WO1997017480A1

WO1997017480A1 - Finely crystalline and/or fast phosphate conversion coating composition and process

Info

Publication number: WO1997017480A1
Application number: PCT/US1996/017086
Authority: WO
Inventors: Gerald J. Cormier; Michael L. Sienkowski; Michael Petschel; Peter Kuhm
Original assignee: Henkel Corporation
Priority date: 1995-11-07
Filing date: 1996-10-31
Publication date: 1997-05-15
Also published as: EP0866887A1; BR9611356A; AR004289A1; KR19990067389A; ZA969146B; CN1201495A; EP0866887A4; JP2000515586A; AU7473196A

Abstract

A combination of difunctional organic acid, preferably a hydroxy acid such as citric acid, or salt thereof with acrylic acid/acrylate polymers in zinc phosphate conversion coating forming liquid compositions, preferably also containing hydroxylamine, results in crystal size refinement in the coating formed and/or faster formation of a sufficiently thick conversion coating to protect against subsequent rusting of a ferrous substrate.

Description

FINELY CRYSTALLINE AND/OR FAST PHOSPHATE CONVERSION

COATING COMPOSITION AND PROCESS

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to compositions and processes for depositing zinc phos¬ phate containing conversion coatings on metal surfaces, particularly the surfaces of iron,

5 steel, zinc-iron alloy, galvanized steel and other predominantly zinciferous surfaces, and aluminum and its alloys that contain at least 45 % by weight of aluminum. The invention particularly relates to such compositions and processes that produce, at a high coating speed, a conversion coating with a very fine average crystal size. Statement of Related Art io The general process of zinc phosphate conversion coating is well known in the art. See, e.g., M. Hamacher, "Ecologically Safe Pretreatments of Metal Surfaces", Hen- kel-Referate 30 (1994), pp. 138 - 143, which, except to the extent that it may be contrary to any explicit statement herein, is hereby incoφorated herein by reference. In brief, con¬ tact of active metals with aqueous acidic compositions containing zinc and phosphate is ions results in the deposition on the active metal surfaces of a conversion coating con¬ taining zinc phosphate. If the active metal is ferrous, iron phosphates are usually includ¬ ed in the coating, and in modern practice nickel and/or manganese are often included in the coating composition and thereby in the coating formed. In order to speed the process and improve the uniformity ofthe coating, it is customary to include in the coating com-

20 position a component called an "accelerator" that does not usually become incoφorated into the coating formed. Typical widely used accelerators include nitrate, nitrite, and chlorate ions, water soluble nitroaromatic organic compounds such as p-nitrobenzene sul¬ fonic acid, and hydroxylamine (the latter almost always in the form of salts or complex¬ es).

₂. A frequently observed problem with prior art conversion coatings, particularly on cold rolled steel, has been the production of small rusty spots on areas ofthe treated substrate metal that were blocked from full contact with the conversion coating forming liquid composition by small gas bubbles that were formed and/or trapped on the substrate surface during the conversion coating treatment process. It is believed that the water vapor inside such bubbles is sufficient to cause rusting before the desired formation of a protective conversion coating can progress sufficiently far to prevent rust, and once a rusty spot has formed, it can not usually be covered satisfactorily later even by full con- tact with the conversion coating forming liquid composition.

DESCRIPTION OF THE INVENTION Obiect ofthe Invention

One object of this invention is to provide a composition and process for phosphat- ing that will provide a protective conversion coating with a more refined crystal size than is now generally achieved by zinc phosphating. Another alternative or concurrent object is to provide a zinc phosphating composition and process that will form a high quality protective conversion coating during a brief contact time with a metal substrate to be coated, so that coil coating and other continuous phosphating operations can be run at higher speeds. Still another concurrent or alternative object is to avoid the formation of surface rust on small areas ofthe treated substrate that are blocked by gas bubbles from full contact with the conversion coating solution. Other objects will be apparent from the description below. General Principles of Description

Except in the claims and the operating 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 ofthe invention. Practice within the numerical limits stated is generally preferred, however. Also, throughout the description and claims, unless expressly stated to the contrary: percent, "parts of, and ratio values are by weight; the description of a group or class of materials as suitable or preferred for a given puφose in connection with the invention implies that mixtures of any two or more ofthe members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, and does not necessarily preclude chemical interactions among the constituents of a mixture once mixed; specification of materials in ionic form implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole; any counterions thus implicitly specified should preferably be selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to the objects of the invention; the terms "molecule" and "mole" and their grammatical variations may be applied to ionic, elemental, or any other type of chemical entities defined by the number of atoms of each type present therein, as well as to substances with well-defined neutral molecules; the first definition of an acronym or other abbreviation applies to all subsequent uses herein ofthe same abbreviation; and the term "polymer" includes "oligomer", "homopolymer", "copolymer", "teφolymer", and the like. Summary ofthe Invention

It has been found that one or more ofthe objects stated above for the invention can be achieved by the use of a conversion coating forming aqueous liquid composition that comprises, preferably consists essentially of, or more preferably consists of, water and: (A) dissolved zinc cations;

(B) dissolved phosphate anions;

(C) a dissolved component selected from the group consisting of organic acids and anions thereof that (i) contain at least two moieties per molecule that are selected from the group consisting of carboxyl and carboxylate moieties and hydroxyl moieties that are not part of a carboxyl moiety and (ii) do not contain more than

12 carbon atoms per molecule; and

(D) a dissolved component selected from the group consisting of polymer molecules which contain more than 12 atoms per molecule and in which at least 50 % ofthe polymer molecule is made up of one or more moieties with one ofthe formulas: CH₃

-(CH₂-CH)- or -(CH₂-C)-,

I I

C=O C=O

OM OM where M represents a hydrogen atom, a monovalent cation, or a monovalent frac¬ tion of a polyvalent cation; and, optionally, (E) a component of dissolved metal cations selected from the group consisting of metal cations, exclusive of zinc cations, with a charge of at least two;

(F) a component of dissolved accelerator molecules, exclusive of any molecules that are part of any ofthe preceding components; and

(G) a component of dissolved simple and/or complex fluoride anions, exclusive of 5 any anions that are part of any of the preceding components.

Various embodiments ofthe invention include working compositions for direct use in treating metals, make-up concentrates from which such working compositions can be prepared by dilution with water, replenisher concentrates suitable for maintaining op¬ timum performance of working compositions according to the invention, processes for o treating metals with a composition according to the invention, and extended processes including additional steps that are conventional per se, such as cleaning, activation with titanium phosphate sols (Jernstedt salts), rinsing, and subsequent painting or some similar overcoating process that puts into place an organic binder containing protective coating over the metal surface treated according to a narrower embodiment ofthe invention. Art- 5 icles of manufacture including surfaces treated according to a process of the invention are also within the scope ofthe invention. Description of Preferred Embodiments

For a variety of reasons, it is sometimes preferred that compositions according to the invention as defined above should be substantially free from many ingredients used o in compositions for similar purposes in the prior art. Specifically, when maximum stor¬ age stability of a concentrate is desired, it is preferred, with increasing preference in the order given, independently for each preferably minimized component listed below, that these compositions contain no more than 25, 15, 9, 5, 3, 1.0, 0.35, 0.10, 0.08, 0.04, 0.02, 0.01, 0.001, or 0.0002, percent of each of the following constituents: nitrite, chlorate, 5 chloride, bromide, iodide, organic compounds containing nitro groups, hexavalent chromium, manganese in a valence state of four or greater, ferricyanide; ferrocyanide; and pyrazole compounds. In contrast, in working solutions, accelerator components such as those included in this list have no known detrimental effect (except for the danger of white specking zinciferous surfaces treated with compositions that contain too much 0 chloride, which is formed in situ from chlorate), but are generally not needed, and their absence may therefore be preferred for economic reasons.

The dissolved zinc cations required for necessary component (A) may be obtained from any soluble zinc salt or from zinc metal itself or any zinc containing compound that reacts with aqueous acid to form dissolved zinc cations. Normally preferred sources, largely for economic reasons, are zinc oxide, zinc carbonate, and zinc dihydrogen phos¬ phate. In a working conversion coating forming aqueous liquid composition according 5 to the invention, the concentration of dissolved zinc cations preferably is at least, with increasing preference in the order given, 0.1, 0.2, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.85, 0.90, 0.95, 0.98, or 1.00 parts per thousand (hereinafter usually abbreviated as "ppt") and independently preferably is not more than, with increasing preference in the order given, 2.0, 1.8, 1.6, 1.4, 1.30, 1.20, 1.15, or 1.10 ppt. o The dissolved phosphate ions that constitute necessary component (B) also may be obtained from a variety of sources as known in the general phosphate conversion coat¬ ing art. Because of a preference noted below for a substantial amount of total acid in a working conversion coating forming aqueous liquid composition according to the inven¬ tion, normally much of the phosphate ion content will preferably be supplied by phos- 5 phoric acid added to the composition, and the stoichiometric equivalent as phosphate ions of all undissociated phosphoric acid and all its anionic ionization products in solution, along with the stoichiometric equivalent as phosphate ions of any dihydrogen phosphate, monohydrogen phosphate, or completely neutralized phosphate ions added to the compo¬ sition in salt form, are to be understood as forming part of component (B), irrespective o ofthe actual degree of ionization that exists in the composition. In a working conversion coating forming aqueous liquid composition according to the invention, the concentration of component (B) preferably is at least, with increasing preference in the order given, 5, 6, 7, 8, 9, 10, 10.5, 11.0, 11.5, 11.9, 12.2, 12.4, 12.6, 12.8, 13.0, 13.2, 13.4, or 13.6 ppt -ind independently preferably is not more than, with increasing preference in the order 5 given, 100, 50, 40, 30, 27, 24, 21, 19, 18, 17, 16.5, 16.0, 15.5, 15.0, 14.5, 14.3, 14.1,

13.9, or 13.7 ppt.

Independently ofthe other preferences, the ratio ofthe concentration of compon¬ ent (A) to the concentration of component (B) in a conversion coating forming aqueous liquid composition according to the invention, whether working or concentrate, preferab- o ly is at least, with increasing preference in the order given, 1.0:50, 1.0:40, 1.0:35, 1.0:30,

1.0:27, 1.0:24, 1.0:21, 1.0:18, 1.0:16, 1.0:15, 1.0:14, or 1.0:13.7 and independently pref¬ erably is not more than, with increasing preference in the order given, 1.0:5.0, 1.0:6.0, 1.0:7.0, 1.0:8.0, 1.0:8.5, 1.0:9.0, 1.0:9.5, 1.0:10, 1.0:10.5, 1.0:1 1.0, 1.0:11.5, 1.0:12.0, 1.0:12.5, 1.0:13.0, or 1.0:13.3.

Component (C) is preferably derived from anions or other molecules each of which contains both at least one carboxyl(ate) moiety and one hydroxyl moiety that is not part of any carboxyl(ate) moiety, more preferably from the group consisting of citric acid, gluconic acid, and heptogluconic acid and the water soluble salts of all of these acids, most preferably from citric acid and its water soluble salts. Independently, the concentration of component (C) in a working conversion coating forming aqueous liquid composition according to the invention preferably is at least, with increasing preference in the order given, 0.1, 0.2, 0.3, or 0.4 millimoles per kilogram of total composition

(hereinafter usually abbreviated "mM/kg") and, if small crystal size of the conversion coating formed is desired, more preferably is at least, with increasing preference in the order given, 1.0, 1.2, or 1.6 mM/kg; if small crystal size ofthe conversion coating formed is desired and the concentration of component (D) is near the lower end of its preferred ranges as further described below, the concentration of component (C) in a working con¬ version coating forming aqueous liquid composition according to the invention still more preferably is at least 3.5 mM/kg. Independently, primarily for reasons of economy, the concentration of component (C) in a working composition according to the invention preferably is not more than, with increasing preference in the order given, 50, 25, 15, 10, 7, 5, 4.5, or 4.1 mM/kg, and if larger crystal size is acceptable, more preferably is not greater than, with increasing preference in the order given, 3.2, 3.0, 2.8, 2.5, 2.2, 1.9. or 1.7 mM/kg.

Component (D) preferably is selected from polymer molecules in which at least, with increasing preference in the order given, 60, 70, 75, 80, 85, 90, or 95 % ofthe mole- cule consists of one or more moieties with one ofthe formulas:

CH₃

I

-(CH,-CH)- or -(CH₂-C)-,

^" I I C=O CO

I I

OM OM more preferably the formula shown on the left, or in other words, acrylate rather than methacrylate moieties. Independently, with increasing preference in the order given, at least 30, 50, 60, 70, or 80 number percent of these acrylate and methacrylate moieties in component (D) have hydrogen rather than any other atom or cation in the position in the formula indicated by the symbol "M" in the formulas shown. Independently of both other preferences, the weight average molecular weight ofthe polymers in the component (D), measured as its stoichiometric equivalent when all the acrylate and methacrylate moieties are in an acid form, preferably is at least, with increasing preference in the order given, at least 400, 500, 600, 700, 750, 800, 850, 900, 950, or 975 and independently preferably is not more than, with increasing preference in the order given, 10,000, 9000, 8000, 7000, 6000, 5000, 4500, 4000, 3500, 3000, 2500, 2000, 1700, 1400, 1300, 1250, 1200, 1150, 1 100, or 1050. Also, independently ofthe other preferences for component

(D), the concentration of component (D) in a working conversion coating forming aque¬ ous liquid composition according to the invention preferably is at least 5, 10, 15, 20, 22, or 24 ppm and independently preferably is not more than 300, 200, 100, 85, 75, 65, or 55 ppm and, unless the concentration of component (C) is not more than 0.4 mM/kg, more preferably is not more than, with increasing preference in the order given, 45, 35,

30, or 26 ppm.

If high corrosion resistance after application of an organic protective coating to a metal substrate, subsequent to forming a conversion coating thereon by contacting the substrate with a working conversion coating forming aqueous liquid composition accord- ing to the invention, is desired, as it usually is, a working conversion coating forming aqueous liquid composition according to the invention preferably contains one or more metal ions selected from optional component (E). Examples of preferred combinations of zinc ions with metal ions of component (E) in a working conversion coating forming aqueous liquid composition according to the invention are: Zn and Mn; Zn, Mn, and Co; Zn, Mn, and Cu; Zn and Cu; Zn, Co, and Cu; and Zn, Mn, and Ni. It is especially pre¬ ferred for a working conversion coating forming aqueous liquid composition according to the invention to contain, as at least part of optional component (E), dissolved divalent manganese cations in a concentration that preferably is at least, with increasing prefer¬ ence in the order given, 100, 200, 300, 400, 500, 550, 600, 650, 700, 750, 800, 825, or 835 ppm and independently preferably is, primarily for reasons of economy, not more than, with increasing preference in the order given, 4000, 3000, 2000, 1500, 1400, 1300, 1250, 1200, 1150, 1100, 1050, 1000, 950, or 900 ppm. Also, independently ofthe prefer- ences for manganese as noted, it is especially preferred for a working conversion coating forming aqueous liquid composition according to the invention to include, as at least part of optional component (E), dissolved divalent nickel cations in a concentration that pref¬ erably is at least, with increasing preference in the order given, 100, 200, 300, 400, 500, 550, 600, 650, 700, 750, 765, 785, or 790 ppm and independently preferably is, primarily for reasons of economy, not more than, with increasing preference in the order given, 4000, 3000, 2000, 1500, 1400, 1300, 1250, 1200, 1150, 1100, 1050, 1000, 950, 900, or 850 ppm.

Independently of other preferences, the ratio ofthe concentration of zinc cations to the sum ofthe concentrations of manganese and nickel cations in a conversion coating forming aqueous liquid composition according to the invention preferably is at least, with increasing preference in the order given, 1.0:5.0, 1.0:4.0, 1.0:3.5, 1.0:3.0, 1.0:2.5, 1.0:2.3, 1.0:2.1 , 1.0: 1.9, 1.0: 1.7, or 1.0: 1.6 and independently preferably is not more than, with increasing preference in the order given, 1.0:0.2, 1.0:0.4, 1.0:0.6, 1.0:0.8, 1.0:1.0, 1.0:1.1, 1.0: 1.2, 1.0: 1.3, 1.0: 1.4, or 1.0: 1.5. Independently, when both manganese and nickel are present in a conversion coating forming aqueous liquid composition according to the in¬ vention, the ratio of manganese to nickel preferably is at least, with increasing preference in the order given, 1.0:2.0, 1.0:1.7, 1.0:1.5, 1.0:1.3, 1.0:1.2, 1.0:1.1, or 1.0:1.0 and inde¬ pendently preferably is not more than, with increasing preference in the order given, 1.0:0.2, 1.0:0.5, 1.0:0.7, 1.0:0.8, or 1.0:0.9.

A working conversion coating forming aqueous liquid composition according to the invention preferably includes, as at least part, and more preferably as all, of optional component (F) a dissolved source of hydroxylamine. The source may be hydroxylamine itself, but most users prefer to avoid potential hazards from handling pure hydroxylamne, so that a salt or complex of hydroxylamine is generally preferred. Hydroxylamine sul¬ fate, which has the chemical formula (NH₃OH)₂SO₄ is particularly preferred for economy and lack of any ions that may be deleterious to the quality of conversion coating formed, e.g., chloride ions, which may induce white specking of any zinc-rich areas ofthe coated substrate. Irrespective of its actual source, the concentration in a working conversion coating forming aqueous liquid composition according to the invention, measured as its stoichiometric equivalent as pure hydroxylamine, preferably is at least, with increasing preference in the order given, 0.2, 0.5, 0.8, 1.0, 1.1 , 1.2, 1.3. 1.4, or 1.5 ppt and independ- ently preferably is not more than, with increasing preference in the order given, 5, 4, 3.5, 3.0, 2.5, 2.3, 2.1, 1.9, or 1.8 ppt.

If the surface ofthe substrate to be conversion coated according to this invention includes a portion that contains at least 45 % of aluminum and/or a portion that contains at least 85 % of zinc, a working conversion coating forming aqueous liquid composition according to the invention preferably includes optional simple and/or complex fluoride anions component (G); more preferably, if the substrate surface includes a portion that contains at least 85 % of zinc, at least part ofthe fluoride present is in the form of fluo- boric, fluosilicic, fluotitanic, and/or fluozirconic acids and their salts, most preferably fluosilicic acid and/or fluosilicate ions.

Because ofthe competing complex-forming-and-dissociating equilibria in which fluoride can participate in a working conversion coating forming aqueous liquid compo¬ sition according to this invention that contains some deliberately added complex fluomet- allate and/or hydrofluoric acid, the preferable concentrations for fluoride in such a co - position are specified in terms of "active free fluoride", as measured by means of a fluor¬ ide sensitive electrode and associated instrumentation and methods that are described in U. S. Patents 3,350,284 and 3,619,300. Suitable apparatus and instructions for using it are commercially available under the name LINEGUARD® 101 A Meter from the Parker Amchem Division ("PAM") of Henkel Coφ., Madison Heights, MI. "Active free fluori- de" as this term is used herein was measured relative to a 120E Activity Standard So¬ lution also commercially available from PAM. In brief, the fluoride sensitive electrode and the reference electrode provided with the LINEGUARD® 101 A Meter are both im¬ mersed in the noted Standard Solution and the millivolt meter reading is adjusted to 0 with a Standard Knob on the instrument, after waiting if necessary for any drift in read- ings to abate. The electrodes are then rinsed with deionized or distilled water, dried, and immersed in the sample to be measured, which should be brought to the same temper¬ ature as the noted Standard Solution had when it was used to set the meter reading to 0. The reading ofthe electrodes immersed in the sample is taken directly from the millivolt (hereinafter often abbreviated "mv" or "mV") meter on the instrument and converted to ppm by comparison with the millivolt readings obtained with solutions of known free fluoride content, usually sodium or potassium fluoride solutions in water.

The free fluoride content of a working conversion coating forming aqueous liquid composition according to the invention, when a surface including areas that are at least 45 % aluminum is being treated, preferably is at least, with increasing preference in the order given, 100, 150, 200, 250, 300, 350, 375, or 400 ppm and independently preferably is not more than, with increasing preference in the order given, 1200, 1000, 900, 800, 750, 725, 700, 675, 650, 625, or 600 ppm. If a surface including areas that are at least

85 % zinc but no areas that are at least 45 % aluminum is to be treated, the free fluoride content preferably is not more than, with increasing preference in the order given, 100, 75, 60, 45, 40, 35, 30, 25, 20, 15, or 10 ppm, but the total content of fluoborate, fluosili- cate, fluotitanate, and fluozirconate, which includes the stoichiometric equivalent as these ions of all corresponding acids and partially acidic salts added to the compositions, ir¬ respective ofthe actual degree of ionization existing in the composition, preferably is at least, with increasing preference in the order given, 0.1 , 0.3, 0.5, 0.7, 0.8, 0.9, 1.00, 1.10, 1.15, or 1.20 ppt and independently preferably is, primarily for reasons of economy and with increasing preference in the order given, not more than 3.0, 2.5, 2.0, 1.8, 1.6, 1.50, 1.45, 1.40, 1.35, or 1.30 ppt. Most preferably, the total amount of these complex fluoride anions is fluosilicate or its corresponding acid or acid salt. When the surfaces being treated are ferrous and do not include any areas that are predominantly either aluminum or zinc, fluoride may be omitted altogether, and such omission is normally preferred for economic reasons. If any fluoride is present in the working compositions according to the invention for treating only ferrous substrates, the same preferences as noted above for the maximum amount of free fluoride activity in a composition for treating alumin¬ um-free zinciferous surfaces apply.

In a working conversion coating forming aqueous liquid composition according to the invention, the Total Acid and Free Acid contents ofthe composition are preferably measured and controlled. These acid contents, consistent with general practice in the phosphating art, are expressed herein in "points", by which is meant the milliliters ("ml") of 0.1 NNaOH required to titrate a 10 ml aliquot sample, to a pH of 8.2 (e.g., with phe- nolphthalein indicator) for Total Acid and to a pH of 3.8 (e.g., with bromophenol blue indicator) for Free Acid. In a working conversion coating forming aqueous liquid composition according to the invention, the content of Free Acid preferably is at least, with increasing prefer¬ ence in the order given, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 points and inde- pendently preferably is not more than, with increasing preference in the order given, 3.0, 2.5. 2.0, 1.8, 1.7, 1.6, or 1.5 points; and, independently, the content of Total Acid prefer¬ ably is at least, with increasing preference in the order given, 15, 16, 17, 18, 19, 20, or 21 points and independently preferably is not more than, with increasing preference in the order given, 50, 40, 35, 32, 30, 29, or 28 points. The Free Acid and Total Acid con¬ tents can be adjusted into the preferred range, without disturbing the preferred values for other constituents of a conversion coating forming aqueous liquid composition according to the invention, by additions, to an otherwise satisfactory conversion coating forming aqueous liquid composition, of small amounts of strongly alkaline materials such as sodi- um and potassium hydroxides or strong acids such as nitric and sulfuric acids, as appro¬ priate for the direction in which it is desired to change the Free Acid and Total Acid con¬ tents, in a manner generally known to those skilled in the art.

Preferably make-up concentrate compositions according to this invention are single package liquid concentrates, i.e., are aqueous liquids that consist of water and each of components (A) through (G), as recited above for working compositions, that are de¬ sired in the working compositions to be prepared from the make-up concentrate composi¬ tions, along with any other ingredients desired in the working compositions, except pos¬ sibly for strong acids or alkalies that are not part of any of components (A) through (G) and are added to working compositions after preparation thereof to slightly less than the final desired volume, in order to adjust the Free Acid and Total Acid contents therein as defined above. Preferably, all the components except water of a make-up concentrate composition according to the invention are present therein in a concentration such that the ratio of the concentration of each component in the make-up concentrate composi¬ tion to the concentration ofthe same component in the working composition that it is de- sired to prepare from the concentrate composition will be at least, with increasing prefer¬ ence in the order given, 5:1.0, 10:1.0, 20:1.0, 30:1.0, 40:1.0, or 50:1.0.

Preferably the concentrates are stable to storage in the temperature range from at least -20 to 50, or more preferably to 80, ° C. Stability may conveniently be evaluated by measuring the free acid and total acid contents as described above. If these values have not changed after storage by more than 10 % of their value before storage, the con¬ centrate is considered storage stable. With increasing preference in the order given, the concentrates according to the invention will be storage stable as thus defined after stor- age for 1, 3, 10, 30, 60, or 200 days.

The actual conversion coating forming step in a process according to this invention preferably is performed at a temperature that is at least, with increasing preference in the order given, 35, 38, 41, 44, 46, or 48 °C and independently preferably is, primarily for reasons of economy, not more than 70, 65, 60, 55, 53, 51, or 50 °C.

Primarily for reasons of economy, the time of contact between the metal surface being coated and a working composition according to the invention preferably is not greater than, with increasing preference in the order given, 200, 150, 120, 100, 80, 70, 60, 50, 40, 30, 25, 20, 17, 14, 11, 9.0, 7.0, 5.0, 4.0, 3.0, or 2.0 seconds, if a uniform and adequately protective coating is formed within that time. Otherwise, a process according to this invention is preferably operated under the conditions conventional in the art for compositions that are otherwise like the compositions according to this invention, except for substituting a conventional amount of nitrite accelerator for -ill ofthe hydroxylamine, acrylate and or methacrylate polymer, and at least difunctional acids and/or hydroxyacids described above for compositions according to this invention. Furthermore, in a process according to the invention that includes other steps than zinc phosphate conversion coating with a composition as described above, the other steps preferably are conven¬ tional per se.

The practice of this invention may be further appreciated by consideration ofthe following, non-limiting, working examples and comparison examples.

General Processing Conditions

The substrates used and their abbreviations as used in later tables are shown in

Table 1 below. The substrates were in the form of conventional rectangular test panels.

The processing sequence used is shown in Table 2 and its notes. All materials identified by one of the trademarks DEOXYLYTE®, FIXODINE®, or PARCO® are commercially available from the Parker Amchem Division of Henkel Coφ., Madison Table 1

Substrate Metal Type Abbreviation

Cold rolled steel CRS

One side electrogalvanized steel 1EG

Hot dip galvanized steel HDG

Both sides electrogalvanized steel 2EG

Zinc-iron alloy Z-I

Table 2

Process Action Fluid Used Temp., °C Time, Sec.

Spray Primary Cleaning 21 g/L of PARCO® 49 90 Cleaner 1502 in water

Spray Rinse Tap Water 49 30

Activation FIXODINE® Z-8 20 - 25 30 Conditioner, 1 1 ppm Ti

Phosphating See later tables 49 10, 120*

Spray Rinse Tap Water 20 - 25 30

Postrinsing 0.25 % DEOXYLYTE® 20 - 25 30 54 NC Postrinse in water

Spray Rinse Deionized water 20 - 25 15

Footnote for Table 2

*The entire panel was dipped into the phosphating composition for 10 seconds. Then the top half of the panel was withdrawn. The bottom half remained immersed for a total of 120 seconds, and the entire panel was then withdrawn from contact with the phosphating composition.

Abbreviations for Table 2 Temp. = Temperature; Sec. = Seconds.

Heights, Michigan and/or Henkel Metallchimie, Dusseldorf, Germany, together with di¬ rections for using them as noted below. Working Phosphating Compositions

The most important components of several working compositions are shown in Table 3; the balance not shown in the table is water or counterions, the latter being pre¬ dominantly sodium to serve as counterions to a substantial fraction of the phosphate content. Aqueous sodium hydroxide solution was used when needed to lower free acid content. Nitric acid was added in small quantities as the concentration of citrate was in¬ creased, to avoid unwanted decreases in free acid content without changing the zinc to phosphate ratio. Any free fluoride content indicated in the Table by a specific number was measured by a fluoride sensitive electrode in the manner described above and was added as hydrofluoric acid. Free fluoride contents preceded by the "less than" sign (<) were measured in the same way, but also mean that no hydrofluoric acid or other known source of uncomplexed fluoride was deliberately added; the free fluoride activity presum¬ ably arose from small concentrations of hydrofluoric acid known to exist in the fluosilicic acid that was deliberately added. The source ofthe acrylate polymer shown in Table 3 was Acusol™ 410 polymer solution in water, a product commercially supplied by Rohm & Haas Co. and reported by its supplier to contain 54 % by weight of a homopolymer of acrylic acid in which 20 number % of the carboxylic moieties are neutralized with sodium hydroxide, the polymer in the all acid form having a weight average molecular weight of 1000 and a number average molecular weight of 650.

Table 3

Ingredient and Amount of Ingredient in Composition Example Number:

Concentration

Unit 1 2 3 4 5 6 7 8 9 10

Zn^*2 ions, ppt 1.1 1.1 1.1 1.1 1.05 1.1 1.1 1.01 1 1

P0₄ ^"3 ions, ppt 14 14 14 14 13.7 14 14 13.7 14 14

Mn^*2 ions, ppt 0.8 0.8 0.8 0.8 0.81 0.8 0.8 0.84 0.8 0.8

Ni⁺² ions, ppt 0.8 0.8 0.8 0.8 0.78 0.8 0.8 0.8 0.8 0.8

Sodium citrate Sit. Sit. Sit. Sit. Sit. Sit. Sit. Sit. Sit. Sit. dihydrate, ppt

(NH₃OH)₂S0₄, 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 ppt

Free Acid, 1.5 1.7 1.0 1.0 1.0 1.0 1.5 1.0 0.7 0.6 points

Total Acid, 27 28 27 21 25 27 27 26 27 27 points

Acrylate 10 10 10 25 25 25 25 50 50 50 polymer, ppm

H-SiF₆, ppt 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25

Free F 690 690 690 <25 <25 680 680 670 670 670 activity, ppm

Abbreviation for Table 3

Sit. = See later table(s).

The citrate concentrations in the working phosphating compositions and the resulting coating weights and crystal sizes are shown in Tables 4 - 1 1.

Table 4: RESULTS WITH 10 PPM OF ACRYLATE POLYMER ON CRS SUBSTRATES

Comp. Citrate Cone. Coating Weights, Crystal Size, Other

# g/m² μ Observa¬ tions

Top Bottom

1 0.10 1.10 2.62 8-10 SRD

1 0.20 1.17 2.83 5-8 SRD

2 0.30 0.70 2.90 5-8 SRD

3 0.30 1.57 2.67 5-8 SRD

3 0.40 0.96 2.68 5-8 SRD

3 0.50 0.99 2.86 3-5 SRD

3 0.65 1.30 2.87 3-5 SRD

3 0.80 1.38 2.71 3-5 DVSR

3 1.00 1.04 2.52 3 D

Additional Abbreviations for Table 4 (See notes for previous tables and main text for others)

Comp. # = Composition Number (from Table 3); Cone. = Concentration; g/m² = grams per square meter; μ = micrometres; SRD = Surface rust and dusting observable after phosphating; DVSR = Dusting and very slight surface rust observable after phosphating; D = Dusting but no rust observable after phosphating.

Table 5: RESULTS WITH 10 PPM OF ACRYLATE POLYMER ON 1EG SUBSTRATES

Comp. Citrate Coating Weight, g/m² Crystal Size, μ Other

# Cone. Obser¬

OSS OGS OSS OGS vations

Top Bottom Top Bottom

1 0.10 1.12 3.01 2.88 2.82 5 - 10 ~ 10 D

1 0.20 0.88 2.80 2.83 2.97 5 - 10 - 8 D

2 0.30 0.70 3.07 2.97 2.76 5 - 10 5 - 10 D

3 0.30 1.59 2.43 2.14 2.78 5 - 10 5 - 10 D

3 0.40 1.14 2.66 2.80 2.83 5 - 10 N.m. D

3 0.50 1.22 2.40 3.06 2.68 8 5 - 10 D

3 0.65 1.27 2.37 2.65 2.72 6 5 D

3 0.80 1.14 2.10 2.72 2.71 5 5 D

3 1.00 1.00 2.07 2.1 1 2.44 5 3 D

Additional Abbreviations for Table 5 (See notes for previous tables and main text for others) OSS = On steel side; OGS = On galvanized side; N.m. = Not measured.

Table 6: RESULTS WITH 10 PPM OF ACRYLATE POLYMER ON OTHER SUBSTRATES

On HDG Substrate On 2EG Substrate On Z-I Substrate

Coat. Wt., g/m² Crystal Coat. Wt., g m² Crystal Coat. Wt., g/m² Crystal Size, μ Size, μ Size, μ

Top Bottom Top Bottom Top Bottom

2.96 2.84 10 3.08 2.52 5 2.13 4.10 15 - 20

Additional Abbreviation for Table 6 (See notes for previous tables and main text for others)

Coat. Wt. = Coating Weight

General Note for Table 6

The phosphating composition used for all results in this table was Number 3 from Table 3 with 1.00 ppt of citrate. No surface rust or dusting ofthe coating was observed. Table 7: RESULTS WITH 25 PPM OF ACRYLATE POLYMER ON CRS SUBSTRATES

Comp. Citrate Cone. Coating Weights, Crystal Size, Other g/m² μ Observa¬ tions

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4 0.00* 0.61* 2.08* 15-20* SRD*

4 0.10 0.93 3.76 15-20 SRD

4 0.20 1.22 3.62 10-15 SRD

4 0.30 1.04 3.15 8-10 SRD

5 0.30 1.30 2.85 5-10 SRD

5 0.40 1.35 2.82 5-10 SRD

5 0.50 1.24 2.99 5-10 DVSR

6 0.50 1.09 3.35 3-6 D

7 0.50 0.34 2.1±0.7 3-6 DVSR

Footnote for Table 7 * Comparison example, not according to the invention.

Table 8: RESULTS WITH 25 PPM OF ACRYLATE POLYMER ON 1EG SUBSTRATES

Comp. # Citrate Coating Weight, g m² Crystal Other Cone. Size, μ, Obser¬

OSS OGS OGS vations

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4 0.00* 0.66* 2.24* 2.51* 3.28* 10 - 15* SRD*

4 0.10 1.09 4.47 2.73 3.14 8 - 10 D

4 0.20 1.04 4.73 3.29 3.10 8 - 10 D

4 0.30 0.91 4.06 3.29 3.15 5 - 8 D

5 0.30 1.36 3.18 2.76 2.90 5 - 8 D

5 0.40 1.34 3.19 2.85 2.96 5 - 8 D

5 0.50 1.52 3.18 2.78 3.04 5 - 8 D

6 0.50 0.83 5.08 2.38 3.95 5 D

7 0.50 0.69 2.98 3.71 3.77 5 D

Footnote for Table 8 * Comparison example, not according to the invention.

Table 9: RESULTS WITH 25 PPM OF ACRYLATE POLYMER ON OTHER SUBSTRATES

Comp. # Citrate On HDG On 2EG On Z-I Cone. Substrate Substrate Substrate

Coat. Wt., g/m² Coat. Wt., g/m² Coat. Wt., g/m²

Top Bottom Top Bottom Top Bottom

4 0.30 1.68 3.04 3.13 2.93 0.41 3.49

7 0.50 3.38 2.81 3.25 3.27 0.64 4.66

General Note for Table 9 Surface dusting but no rust after phosphating was observed for both examples in this table. Table 10: RESULTS WITH 50 PPM OF ACRYLATE POLYMER ON CRS SUBSTRATES

Top Bottom

8 0.10 1.06 1.87 8-10 DVSR

9 0.10 0.58 2.81 8-10 SRD

10 0.15 1.05 4.80 8-10 SRD

9 0.20 0.93 3.64 8-10 SRD

Table 11 : RESULTS WITH 50 PPM OF ACRYLATE POLYMER ON 1EG SUBSTRATES

Comp. Citrate Coating Weight, g/m² Crystal Size, μ Other Cone. Obser¬

OSS OGS OSS OGS vations

Top Bottom Top Bottom

8 0.10 0.48 2.62 3.11 4.21 10 15 D

9 0.10 1.04 4.71 4.02 4.20 8-10 15 D

10 0.15 0.91 3.02 3.84 4.27 8-10 10 D

9 0.20 0.69 3.75 3.79 3.84 8 5 D

Claims

1. An aqueous liquid composition of matter suitable either as such or after dilution with water for forming a phosphate conversion coating on a metal substrate by contact therewith, said composition comprising water and: 5 (A) a concentration of dissolved zinc cations;

(B) a concentration of dissolved phosphate anions;

(C) a concentration of a dissolved component selected from the group consisting of organic acids and anions thereof that (i) contain at least two moieties per molecule that are selected from the group consisting of carboxyl and carboxylate o moieties and hydroxyl moieties that are not part of a carboxyl group and (ii) do not contain more than 12 carbon atoms per molecule; and

(D) a concentration of a dissolved component selected from the group consisting of polymer molecules which contain more than 12 atoms per molecule and in which at least 50 % of the polymer molecules is made up of one or more s moieties with one ofthe general chemical formulas:

CH₃

-(CH₂-CH)- or -(CH_.-C)-,

I I o C=O C=O

OM OM where M represents a hydrogen atom, a monovalent cation, or a monovalent fraction of a polyvalent cation. 5

2. An aqueous liquid composition of matter according to claim 1, wherein: the concentration of component (A) has a ratio to the concentration of component (B) that is from about 1.0:40 to about 1.0:5.0; component (C) is selected from the group consisting of anions and molecules each of which contains both at least one carboxyl or carboxylate moiety and at least one hydroxyl moiety that is not part of any carboxyl 0 or carboxylate moiety; at least about 30 number % of the moieties "M" shown in the general chemical formulas in claim 1 for component (D) are hydrogen; component (D) has a weight average molecular weight from about 500 to about 9000; and the composition additionally comprises at least one of divalent manganese and divalent nickel cations in a total amount such that the concentration of zinc cations has a ratio to the total amount of divalent manganese and divalent nickel cations that is from about 1.0:3.5 to about 1.0:0.6.

3. An aqueous liquid composition of matter according to claim 2, wherein: the ratio of the concentration of component (A) to the concentration of component (B) is from about 1.0: 18 to about 1.0: 10; at least about 60 number % of said moieties "M" are hydrogen; at least about 60 % of component (D) consists of acrylate moieties; component (D) has a weight average molecular weight from about 700 to about 1300; the composition comprises both dissolved divalent manganese and divalent nickel cations in concentrations such that the concentration of manganese has a ratio to the concentration of nickel that is from about 1.0:1.5 to about 1.0:0.7; and the ratio ofthe concentration of zinc cations to the total amount of divalent manganese and divalent nickel cations is from about 1.0:3.5 to about 1.0:0.6.

4. An aqueous liquid composition according to claim 2, wherein: the concentration of component (A) is from about 0.30 to about 2.0 ppt; the concentration of component

(B) is from about 6 to about 50 ppt; the concentration of component (C) is from about 0.2 to about 25 mM/kg; the concentration of component (D) is from about 5 to about 200 ppm; and the concentration of dissolved divalent manganese cations is from about 300 to about 3000 ppm.

5. An aqueous liquid composition according to claim 4, wherein: the concentration of component (A) is from about 0.50 to about 1.8 ppt; the concentration of component (B) is from about 8 to about 30 ppt; the concentration of component (C) is from about 0.3 to about 15 mM/kg; the concentration of component (D) is from about 10 to about 100 ppm; the concentration of dissolved divalent manganese cations is from about 500 to about 2000 ppm.

6. An aqueous liquid composition according to claim 5, wherein: the concentration of component (A) is from about 0.60 to about 1.6 ppt; the concentration of component (B) is from about 10 to about 21 ppt; the ratio ofthe concentration of component (A) to the concentration of component (B) is from about 1.0:30 to about 1.0:8.0; the concentration of component (C) is from about 0.4 to about 10 mM/kg; at least about 70

% of component (D) consists of acrylate and methacrylate moieties, of which at least 50 number % have hydrogen as said moieties "M"; the weight average molecular weight of component (D) is from about 700 to about 7000; the concentration of component (D) is from about 15 to about 85 ppm; the concentration of dissolved divalent manganese cations is from about 600 to about 1500 ppm; and the stoichiometric equivalent concen- tration of hydroxylamine is from about 1.0 to about 5 ppt.

7. An aqueous liquid composition according to claim 6, wherein: the concentration of component (A) is from about 0.70 to about 1.4 ppt; the concentration of component (B) is from about 11.5 to about 19 ppt; the ratio ofthe concentration of component (A) to the concentration of component (B) is from about 1.0:27 to about 1.0:10.0; compon- ent (C) is selected from the group consisting of citric acid, gluconic acid, and heptoglu- conic acid and the water soluble salts of all of these acids; the concentration of compon¬ ent (C) is from about 1.0 to about 7 mM/kg; at least about 75 % of component (D) consists of acrylate and methacrylate moieties, of which at least about 60 number % have hydrogen as said moieties "M"; the weight average molecular weight of component (D) is from about 750 to about 4500; the concentration of component (D) is from about 15 to about 45 ppm; the concentration of dissolved divalent manganese cations is from about 700 to about 1300 ppm; and the composition additionally comprises a dissolved source of hydroxylamine in an amount to provide a stoichiometric equivalent concentration of hydroxylamine that is from about 1.2 to about 2.3 ppt.

8. An aqueous liquid composition according to claim 7, wherein: the concentration of component (A) is from about 0.80 to about 1.3 ppt; the concentration of component (B) is from about 12.2 to about 17 ppt; the ratio ofthe concentration of component (A) to the concentration of component (B) is from about 1.0:21 to about 1.0: 10.0; the concentration of component (C) is from about 1.2 to about 5 mM/kg; the weight average molecular weight of component (D) is from about 750 to about 3000; the concentration of component (D) is from about 15 to about 35 ppm; the concentration of dissolved divalent manganese cations is from about 750 to about 1200 ppm; and the stoichiometric equivalent concentration of hydroxylamine is from about 1.3 to about 2.1 ppt.

9. An aqueous liquid composition according to claim 8, wherein: the concentration of component (A) is from about 0.85 to about 1.20 ppt; at least about 70 % of component (D) consists of acrylate moieties, of which at least 70 number % have hydrogen as said moieties "M"; the weight average molecular weight of component (D) is from about 900 to about 1700; the concentration of dissolved divalent manganese cations is from about 800 to about 1000 ppm; and the composition also comprises dis¬ solved nickel cations in a concentration from about 200 to about 1200 ppm.

10. An aqueous liquid composition according to claim 9, wherein: the concentration of component (A) is from about 0.95 to about 1.15 ppt; the concentration of component (B) is from about 13.0 to about 16.0 ppt; the ratio ofthe concentration of component (A) to the concentration of component (B) is from about 1.0:18 to about 1.0:13.0; component (C) is selected from the group consisting of citric acid, gluconic acid, and heptogluconic acid and the water soluble salts of all of these acids; the concentration of component (C) is from about 1.6 to about 4.1 mM/kg; at least about 80 % of component (D) consists of acrylate moieties, of which at least 80 number % have hydrogen as said moieties "M"; the weight average molecular weight of component (D) is from about 900 to about 1200; the concentration of component (D) is from about 20 to about 30 ppm; the concentration of dissolved divalent manganese cations is from about 800 to about

1000 ppm; the concentration of dissolved nickel cations is from about 600 to about 900 ppm; and the stoichiometric equivalent concentration of hydroxylamine is from about 1.5 to about 1.8 ppt.

11. A process for forming a phosphate conversion coating on a surface selected from the group consisting of at least one of iron, steel, zinc-iron alloy, galvanized steel and other predominantly zinciferous surfaces, and aluminum and its alloys that contain at least 45 % by weight of aluminum, said process comprising contacting the surface with a composition according to claim 10 at a temperature from about 35 to about 70 °C for a time not greater than 100 seconds, said composition according to claim 10 having a Free Acid content from about 1.0 to about 1.5 points, and a Total Acid content from about 20 to about 28 points; wherein, (i) if said surface includes a portion that contains at least 45 % of aluminum, said composition according to claim 10 additionally comprises fluorine containing constituents in an amount so as to result in a value from about 400 to about 600 ppm of free fluoride as measured by means of a fluoride sensitive electrode; and (ii) if said surface includes a portion that contains at least 85 % of zinc but does not include any portion that contains at least 45 % of aluminum, said composition according to claim 10 additionally comprises a content of fluosilicate that is from about 1.10 to about 1.40 ppt, and said composition according to claim 10 has a free fluoride value that is not greater than about 20 ppm as measured by means of a fluoride sensitive electrode.

5 12. A process for forming a phosphate conversion coating on a surface selected from the group consisting of at least one of iron, steel, zinc-iron alloy, galvanized steel and other predominantly zinciferous surfaces, and aluminum and its alloys that contain at least 45 % by weight of aluminum, said process comprising contacting the surface with a composition according to claim 9 at a temperature from about 35 to about 70 °C for o a time not greater than 100 seconds, said composition according to claim 9 having a

Free Acid content from about 0.6 to about 1.5 points, and a Total Acid content from about 15 to about 40 points; wherein, (i) if said surface includes a portion that contains at least 45 % of aluminum, said composition according to claim 9 additionally comprises fluorine containing constituents in an amount so as to result in a value from s about 250 to about 1200 ppm of free fluoride as measured by means of a fluoride sensitive electrode; and (ii) if said surface includes a portion that contains at least 85 % of zinc but does not include any portion that contains at least 45 % of aluminum, said composition according to claim 9 additionally comprises a total content of fluoborate, fluosilicate, fluotitanate, and fluozirconate that is from about 0.5 to about 2.5 ppt, and 0 said composition according to claim 9 has a free fluoride value that is not greater than about 100 ppm as measured by means of a fluoride sensitive electrode.

13. A process for forming a phosphate conversion coating on a surface selected from the group consisting of at least one of iron, steel, zinc-iron alloy, galvanized steel and other predominantly zinciferous surfaces, and aluminum and its alloys that contain at 5 least 45 % by weight of aluminum, said process comprising contacting the surface with a composition according to claim 8 at a temperature from about 35 to about 70 °C for a time not greater than 100 seconds, said composition according to claim 8 having a Free Acid content from about 0.6 to about 1.5 points, and a Total Acid content from about 15 to about 40 points; wherein, (i) if said surface includes a portion that contains o at least 45 % of aluminum, said composition according to claim 8 additionally comprises fluorine containing constituents in an amount so as to result in a value from about 250 to about 1200 ppm of free fluoride as measured by means of a fluoride sensitive electrode; and (ii) if said surface includes a portion that contains at least 85 % of zinc but does not include any portion that contains at least 45 % of aluminum, said composition according to claim 8 additionally comprises a total content of fluoborate, fluosilicate, fluotitanate, and fluozirconate that is from about 0.5 to about 2.5 ppt, and said composition according to claim 8 has a free fluoride value that is not greater than about 100 ppm as measured by means of a fluoride sensitive electrode.

14. A process for forming a phosphate conversion coating on a surface selected from the group consisting of at least one of iron, steel, zinc-iron alloy, galvanized steel and other predominantly zinciferous surfaces, and aluminum and its alloys that contain at least 45 % by weight of aluminum, said process comprising contacting the surface with a composition according to claim 7 at a temperature from about 35 to about 70 °C for a time not greater than 100 seconds, said composition according to claim 7 having a Free Acid content from about 0.2 to about 1.5 points, and a Total Acid content from about 15 to about 40 points; wherein, (i) if said surface includes a portion that contains at least 45 % of aluminum, said composition according to claim 7 additionally comprises fluorine containing constituents in an amount so as to result in a value from about 250 to about 1200 ppm of free fluoride as measured by means of a fluoride sensitive electrode; and (ii) if said surface includes a portion that contains at least 85 % of zinc but does not include any portion that contains at least 45 % of aluminum, said composition according to claim 7 additionally comprises a total content of fluoborate. fluosilicate, fluotitanate, and fluozirconate that is from about 0.5 to about 2.5 ppt, and said composition according to claim 7 has a free fluoride value that is not greater than about 100 ppm as measured by means of a fluoride sensitive electrode.

15. A process for forming a phosphate conversion coating on a surface selected from the group consisting of at least one of iron, steel, zinc-iron alloy, galvanized steel and other predominantly zinciferous surfaces, and aluminum and its alloys that contain at least 45 % by weight of aluminum, said process comprising contacting the surface with a composition according to claim 6 at a temperature from about 35 to about 70 °C for a time not greater than 100 seconds, said composition according to claim 6 having a

Free Acid content from about 0.2 to about 1.5 points, and a Total Acid content from about 15 to about 40 points; wherein, (i) if said surface includes a portion that contains at least 45 % of aluminum, said composition according to claim 6 additionally comprises fluorine containing constituents in an amount so as to result in a value from about 250 to about 1200 ppm of free fluoride as measured by means of a fluoride sensitive electrode; and (ii) if said surface includes a portion that contains at least 85 % of zinc but does not include any portion that contains at least 45 % of aluminum, said composition according to claim 6 additionally comprises a total content of fluoborate, fluosilicate, fluotitanate, and fluozirconate that is from about 0.5 to about 2.5 ppt, and said composition according to claim 6 has a free fluoride value that is not greater than about 100 ppm as measured by means of a fluoride sensitive electrode.

16. A process for forming a phosphate conversion coating on a surface selected from the group consisting of at least one of iron, steel, zinc-iron alloy, galvanized steel and other predominantly zinciferous surfaces, and aluminum and its alloys that contain at least 45 % by weight of aluminum, said process comprising contacting the surface with a composition according to claim 5 at a temperature from about 35 to about 70 °C for a time not greater than 100 seconds, said composition according to claim 5 having a Free Acid content from about 0.2 to about 1.5 points, and a Total Acid content from about 15 to about 40 points; wherein, (i) if said surface includes a portion that contains at least 45 % of aluminum, said composition according to claim 5 additionally comprises fluorine containing constituents in an amount so as to result in a value from about 250 to about 1200 ppm of free fluoride as measured by means of a fluoride sensitive electrode; and (ii) if said surface includes a portion that contains at least 85 % of zinc but does not include any portion that contains at least 45 % of aluminum, said composition according to claim 5 additionally comprises a total content of fluoborate, fluosilicate, fluotitanate, and fluozirconate that is from about 0.5 to about 2.5 ppt, and said composition according to claim 5 has a free fluoride value that is not greater than about 100 ppm as measured by means of a fluoride sensitive electrode.

17. A process for forming a phosphate conversion coating on a surface selected from the group consisting of at least one of iron, steel, zinc-iron alloy, galvanized steel and other predominantly zinciferous surfaces, and aluminum and its alloys that contain at least 45 % by weight of aluminum, said process comprising contacting the surface with a composition according to claim 4 at a temperature from about 35 to about 70 °C for a time not greater than 100 seconds, said composition according to claim 4 having a Free Acid content from about 0.2 to about 1.5 points, and a Total Acid content from about 15 to about 40 points; wherein, (i) if said surface includes a portion that contains s at least 45 % of aluminum, said composition according to claim 4 additionally comprises fluorine containing constituents in an amount so as to result in a value from about 250 to about 1200 ppm of free fluoride as measured by means of a fluoride sensitive electrode; and (ii) if said surface includes a portion that contains at least 85 % of zinc but does not include any portion that contains at least 45 % of aluminum, said o composition according to claim 4 additionally comprises a total content of fluoborate, fluosilicate, fluotitanate, and fluozirconate that is from about 0.5 to about 2.5 ppt, and said composition according to claim 4 has a free fluoride value that is not greater than about 100 ppm as measured by means of a fluoride sensitive electrode.

18. A process for forming a phosphate conversion coating on a surface selected from s the group consisting of at least one of iron, steel, zinc-iron alloy, galvanized steel and other predominantly zinciferous surfaces, and aluminum and its alloys that contain at least 45 % by weight of aluminum, said process comprising contacting the surface with a composition according to claim 3, wherein, in said composition according to claim 3: the concentration of component (A) is from about 0.40 to about 2.0 ppt; the 0 concentration of component (C) is from about 0.2 to about 25 mM/kg; the concentration of component (D) is from about 5 to about 200 ppm; if said surface includes a portion that contains at least 45 % of aluminum, said composition additionally comprises fluorine containing constituents in an amount so as to result in a value from about 250 to about 1200 ppm of free fluoride as measured by means of a fluoride sensitive elec- 5 trode; if said surface includes a portion that contains at least 85 % of zinc but does not include any portion that contains at least 45 % of aluminum, said composition ad¬ ditionally comprises a total content of fluoborate, fluosilicate, fluotitanate, and fluozir¬ conate that is from about 0.5 to about 2.5 ppt, and said composition has a free fluoride value that is not greater than about 100 ppm as measured by means of a fluoride 0 sensitive electrode; and said composition has a Free Acid content from about 0.2 to about 1.5 points and a Total Acid content from about 15 to about 40 points.

19. A process for forming a phosphate conversion coating on a surface selected from the group consisting of at least one of iron, steel, zinc-iron alloy, galvanized steel and other predominantly zinciferous surfaces, and aluminum and its alloys that contain at least 45 % by weight of aluminum, said process comprising contacting the surface with a composition according to claim 2, wherein, in said composition according to claim 2: the concentration of component (A) is from about 0.2 to about 2.0 ppt; the concentration of component (C) is from about 0.1 to about 50 mM/kg; the concentration of component (D) is at least about 5 ppm; if said surface includes a portion that contains at least 45 % of aluminum, said composition additionally comprises fluorine containing constituents in an amount so as to result in a value from about 250 to about 1200 ppm of free fluoride as measured by means of a fluoride sensitive electrode; if said surface includes a portion that contains at least 85 % of zinc but does not include any portion that con¬ tains at least 45 % of aluminum, said composition additionally comprises a total content of fluoborate, fluosilicate, fluotitanate, and fluozirconate that is from about 0.5 to about 2.5 ppt and said composition has a free fluoride value that is not greater than about 100 ppm as measured by means of a fluoride sensitive electrode; and said composition has a Free Acid content from about 0.2 to about 1.5 points and a Total Acid content from about 15 to about 40 points.

20. A process for forming a phosphate conversion coating on a metal surface, said process comprising contacting the surface with a composition according to claim 1 , wherein, in said composition according to claim 1 : the concentration of component (A) is from about 0.2 to about 2.0 ppt; the concentration of component (B) is from about 5 to about 100 ppt; the concentration of component (C) is from about 0.2 to about 25 mM/kg; the concentration of component (D) is from about 5 to about 200 ppm; and said composition has a Free Acid content from about 0.1 to about 3 points and a Total Acid content from about 15 to about 50 points.