises at 0.5 rpm and is not more than about 250 poises at 20 rpm; the amount of anionic surfactant is from about 0 8 to about 30 g/kg; and the amount of nonionic surfactant has a ratio to the amount of anionic surfactant that is from about 0.060:1.0 to about 0.40:1.0.

7. A composition according to claim 6, wherein: the amount of fluoride ions is from about 12.0 to about 28 g/kg; the amount of ionized hydrogen atoms is from about 0.55 to about 2.0 mH/kg and has a ratio to the amount of fluoride ions in g/kg that is from about 0.030:1.0 to about 0.080:1.0; the viscosity of the composition, measured at 25 ┬░C

5 with a Brookfield viscosimeter using spindle # 4, is at least about 600 poises at 0.5 rpm and is not more than about 170 poises at 20 rpm; the amount of anionic surfactant is from about 11.0 to about 25 g/kg; the amount of nonionic surfactant has a ratio to the amount of anionic surfactant that is from about 0.100:1.0 to about 0.20:1.0, and component (E) is selected from molecules that conform to general chemical formula (I) when R¹ has o from 5 to 12 carbon atoms, the average value of y is from 5 to 14, and z is 1 or 0.

8. A composition according to claim 7, wherein: component (B) is selected form the group consisting of sulfuric, nitric, and hydrochloric acids; component (C) is selected from natural and modified xanthan gums; component (D) is selected from linear alkyl benzene sulfonic acids in which the alkyl moiety has from 4 to 14 carbon atoms and salts s of said linear alkyl benzene sulfonic acids; and component (E) is selected from molecules that conform to general chemical formula (I) when R¹ has from 7 to 12 carbon atoms, the average value of y is from 7 to 12, and z is 0.

9. A composition according to claim 8, wherein: the amount of fluoride ions is from about 16.0 to about 22 g/kg; the amount of ionized hydrogen atoms is from about 0.70 0 to about 1.2 mH/kg and has a ratio to the amount of fluoride ions in g/kg that is from about 0.038:1.0 to about 0.050:1.0; the viscosity of the composition, measured at 25 ┬░C with a Brookfield viscosimeter using spindle # 4, is at least about 800 poises at 0.5 rpm and is not more than about 105 poises at 20 rpm; the amount of anionic surfactant is from about 14.0 to about 18.0 g/kg; the amount of nonionic surfactant has a ratio to the amount 5 of anionic surfactant that is from about 0.115 : 1.0 to about 0.140: 1.0; and component (E) is selected from molecules that conform to general chemical formula (I) when R¹ has from 8 to 10 carbon atoms and the average value of y is from 8 to 10.

10. A composition according to claim 9, wherein: component (A) is ammonium bi- fluoride; component (B) is sulfuric acid; component (C) is modified xanthan gum having o the property that a solution of 0.3 % of each of potassium chloride and the modified xanthan gum in water has a viscosity of about 800 centipoises at a shear rate of 0.1 sec^"1 and a viscosity of about 100 centipoises at a shear rate of 10 sec^"1; component (D) is selected from linear alkyl benzene sulfonic acids in which the alkyl moiety has from 6 to 12 carbon atoms and salts of said linear alkyl benzene sulfonic acids; component (E) is selected from nonylphenol ethoxylates; the composition also contains sodium salt of 5 cumene sulfonic acid in an amount that has a ratio to the amount of nonylphenol ethoxylates that is from about 6: 1.0 to 9: 1.0; and the composition contains a colorant in an amount sufficient to facilitate visual judgment of the uniformity of thickness of a coating formed with the composition.

11. A process for deoxidizing and etching at least a portion of a surface of an alumin- o um substrate, said process comprising steps of:

(I) forming on said portion of said surface of an aluminum substrate to be deoxidized and etched a coating of a viscous liquid composition according to any one of claims 1 through 10;

(II) maintaining in place the coating formed in step (I) for a time sufficient to deoxi- 5 dize and etch the portion of the surface covered by the coating formed in step (I); and

(III) subsequently removing the coating of viscous liquid composition formed in step (I) from further contact with the aluminum substrate surface.

12. A process according to claim 11 , wherein during step (II) the portion of the sur- o face covered by the coating formed in step (I) is etched at a rate of about 2.5 ┬▒ 0.5 ╬╝m/hr.