CA2230278A1 - Precoat conditioning treatment for autodeposition - Google Patents

Abstract

Blemish and blister formation during autodeposition coating of non-ferrous metal surfaces, particularly galvanized steel and similar zinciferous surfaces, can be greatly reduced by exposing the surfaces to a blemish inhibiting aqueous solution of phosphonates, preferably from an aminophosphonic acid, before autodeposition coating.

Description

W O 97/09127 PCT~US96/13480 Description PRECOAT CONDITIONING TREATMENT FOR AUTODEPOSITION
.

F~T n OF T~lF. INVF~TION
This invention relates to the use of liquid, usually aqueous, solutions or disper-sions in which active metal surfaces of inserted objects are coated with an adherent poly-mer film that increases in thickness the longer the metal object ,~l-lah,s in the bath, even though the liquid is stable for a long time against spontaneous precipil~Lion or floccula-tion of any solid polymer, in the ~bsence of contact with active metal, i.e., metal that ~ol IlA~u~ly begins to dissolve at a sub~ lial rate when introduced into the liquid so-lution or dispersion. Such compositions, and processes of rollllhlg a coating on a metal surface using such compositions, are commonly denoted in the art, and in this specifica-10 tion, as "autodeposition" or "autodepositing" compositions, dispersions, ~m~ iQn~, sus-pensions, baths, solutions, processes, methods, or a like term. Autodeposition is often collll~Led with electrodeposition, which can produce very similar adherent films but re-quires that metal or other objects to be coated be connected to a source of direct current electricity for coating to occur. No such external electric current is used in autodeposi-tion.
Autodeposition compos;Lions previously known in the art are effective for coatingmany metals of practical interest, but it has been observed that allt;llll)Lillg autodeposi tion coating of most zinc-rich metal surfaces such as galvanized steel often results in coatings with many small "pinholes" or larger blisters. Such coatings are usually regarded as aes-thetically llnplç~ing and often fail to provide the protection against the en~/hulllnel~L thatis normally wanted from autodeposition co~ting~ d~lcing or çl;,.,i~ g the formation of pinholes or larger blemishes in autodeposited coatings, particularly on ~hlcireloLIs sur-faces, more particularly galvanized steel or some variation thereof, is a major object of this invention.
DESCRIPTIQN OF RELATED ART
Autodeposition has been in colll,ll~ ,ial use on steel for about thirty years and is now well e~L~blished for that use. For details, see for example, U. S. Patents 3,592,699 of July 13, 1971 to Sleil~ er et al.; 4,108,817 of Aug. 22, 1978 and 4,178,400 of Dec.
11, 1979, both to Lochel; 4,242,379 of Dec~ el 30, 1980 and 4,243,704 of Jan. 6, 1981, both to Hall et al.; and 5,342,694 of Aug. 30, 1994 to Ahmed. (The ~li.eclosl-res of all of these ;..~ ,ly above noted U. S. Patents, except to the extent that they may be incon-5 sistent with any explicit ~ herein, are hereby incorporated herein by reference.) However, p.~Lion of CGAI;ll,~,.'. free from flaws on more electro~hPmic~lly active sub-strates such as zinc has continued to prove çh~llPn~iny especially when using an often p-Gr~ -~;d r~ ~ ' type of autodeposition resin, an internally stabilized crystalline copol-ymer of vinylidene chloride.

General Principles of Description Except in the claims and the operating examples, or where otherwise ~lessly indicated, all numerical q~ntitip~s in this description intlic~ting amounts of material or conditions of reaction and/or use are to be understood as modified by the word "about"
15 in describing the broadest scope of the invention. Practice within the numerical limits stated is generally p t;rt: -~d, however. Also, unless e,~ ~e~ly stated to the cGllLl~y: per-cent, "parts of', and ratio values are by weight; the term "polymer" in~ des "oligomer~", "copolymer", "terpolymer", and the like; the description of a group or class of materials as suitable or p-t;r~--ed for a given purpose in connecl;on with the invention implies that 20 mixtures of any two or more of the ~--~;---be- ~ of the group or class are equally suitable or p.ere,led; description of con~ Pnts in rhPmic~l terms refers to the con.etit~-çnts at the time of ~ litir~n to any combination specified in the description, and does not necçce~rily preclude chemical interactions among the cone~ .çnt~ of a mixture once mixed; specifi-cation of m~tP.ri~le in ionic form implies the plesellce of sufficient counterions to produce 25 electrical neutrality for the composition as a whole, and any counterions thus implicitly specified preferably are selected from among other conetit~lçnte explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, ex-cept for avoiding counterions that act adversely to the objects of the invention; and the term "mole" and its variations may be applied to ionic, chPmic~lly unstable neutral, or 30 any other chemical species, whether actual or hypothetical, that is specified by the types of atoms present and the number of each type of atom inclll(led in the unit clPfine-l, as well as to substances with well defined neutral molecules.

W O 97/09127 PCTrUS96/13480 S~lnl~ of the Invention It has now been found that contact of metal surfaces, particular1y of galvani_edsteel or like ~h~ir~,o~ls surf~ces and of ~hlmimlm and its alloys that contain at least 45 % Of ~lllmimlm after any r,l.~ninf~ needed or desired but before autodeposition, with an 5 aqueous solution having a surface tension value at 30~ C not greater than 55 dynes per cel-l;...tet~. and cons;s~ g çesenti~lly of, or pLGrGI~bly consisting of, water and:
(A) at least 0.008 %, based on the total solution, of a component of dissolved phos-phcm~t~s, and, optionally, one or both of the following components:
(B) a coillpol1ent of dissolved surfactant, exclusive of phosphonates; and 10 (C) a component of dissolved non-o~itli7in~ mineral acid, exclusive of any material that is part of colllpollent (A) or (B), is exceptionally effective in re~ cing formation of pinholes or similar surface blçmiehes after subsequent autodeposition. For purposes of this description, a "non-oxidi_ing min-eral acid" is defined as in column 2 line 50 - 56 of U. S. Patent 4,477,390 of Oct. 16,1984 to Ledent et al., the entire srecific~tic n of which, except to the extent collLI~l y to any ex-plicit st~tement herein, is hereby incorporated herein by IcrGlellce. Such metal ~IcL.Ga~-ment compositions con~LiLuLe one embodiment of this invention. Another composition embodiment ofthe invention is a con~ e from which a wulkhlg composition accord-ing to the invention can be plt;paled by dilution with water.
In its ~ embodiment, a process accordillg to this invention comprises three steps: (i) co..l~il;.~ a metal s~ ced object with a blemish inhibiting aqueous liquid pre-coating composition as described above at a suitable t~nlpcl~LIlre for a sufficient time to result in fewer b'-~iehes in a subse~ently autodeposited coating, this step being denoted briefly as "blemish h~ g precoalil~ Ll~l...e~l" or "BIPT" and the aqueous liquid25 composition used being usually briefly denoted helein~ner as l'BIPTC"; (ii) removing the metal sl~ ced object from contact with the BIPTC; and (iiij applying an autodeposit-ed coating on the surface treated with the BIPTC in step ~i).
Detailed Description of Preferred Embodiments The autodeposition composition and process themselves and tre~tmente with oth-30 er compositions before the BIPT and after autodeposition, for example, cleaning the sub-strate before contact with the BIPTC, simple and/or reactive rinses after autodeposition, the use of chromium co,~ g or other known advantageous po~U~ nt composi-tions after autodeposition and rinsing, and heating or other processes such as steam treat-ment to stabilize the initially formed coating film, are generally the same in an e~t~n~ed process according to this invention as in the prior art. Specific prere. l ed conditions are described in the wolking ex~mrles below.
~.erel~ly, a process according to this invention also incll-(les a rinse of the wet, although drained, uncured coating formed in the autodeposition bath with one of the aqueous compositions often known in the art as "reactive rinses", also known simply as "rinses". Particularly plerellt;d reactive rinses are described in U. S. Patent 5,372,853 of Dec. 13, 1994 and in U. S. Application Serial No. 08/316,437 filed Sep. 30, 1994, which, except to the extent that they may be inconsistent with any explicit st~tçm~nt herein, are hereby inco,l,o,~led herein by reference. Other suitable reaction rinses are described in the following U. S. Patents, the speçific~tion.e of all of which, except to the extent that they may be inconeietçnt with any explicit st~tement herein, are hereby incor-porated herein by ,c;r~lence: 5,432,694 of Aug.30, 1994; 5,428,525 of Sep. 30, 1993; and 5,164,234 of Nov. 17, 1992.
Any ~ ;"~ ofthe ~l~,irer~us s~lrf~ced object that is known to be needed or de-sired before autodeposition coating in the prior autodeposition art may advantageously be, and plefel~bly is, utilized in colln~ction with this invention before the blemish inhib-iting precoating Lle~ l instead.
Under certain con~itione~ it may be advantageous to rinse with water a substratesurface treated with a BIPTC accoldii~ to the invention before introducing the substrate into the autodeposition bath. Such rinsing is often unnecessary, however, and if not needed is preferably avoided for economy.
Char~ct.qli.~tic co",~ol1ellL (A) of a colll~os;lion accordh,g to this invention prefer-ably is selected from the group col1~;sLiilg of phosphonate ions that contain at least one amino nitrogen atom, preferably a tertiary amino nitrogen atom, per ion. Independently, the ions of this characteristic component (A) are preferably selected from ioms that con-tain at least 2, or more preferably at least three, phosphonate moieties per ion. Also in-dependently, when amino nitrogen is present, divalent hydrocarbon moieties selected from the group of methylene and polymethylene moieties preferably connect the phos-phorus atoms in each pho.cpl~ le moiety with an amino nitrogen atom; most pl~rel~bly, these connecting moieties are methylene, with oligomers of methylene increasingly less W O 97/09127 PCTrUS96/13480 plcrell~;d as the llullll~el of carbon atoms in these oligomers increases.
For convenience and econo,l,y, the ions of co",pollellL (A) are ~,ere,~bly addedto the BIPTC in the form of the commercially available corresponding phosphonic acids.
The single most plcrc~cd source for characteristic co".pollent (A) is diethylene triamine-penta{methylene phosphonic acid} with the ~~hemic~l formula:
H~PO3CH2N~(CH~ (CH2PO~H~)2}2 and the second most p~erel,cd is aminotri~methyl-ene phosphonic acid} with the chPmiC~l formula: N-(CH2PO3H2)3 The conccll~ ion of characteristic component (A) in the BIPTC can generally vary over a wide range without ~rre~ P. the effectiveness of blemish inhibition very strongly, particularly with the most effective inhibitors. For each particular molecular type in component (A), there is ~ ecLed to be a "threshold" value below which little or no inhibition will be achieved. In many cases, there is also expected to be a value, usual-ly at least t~,vo orders of m~gnitllde above the threshold value, above which the blemish inhibiting effectiveness of a particular molecular type decreases, perhaps because the acidity becomes too high. Therefore, the technic~lly plcrel~le values of concellLl~Lion of colllpoll~cllL (A) will depend in detail on the particular molecules used. In addition, the practically pler;;l~'c value will depend on economics: If the rinse solution is not recycl-ed, as is usually more convenient, it is pr~r~l ~le from the cost point of view to use as little of the inhibiting additive as will be ~deq~l~tPly effective for the purpose.
Generally, from the viewpoint of obLail~ g nlOxilllulll inhibition of blemi~hç~ the concentration of component (A) in a working precoat l~ composition according to the invention preferably is, with incleasil~ pler~rence in the order given, at least 0.0085, 0.0088, 0.0091, 0.0094, 0.0097, or 0.0100, %, and for less preferable molecular types more preferably is, with ill.ireasillg pltir~ ce in the order given, at least 0.020, 26 0.030, 0.040, or 0.080 %. Independently, for economic reasons, the concellLl~Lion of component (A) in a working precoat tre~tm~ont composition according to the invention preferably is, with increasing pre~lel,ce in the order given, not more than 50, 25, 10, 5, 3, 2, 1, 0.5, 0.3, 0.2, 0.10, 0.080, 0.060, or 0.050 % and for the most prere.,~d molecules for ~Ill~on~ (A) more preferably is, with increasing p~ e~, ~.,ce in the order given, not ~ 30 more than 0.040, 0.020, or 0.015 %.
The concell~ ion of phosphonate was determined by titration of a 250 millilitçr (hereinafter usually abbreviated "mL") sample of working composition with 0.025 N

W O 97/09127 PCT~US96/13480 thorium nitrate solution, after ~c;~ifir~tiQn of the sample with a solution of 1 % nitric acid in water to the extent l-ecç~s~ y to make the sample dear and light yellow in color and then addition of 1 mL of a solution of 9.45 grams of monochloroacetic acid in a mixture of 40 mL of 5 % NaOH solution in water and 60 mL of additional deionizedwater, using alizarin indicator, to the first salmon pink end point that persists for at least 30 seconds. Each mL of the titrant solution consumed co-lGspol1ds to 12.8 part per million of phosphonates in the working composition.
In general, the p. crGllGd phosphonic acid sources of component (A) are commer-cially available only in solution in con~ina~ion with non-oxidizing mineral acids that act to stabilize the acids against cryst~ tion, as described in U. S. Patent 4,477,390 al-ready cited above. Accordingly, compositions acco- .Ihlg to the invention normally pref-erably contain optional component (C). The amount of component (C), when it is made up of hydrochloric acid as is generally most p.Gre..ed, preferably is such that the ratio of COIIIPO1IGIIL (C) to co...pol1ent (A), the latter measured as its stoichiometric equivalent of corresponding phosphonic acids, is at least, with increasing plefelGllce in the order given, 0.10. 0.15, 0.20, 0.25, 0.28, 0.30, or 0.32:1.0 and independently preferably is not more than, with increasing p-Gre-G..ce in the order given, 1.0:1.0, 0.80:1.0, 0.70:1.0, 0.65:1.0, 0.60:1.0, 0.55:1.0, 0.50:1.0, 0.45:1.0, 0.40:1.0, 0.37:1.0, 0.35:1.0, orO.33:1Ø
In order to Illhx;lll;~e the probability for avoiding blçmi~hes, the surface tension 20 of the precoat Lle~ composition according to this invention preferably is, with in-c~ lg prGrt;lence in the order given, not more than 50, 48, 46, 44, 42, 41, 40, 39, 38, 37,36,35, or 34 dynes per cGn~ Ler when measured at 30 ~C by the Whilmey slide (or plate) method. For details ofthe measurement of surface tension, see A. Ati~m.con~ Phys-ical Chemistry of Surfaces, 3rd Ed., (John Wlley & Sons, New York, 1976), p. 23 - 25 2~ and C. Weser, ~IMea~ulGlllGlll of Interfacial Tension and Surface Tension - General Re-view for Practical Man", GITFachzeitschrift fur das Laboratorium, 24 (G-I-T Verlag Ernst Giebeler, Darmstadt, Germany, 1980),642-648 and 734-742.
Component (A) generally has a slight surface tension red~l~ing effect on other-wise pure water, but in order to achieve more preferable values of surface tension for a 30 wulking precoat l~efl~llç~ll composition accol-lhlg to the invention, additional surfactant is generally pl Gr~llGd as a co---po~ of the BIPTC. Any surfactant that is (i) chemically stable in con~inalion with component (A) and water, (ii) is effective in recluçing the sur-face tension, and (iii) does not have any adverse effect on the quality of the coating sub-sequently formed by autodeposition may be used One group of surf~ct~nts that have been found particularly suitable and are effective in economically small conce.,L.~Lions are aromatic s~lfon~tes and their salts, particularly the disulfonated derivatives of dodec-Y1diPhtnYI ether c~ ercially supplied by Dow Chemical Co, ~irll~ntl, ~ichig~n un-der the names DOWFAX~M 2Al and 2A0 Solution Surf~ct~nt~ The plt;r~llt;d amounts of any sll r~ c are those required to attain the p-~relled surface tension values stated in detail herein For DOWFAXrM 2Al, which is normally most prerel.ed, the concentra-tion in a wu~ g BrPTC p- t;re ~bly is, with increasing ,ol ~re ~nce in the order given, at least 0 0003, 0 0006, 0 0009, 0.0012, 0.0015, 0.0018, 0.0021, 0.0024, 0.0027, 0.0030, 0 0032, or 0 0034 % and, primarily for reasons of economy, independently preferably is, with ill~ a~ l~ p.ere.el~e in the order given, not greater than 0 05, 0.03, 0.010, 0.0070, 0 0050, or 0 0040 %
The time of contact b~Lween the metal substrate being treated and the BIPTC ac-16 cording to this invention and the telllpel~Lu-e during this contact may vary within wide lirnits G~ lly, with the p-t;r~ -t;d tre~tm~nt compositions, the contact time p-t;rt;-~bly is, with ill;lGasillg p-ere-ence in the order given, at least 5, 10, 15, 25, 35, 45, 50, 55, or 60 seconds (he-ein~Ller usually abbreviated "sec") and indepen-l~ntly, primarily for rea-sons of economy, preferably is, with increasing pl ~;rerence in the order given, not more than 30, 15, 10, 5, 4, 3, 2, 1.7, 1.5, 1.3, or 1 1 mimltes (he.eind~ler usually abbreviated "min") The L ~e~ 1 compositions acco- di..g to the invention generally are adequately effective at normal ambient te-..l)e. ~Lures of 20 - 25 ~ C and for convenience and econo-my are generally p,~;re ~bly used within such a te ..pe ~Lu-e range, although they may be used at any telll~ U1'eb~LWeen their r. ~ h.g and boiling points The autodeposition bath used for a process acco-ding to this invention prere-~bly comprises, more preferably consists essenti~lly of, or still more preferably consists of water and (A') from 5 to 550, more preferably from 30 to 300, still more preferably from 40 to 120, and most l"~r~ly from 40 to 80, g/L of a stably dispersed organic coating ~ 30 resm;
(B') from about 0.4 to about 5, more preferably from 0.5 to 4.0, still more preferably from 1 0 to 3 0, g/L of fluoride ions;

W O 97/09127 PCT~US96/13480 (C') an amount ~"~r.": .. l to provide from about 0.010 to about 0.20, more pl~;r~l~bly from 0.011 to 0.09, still more preferably from 0.012 to 0.045, ox~ in~ equival-ents per liter of an oxi~ ing agent s~lected from the group co~ of dichrom-ate, hydrogen peroxide, ferric ions, and mixtures thereof; and (D') a source of hydrogen ions in an amount sufficient to impart to the autodeposition composition a pH in the range from 1.6 to 3.8, more preferably from 1.7 to 3.0, still more "~rt;-~ly from 1.8 to 2.5.
One plert;..ed type of coating resin for use in forming autodeposited coatings in a process acco- lhl~, to the present invention comprises internally stabilized vinylidene chloride copolymers or externally stabilized vinylidene chloride copolymers co~ -g in excess of 50 %, or more preferably at least 80 %, of residues from polymerizing vi-nylidene chloride. Most prer~.~bly, the vinylidene chloride copolymer is crystalline in nature. F~emrl~ry crystalline resins are described in U.S. Patents 3,922,451 and 3,617, 368, the disclosures of which, except for any part that may be incon.cictent with any ex-plicit st~t~m~nt herein, are hereby incorporated herein by reference. Generally, crystal-line poly(vinylidene chloride) co.~ np~ resins comprise a relatively high proportion of residues from vinylidene chloride, for example, at least about 80 % by weight thereof.
A second plt;relled type of resin for use in autodeposition coating in connection with this invention is an acrylic type, particularly copolymers of acrylonitrile. Further details are given in U. S. Patent 4,313,861 of Feb. 2, 1982 to Bassett et al., the disclosure of which, except for any part that may be h~c~ ent with any explicit statem~.nt herein, is hereby incorporated herein by rere. el1ce.
The working BIPTC's may be conveniently p-epaled on site where used by dilut-ing concentrates with water, and such concentrates are also within the scope of this in-vention. Co"cc"l,~es nollllally plt;rel~bly contain from 3 to 20 times the concentrations of components (A), (B), and (C) as described above for wo~king compositions.
The practice of the invention, especially in its preferred embodiments, may be further appreciated from the following non-limiting examples and comparison examples.
Group 1 ~eneral Expe~ lal Procedure The process sequence used for this group of examples is shown in Table 1-1 be-low. (Note: All products identified herein by the trademarks PARCO~, RIDOLINE~, W O 97/09127 PCT~US96/13480 Table 1-1 PROCESSING STEPS USED, GROUP 1 Process Step ~'luid Used Fluid Temper- Contact ature, ~C Time, Min Spray ~ 72 g/L of PCL lS30A' 49 1 0 Dip Clean 144 g/L of PCL 1530A' in 60 2.0 water Dip Rinse < 10 g/L of PCL 1530AI 2 in 20 - 25 1 0 water Dip BIPTC See Table 2 20 - 25 1.0 Dip Rinse DI water 20 - 25 1.0 Dip A ~a r~ 6 - 7 % solids; see detailed 20 - 25 See Note3 el~. h~
Dwe.l Ambient air 20 - 2S 0.25 Dip Rinse Solutionmadebymixing49.6 20-25 parts of CoCO3,330 3 parts of a solution in water of 20 %
nuù~..w ..c acid and 2.1 %
HF, and 638.5 parts of DI
water4 Cure Hot air 88 20 General Notes for Table 1-1 "PCL" is an abb.~,~iatiol. for "PARCO(~) Cleaner". PCL 1530A, with or without added PCL lS30S
(see footnote 1 below), is a w~ iunal ~u~ ~ly strong a.kaline cleamer with - fi Footnotes for Table 1-1 'If .,ub.,l.alt;s were not free from water brealcs when using PARCO~) Cleaner 1530A alone, 2 g/L
of PARCO~) Cleaner lS30S were also dissolved i.-. the spray ".c; -le~ g and dip cleaning f.uids 2No PCL 1530A or S was de.iberately added to this f.uid, but because of drag-out from the preced-ing stage, it may have c~ ~1 as much as 10 g/L
3The i~u~ .,ioll time, along with the solids cu~ Lalion of the ~nth~e~.~ g cu.-.,~silion (within the 6 - 7 % range ~pe~ifiçd)~ was adjusted to produce a d.-y ~lltod~ d coating thirl~n~s$ of 17 8 + 2 5 mic.u.l.- k; ~
4The solute in this solution is believed to consist ".~ ;. ~ y of cobalt nuu~ u..alt; after mixing and evolution of gas, ,vl~ u...dl)ly carbon dioxide, which occurs after mixing. The solution was replaced after every 100 panels ,,.uccssel W O 97/09127 PCT~US96/13480 and AUTOPHORETIC~, togethP,r with detailed directions for using them as described below, are col-lme~ dlly available from the Parker ~mrhPm Div. of Henkel Corp., Madi-son Heights, Michig~n ) The precoat Ll~ l bath compositions are shown in Table 1-2 below.
Ple~ ion of 18.5 liters (helein~ler usually abbreviated "L") of a "normal acti-vation" autodeposition bath was accomplished as follows: Into an adequate size high density polyethylene (helein~flel usually abbreviated as " HDPE") colll~illGl for the final mixture were added 3.37 kilograms (helehl~Qer usually abbreviated "kg") of AUTO-PHORETIC~ 866 Replenisher (hereinafter usually abbreviated "866 Replenisher" or simply "866"), which cont~inc 37.5 % solids, and 12.1 kg of industrially deionized (here-inafcer usually abbreviated "DI") water. To this first mixture, a sepal~ely mixed solution of 0.99 kg of AUTOPHORETIC~ Starter 300 (helGill~lGl usually abbreviated as "Starter 300" or "S 300") and 2.96 kg of DI water was then slowly added with consL~ll stirring, using a motor driven stirrer. ~ltlition of the starter solution to the solution of 866 took approkimalely 20 mimltçs S-lfficiP-nt hydrofiuoric acid was then added to result in a reading of 248 micro~llpelGs (heleil,~ne, usually abbreviated ",uA") on a LINE-GUARD~) 101 fluoride activity meter (helGinaner usually abbreviated "101 Meter").
This composition had an o~ tit~n-reduction potential (he,einaner usually abbreviated "ORP") value for a smooth platinum electrode immersed in the composition, co"lpalGd to a standard hydrogen electrode, of 375 l 25 millivolts (herGill~le, usually abbreviated "mv") P~Gpa,~lion of a "low activation" autodeposition bath was pG,~"lled ;dentic~lly to the "normal activation" bath, except for using the following amounts of materials:

3.37 kg of 866 P~ q~F' -.nich~.r with 9.24 kg of DI water; 0.70 kg of Starter 300 diluted with 3.12 kg of DI water; and a reading of 110,uA on the 101 Meter. The ORP was the same as for the "normal activation" bath The coating resin in both these examples of autodep-osition baths is a crystalline copolymer of vinylidene chloride~
During use, autodeposition baths were ...A;..~ ed between 6 - 7 % of total solids by the addition of 866 Replenisher as needed to compensate for the loss of coating resin 30 from the baths, primarily by transfer of the resin into the autodeposited coatings formed during use. AUTOPHORETIC~ Oxidizer 24 was added to ~"~ the ORP range specified aboveforeachbath, and hydrofluoricacidwasaddedto ",~;"~ , 101 Meter ~ 10 W O 97/09127 PCT~US96/13480 Table 1-2 PRECOAT TREATMENT BATH COMPOSITIONS, GROUP 1 PRECOATACTIVE INGREDIENT
DESIGNATION INGREDIENT(S) CONOENTRATION
D2060 A DequestTM 2060 0 01 % Active DowfaxTM 2A 10 0031 Wt-Vol % Active D2060 B DequestTM 2060 0 02 % Active DowfaxTM 2A 10 0031 Wt Vol % Active D2060 C DequestTM 2060 0 04 % Active DowfaxTM 2A1 0 0031 Wt-Vol % Active D2000 A DequestTM 2000 0 01 % Active DowfaxTM 2A 10 0031 Wt-Vol % Active D2000 B DequestTM 2000 0 02 % Active DowfaxTM 2A 10 0031 Wt-Vol % Active D2000 C DequestTM2000 0 04 %Active DowfaxTM 2A1 0 0031 Wt-Vol % Active D2060/2A0 DequestTM2060 0 04 %Active DowfaxTM 2A0 0 0031 Wt-Vol % Active H3PO4 A H3PO4 0 20 Molar H3PO4B H3PO4 0.40 Molar H3PO4 C H3PO4 0.80 Molar HF + H2~2 HF 0.0011 % Active H2~2 1 0 % Active DI DI Water Notes for Table 1-2 Precoat Decign~tion DI and all other Precoat Desi~n~tionc not beginning with the letter "D" are colll~allson examples, not accol.lillg to the invention "Wt-Vol %" means that the volume of the liquid solution in which the DOWFAXTM .,ulra~;~ll~, are supplied was Ill~a~ d directly, then the volume percent coll~i",olldillg to this volume in respect to the volume of the entire cwll~osilion was multiplied by the weight percent of ph~ .hr,l~ic acid(s) in the liquid solution to obtain the "Wt Vol % "

W O 97/09127 PCTrUS96/13480 re~lin~e of 250+25 ~lA in the "normal activation" ~he,t;;l,~ler usually abbreviated as "NA") autodeposition bath and 110+10 ~lA in the "low activation" (hereil1~ler usually abbreviated as "LA") bath. A separate BIPTC was used for each type (i.e., NA or LA) of autodeposition bath.
Allmetalsul~ lesprocessedwerele~ rpanels 10.16x 15.24cç.~1i.. le i.~lel usually abbreviated "cm") in size; these were prepaled by bieecting rect~n~
lar panels 10.16 x 30.48 cm in size supplied by ACT Laboratories, Inc., ~illc-l~le7 Michi-gan. Three types of metal were used: Cold Rolled Steel (hereinafter usually abbreviated "CRS"), Code APR 11721, 6.6 millimeters (hereill~[ler usually abbreviated "mm") thick, clean, unpolished, Batch 30425414 or 31021314; Hot-dipped Galvanized Steel (he~t;illar-ter usually abbreviated "G60"), Code APR 10260, 8.9 mm thick; and Galv~nn~led Steel (herei"~ler usually abbreviated "A60"), Code APR 16966, 7.6 mm thick, clean, unpol-ished, Batch 20622416 or 20315416. Panels were dipped two at a time, using two hooks att~-h~.d to the same ~U~pOl L~l~ rod, for the process sequence. A total of 18 panels were processed for each BIPTC: six of CRS, six of G60 and six of A60.
Physical testing included GM 951 lP, 20-cycle, scribe/scab, 504-hour salt spray (ASTM B117-90), impact (ASTM 2794-87, except that no evaluation ofthe pattern ofcoating removed by the tape was made), and initial adhesion (ASTM D3359-87) testing.
Table 1-3 lists observations of the presence of pinholing/blistering on the initially oven cured coated panels as well as impact, GM 951 lP, 20-cycle scribe/scab, salt spray and initial adhesion results. Coatings having ~ignific~nt blistering and/or pinholing after oven cure were not tested further.
The following conclusions were drawn from the results shown in Table 1-3:
The expe~ l BIPTC's found to give the best overall l~e,ro"~ ce were those Col,l;~ DEQUESTrM 2060. Conce~ lions of at least 0.02 % of this material (which contains only about 50 % of its active phosphonic acid ingredient) appeared to give the best overall results under both low and normal activation conditions for the autodeposi-tion bath. G60, A60 and CRS panels were all pinhole and blister-free after oven cure.
Initial adhesion was not affected by the precoat tre~tment step when coll,pared to a DI
co~ cuisoll precoat Ll~llllt;lll step, but corrosion results after subsequent autodeposition coating were s~l~,lially better with a ll~llllelll composition according to the invention.
Differences in salt spray and scribe/scab pe~ro~lllallce results between low and normal Table1-3 STEEL AND ZINC-AILOY ST EL COATING PROCESS RESULTS, GROUP 1 t PrecoatBathlPinhol- Iniffal Im-S04 Hr SS Scribe/
Desig- Panelin~lBli~- Adhe- pact Scab natlon Typestering rion Creep, Mm LA/G60 None 5B 690-4~35 o 355 1,1 D2A060LA/A60 None >4B 690-495, 0 495 1,1 LA/CRS None >4B 115o-12S, 1-2 2,2 LA/G60 None SB 462-345, 0-3 ~os I, I
D2B060LA/A60 None 5B 460-12sVF6 0-145 1,1 LA/CRS None >4B 1610-2, 0-2 4,3 LA/G60 None 5B 231-265,1-2'55 1,1 C LA/A60 None >4B 690-125 VF8, 0 31os 1,1 LA/CRS None >4B 69 1-1,1-1'5 2,2 LA/G60 None SB 23~-355,1-355 1,1 D2A000LA/A60 None IB <230-25 VF5, 0-2 VF5 1,1 LA/CRS None >4B 1841-1, 1_125 3,3 LA/G60 None SB 460-2JS F6, 0-2JS F6 1, I

B WA60 None IB 230-3'5, 0-2"5 1,1 LA/CRS None >4B 1380-125, 0-1 2,2 LA/G60 None SB 23o-48S VF6, 0-3"5 1,1 C LA/A60 None >4B <46o-235 VF6, 0-125 VF6 1,1 LA/CRS None >4B 138 1-1,1-1 2,2 H3PO4LA/G60Vely Few 2B <230-355 VF6, 0-235 so/OpI ~ I
A Pinholes LA/A60Medium - - - -Pinholes LA/CRSVeryfew >4B 1840 l2s 0 1 2,3 blisters ...Table continued on next page ...

W O 97/09127 PCT~US96/13480 Precoat Batb~Pinhol- Initiai Im-504 HrSS Scribe/
Desig- Paneling/Bli~- Adhe- pact Scab nation Typestering don Creep, Mm H,PO4 WG60 Few 3-4B <230-235 FM4, 0-255 2,2 B pinholes FM6 WA60 Medium - - -pinholes WCRS Veryfew >4B 1840-1, 0-125 2,2 pinholes H3PO4 WG60Very few 3B <230-245, 0-345 1,1 C blisters WA60 Medium pinholes LA/CRSVeryfew >4B 1840-125, 0-125 2,2 blisters HF + WG60 None SB <461-365 VF8, 0-2'5 VF6 1,1 H2O2 WA60 Pinholes WCRS None >4B 1841-1, 0-1 2,2 DI LA/G60 None SB 1613-11 5%P, 0-35sF6 1,1 LA/A60 None 2B <230-355 VF6, 0-14sF6 1,1 LA/CRS None >4B 1841-1,1-1 1,2 Com. A NA/CRS None SB <231-2,1-2 F9 2,2, 2,2 Com. B - None SB <23N, 0-15 3,3, 2,3 D2060 NA/G60 None >4B <230-3~C5 50/oP, o 4ss1, <I
NA/A60 None >4B 460-25sF8, o-24sF2 ~1, 1 NA/CRS None >4B 461-2, 1-2 2, 2 D2060 NA/G60 None >4B <230-4 VF6, 0-345 5%P<1, 'I
NA/A60 None >4B <23o-25S VF8, 0-25 VF8<1, <I
NA/CRS None >4B 46 1-1,1-2 2,2 D2060 NA/G60 None >4B <230-245 VF8,0-4~ VF6 <1, 1 NA/A60 None >4B <230-25 VF8, 0-25 VF8 <1, 1 NA/CRS None >4B 231-I, 1-I 2,2 D2000 NA/G60 None >4B ~230-3gS VF4, 1-4 VF6 1,1 NA/A60Vely few 2B <230-2 F8, 0-235 F8 1, I
blisters NA/CRS None >4B <231-2,1-2 3,2 ...Table continued on next page ...

W O 97/09127 , PCT~US96/13480 Precoat BYth/Pinhol~ Uial Im- S04 Hr SS Scribe/
Dcsig- P~nelingtBlis- Adhe- p~lCt Scab nation TypeJtering sion Creep~ Mm D2000B NA/G60 None SB c23 0-4'~sF6, 1-3VF8 <1,1 NA/A60 Very few 2B <23 0-45 F8, 0-45 F6 1, I
blisters NA/CRS None ~4B <46 I l2s l l2s 2,2 D2000 C NA/G60 None >4B <23 1 -4~5 F6, 1 -455 F6 1, I
NA/A60 F~,..M~i. 4B c23 0-3sVF8,0-lsVF8 <I,cl pinholes NA/CRS None 5B 69 1-2, 1-2 2,3 H3PO~A NA/G60 Veryfew IB ~23 0-26sF6,0-46sF6 1,1 (VF9, pinholes VF9) NA/A60 Mediu~n pinholes NA/CRS None >4B 46 1-125, 1-125 1,1 H3PO4 B NA/G60 Very few I B c23 0-3 F6, o-365 F6 1, I (VFg, VFg) pinholes NA/A60 Medium ~J".1...1;i-~
NA/CRS None >4B 46 1-2, 1-2 2,3 H3PO4C NA/G60 Veryfew IB <23 o 35sF6~o-3F6 1,1 (VF8,VF8) pinholes NA/A60 Medium olil~g NA/CRS None >4B 46 1 I I 1 2S 4,2 HF+ NA/G60 Few- 3-4B <~!3 1-235, 1-2 1,1 (FM8, H2O2 medium FM8) pinholes NA/A60 Medium oL~g few blisters NA/CRS None SB 46 1-2, 1-235 2,2 DI NA/G60 Few 3B <23 1 365F6,1-3F4 1,I
piIlholes NA/A60 Medium IB <23 pinholes few blisters NA/CRS None >4B c69 1-2, 1-2 2,2 ...Table conhnued on next page ...

W O 97/09127 PCT~US96/13480 Precoat B~th/ Pinhol-InUial Im- S04 HrSS Scribe/
De~ig- P~neling/Blis-Adhe- pact Scab nation Types tering ~ion Creep, Mm D2060/ NA/G60 None >4B '23 o-36S, 0-2'~S <1,1 2A0 NA/A60 None >4B <23 0-45 F8, 0-25 F8 1,1 NA/CRS None >4B >23 1 -2,1 - I 2,2 N- t~ for Table 1-3 "Comp. A" is a ~ ;co" example in which no precoat L~ was used and the rinse after autoJ~ ition was an aqueous solution of n~ dtt;~ but other process steps were the same as for "normal activation" autodeposition acc~l~li-lg to the invention.
"Comp. B" is a culll~ example in which the metal ~ul.~l-..Le was coated with an ~ d.,~os-ited paint (I~u..~ unTM 500) that is generally ~ù ~id~,.~ very high in quality, instead of any auto-deposited coating.
activation baths were not signific~nt Coatings after DEQIlESTIM 2000 C.J..~ g pl~ nl ~~-P.nt compositions had com-parable salt spray and scribe/scab p~lrulll~lce to those after DEQUESI~M 2060. Howev-er, DEQUESI~M 2000 COI~IA;~ Ig precoat 11'eAI~ ; were less effective at pinhole pre-5 vention over galv~nne~led A60 panels under "normal activation" bath conditions (101 Meter reading = 250 ,uA), and appeared to require at least twice as high a concentration as with DEQUEST~ 2060 co..l ~ compo~ilions to provide the most corrosion resist-ance on the more ~lifficl-lt to protect galv~nnP~lPd substrates.
H3PO4 co~ g con~itinning rinses were unable to produce pinhole-free co~tings over galvannealed A60 steel at all precoat conce.. l.~lions and ACC-866 bath activation levels tested. Salt spray and scribe/scab pelru~ allce results were slightly lower than for the DEQUESTTM arninophosphonic acid c~-."~ g BIPTC's.
H~ - H2O2 nlixl~llts were not effective in çl;,~ g pinholes and blisters on gal-v~nne~led steel.
Salt spray (ASTM B117-90) tests resulted in some field blistering and cathodic de-l~min~tion spots on both G60 and A60 panels for all precoat conditioning rinses tried here. Such results are always or almost always observed during this type of testing of samples with ~.ncire.olls surfaces, even when these surfaces are protected with coatings known to give çxcP.llP.nt corrosion l~ .e under practical use conditions. However, the precoat contlitioning rinses do appear to reduce the severity of the salt spray in~lced field blislelillg and dPl~min~finn, which are much less severe for A60 panels than for G60 pan-W O 97/09127 PCT~US96/13480 .}
els in general.
GM 951 lP, 20-cycle scribe/scab data were excellent for all DEQUESTTM amino-pho~ ~h --- acid co.~ BIPTC's and both ACC-866 bath activation levels tried. Typi-cal creep widths for all A60 and G60 panels were 1 mm or less in total creep. Total creep 5 widths over CRS were typically 2 mm, comp~ble to those now achieved with the best prior art autodeposition teçhnolQgy, in(1ie~ting that autodeposition coatings applied after a BIPT accc Idil,g to the invention are at least as s~ti.~f~ctory as other autodeposition coat-ings on CRS and therefore may be used on composite objects co~ il-il-g both CRS and z inc coated ~rf~s without deterioration of the best pel r~,llllance now achieved by auto-10 deposition coating of CRS alone.
Impact test results were somewhat erratic as is normal for autodeposition coatedCRS ~ubsll~les~ but there is no evidence that the aminophosphonic acid CO..~ g BIPT
nifc~ntly afffects impact test pe.rollllance either adversely or positively.
Group 2 A major objective of this group of examples was to establish consumption levels ofthe BIPTC active i.l~enl~ during prolonged use. Unless otherwise stated below, op-erating conditions were the sarne as for Group 1.
General Conditions of Operation In plGIJalillg the a llode~o~lion baths, 0.94 rather than 0.99 kg of AUTOPHORET-IC~ Starter 300 and 2.45 kg instead of 2.96 kg of water were used. The 101 Meterfluoride sensing reading was 150 instead of 240 ~lamps.
A BIPTC concentrate was pl~aled as follows: In an adequate size HDPE jug were mixed 54.00~0.01 g of Dequest 2060, 4.41 ~0.01 g of Dowfax 2Al and sufficient DI water to produce a total conc~ e mass of 3000+ 1 g. To prepare a WOlhillg BIPTC, 150.0+0.1 g ofthe ~l~n~.l;oned BIPTC co~ le was then diluted to 3000~ 1 g with DI water and stirred. 1300 l l g of this solution was added to a narrow stainless steel panel coating tank designed to accommodate the rect~n~ r test panels, which were 10 by 30 cm in size, with minim~l solution volume.
Phosphonate concentrations in the working BIPTC's were monitored and main-tained at intervals after use of the BIPTC by removing a 250 11 g sample of the BIPTC
(while no substrates were being processed) and titrating this sample with a thorium nitrate solution as already described above. The l~ ;llg 1050~1 g of the used working W O 97/09127 PCT~US96/13480 BIPTC was then mixed with an amount of the BIPTC conce~ e described above that was calc~ ted, based on the results of the titrated sample, to result in a mixture having the origirial phosphonate conce~ lion ofthe working BIPTC in a total mass of 1550+ 1 g ofthe mixture, and sllfficient DI water to bring the total mass ofthis mixture to 1550 l 3 1 g was then added and well mixed. A second 250+ 1 g sample was then taken from this mixture and titrated as described above, to d~Lel ll~ine whelllel the col-ce~ Lion of phos-phon~te in the mixture had been restored to at least the value originally present in the freshly made BIPTC. If it had, the r~ 1300+1 g ofthe mixture was usually con-tinued in use as l~r ' ~ used BIPTC to pretreat more substrate panels, as noted in spe-cific in~t~nces below.
The general process sequence used for this group is shown in Table 2-1 below.
The substrate materials used, with the abbreviations for them used in the following de-s~ription shown within quotation marks in par~ .es;~ after each substrate type name be-low, were as follows:
Cold Rolled Steel ("CRS"), Code APR 11721, 6.6 mm thick, clean, unpolished, Batch 31216414.
Hot-dipped Galvanized ("G60"), Code APR 10260, 8.9 mm thick, clean, unpolished, Batch 20109516.
Galv~nne~led ("A60"), Code APR 16966, 7.6 mm thick, clean, unpolished, Batch 31004416.
Hot-dipped Galvanized/Cold Rolled Steel, Bimet~llic, end-to-end lap joint ("G60/CRS"), Code 10270, Batch 21214416, Panel A: ACTCRS, Panel B: ACT G60.
Galvannealed/Cold Rolled Steel, Bimet~llic, end-to-end lap joint ("A60/CRS"), Code 10270, Batch 21214416, Panel A: ACTCRS, Panel B: ACT A60.
Cured coating ~peal~ce data as a function of substrate and use or non-use of theacid cleaning and subsequent rinse steps are shown in Table 2-2 below. "Comparison I"
in this table was a commercial product, AUTOPHORETIC~ Conditioning Rinse 3180.
Panels in this processing sequence were processed one at a time, with the sub-strates being processed in the following sequence: First, six each of G60/CRS and A60/
CRS type panels were processed in alternating sequence. Secondly, nine CRS, nine A60 and nine G60 panels were processed, one of each type being processed before a second one of any type was processed, etc. Thirdly, six G60/CRS and six A60/CRS panels were W o 97/09127 PCT~US96/13480 Table 2-1 Process Step Fluid Used Fluid Temper- Colltact ature,~C Time, Min Spray ~ Clean 60 g/L of RDL 1007 77 2.0 Dip Rinse Tap water 20 - 25 1.0 Dip Acid Cleanl2 % by volume of AC 7150 66 1.0 Dip Rinsel Tap water 20 - 2S 1.0 Dip BIPTC See Table 2-2 20 - 2S 1.0 Dip Rinse DI water 20 - 25 1.0 Dip ~ ' I r 6 - 7 % solids; see detailed 20 - 25 See Note2 C~J~ ~ cl~... G
Dip Rinse Tap water 20 - 25 1.0 Dip Rinse Solution made by mixing 49.6 20 - 25 1.0 parts of CoCO3, 330.3 parts of a solution in water of 20 %
lluo~ilwluc acid and 2.1 % HF, and 638.5 parts of DI water3 Cure Hot air 110 30 General Notes for Table 2-1 "RDL" is an ~l,.ciYi~ion for "RlDOLrNE~) Cleaner"; RDL 1007 is a solid, puvvd~ ,d, ~ t~l strongly alkaline cleaner cullce~ ..t~. "AC 7150" is an ~I-eY;aljO - for AUTOPHORETIC(~9 7150 Acid Cleaner, a liquid C~ GIIh ~ for ~ ~i..g a spray cleaning solution APC;gl1~d to remove light rust and r~Yi~l~ti~n from oil- and grease-free iron and steel surfaces before applying an ~nto~
coating.
Footnotes for Table 2-1 IThis step was used only on ~ .~;. that included some wld rolled steel, and not on all such su~ dlG~, ~ r~ c are noted in the following tables.
2The immersion time, along with the solids COII~II1d~iUII of the ~lto~ x~ g c~ n~ ion (within the 6 - 7 % range sperified), was adjusted to produce a dry autodGposiLtd wating ~ LIIeCC of 25.4 + 2.5 ~lliGl~UUGI~
3The solute in this solution is believed to consist ~ ly of cobalt fluu~uwlldlG after mixing and Gvululiull of gas, IJ-G~u uably carbon dioxide, which occurs after mixing.

CA 02230278 l998-02-24 W O 97/09127 PCT~US96tl3480 Sub~ g Rin~ing C~
~tr~te Type ,~ ~ gtotheIh.~ '- C~, ~ I DIW~ter With Acld Clean No Acid Cle~m CRSNo blistering and/orNo blistering and/or Blistering and/orBlistering and/or ,~.. "llolillg ~,illl.olillg pinholing pinholin~
G60No hli~ing and/orNo blistering and/or Trace of ~.;.. l~f~l;.l~ Slight to moderate ~ lhollllg ~ blistering at edges A60Tracepinholing,trace Trace~.;... 1.,-1;.. ~ trace Severe~,...... ,lloLIg Severepish~olirlg blistering blistering and blistering and blistering G60/ Trace ~.;l~nl;~ in spots Trace ~ in spots Coating missing in Coating missing in CRSat joint interface. Coating at joint interface. spots near joint spots near joint missing in spots near joint inte~face. Rlict~rin~ interface interface. and pinholing at lap joint and welds.
A60/ Coating missing in spot~,Trace blict~in~ alongDen~,e to severe ---CRSnear joint interface. Trace joint interface edges.blistering on A60 rinhr~lin~ on A60 panel Trace l.;.. h- I;... g on A60 panel half.
half. panel half. Rli~t~rin~ at interface joint.

again processed in allel-~Lillg sequence. Fourthly, another eleven each of CRS, A60, and G60 panels were processed in the same sequence as before, followed by three each of G60/CRS and A60/CRS panels in ~ I ;Ol~ with each other. Finally, various control and other test panels were processed as needed.
Table 2-3 shows data relevant to the co~ ;on of phosphonate during a process accc,ld;ng to the invention. The average con,ulnplion calculated from the values in Table 2-3 is 7.6 g of the BITC concentrate per square meter of substrate surface processed.
The working BIPTC was analyzed for various el~ment~ at the beginning and end of use as described above. Results are shown in Table 2-4. They indicate that zinc is the primary metal dissolved from the substrates during BIPT of galvanized steel according to the invention and that the phosphonate active ingredient is converted to some other sol-uble phosphorus cont~ining compound, at least part of which remains in solution in the BIPTC.
Physical testing results for Group 2 are shown in Tables 2-5, 2-6, and 2-7 below.

W O 97/09127 PCT~US96/13480 Square Titration O~re.~ ~ ~~ and D~ Actions Meters of ~ ~ t, Substrate mL of 0.025 ~r.,ce~s~d ArThorium per Liter of Mtrate BIPI C Solution o 10.2 . Titration value for freshly made unused working BIPTC
1.19 6.5 . Pillllolillg increase ol~ ~ on A60 panel coated.
. Added BIPTC co~ lLI~t~, to bring to 10.3 ml titration for the working collll,o~;Lioll, and c~ ~ S';-'.
3.09 - . Observed coating w~hoffin areas on G60 panel during tap water rinse after ~.. lod~,~osilion step.
. Added 130 mL of ~ viou~l~/ unused working BIPTC and .u~d p~
3.38 5.3 . Observed .~ ~lo(~ o~it~ coating washoffin areas during tap water rinse step.
. Adjusted c~ m with BIPTC c..ll~..L.~te to 10.6 ml titration value for the working cc,l..~o~ilion and c~

5.46 3.8 . Autodci~,o~iled coating washoff in areas obs~ d on G60 panel.
. Adjusted col~c~,l-L.~.~ion with BIPTC C~ lale to 11.7 ml titration value for the working c~ )o~ilion. C~ i until a total of 5.85 square meters per liter had been ~l~S .~l.

The results of Group 2 led to the follovving conclusions:
The D2060/2A1 type BIPTC gave superior coating panel appearance compared s to the best previous commercial BIPTC, AUTOPHORETIC~) 3180 Conditioning Rinse.Tre~ ..l accolding to the invention described herein gave co~ting~ with no blistering and/or pinhr~ling over CRS and G60 ~ul~sll~le~ and only trace pinholing over A60 galvan-nealed steel was observed.
F.limin~tion of the 7150 acid cleaning step improves coating coverage over a zinc 10 coated steel-to-steel lap joint region with the best example of a BIPT according to the in-vention.
- The initial consumption rate of active ingredient from the BIPTC was calculated to be 39.8 g of phrsphon~te per 1000 m2 of substrate processed. Consumption rate dimin-ished to a~p~ alely 23.7 g of phosphonate per 1000 m2 between 3.4 and 5.5 m2 of Element Concentration of Element in the BIPTC
For Before UseAfter r~ ocessing 5.85 m2/L
Fe C 1 ppm 4 ppm Zn <lppm 0.16%
Si < 1 ppm 4 ppm Al < 1 ppm < 1 ppm P 0.013 % 0.12 %
Abbreviations for Table 2-4 "ppm" = "parts per million"; "m2/L" = square meters of substrate per liter of BIPTC.

Substrate M2~ Initial ~(ll: ~r Values T~p-~t Test Values Previously Treatedl Zn Coated CRS Lap Joint Zn Coated CRS
Portion Portion Interface Portion Portion A60/CRS 0.24 >4B >4B 4B >40 >160 A60 1.34 >4B >140 A60 1.90 >4B >120 A60/CRS 2.37 >4B >4B >4B 120 >160 A60 3.80 >4B >120 A60/CRS 4.51 >4B >4B 4B >120 >160 A60 5.24 4B >120 A60/CRS2 5.71 3-4B 4B 3-4B >80 >160 G60/CRS 0.29 >4B >4B 4B >80 >160 G60 1.38 >4B >140 G60 1.81 >4B 120 ...Table cont~nued on next page ...

W O 97/09127 PCT~US96/13480 Substrate M2/LInitial Adhesion Values Impact Test V~lues Previously Treated' Zn Coated CRS L~p Joint Zn Coated CRS
Portion Portion Interface Portion Portion G60/CRS 2.43 >4B >4B >4B >120 >160 G60 3.85 >4B >100 G60 4.56 >4B >4B 2B >120 >160 G60/CRS2 4 66 >4B >4B 4B >100 >160 G60/CRS2 5.27 4B >20 G60/CRS -3 >4B >4B 4B >100 >160 G60 -3 4B >100 G60/CRS -4 4B >4B 3~B >80 > 160 CRS 1.28 >4B >160 CRS 1.85 >4B >160 CRS 3.75 >4B >160 CRS2 5.19 4B >160 CRS -3 4B > 160 CRS -4 >4B >160 CRS -5 >4B >160 CRS _6 >4B <20 Footnotes for Table 2-5 'With the same batch of BIPTC, except for repleni~hm~nt 2The acid çle~ning step and immedi-ately following rinse step were omitted for this substrate in this in~t~nce. 3Comparison example with AUTOPHORETIC~) Conditioning Rinse 3180 rather than a BIPT according to this inven-tion. 4Co...~ ;con PY~mrle with no BIPT other than rinsing with DI water. 5Comparison examp-le with no BIPT and with a di~t;lelll reactive rinse, AUTOPHORETIC~ Reaction Rinse 2150.
6Comparison example with electrophoretic paint coating rather than autodeposited coating.
substrate processed per liter of starting BIPTC. This may be due to build up of soluble metal phosphonate byproducts in the used BIPTC.
A miniml-m con~ lion of about 83 ppm of phosphonate in the BIPTC is neces-sary for cured co~tingc to have the best appearance obtained. The nature of the failure or defects depended on the amount of substrate processed through the precoat bath. Lower W O 97/09127 PCT~US96/13480 Substrate M2/LP~ c- ~ Scribe-Scab TestResult, mm Treatedl Zn Coated Portion CRS Portion A60/CRS 0.14 <1, F-M9 3, Field ~st A60/CRS 0.33 <1, F-M9 2, Field ~st A60 0.76 <1, F-M9 A60 1.05 <1, F-M8 A60/CRS 2.09 1, F-M9 2, Field ~st A60/CRS 2.28 1, F-M9 2, Field ~st A60 2.62 l,F-M8 A60 2.92 1, F-M9 A60 3.68 <1, F-M' A60 3.94 l,F-M6 A60/CRS 4.34 <l,F-M8 2, Field ~st A60/CRS 4.43 l,F-M8 2, Field ~st A60/CRS2 4.61 1, F-M9 2, Field ~st G60/CRS 0.19 <1, F-M9 2, Field ~st G60/CRS 0.58 <1, F-M9 2, Field ~st G60 0.81 <l,F-M8 G60 1.10 1, F-M9 G60/CRS 2.14 <l,F-M8 2, Field ~st G60/CRS 2.33 <l,F-M8 2, Field ~st G60 2.67 <l,F-M8 G60 2.96 <l,F-M8 G60 3 .58 1, F-M4 G60 3.99 <1, F-M6 2, Field rust G60/CRS 4.29 <1, F-M9 2, Field ~st ...Table contfnued on next page ...

W O 97/09127 PCT~US96/13480 SubstrateM~ G- C ~IY S~--' Z Scab Test Result, mm Treatedl Zn Coated Portion CRS Portion G60/CRS 4.39 <1, F-M9 2, Field rust G60/CRS 4.70 <1, F-M9 2, Field rust ~ G60/CRS 4.75 <1, F-M9 2, Field rust G60/CRS -3 <1, F-M9 2, Field rust G60/CRS -3 <1, F-M9 2, Field rust G60 _4 <1, F-M4 G60 4 1, F-M4 ---CRS 0.71 --- 2, Field rust CRS 1.00 --- 2, Field rust CRS 2.S7 --- 2, Field rust CRS 2.87 --- 2, Field rust CRS 3.63 --- 2, Field rust CRS 3.90 --- 2, Fieldrust CRS 4 2, Field rust CRS -4 --- 2, Field rust CRS _5 3,4,3,36, Field rust CRS _7 1,1,1, Footnotes for Table 2-6 IWith the same batch of BIPTC, except for replPni.~hmP-nt 2The acid cleaning step and immedi-ately following rinse step were omitted for this substrate in this in~t~nce. 3Comparison example with AUTOPHORETIC~ Conditioning Rinse 3180 rather than a BIPT accol dh-g to this inven-tion. 4Comparison c;x~llpl~ with no BIPT other than rinsing with DI water. 5Comparison examp-le with no BIPT and with a diLrerellL reactive rinse, AUTOPHORETIC~ Reaction Rinse 2150.
6Individual results from four replicate samples. 7Comparison example with electrophoretic paint coating rather than autodeposited coating.
concentrations of phosphonate appea~ed to be adequate to produce cured coating with good appearance as phosphorus co,.~ il-g byproducts built up in the BIPTC.

W O 97/09127 PCT~US96/13480 Substrate M2/L Previousb R~lting after 504 Hours of Salt Spray TreatedlZn Coated Portion, Field CRS Portion, Field A60/CRS 0.43 0-15S,Fx,7 ol2s 7 A60/CRS 0.52 o-23S 6 Ol~ 7 A60 0.90 0-2S,FM8,8 A60 1.19 0-4S,F8,8 A60 1.47 ol3s Fs 7 A60 1.61 0-12S, FM8,7 A60/CRS 1.99 0lss Fs 7 0-1,7 A60/CRS 2.19 0-l~,FM9,7 0-1,7 A60 2.74 0_13S 7 A60 3.04 0l3s 7 A60 3.33 0-4S,F2,8 A60/CRS 4.04 ol3s Ft 7 0-1,7 A60/CRS 4.24 o-35S,FM8,5 0-1,7 A60/CRS 5.81 0-l,F8,7 Ol~ 7 A602 4.95 0-2,MD8,6 A602 5.10 0-2S,F~,8 A60/CRS2 5.76 0-l,F8,7 ol2s 7 G60/CRS 0.48 0 36S,D9,5 O_l~s 7 G60/CRS 0.67 0 34s VF6 5 0-1,6 G60 0.96 0-2,D9,7 G60 1.23 0 1 2S D9 7 G60 1.52 0-2,D9,6 G60 1.66 0-2,MD9,6 G60/CRS 2.05 o-3,~8,5 0l2s 7 G60/CRS 2.23 0 3s,~8,5 0-1.7 ... Table continued on next p~ge ...

W O 97/09127 PCT~US96/13480 SubstrateM2/L Previously Rating after 504 Hours of Salt Spray Treated'Zn Coated Portion, FieldCRS Po _:, Field G60 2.82 ol2s 7 G60 3.38 o-36s, M D8,5 G60 3.85 0-l,D6,7 G60/CRS 4.09 0-2,MD8, 5 0-1,7 G60/CRS 4.19 0-3,MD8, 5 0-1,7 G602 500 0-2,D3,6 G6o2 5.14 o_38s D9 5 G603 - 0-2,MD8, 6 G603 - o34s ~DD8 5 G6O4 - ol4s,7 G604 - 0_13S 7 CRS 0.85 0-1,7 CRS 1.14 0-1,7 CRS 1.57 ol2s 7 CRS 1.72 0-l,VFg,7 CRS 2.72 01,7 CRS 2.99 0-l,VF3, 7 CRS 3.14 0-1,7 CRS 3.28 0-1,7 CRS 3.48 0-l,VF8, 7 CRS 5.05 0-1,7 CRS 5.19 0-1,7 CRS3 - 0-1,7 CRS3 - 0-1,7 CRS4 0-1,7 CRS4 - 0-1,7 ... Table continued on next page ...

CA 02230278 l998-02-24 W O 97/09127 PCTrUS96/13480 Substrate M2/L Previously RAting after 504 Elours of Salt Spray Treatedl Zn Coated Portion, Field CRS Portion, Field CRS5 - 0-1, VF6? 7 CRS5 - 0-1, 7 CRS5 - 1-1, VF8, 7 CRS5 - 0-1, 7 CRS6 - o-lS~ g CRS6 - 0 ls 7 CRS6 - 0-1 s, 9 CRS6 - O-lS~ 9 Footnotes for Table 2-7 'With the same batch of BIPTC, except for replç~ 2The acid cle~ning step and immedi-ately following rinse step were omitted for this substrate in this i.lsl~lce. 3Comparison example with AUTOPHORETIC~ Conditioning Rinse 3180 rather than a BIPT according to this inven-tion. 4Co...~ on ~ ..pl~ with no BIPT other than rinsing with DI water. 5Comparison examp-le with no BIPT and with a di~elell~ reactive rinse, AUTOPHORETIC~ Reaction Rinse 2150.
6Colllp~isol1 example with elc~,~lophoretic paint coating rather than autodeposited coating.
Initial adhesion and impact coating test results for co~ting~ over G60 and A60 s~sLl~es were undrrel;led by the amount of sub~ e processed in the best BIPTC ac-cording to the invention, until at least about 3.7 m2/L of original BIPTC had been pro-cessed. Confinl-ed use of replenished used BIPTC after that extent of processing resulted 5 in somewhat lower adhesion and impact test values. Coating pelr~ ce for co~ting~
over a CRS substrate did not ~limini~h with continued use of replçni~hed used BIPTC.
Salt spray tests resulted in some field blistering and cathodic del~min~tion spots for coatings after Lle~ according to the invention on both G60 and A60 substrates.
Variable field blistering was also observed but blister size and/or frequency had no con-1C sistent trend. All ofthese results are normal for almost any organic coating over zinc-rich metal surfaces, even for coatings known to give good practical performance. Ratings showed variability with no appalell~ trend as the area of substrate processed was in-creased. Coating pelro....~ e was slightly better for coatings over the A60 substrate than the G60. Salt spray results over CRS were typically 0-1, colll,ual~ble to all the types of 5 co...l-A.;~:oll examples tested, indicating that BIPT according to the invention is not detri-W O 97/09127 PCT~US96/13480 mental to the quality of autodeposited coatings over CRS, which already give fully satis-factory coating pelrul-n~lce.
Sclibe/sc~ test results were excell~nt for coating~ aflcer BIPT accordillg to the in-vention over G60 and A60 substrates: Typical total creep widths for all A60 and G60 s panels were 1 mm or less. Typical creep widths over CRS were 2 mm, closely co-llp~b-le to those achieved with ~,ullcll~ly prGrellGd coll,-llelcial autodeposition coatings from the same autodeposition compositions as used here.

Claims (20)

1. A process for forming a protective coating on a solid metallic surface, said process comprising steps of:
(I) contacting the solid metallic surface with an aqueous liquid blemish inhibiting pre-coating treatment composition ("BIPTC") having a surface tension value at 30°
C not greater than about 55 dynes per centimeter and comprising water and at least about 0.008 % of dissolved phosphonate anions;
(II) removing the solid metallic surface from contact with the BIPTC contacted in step a); and subsequently (III) autodepositing an organic protective coating on the solid metallic surface from step (II) by contacting the surface with an autodeposition bath.

2. A process according to claim 1, wherein the BIPTC additionally comprises at least about 0.0003 % of a second surfactant in addition to phosphonate anions and has a surface tension not more than about 46 dynes per centimeter.

3. A process according to claim 2, wherein the BIPTC comprises at least about 0.0009 % of surfactant molecules selected from the group consisting of aromatic sulfonates and their salts.

4. A process according to claim 3, wherein the surface tension of the BIPTC is not more than about 40 dynes per centimeter.

5. A process according to claim 4, wherein the BIPTC contains from about 0.0021 to about 0.010 of surfactant molecules selected from the group consisting of dodecyl diphenyl oxide disulfonic acids and their salts.

6. A process according to claim 5, wherein the ions of component (A) are ions ofdiethylene triamine penta{methylene phosphonic acid}.

7. A process according to claim 4, wherein the ions of component (A) are selected from the group consisting of ions of diethylene triamine penta{methylene phosphonic acid) and ions of aminotri{methylene phosphonic acid}.

8. A process according to claim 3, wherein the ions of component (A) are selected from the group consisting of ions that (a) contain (a. 1 ) at least one tertiary amino nitrogen atom and (a.2) at least three phosphonate moieties per ion and (b) contain divalent hydrocarbon moieties selected from the group consisting of methylene and polymethylene moieties connecting each phosphorus atom in a phosphonate moiety in the ion to an amino nitrogen atom in the ion.

9. A process according to claim 2, wherein the ions of component (A) are selected from the group consisting of ions that contain at least two phosphonate moieties per ion and in which, if the ions contain an amino nitrogen atom, this atom is bonded to a divalent hydrocarbon moiety that is also bonded to a phosphorus atom in a phosphonate moiety.

10. A process according to claim 1, wherein the ions of component (A) are selected from the group consisting of ions that contain at least two phosphonate moieties per ion.

11. An aqueous liquid composition which either as such or after dilution with additional water is suitable as a blemish inhibiting precoating treatment composition ("BIPTC") before autodeposition, said aqueous liquid composition consisting essentially of water and:
(A) at least 0.008 %, based on the total composition, of a component of dissolved phosphonate anions, and, optionally, one or both of the following components:
(B) a component of dissolved surfactant, exclusive of phosphonates and their counterions; and (C) a component of dissolved non-oxidizing mineral acid, exclusive of any material that is part of component (A) or (B).

12. An aqueous liquid composition according to claim 11, wherein said composition includes component (B) to an extent of at least about 0.0003 % and has a surface tension not more than about 46 dynes per centimeter.

13. An aqueous liquid composition according to claim 12, wherein said composition includes at least about 0.0009 % of surfactant molecules selected from the groupconsisting of aromatic sulfonates and their salts.

14. An aqueous liquid composition according to claim 13 having a surface tension that is not more than about 40 dynes per centimeter.

15. An aqueous liquid composition according to claim 14 including from about 0.0021 to about 0.010 % of surfactant molecules selected from the group consisting of dodecyl diphenyl oxide disulfonic acids and their salts.

16. An aqueous liquid composition according to claim 15, wherein the ions of component (A) are ions of diethylene triamine penta{methylene phosphonic acid}.

17. An aqueous liquid composition according to claim 14, wherein the ions of component (A) are selected from the group consisting of ions of diethylene triamine penta{methylene phosphonic acid} and ions of aminotri{methylene phosphonic acid}.

18. An aqueous liquid composition according to claim 13, wherein the ions of component (A) are selected from the group consisting of ions that (a) contain (a. 1) at least one tertiary amino nitrogen atom and (a.2) at least three phosphonate moieties per ion and (b) contain divalent hydrocarbon moieties selected from the group consisting of methylene and polymethylene moieties connecting each phosphorus atom in a phosphonate moiety in the ion to an amino nitrogen atom in the ion.

19. An aqueous liquid composition according to claim 12, wherein the ions of component (A) are selected from the group consisting of ions that contain at least two -phosphonate moieties per ion and in which, if the ions contain an amino nitrogen atom, this atom is bonded to a divalent hydrocarbon moiety that is also bonded to a phosphorus atom in a phosphonate moiety.

20. An aqueous liquid composition according to claim 11, wherein the ions of component (A) are selected from the group consisting of ions that contain at least two phosphonate moieties per ion.