CA1043922A - Aqueous acidic metal-containing coating composition and method of coating metal surfaces - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Method and composition for applying a coating to a metal surface, the surface being contacted with an acidic aqueous coating composition comprising an organic coating-forming material, an acid, and a metal selected from Cr, Co, Cu, Ag, Cd, Sn, Pb and Fe(ous) from a compound containing said metal, wherein the thickness and weight of the coating formed on the surface can be controlled by varying the amount of metal present in the composition and by varying the time the surface is contacted with the composition.

Description

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A conventional composition comprising a resin dispersed in water which is utilized to form an organic coating on metal surfaces by immersing the surfaces in the composition, will result in a coating whose thickness is the same regardless of the time the composition is contacted with the surface. In order to obtain a thicker coating, it has been necessary to subject the metal surface to a multiple stage coating operation or to employ a bath having higher solids content - ~`
therein. In addition, these conventional systems ordinarily do not form organic coatings on the metal surface which will initially resist rinsing, without a drying or fusing operation performed thereon. ` ; ~ `
United States Patent No. ~,585,084 discloses compositions for coating metal surfaces comprising an organic coating-forming ma-terial, an oxygen containing oxidizing agent, hydrogen ion and an anion. Compositions comprising a resin dispersion, ~ , ~

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hydrogen ion, fluorlde ion, and an oxidiæing agent selected from the group co~sisting of hydrogen peroxide and dichromate, ~or coating me-tal surface~ are disclosed in United states Patent No. 3,592,69~ The coating weight of coatings produced employing composltions of this kind i5 a function of the time the surface is contacted with thle composition. These coatings are capable of being rinsed prior to baking without removin~
all of the polymer or resin deposi~ed on the surface.

Attempts have been made to adjust the rate at which these compositions form a coating on metal surfaces, by varying the concentration of hydrogen ion or oxidizing agent therein. It has been found that varying the concentrations and ratio of the constituants in these coating compositions in order to control the film-foxming rate can affect the uniformity and appearance of the coating as well as the stability of the working coating bath.

A serious problem that has been encountered in the use of coating compositions desaribed in the aforementioned ref-erences is that as the composition is used to coat quantities of metal surfaces, the composition becomes unstable. This instability is characterized by flocculation, coagulation or jelling of the organic coating-forming materials in the compo-sition. After these compositions become unstable, they can no longer be used effectively to coat metal surfaces and are thereby rendered inoperative.

Apparently, these compositions are rendered unstable by the build-up of large amounts of metal ions which are dissol~ed from the metallic surface and are then oxidized by the oxidizing agent in the composition. As metal surfaces are continuously processed in the~e ~ompositions, the amounts of these metal ions tend to buil~ up to an undesirable level, thereby result-ing in coagulation, Elocculation or jelling o the dispersed resin therein. ~ttempts have been made to prevent the compo-sition from becoming unstable by either removing the excess metal ions from the composition or by adding additional dis-persing agent to the composition.

When these known compositions are contacted with, for instance ferrous metal surfaces, apparently iron is dissolved from the surface by the hydrogen ions present in the compo-sition to form ferrous ions. The oxidi~ing agen~ in the composition acts on these ferrous ions to form ferric ions.
Due to the action of the oxidizing agent which oxidizes the already dissolved metal ions to a higher valence state, thereby causing the metal surfaces to be constantly attacked by the hydrogen ion present, undesirably high concentrations of ferric ions are accumulated. In a commercial operation, where large quantities of metal are processed, these known coating compo-sitions will require constant replenishment of dispersing agent or removal of metallic ions since the acid and oxidizi~g agant therein causes quch high amounts of the ferric ion to enter the bath, due to the vigorous attack of the metal suxface by these constituents.

A constant stability problem arises in these compositions, since there is constant generation of ferric ion, due to the conversion of ferrous ion, and apparent interaction between the ferric ion and the dispersing agent which maintains the resin par~icles in the dispersed state, thereby causiny ro-agulation and jelling.

, . . .
, , It is an object of the present invention to provide an improved process for forming an organic resinous coating on a metal surface. It is also an objection of this invention to provide a method and composition for applying resinous coatings to metal surfaces, the coating rate at which said coatings are deposited, controlled by the amount of appropriate metal `
present in the coating composition.
It is an object of this inven~ion to provide a process for con~
tinuously depositing an organic coating on quantities of metal surfaces without the rapid generation of large amounts of metallic ions which affect the stability of the composition.
A concomitant object of the present invention is to provide organic coatings on metal surfaces, whose coating weight is a function of contact time with the coating composition.
It has been discovered that a uniform smooth organic coating can be formed on a metal surface in a short time by the use of an aqueous coating composition consisting of a metal compound, acid, and particles of resin dispersed therein. The coating thickness, or the rate at which a coating is formed, can be readily controlled by adjusting the amount of metal added to the aqueous coating composition in the form of a metal com-pound.
The invention accordingly provides a process for applying a resinous coating to a metal surface comprising immersing the surface in an acidic aqueous coating composition comprising about 5 to about 550 g/l of dispersed solid resin particles, and of pH within the range of about 1.6 to about 5 and prepared from hydrofluoric acid, and including metal selected from the group consisting of chromium, cobalt, copper, silver, cadmium, tin, lead, and ferrous iron, the source of said metal being about 0.025 to about 50 g/l of a metal-containing compound which is soluble in said composition and contains said metal, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the ~ - 4 _ . - - .. .. . . . .. . . . . .

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longer said surface is immersed in said composition, and withdrawing the resinous coated surface from said composition.
According to ano~her aspect of the invention, there is provided a process for applying a resinous coating to a metal surface comprising immersing the surface in an acidic aqueous coating composition comprising about 5 to about 550 g/l of dispersed solid resin particles, and of pH
within the range of about 1.6 to about 5 and prepared from hydrofluoric acid, and about 0.025 to about 50 g/l of a metal-containing compound which is soluble in said co~position, the cationic species of said compound contain-ing a metal selected from the group consisting of non-ferric transition ele-ments and Group IV elements of the Periodic Table, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is immersed in said composi-tion, and withdrawing the resinous coated surface from said composition.
The invention also provides acidic aqueous coating compositions as defined in these processes.
It should be understood that "aqueous coating composition"
means the aqueous acidic composition having dispersed resin, metal from a metal containing compound, acid, and suitable additive ingredients as de-scribed herein, which is employed in the process of this invention.

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It should be understood that: "metal surfaces" means various metal surfaces, ~uch as aluminum, zinc, iron, nickel, tin and lead surfaces and any other surface of metal~
which are selected from a group of metals ranging from aluminum to copper in the order of the "ionization tendency", and which are present in the forms of pure metal and its alloys and also in the forms of plated metal surfaces. The term "iron surfaces" or "ferrous metal surface~" employed herein thus encompasses a wide variety of steels, iron, and iron alloys, including alloys of iron with chromium and/or nickel. The term "aluminum surfaces" employed herein encom-passes a wide variet~ of aluminum and aluminum alloys, inclu-ding heat resistant alloys, corrosion resistant alloys and high strength aluminum alloys.

The term "zinc surfaces" employed herein encompasses a wide variety of zinc, zinc alloys and zinc plated metals, in-cludin~ hot dip galvanized steel and electrogalvanized steel.
The term "copper surfaces" employed harein encompasses a wide -variety of copper and copper alloys, including brass, bronze and German silver. The term "lead surfaces" employed herein encompasses a wide variety of lead and lead alloys, including soldering metals. The term i'tin surfaces" employed herein encompasses a wide ~ariety of tin, tin alloys, and tin plated metals, including tin plate. The term "nickel surfaces" em-ployed herein encompasses a wide variety of nickel; nickel alloys and nickel plated metals, including nickel plated steel.

Of course, it is understood that the process of the present invention i9 carried out in a s~bstantially electro-static field-free environment, and the use o~ electricity and equipment and control instruments required to operate an electro-coat proce~s i9 avoided.

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The p? icles of resin dispersed in the compo3ition, will ordinarily b~ in the form of latex of the resin. Latices, dis-persions o~ insoluble resin par~icles in water, are readily available and those sold commercially can be utilized herein.
These commercially available la~ices will usually contain other ingredients such a-~ emulsifiers and protective colloid~. E~-amples of commerciall~ available latices which can be employed and which can be regarded as the preferred materials for use in the aqueou~ coating composltions of this invention axe Hycar X 407 (manufactured by Japanese Geon Co.j Ltd.) .~. styrene butadiene copolymer Goodrite 1800 X 72 (manufactured by Goodrich Chemical Corp.) ... styrene butadiene copolymer Durex 637 (manufactured by W.R. Grace) ... styren~ butadiene copolymer Pliolite 491 (manufactured by Goodyear Rubber and Chemical Corp.) ... styrene butadiene copolymer Hycar ~X 814 (manufactured by Japane~e Geon Co., Ltd.) ... acrylic copolymer Boncoat 9404 (manufactured by Dainippon Ink & Chemicals, Inc.) ... acrylic copolymer Nipole 1571 (manu~actured by Japanese Geon Co. r Ltd.
... acrylnitrile butadiene copolymer Synthemal~9404 (manufactured by Nihon Reichold Co. Ltd.) ... ac~ylic copolymer Polysol~AP 300 ~manufactured by Kobunshi Kagaku Kogyo Co., ~td.) ... acrylic copolymer Polysol EVA P 1 (manufactured by Kobunshi Kagaku Koyyo Co., Ltd.) ... ethylene-vinyl acetate copolymer Poly-em 40 ~manufactured by Gulf Oil Corp.) ... polyethylene f f~ 6-, ~ 4~ ~

Other coating-forminy resin dispersions or emulsions can be employed herein so long a~ the latex is stable in the presence of the other ingr~dients in the compositions of the present invention.

The amount of ~ispersed resi;n employed in the coating composition will depend on the amount of resin which can be dispersed therein and the amount needed to provide suffi~ient resinous material to form a coating. The concentration of dis-persed resin can vary over a wide range and should prefexably be from about 5 to about 550 g/l of re~in. It is un~er~tood that the volume of latex necessary to provide the paxticular amount of resi~ in the coating composition will depend on the speai~ic amount of resin solids dispersed in the latex to be employed.

For the coating process of the present invention to be efected, the concentration o~ metal in the coating composition should be maintained by employing a water soluble metal com-pound or a metal compound soluble in acidic aqueous compositions.
The metal compound can be present in the composition in an amount from about .025 grams/liter to about 50 grams/liter.
The concentration of metal in the composition will depend on the particular metal and metal compound employed. For example, ferric fluoride can be added to the coating composition in an amount from about 1.0 gram/liter to about 50 grams/liter and silver fluoride can be added to the bath in an amount from about 0.1 grams/li~er to about 10 grams/liter. A wide variaty of metal compounds can be employed in the practice of the present inve~tion. Selection of the compound to be employed will depend on its commercial availability and its ability to liberate metal in the aqueous cohting composition.

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For example, me~al compounds which will yield ~uffioient metal in the aqueous acidic coat:ing composition for aluminum surfaces and zinc surfaces are ferric fluoride, ferrous oxide, ferric oxide, cupric sulfate and cobaltous nitrate. Metal compounds which will yield sufficient metal in the aqueous acidic coating compositions for ferrous,tin, and laad surfaces are ferric fluoride, ferrous oxids, ferric phosphate and silver fluoride. Metal compounds which will yield sufficient metal in the aqueous acidic coating composition for copper surfaces are silver fluoride and silver acetate.

The acid to be employed in the composition of the present invention can be an inorganic or an organic acid. Typical examples of inorganic acids that can be employed are sulfuric, hyrochloric, hydrofluoric, nitric, and phosphoric acid. Ex-amples of organic acids that can be employed are acetic~
chloracetic, and trichloracetic acid. The acid to be employed in the process of the present invention mu~t be present in sufficient quantity to maintain the pH of the solutian at its desired level. The p~ of the coating composition should be maintained at a level within the range of from about 1.6 to about 5Ø

The ac1d employed in the composition will dissociate to yield hydrogen ion and an anion. It has been observed that particularly good resul s are obtained when the acid employed in the coating composition is hydrofluoric acid. The preferred method of making the composition acidic comprises the use o hydrofluoric acid, which permits a simple means for control of pH in the coating composition and introduces an anion, that is fluoride ion, which allows for satisfactory operation Gf the process. The use of hydrofluorlc acid prevents the deliberate _~_ - ~7~ J~

inclusion of anions which may be undesirable and detrimental to the coating process. It ~hould ~e understood that hydro-fluoric acid is a preferred acid ko be employed in the aqueous coating composition, but that oth~r acids such as those de-scribed above can be employed with satisfactory results.

A preferred embodiment of this in~ention is to employ an operating aqueous coating composition comprising a combination of constituents consisting essentially of an anionic stabilized resin dispersion (negatively charged disper~ed resin particles) having about 5 to about 550 grams/liter of resin ~olids, from about 1 to about 5 grams/liter of erric fluoride trihydrate, and an acid in an amount 9ufficient to impart a pH to the aqueous composition of from about 1.6 to aboùt 5Ø

A distinct advantage of the present process is that large quantities of metal surfaces can be contacted with the aqueous coating composition, for example, with little build-up of ferric ion caused by the acid attack on the ferrous metal surface. The present invention allows for controlled amounts of ferric ion in the coating composition. It has been found that the metal loss from a surface contacted with the aqueous coating composition will not exceed 40 mg per square foot per minute. The process of the present invention can be contin~
uously effected for longer periods of time o~ greater ~uantities of metal.

In the coating operation, the metal substrate to be treated is brought into contact with the aqueous coa~ing compo~ition under suitable conditions of ~emperature and contact time. The time of treatment ofthe metal surface with the aqueous coating composition can be from about 15 seconds to about 10 minute~.

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It will be appreciated that with the use of the aqueous coating composltion desc~ibed herein, the coating weigh~ of the deposited coating will increase with longer exposure of the metal ~urface to the action of the coating composition. Therefore, the coating time to be employed will depend on the coating wei~ht ~esired.
Preferably, contact time between metal substrate and coatlng composition should be from about 30 seconds to about 5 minutes.
It should be noted that the coating weight for a particular coating composition will increase up to a maximum a3 the time of treatment is increased.

The coating procesR can be operated at temperatures from about 40F to about 120F. It is preferable to operate the coating bath at ambient temperature, that is from about 60F
to about 90F. Generally, a slight change in the temperature of the aqueous coating composition will not necessitate sub-stantial alteration of treating time and conc2nt~tion para-meters.

The process of the present invention can be effected by employing known contacting techniques. Contact can be effected by either immersion or flowcoating to produce the desired surface coating. Preferably, the aqueous coating composition will be contacted with the metal surface by conventional immer~ion methods.

Subse~uent to contact with the a~ueous coating composition, the surface should be dried to allow the resin to be fused.
Prior to the drying operation, the coated surface can be ex-posed to an oxidative environment and then rinsed with water.
It has been found that when the surface is exposed to an oxidative environment, such as allowing the surface to stand in air, for a time from about 15 seconds to about lO minutes, .

follow~ by water rinsing, and ~hen dried, the surface possesses a tigh~, adheren~, and uniform coating. It ~hould be understood that the time of exposure to air or other oxidati~e environment should not be long enouyh to allow the deposited coating to dry prior to rinsing. The exposure time to be employed will depend somewhat on the type of resin ut:ilized to form the coating.

Subsequent to the water rinse, the coated surface can be rinsed with an aqueous rinse solution containing hexavalent chromium or hexavalent chromium and reduced forms of chromium.
Subsequent to the rinse treatment, the coated surface should be dried or baked. This can be accomplished by conventional techniques, such as passing the metal surface through a heated environment such as an oven, qubjecting it to a warm air stream, or by allowing it to dry at ambient temperature. Should speed be a necessaxy factor, any method of forced drying the surface can be accomplished. When a heated environment is used, ~rying may be carried out at tempexatures above 150~F, and preferably from about 300F to about 500F. It should be understood that whatever temperature is employed will depend to some extent on the type of latex or resin dispersion and the drying time that has been utilized.

The aqueous coatlng compositions of the present invention described hereinabove are capable of producing coatings on a metal s~rface which portray excellent adhesion to the surface and have excellent corrosion resi tant properties. However, the aqueous coating compositions and the coatings deposited can be enhanced by incorporation into the coating composition of added constituents described hereinbelow.

An oxidi~ing agent may be incorporated into the aqueous coating compo~ition. Any oxidizing agent can be employed and can be conveniently added to the composition as a water soluble 3t~ ~

compoun~. Typical examples of oxldlzing agents that can be used are hydrogen peroxide, dichromate, perman~anate, nitrate, persulfate, and perborate. In some instanceq, ~he addition of an oxidizing agent to the composition in an amount sufficient to providq from about .01 to about 0.2 of oxidizing equivalent per liter of composition may be desirable to obtain a coating having particular properties, sueh as heavier coating weights.
It has been observed that addition of an oxygen containing oxidizing agent to the aqueous coating composition can result in highex coating weights than would ordinarily be obtained employing the same contact time. Should an oxygen containing oxidizing agent be employed in the composition, it will be appreciated that the working coating bath will re~uire regorous eontrol proeedures, since the composition, when in contact with the metal workpieces, will generate large amounts or metal ions. It will be appreciated that addition of an oxidizing agent to the aqueou~ eoating composition is not deemed dèsirable when large quantities of metal are to be processed. (The term "oxidizing equivalent" when used herein means the number of grams of oxidizing agent used, divided by the equivalent weight of the oxidizing agent. The equivalent wei~ht of the oxidizing agent i5 the gram molecular weight of the agent divided by the changing valence of all stoms in the molecule whieh ehange valenca, usually one element.) A eoalescing agent can be incorporated into the aqueous eoating composition. The addition of a coalescing agent will further enhance the appearance and the corrosion resistant qualities of the deposited coating. A typieal example of a coaleseing agent which can be employed is ethylene glycol monobutyl ether. The coalescing agent can be present in the compo.sition in an amoun'c from about S grams/liter to abo~t 30 grams~ er.

. . . ~ , .
.

The co~ting ~omposition of the present invention may be formulated so as to incorporate water dispersible pigments known to the art. Vaxiations in the color of the deposited coating can be realized by adding pigments such as phthalocyanine blue, phthalocyanine green carbon black, quinacridone xed, iron oxide red, iron oxide yellow, lead chromate, and chrom~ oxide green. These pigments provide excellent color variations with no sacrifice in coating ~uality or corrosion resistance.

To assure satisfactory wetting of the metallic surface during treatment with the coating composition, it may be desirable to inc0~porate into ~he composition a small amount of a wetting agent or surface active agent. Preferably~ nonionic or anionic type wetting agents should ~e employed. T~pical examples of wetting agents which can be utilizèd are alkyl phenoxy polyethoxy ethanol and sodium salts of alkylaryl polyether sulfonate.

Should a dry pigment be used in the coating composition, it can be dispersed in the aqueo~s coating composition by conventional procedures, such as mixing the pigment with a small amou~t o nonionic or anionic surface active agent and water, sald mixture agitated with a high speed mixer, then adding the pigment - surface active agent mixture to the already prepared coating composition with further agitation.

A pigment, such as iron oxide red or iron oxide yellow, which is partially soluble in the aqueous coating composition, can be employed as a source for metal~ particularly iron.
Should the pigment be employed to ~erve as a source for iron, a sufficient amount of piyment must be added to pxovide suf-ficient iron in the composition to effect the process of the present invention.

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To demon~trate th~ present inventicn, a series of examples are presented showing -the use of particular aqueous coating compositions. It will be observed that some of the examples include the use of various other additives which have been found to be suitable for usP in the compositions. The examples presented below are illustrative of this invantion and are not considered as limiting for other ~aterials and operative oon-ditions falling within the scope of the invention that miyht be substituted.

In some of the examples below, corrosion tests and adhesion te~ts were run on the test panels. When salt spray corrosion tests were run on representative panels, the treated panels were scribed so that base metal was exposed. Panels were subjected to 5~ salt spray and were rated inaccordance with ASTM~-1654-61, by mea~uring tha average failure of the paint film rom the scribe.

Adhesion tests were run on panels, using impact and cross-hatch test prQcedures which are commonly employed in the testing of paints. In the impact test, the test surface is impacted by a falling 1/~" ball with a force measured as 50 kilogram centimeters, thereby deforming the test surface.
Subsequent to impact, the deformed surface is inspected ~or loose or cracked paint, usually on the reverse side of the impact, and rated in inches of paint failure. In the cross-hatch test, the surface is scrib~d with parallel lines, ap-proximately 1 millimeter apart and out through to bare metal.
Duplicate lines are scribed at right angles to make a cross-hatch pattern. Scotch brand cellophane tape is pressed smoothly over the scribed area. After several seconds, the tape is pulled back rapldly so that the tape is turned back upon itself approximately 180 from i~s original pressed position Results are reported in the degree of failure noted, that is none, slight, moderata, or heavy loss of coating.

Panel~ of each metal described in Table 1, cleaned in a conven~ional alkali metal silicate cl~eaning solution, were immersed for 3 minutes in an a~ueous coating composition comprising the following conRtituents:

Grams Styrene-butadiene re~in (HYCA ~ ~X 407) 180 Hydrofluoric acid 3 Ferric fluoride (trihydrate) 5 Water to make 1 liter Hycar LX 407 was employed as tha source for the styrene-butadiene re~in, (manufactured by Japanese Geon Co., Ltd., and containing 48% resin solids). The aqueous composition was prepared by mixing the resin with water, and adding hydrofluoric acid, and ferric fluoride with continuous agitation.

The test pa~els were removed from the coating bath and dried in an oven at 356F for 10 minutes. The average coa~ing ~ -weight for the panels were as shown in Table 1, and the coatings produced were obser~ed to be smooth and uniform.
,. ' Table 1 ¦ E~LE ~) r Metal Surface Coat ng Weigh~
' ~1' . ~.
1 dull steel 1673 ~18) ~ 2 r r

2 aluminum 1951 (21) _ .... .. ....

3 hi~h strength Al alloy 213~ (23) . ..................... f4 - . ~

4 zillc 1673 tl8) . . . _ ~-1 5 h~t ~ip g~llv~nized stcel 1766 (19) --~ . .~ .. _.___ - 6 tin ylute 1394 (15) . ':
l 1301 (14~
... . . . .....

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~1. JIS G-31~1, SPC-C
*2. JIS H-4000, ~-1050P
*3. JIS H-4000, A-2024P
*4. JIS H-4321, First Clas~; ;
*5. JIS G-3302, SPG-2C
*6. JIS G-3303, SPT-E
*7. JIS H-4301, PbP

.. , .. __ ' These Examples were run to illustrate the use of various metal compounds as the source for metal ion in the aqueous coating composition.

The constituents in the respective compositions are re-ported below in Table 2, along with the measured average weight of the coatings produced.

The aqueous compositions employed in Examples 8 - 58 were prepared as set forth in ~Xample 1 - 7, except that different ~ources for metal were employed in each case.

Panels of each metal described in Table 2 were cleaned in a conventional alkali metal silicate cleaning solution, then immersed in the respective coating composition set forth in Table 2 for 3 minutes. The pH of each aqueous coating composi-tion employed herein was between 1.6 and SØ The panels were dried in an oven at ~56F for 10 minutes.

The average weight of the coating on the test panels was measured and is noted in Table 2.

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EXAMPL~ 59 - 72 These Examples were run to illustrate the use of various acids as the source for acid in the aqueous coating composition.
~he constituent~ in the respective coating compo itions are reported below in Table 3, along with the measured average w ight of the coatings produced.

The aqueous coating composltion employed in Example 59 -72 were prepared as set forth in Example 1 7, except that different sources for acid were employed in each case.

Panels o~ each metal described in Table 3 were cleaned in a conventional alkali metal silicate cleaning solution, then immersed in the respective coating composition set forth in Table 3 for 3 minutes. The pH of each a~ueous coating composition employed herein waq between 1.6 and 5Ø

The panels were then dried ln an oven at 356CF or 10 minutes. The average weight of the coating on the test panels was measured and is noted in Table 3.

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EXAMPL.E 7 3 - 8 3 These ExAmples were run to illustrate the use of various resins as the ~ource for resin in the aqueous coating composition.
The constituents in the respective coating compositions are reported below in Table 4, along with the measured average weight of the coatings produced.

The aqueous coating compositions employed in Example 73 -83 wexe prepared as set forth in Example 1 - 7, except that different sources for resin wPre employed in each case~

Panels o each metal described in Table 4 were cleaned in a conventional alkali metal silicate solution, then immer~ed in the respective coating composition set forth in Table 4 for 3 minutes. The pH of each aqueous coating compo~ition employed herein was between 1.6 and 5Ø

The panels were then dried in an oven at 356F for 10 minutes. The average weight of the coating on the test panels was measur~d and is noted in Table 4.

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; Panels of each metal described in Table S were immersed in the aqueous coating composition comprising the following ~on~tituents:
~e~ Grams A Styrene-butadiene resin ~HYCAR~ X 407) 200.0 Hydrofluoric acid . - 2.5 Hydrogenperoxide 1.5 Ferric fluoride (trihydrate) 3,0 ~ water to make 1 liter : .
The test panels were contacted with the coating composition -.
for a period of 3 minutes, then dried in an oven at 320F for 15 minutes. The average weight of the coatings is also listed ~ in ~sble 5. It has be~n also observed in further experiments :~ that the average weight of the coatings decreased by about 3 - .
10 ~rams/m2 when each metal panel described in Table 5 were .
, ~mmersed ln the aqueous coating composition comprising the .`
.~ above-mentioned constituents but hydrogenperoxide.
~ . . .
.
`! Table 5 ~ ~ Metal panel used as a Coat mg weight : :
. Nb. substrate (g/~2) mg/ft2 ~
.` . . .~ . . . _ . __~
. 8~ Dull steel (31~ ~ 2881 :~

. B5 Aluminun (1~3 1673 ~: :
.,, , . ........ . .. ___ _ ~.. , ~86 2i~c : t~6) 2416 ~ :
.. ~, ._ _ _ ~ _ . ~, ~ . 87 T m plate (15~ 1394 .i ~
.~ 88 Lead tl2) 1115 .. _ . _ . _ _ _ 89 Copper (13~ 1208 .. . .

. ~ . . . . . . . . . . ... .. ... ..... . ~ .
: . , :: .

3~

.
Panels of each metal described in Table 6 were immersed in the aqueous coating composil:ion comprising the following constituents. The test panel~ were contacted with the coating compo~ition fox a period of 2 minutes, then dried in an oven at 392F for S minutes. The average weight of the coatings produced is also listed in Tab].e 6.

It should be noted that the aqueous coating composition employed herein contained chromic acid as an oxygen containing oxidizin~ agent, and butylcellosolve as a coalescing agent.

Component Grams Styrene butadiene re~in (HYCAR LX 407) 160 Hydrofluoric acid 3 Chromic acid anhydride Ferric phosphate (tetrahydrate) 8 Butylcellosolve 10 Water to make 1 liter Table 6 . . _ ... _ ..... _ _ . _ _ ~
E~L~ Metal gurface Co;t ~ wci 90 ~lll steel ~21) lg52 , ..... _._ 91 ~igh s~rength A1 alloy (Z7) 2509 .... . ... ... _ ~
92 f~t dip galvanized steel (23) 2138 ~ , . " . .. ~. . . __ 93 Tin plate (1~ lil5 _, . ~ . . _ Brass (15) 139~
~ .

~29--~.~ i L'7/~ 4)~

various metal panels noted in Table 7 were employed in this procedure. The test panels were cleaned in a conventional alkali metal ~ilicate cleaning solution and then immersed in the aqueous coating composition described below. ~he panels . were then baked in an oven at :392F for 5 minutes. The average i.!
` coating weight of the coatings produced waq measured and is ~
listed in Table 7.

Component Grams Styrene butadiene resin (HYCA ~ LX 407) 180 ' Lead chromate pigment 95 .~ ~
Anionic surface active agent ~Demol-P) 5 Ferric fluoride ~trihydrate) 8 ~: Hydrofluoric acid 3 :~- Water to make 1 liter .: It will be observed that lead chromate piyment was employed in the composition. The lead chromate, an anionic surfactant ~Demol-P) and water were mixed together and milled for 16 hours ' prior to addition to the already prepared composition containing :~, the styrene butadiene resin, hydrofluoric acid and water.
....
~ The lead chromate pigment employed in the composition -~ was Kiku-Jirushl G ~manufactured by Kikuchi Kogyo).

t .i . 1 '~
.' e -30 . -, .

':!

Table 7 ._ _ ___ ___ - ~. Metal panol us~d a-~ a Coating weight Ab. substrate ~g~m~) mg/~t2 ~.: __ ~ , .~
Dull steel (120) 11152 ... ~ . ~ .. .. ~
96 Aluminl~ (4s) 4182 ~7 aluminum alloy ~44) 4089 ~ . __ .. ... ~ . _ : 98 2inc (66) 6134 __ _. _ ... .. ,_ ...
~ 99 Hot ~ip galvanized steel (89~ 8271 .
. :- . , ~ . . ,~ , .~
100 Tin plate (110) 10~23 .
, . . .. . _ __ .. ~., 101 Lead ~32) 2974 _ _ -, EXAMPL-E 102 - 107 Panels o each metal described in Table 8 was immer~ed ' in the aqueous coating compo~ition comprising the following :` constituents:
Grams ~ Styrene-~utadiene resin (HYCAR LX 407) 200 .~:: Lead chromate pigment (KIXU-JIRUSHI SG-3KB, manufactured by Kikuchi Kogyo) 50 .~; Ferric oxide pigment (L~APICO~YELhOW LL.XL0, manufactured by Titan Industry) 30 Anionic Jurface active agent (EMA~ 10, manu~actured by Kao-Atlas) 3 . - Bydrofluoric acid 3.5 Tap water to make 1 liter , .
The test panels w~re contacted with the coating composition - for a period of 3 minutes, then dried i.n an oven Rt 356F for .. 10 minutes. The average coating weight for the panels were ., :
.,;, . .. .

~ l~3~
shown in Table a, and the coatings produced were observed . to be smooth and uniform.

. Table 8 , __ . .~
: No Metal Surface C(o/t2)g w~/8ht ., . . .~ _ .~ .
. 102 Dull steel 75 6970 :~ 103 Aluminum 57 5297 . 104 Zinc 72 6~91 105 Nickel plated steel 10 929 106 Tin plate 76 7063 107 Lead 37 3439 .~.
.., .. ' ~.
~;~ EXAMP~E 108 - 130 s Various metal panels were cleaned in a conventional alkali .~ metal silicate cleaning solution and then immersed in the aqueous coating composition described in Table 9 for 3 minutes.
The panels were then baked in an oven at 392F for S minutes.
.~ ., .
The average ¢aating weight of the coatings produced was measured and is listed in Table 9.

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Steel panels were employed in this procedure. The test panels were cleaned in a conventional alkali metal silicate cleaning solution and then immersed in the aqueous coating composition described below for different contact times.
The test panels were then allowed to stand i~ air for 3 minutes and th~n xinsed with water. The panels were then baked in an oven at 356F for 10 minutes. The average coating weight of the coatings produced was measured and i5 listed in Table 10.

Component Grams Styrene butadiene resin (HYrAR LX 407) 180 ' Lead chromate pigment 50 Iron oxide red pigment 50 Anionic surface active agent (Demo ~ P) 5 Hydrofluoric acid 3.5 Water to make 1 liter It will be observed that lead chromate pigment and iron oxide red pigment were employed in the composition. The lead chromate, iron oxide red, an anionic surfactant (Demol-P~ and water were mixed together ànd milled for 16 hours prior to addition to the already prepared composition containing the -~ styrene butadiene resln, hydrofluoric acid and water. The pH of the aqueous coating composition was measured at 2~8O

, The lead chromate pigment employed in the composition was -s' Xiku-Jirushi~SG (manufàctured by Kikuchi Kogyo) and iron oxide ~( red pi~ment was Tenyo Bengara 501 ~manufactured by Tone Sangyo).
:;' -, .'''., . . '' .

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T le 10 Coating Weight Time of I~nerslon _mg/ft2 15 sec. 649 30 sec. 803 1 min. 1224 2 min. 2257 3 min. . 3544 5 min. 5608 - .
As can be seen from Table 10, the coatings deposited on test ~anels treated in accordance with the present invention have the property of increased coating weight with increa~ed ; contact time.
.',. ~ - . '.

. , : . . :
Steel panels were employed in this procedure. The test panels were cleaned in a conventaonal alkali metal silicate cleanin~ solution and the immersed in the aqueous coating composition described below for 3 minutes. The coated test .~ . . ~ .
panels were then exposed to the air for periods of time as noted below and then were rinsed with water. The panels were - then ~aked in an oven at 356~F for 10 minutes. ;;~ ~ ;

Component Grams Styrene butadiene resin (HYCAR LX 407) 180 Léad chromate (Xaku Jirushi~5G) 50 Iron oxade (Tenyo ~engara 501) 50 - Anionic surface active agent ~Demol-P) 5 i Hydrofluoric acid ~ 3 / Wa~er to ma~e 1 liter ~ . :

!
?~ 37-;

.
, :

3~

It will be observed that lead chromate pigment and. iron oxide red plgment wer~ employed in the composition. The lead chromate, iron oxide, and anionic surf~ctant (Demol-P) and water were mixed together and milled for 16 hours prior to addition to the already prepared composition containing the styrene butadiene resin, hydrofluoric acid and water. The coatings produced were observed to be smooth and uniform. ~he average film thickness was measured and is listed in Table 11. The test panels were subjected to 168 hours salt spray corrosion ~ests and the results are listed in Table 11.
.
Table 11 Film thickness Scribe failure (microns) ~in inches) .5 sec. 13 1~32 15 sec. 17 1~32 30 sec. 22 1/32 1 min. ~ 25 1~32 2 min. 28 1~32 3 min. 28 3~32 Impact test~, c~oss-hatch tests, and salt spray corro~ion te~t were run on representative panels treated in accordance with some of the aforementioned procedures, that is, Example 1, 2, 4, 6 and Sl. The results of these tests are listed in .-Tablo 12 and also in Table 13. ' Table 12 I:ilm Ap~e.lrance Co~ting coatin~ height Imp~ct Test Cross Hatch ~tal C~osition il~ !gr~m2~ ft2 Result~ Test Result~ Surface Ex. N~. 1 t~o~ 1673 No f.ailure None null st~el Ex. Nb. 2 ~-ellelll No f~ilure None Al~inwn ~l) 1952 Ex. ~. 4 ~ d ~l8) 1673 No failur~ None Z~c ~. N~. t~ E~cellent ,~o f~ilure None Tin plat~
(15) l3'34 . N~. Sl ~o~d (l7) tS~O ~o f~ilule None (`~prer . Table 13 Film Appe~rancc L`o~tin~ ~ coatillg~ei~ht Salt spray Met:-l _npositi~ (gr/m2) m~/ft2 test results ~ surface . ~o. 102 ~xcellent (75) ~970 No fail~re Dull steel Ex. No. 103 Caod (57) 5291 Nb failure Aluminum . Ex. Na. 104 F~cellent (72) 6691 Slight white-rust Zinc Ex. No. 106 Excellent (76) 7063 No failure Tin plate o. 12~ ~ood (20) 1859 No failure Copper (~ Exposure time : lS0 hours3 As can be seen from Table 12 and 13, test panels treated in accordance with the present invention give acceptable a~hesion and corrosion test results.

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Claims (49)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for applying a resinous coating to a metal surface comprising immersing the surface in an acidic aqueous coating composition comprising about 5 to about 550 g/l of dispersed solid resin particles, and of pH within the range of about 1.6 to about 5 and prepared from hydro-fluoric acid, and about 0.025 to about 50 g/l of a metal-containing compound which is soluble in said composition, the cationic species of said compound containing a metal selected from the group consisting of silver, iron in its divalent state, copper in its divalent state, cobalt in its divalent state, chromium in its trivalent state, cadmium, tin in its divalent state and lead in its tetravalent state, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is immersed in said composition, and withdrawing the resinous coated surface from said composition.

2. A process according to claim 1 wherein said metal-containing com-pound is selected from the group consisting of silver fluoride, silver acetate, silver nitrate, ferrous oxide, ferrous phosphate, cupric sulfate, cobaltous nitrate, chromium fluoride, cadmium fluoride, stannous fluoride, and lead dioxide.

3. A process according to claim 1 wherein said surface is immersed in said composition for a period of time within the range of about 15 seconds to about 10 minutes.

4. A process according to claim 3 wherein said surface is immersed in said composition for a period of time within the range of about 30 seconds to about 5 minutes.

5. A process according to claim 1 wherein said composition has a temperature within the range of about 40°F to about 120°F.

6. A process according to claim 5 wherein said composition has a temperature within the range of about 60°F to about 120°F.

7. A process according to Claim 1 including fusing the resin of said coated surface after it is withdrawn from said composition.

8. A process according, to claim 7 wherein said resin is fused by subjecting the coating surface to a temperature within the range of about 150°F to about 500°F.

9. A process according to claim 7 wherein prior to fusing said resin, the resinous coated surface is subjected to an oxidative environment.

10. A process according to claim 9 wherein said resinous coated surface is exposed to an oxidative environment by exposing it to air for a period of time within the range of about 15 seconds to about 10 minutes.

11. A process according to claim 9 wherein subsequent to being ex-posed to said oxidative environment, the resinous coated surface is rinsed with water and thereafter the resin is fused.

12. A process according to claim 7 wherein the resinous coated sur-face is contacted with an aqueous solution of hexavalent chromium or hexa-valent chromium and reduced forms of chromium prior to fusing said resin.

13. A process according to claim 1 wherein said coating composition includes an oxidizing agent.

14. A process according to claim 13 wherein said oxidizing agent is hydrogen peroxide in an amount of about 0.01 to about 0.2 oxidizing equi-valent per liter of composition.

15. A process according to claim 1 wherein said composition includes a coalescing agent.

16. A process according to claim 15 wherein said coalescing agent is echylene glycol monobutylether in an amount of about 5 to about 30 g/l.

17. A process according to claim 1 wherein said coating colnposition comprises a pigment.

18. A process according to claim 17 wherein said metal-containing compound and said pigment comprise iron oxide red or iron oxide yellow.

19. A process according to claim 1 wherein said resin is anionically stabilized.

20. A process according to claim 1 wherein said composition includes a pigment, wherein said composition has a temperature within the range of about 60°F to about 90°F, wherein said surface is immersed in said composi-tion for a period of time of about 30 seconds to about 5 minutes and wherein said resinous coated surface is exposed to air for a period of time of about 15 seconds to about 10 minutes after it is withdrawn from said composition, and including contacting the resinous coated surface with an aqueous solu-tion of hexavalent chromium or hexavalent chromium and reduced forms of chromium, and thereafter fusing the resin of said resinous coated surface at an elevated temperature.

21. A process according to claim 20 wherein said resin is anionically stabilized.

22. A process for applying a resinous coating to a metal surface comprising immersing the surface in an acidic aqueous coating composition comprising about 5 to about 550 g/l of dispersed solid resin particles, and of pH within the range of about 1.6 to about 5 and prepared from hydrofluoric acid, and including metal selected from the group consisting of chromium, cobalt, copper, silver, cadmium, tin, lead, and ferrous iron, the source of said metal being about 0.025 to about 50 g/l of a metal-containing compound which is soluble in said composition and contains said metal, said composi-tion being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is immersed in said composition, and withdrawing the resinous coated surface from said composition.

23. A process according to claim 22 wherein said resin is anionically stabilized.

24. A process according to claim 22 wherein said metal is silver, the source of which is about 0.1 to about 10 g/l of silver fluoride.

25. A process according to claim 22 wherein the metal loss from said surface is not in excess of 40 mg/sq.ft./min.

26. A process for applying a resinous coating to a metal surface com-prising immersing the surface in an acidic aqueous coating composition compris-ing about 5 to about 550 g/l of dispersed solid resin particles, and of pH
within the range of about 1.6 to about 5 and prepared from hydrofluoric acid, and about 0.025 to about 50 g/l of a metal-containing compound which is sol-uble in said composition, the cationic species of said compound containing a metal selected from the group consisting of non-ferric transition elements and Group IV elements of the Periodic Table, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is immersed in said composition, and withdrawing the resinous coated surface from said composition.

27. A process according to claim 26 wherein said metal surface is selected from the group consisting of iron, aluminum, zinc, copper, lead, tin, and nickel surfaces.

28. A process according to claim 26 wherein said metal surface is an iron surface.

29. A process for applying a resinous coating to a metal surface comprising immersing the surface in an acidic aqueous coating composition comprising about 5 to about 550 g/l of dispersed solid resin particles, and of pH within the range of about 1.6 to about 5 and prepared from about 0.025 to about 50 g/l of a metal-containing compound which is soluble in said com-position, the cationic species of said compound containing a metal selected from the group consisting of silver, iron in its divalent state, copper in its divalent state, cobalt in its divalent state, cadmium, tin in its divalent state and lead in its tetravalent state, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is immersed in said composition, and withdrawing the resinous coated surface from said composition.

30. A process for applying a resinous coating to a metal surface com-prising contacting the surface with an acidic aqueous coating composition comprising about 5 to about 550 g/l of dispersed solid resin particles, and of pH within the range of about 1.6 to about 5 and including metal selected from the group consisting of cobalt, copper, silver, cadmium, tin, lead, and ferrous iron, the source of said metal being a metal-containing compound which is soluble in said composition and contains said metal, said composi-tion being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is contacted with said composition.

31. A process for applying a resinous coating to a metal surface comprising contacting the surface with an acidic aqueous coating composition comprising about 5 to about 550 g/l of dispersed solid resin particles ani-onically stabilized, and of pH within the range of about 1.6 to about 5 and prepared from a metal-containing compound which is soluble in said composi-tion, the cationic species of said compound containing a metal selected from the group consisting of non-ferric transition elements and Group IV elements of the Periodic Table, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is contacted with said composition.

32. A process for applying a resinous coating to a metal surface com-prising contacting the surface with an acidic aqueous coating composition comprising about 5 to about 550 g/l of dispersed solid resin particles, the resin being selected from the group consisting of styrene-butadiene, acrylic copolymers, actylonitrile-butadiene, ethylene-vinyl acetate, polyethylene, and polyacrylic acid, and of pH within the range of about 1.6 to about 5 and prepared from a metal-containing compound which is soluble in said composi-tion, the cationic species of said compound containing a metal selected from the group consisting of non-ferric transition elements and Group IV elements of the Periodic Table, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is contacted with said composition.

33. An acidic aqueous coating composition comprising about 5 to about 550 g/l of dispersed solid resin particles, and of pH within the range of about 1.6 to about 5 and prepared from hydrofluoric acid, and about 0.025 to about 50 g/l of a metal-containing compound which is soluble in said composi-tion, the cationic species of said compound containing a metal selected from the group consisting of silver, iron in its divalent state, copper in its divalent state, cobalt in its divalent state, chromium in its trivalent state, cadmium, tin in its divalent state and lead in its tetravalent state, said composition being effective in forming on said metal surface a resinous coat-ing which increases in weight or thickness the longer said surface is im-mersed in said composition.

34. A composition according to claim 33 wherein said metal-containing compound is selected from the group consisting of silver fluoride, silver acetate, silver nitrate, ferrous oxide, ferrous phosphate, cupric sulfate, cobaltous nitrate, chromium fluoride, cadmium fluoride, stannous fluoride, and lead dioxide.

35. A composition according to claim 33 wherein said coating composi-tion includes an oxidizing agent.

36. A composition according to claim 35 wherein said oxidizing agent is hydrogen peroxide in an amount of about 0.01 to about 0.2 oxidizing equi-valent per liter of composition.

37. A composition according to claim 33 wherein said composition in-cludes a coalescing agent.

38. A composition according to claim 37 wherein said coalescing agent is ethylene glycol monobutylether in an amount of about 5 to about 30 g/l.

39. A composition according to claim, 33 wherein said coating coin-position comprises a pigment.

40. A composition according to claim 39 wherein said metal-containing compound and said pigment comprise iron oxide red or iron oxide yellow.

41. A composition according to claim 33 wherein said resin is anion-ically stabilized.

42. An acidic aqueous coating composition for applying a resinous coating to a metal surface comprising about 5 to about 550 g/l of dispersed solid resin particles, and of pH within the range of about 1.6 to about 5 and prepared from hydrofluoric acid, and including metal selected from the group consisting of chromium, cobalt, copper, silver, cadmium, tin, lead, and ferrous iron, the source of said metal being about 0.025 to about 50 g/l of a metal-containing compound which is soluble in said composition and con-tains said metal, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is immersed in said composition.

43. A composition according to claim 42 wherein said resin is anion-ically stabilized.

44. A composition according to claim 42 wherein said metal is silver, the source of which is about 0.1 to about 10 g/l of silver fluoride.

45. An acidic aqueous coating composition for applying a resinous coating to a metal surface comprising about 5 to about 550 g/l of dispersed solid resin particles, and of pH within the range of about 1.6 to about 5 and prepared from hydrofluoric acid, and about 0.025 to about 50 g/l of a metal-containing compound which is soluble in said composition, the cationic species of said compound containing a metal selected from the group consist-ing of non-ferric transition elements and Group IV elements of the Periodic Table, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said sur-face is immersed in said composition.

46. An acidic aqueous coating composition for applying a resinous coating to a metal surface comprising about 5 to about 550 g/l of dispersed solid resin particles, and of pH within the range of about 1.6 to about 5 and prepared from about 0.025 to about 50 g/l of a metal-containing compound which is soluble in said composition, the cationic species of said compound containing a metal selected from the group consisting of silver, iron in its divalent state, copper in its divalent state, cobalt in its divalent state, cadmium, tin in its divalent state and lead in its tetravalent state, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is immersed in said composition.

47. An acidic aqueous coating composition for applying a resinous coating to a metal surface comprising about 5 to about 550 g/l of dispersed solid resin particles, and of pH within the range of about 1.6 to about 5 and including metal selected from the group consisting of cobalt, copper, silver, cadmium, tin, lead, and ferrous iron, the source of said metal being a metal-containing compound which is soluble in said composition and con-tains said metal, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is contacted with said composition.

48. An acidic aqueous coating composition for applying a resinous coating to a metal surface comprising about 5 to about 550 g/l of dispersed solid resin particles anionically stabilized, and of pH within the range of about 1.6 to about 5 and prepared from a metal-containing compound which is soluble in said composition, the cationic species of said compound contain-ing a metal selected from the group consisting of non-ferric transition ele-ments and Group IV elements of the Periodic Table, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is contacted with said com-position.

49. An acidic aqueous coating composition for applying a resinous coating to a metal surface comprising about 5 to about 550 g/l of dispersed solid resin particles, the resin being selected from the group consisting of styrene-butadiene, acrylic copolymers, acrylonitrile-butadiene, ethylene-vinyl acetate, polyethylene, and polyacrylic acid, and of pH within the range of about 1.6 to about 5 and prepared from a metal-containing compound which is soluble in said composition, the cationic species of said compound contain-ing a metal selected from the group consisting of non-ferric transition ele-ments and Group IV elements of the Periodic Table, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is contacted with said com-position.