CA1060287A - Metal coating method - Google Patents
Metal coating methodInfo
- Publication number
- CA1060287A CA1060287A CA235,044A CA235044A CA1060287A CA 1060287 A CA1060287 A CA 1060287A CA 235044 A CA235044 A CA 235044A CA 1060287 A CA1060287 A CA 1060287A
- Authority
- CA
- Canada
- Prior art keywords
- coating
- composition
- coalescing agent
- aqueous
- resinous
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
- B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
- B05D7/142—Auto-deposited coatings, i.e. autophoretic coatings
- B05D7/144—After-treatment of auto-deposited coatings
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
- C09D5/08—Anti-corrosive paints
- C09D5/088—Autophoretic paints
Abstract
METAL COATING METHOD
ABSTRACT OF THE DISCLOSURE
The appearance and performance characteristics of a polymeric resinous coating are improved by treating the coating with an aqueous rinse composition containing a coalescing agent. The coating is formed on a metal surface by contacting the surface with an acidic aqueous coating composition having dispersed resin particles, wherein the thickness or weight of the coating formed on the surface is controlled by varying the time the surface is contacted with the coating composition.
ABSTRACT OF THE DISCLOSURE
The appearance and performance characteristics of a polymeric resinous coating are improved by treating the coating with an aqueous rinse composition containing a coalescing agent. The coating is formed on a metal surface by contacting the surface with an acidic aqueous coating composition having dispersed resin particles, wherein the thickness or weight of the coating formed on the surface is controlled by varying the time the surface is contacted with the coating composition.
Description
Polymeric or resinous coating compositions have been developed for applying coatings to metallic surfaces, without the aid of electricity. Such compositions are effective in forming resinous coatings, the weights or thicknesses of which are related to the time the metal surface is contacted with the composition. Generally, these coating materials comprise an acidic aqueous coating composition having dispersed therein an organic, polymeric, or resinous film-forming material such as styrene buta-diene copolymer. These polymeric coatings, which are formed by contacting the metal surface with the acidic aqueous coating composition, are referred to as auto-deposited coatings.
U.S. Patent Nos. 3,585,084 and 3,592,699 assigned to the same assignee as the present invention, disclose compositions for coating metal surfaces comprising an organic coating-forming material, an oxidizing agent and an acid. Among the preferred compositions disclosed therein is one comprising a resin dispersion, hydrofluoric acid, -1- ~
: - . : . .
, . . ~ , :
.. ,, - : . . -.
.: .
. .
. 106~2~7 11767 and an oxidizing agent selected from the group consisting of hydrogen peroxide and dichromate.
U.S. Patent No. 3,709,743 discloses aqueous acidic coating compositions having dispersed resin solids and nitric acid. South African Patent No. 72/1146 discloses an aqueous acidic coating composition prepared from an acid, a soluble iron compound, dispersed resin solids, and optionally, an oxidizing agent. The preferred coating composition de-scribed therein is prepared from hydrofluoric acid, ferric fluoride, and dispersed resin solids. Belgian Patent of Addition No. 811,841 discloses the use of other metal compounds such as, for example, a compound of copper, cobalt, or silver in aqueous acidic coating compositions which form resin coatings which grow with time.
Coatings formed from such compositions are dis-tinctly different from coatings formed by immersing a metal surface in a conventional latex composition comprising a resin dispersed in water. The weight or thickness of a ~-coating formed by immersing a metal surface in a conven- -tional latex is not affected by the time the surface is immersed in the coating composition. In order to obtain a thicker coating it has been necessary to subject the surface to a multiple stage coating operation or to employ coating compositions having a higher solids content, that is a higher amount of resi~ solids dispersed therein.
Autodeposited coatings offer a number of impor-tant advantages. Thicker resinous coatings can be formed on a metal surface in a shorter period of time and in a one step operation. Coatings produced also have been found to have improved corrosion resistant properties and improved uniformity and appearance.
~06~Z87 11767 In general, autodeposited coatings are formed from the aqueous acidic coating composition as a result of attack and dissolution from the metal surface of metal ions in amounts which cause the dispersed resin particles to deposit on the surface in a manner such that there is a con~inuous buildup of resin coating on the surface.
Prob~ems which may be encountered with auto-deposited coatings is that the coating may be imperfect in that it contains blisters or cracks and/or bridges.
For some applications this may not be critical, but for other applications it is not tolerable. By way of example, blistering may be evidenced in the cured or fused coating by a pocket of air, water, and/or other foreign material, for example, oils or lubricant trapped between the metal surface and the cured coating. Such foreign materials may be present when insufficient cleaning has been accom-plished. With respect to cracking this can be evidenced by hairline cracks in the cured coating. With regard to ;~
bridging of the coating, this is evidenced by the coating separating from the underlying metal surface, on the under-side of the surface, where the surface is non-planar, such as when bent, curved or cornered.
It is a purpose of the present invention to pro-vide autodeposited coatings on metal surfaces, which can be cured or fused while reducing blistering, bridging, -and/or cracking. -~
This invention relates to a method for treating a coated metal surface having thereon an uncured auto-deposited coating formed by contacting said surface with an aqueous acidic coating composition containing a water dispersible resinous material which comprises contacting said uncured autodeposited coating with a coalescing agent .
~6~Z87 11767 with the result that blistering, bridging and cracking of said coating, after curing, is reduced.
The present invention relates to treating an autodeposited coating prior to its being cured or fused, with an organic material of the type generally known as a coalescing agent. Coalescing agent, as used herein, refers to the generally accepted function of a material which is added to a latex paint for the purpose of causing the resinous particles of the paint to coalesce more readily into a continuous film.
In general, the coalescing agent to be used in the present invention is a polyfunctional material.
Polyfunctional, when used herein, refers to coalescing agents having two or more oxygen containing functional groups, such as ester groups, ether linkages, hydroxy groups and carbonyl groups. Such coalescing agents are described in detail hereinafter.
The aqueous acidic coating compositions of the aforementioned type when contacted with the metal surface function to attack and dissolve from the surface metal ions, in an amount sufficient to directly or indirectly -cause resin particles in the region of the surface to deposit thereon in a continuous fashion, that is in a manner such that there is a buildup in the amount of resin ~-deposited on the surface the longer the time the surface is in contact with the composition. This deposition of the resin on the metallic surface is achieved through chemical action of the coating composition on the metallic surface. The use of electricity which is necessary for the operation of some coating methods, such as the electro-coating method, is not required.
lQ6~Z87 11767 The amount of the resin in the coating composi-tion can vary over a wide range. The lower concentration limit of the resin particles in the composition is dictated by the amount of resin needed to provide sufficient material to form a resinous coating. The upper limit is dictated by the amount of resin particles which can be dispersed in the composition. In general, the higher the amount of resin particles in the composition, the heavier the coating formed, other factors being the same. Although coating ~
compositions can be formulated with about 5 to about 550 -grams/liter of resin solids, the amount of resin solids will tend to vary depending on the other ingredients comprising the composition and also on the specific latex or resin used.
Latices, dispersions of insoluble resin particles in water, for use in the composition of the present inven-tion are readily available commercially. Examples of such ~
commercially available latices are: ~;
Hycar LX 407* (manufactured by Nihon Geon Co., Ltd.~... styrene butadiene copolyme~
Goodrite 1800 x 72* (manufactured by Goodrich ChemicalCorp.)...styrene butadiene copolymer Pliolite 491* (manufactured by Goodyear Rubber and Chemical Corp.) ...styrene butadiene copolymer Hycar LX 814* (manufactured by Nihon Geon Co., Ltd.)...acrylic copolymer Synthemal 9404* (manufactured by Nihon Reichold Co. Ltd.)...acrylic copolymer . : . ' .. :
. .
106~2t~7 Polyol AP 300* (manufactured by Kobunshi Kagaku Kogyo Co., Ltd.) ...ethylene-vinyl acetate copolymer Poly-em 40* (manufactured by Gulf Oil Corp.) ...polyethylene Hycar 1870 x 4* (manufactured by Nihon Geon Co., Ltd.)...acrylonitrile Hycar 2600 x 112* (manufactured by Nihon Geon Co., Ltd.)...polyacrylaté
*(trade marks) As to other ingredients contained in the coating composition, U.S. Patent Nos. 3,585,084 and 3,592,699 dis-close the use of a variety of acids, for example, hydro-fluoric, nitric, phosphoric, and acetic, and the use of a variety of oxidizing agents, for example, hydrogen peroxide, dichromate, nitrite, and chlorate. The ingredients are present in amounts which are effective in dissol~ing metal from the metallic surface immersed therein to form in the composition ions in a sufficient amount to cause the resin particles to deposit on the metallic surface in a manner such that the resinous coating grows with time. Exemplary compositions disclosed in said patents are effective in dissolving at least about 25 mg/sq.ft. of an iron surface ~
within the first minute of time the surface is immersed -in the composition. For this purpose, the composition contains sufficient acid to impart a pH of less than 7 to the composition, and preferably a pH within the range of about 1.6 to about 3.8. The oxidizing agent is present in an amount sufficient to provide an oxidizing equivalent of at least about 0.01 per liter of the composition. The preferred composition described in the aforementioned :1060287 patents comprises about 5 to about 550 grams/liter of resin solids, hydrofluoric acid in an amount sufficient to impart to the composition a pll within the range of 1.6 to about 3.8 and equivalent to about 0.4 to about 5 grams/liter of fluoride, and an oxidizing agent preferably dichromate or hydrogen peroxide, in an amount to provide about 0.01 to about 0.2 of oxidizing equivalent per liter of composition.
United States Patent No. 3,709,743 discloses an aqueous acidic coating composition having a resin solids content of about 2 to about 65 wt. percent, preferably about 5 to about 20 wt. percent and nitric acid in an amount of about .1 to about 5 wt. percent, preferably about 0.5 to about 2 wt. percent with the preferred pH of the composi-tion being below about 2.
South African Patent No. 72/1146 discloses an aqueous acidic coating composition containing about 5 to about 550 grams/liter of resin solids, a soluble ferric-containing compound in an amount equivalent to about 0.025 to about 3.5 grams/liter ferric ion, preferably about 0.3 to about 1.6 grams/liter of ferric ion, and acid in an amount sufficient to impart to the composition a pH within the range of about 1.6 to about 5Ø Optionally an oxidizing agent may be used in an amount to provide from about 0.01 to about 0.2 oxidizing equivalent per liter of composition.
Examples of the aforementioned ferric-containing compounds are ferric fluoride, ferric nitrate, ferric chloride, ferric phosphate and ferric oxide. Examples of acids are sulfuric, hydrochloric, hydrofluoric, nitric, phosphoric, and organic -acids, including, for example, acetic, chloracetic and tri-chloracetic. Examples of oxidizing agents are hydrogen peroxide, dichromate, permanganate, nitrate, persulfate and .
106()287 perborate. The preferred composition is described as being prepared from about 5 to about 550 grams/liter of resin solids, about 1 to about 5 grams/liter of ferric fluoride trihydrate, and hydrofluoric acid in an amount sufficient to impart to the composition a pH within the range of about 1.6 to about 5Ø
Belgian Patent of Addition No. 811,841 discloses a coating composition containing about 5 to about 550 grams/liter of resin solids, a metal-containing compound which is soluble in the composition and acid to impart to the composition a pH within the range of about 1.6 to about 5Ø Examples of the soluble metal-containing com-pound are silver fluoride, ferrous oxide, cupric sulfate, cobaltous nitrate, silver acetate, ferrous phosphate, chromium fluoride, cadmium fluoride, stannous fluoride, lead dioxide, and silver nitrate. The metal compound is present in the composition in an amount within the range of about 0.025 to about 50 grams/liter. Examples of acids that can be employed are sulfuric, hydrochloric, hydro- ~ -fluoric, nitric and phosphoric and organic acids such as acetic, chloracetic and trichloracetic. The use of hydro-fluoric acid is preferred. Optionally, an oxidizing agent may be used in an amount sufficient to provide from about 0.01 to about 0.2 oxidizing equivalent per liter of composition. Examples of oxidizing agents are hydrogen peroxide, dichromate, permanganate, nitrate, persulfate and perborate.
British Patent No. 1,241,991 discloses an acidic aqueous coating composition containing an oxidizing agent and solid resin particles stabilized with an anionic sur-factant. The composition is substantially free of nonionic .
~L~6~287 ll767 surfactant. The resin particles comprise about 5 to about 60 wt. percent, preferably about 10 to about 30 wt.
percent, of the composition. The anionic surfactant com-prises about 0.5 to about 5 wt. percent, preferably about
U.S. Patent Nos. 3,585,084 and 3,592,699 assigned to the same assignee as the present invention, disclose compositions for coating metal surfaces comprising an organic coating-forming material, an oxidizing agent and an acid. Among the preferred compositions disclosed therein is one comprising a resin dispersion, hydrofluoric acid, -1- ~
: - . : . .
, . . ~ , :
.. ,, - : . . -.
.: .
. .
. 106~2~7 11767 and an oxidizing agent selected from the group consisting of hydrogen peroxide and dichromate.
U.S. Patent No. 3,709,743 discloses aqueous acidic coating compositions having dispersed resin solids and nitric acid. South African Patent No. 72/1146 discloses an aqueous acidic coating composition prepared from an acid, a soluble iron compound, dispersed resin solids, and optionally, an oxidizing agent. The preferred coating composition de-scribed therein is prepared from hydrofluoric acid, ferric fluoride, and dispersed resin solids. Belgian Patent of Addition No. 811,841 discloses the use of other metal compounds such as, for example, a compound of copper, cobalt, or silver in aqueous acidic coating compositions which form resin coatings which grow with time.
Coatings formed from such compositions are dis-tinctly different from coatings formed by immersing a metal surface in a conventional latex composition comprising a resin dispersed in water. The weight or thickness of a ~-coating formed by immersing a metal surface in a conven- -tional latex is not affected by the time the surface is immersed in the coating composition. In order to obtain a thicker coating it has been necessary to subject the surface to a multiple stage coating operation or to employ coating compositions having a higher solids content, that is a higher amount of resi~ solids dispersed therein.
Autodeposited coatings offer a number of impor-tant advantages. Thicker resinous coatings can be formed on a metal surface in a shorter period of time and in a one step operation. Coatings produced also have been found to have improved corrosion resistant properties and improved uniformity and appearance.
~06~Z87 11767 In general, autodeposited coatings are formed from the aqueous acidic coating composition as a result of attack and dissolution from the metal surface of metal ions in amounts which cause the dispersed resin particles to deposit on the surface in a manner such that there is a con~inuous buildup of resin coating on the surface.
Prob~ems which may be encountered with auto-deposited coatings is that the coating may be imperfect in that it contains blisters or cracks and/or bridges.
For some applications this may not be critical, but for other applications it is not tolerable. By way of example, blistering may be evidenced in the cured or fused coating by a pocket of air, water, and/or other foreign material, for example, oils or lubricant trapped between the metal surface and the cured coating. Such foreign materials may be present when insufficient cleaning has been accom-plished. With respect to cracking this can be evidenced by hairline cracks in the cured coating. With regard to ;~
bridging of the coating, this is evidenced by the coating separating from the underlying metal surface, on the under-side of the surface, where the surface is non-planar, such as when bent, curved or cornered.
It is a purpose of the present invention to pro-vide autodeposited coatings on metal surfaces, which can be cured or fused while reducing blistering, bridging, -and/or cracking. -~
This invention relates to a method for treating a coated metal surface having thereon an uncured auto-deposited coating formed by contacting said surface with an aqueous acidic coating composition containing a water dispersible resinous material which comprises contacting said uncured autodeposited coating with a coalescing agent .
~6~Z87 11767 with the result that blistering, bridging and cracking of said coating, after curing, is reduced.
The present invention relates to treating an autodeposited coating prior to its being cured or fused, with an organic material of the type generally known as a coalescing agent. Coalescing agent, as used herein, refers to the generally accepted function of a material which is added to a latex paint for the purpose of causing the resinous particles of the paint to coalesce more readily into a continuous film.
In general, the coalescing agent to be used in the present invention is a polyfunctional material.
Polyfunctional, when used herein, refers to coalescing agents having two or more oxygen containing functional groups, such as ester groups, ether linkages, hydroxy groups and carbonyl groups. Such coalescing agents are described in detail hereinafter.
The aqueous acidic coating compositions of the aforementioned type when contacted with the metal surface function to attack and dissolve from the surface metal ions, in an amount sufficient to directly or indirectly -cause resin particles in the region of the surface to deposit thereon in a continuous fashion, that is in a manner such that there is a buildup in the amount of resin ~-deposited on the surface the longer the time the surface is in contact with the composition. This deposition of the resin on the metallic surface is achieved through chemical action of the coating composition on the metallic surface. The use of electricity which is necessary for the operation of some coating methods, such as the electro-coating method, is not required.
lQ6~Z87 11767 The amount of the resin in the coating composi-tion can vary over a wide range. The lower concentration limit of the resin particles in the composition is dictated by the amount of resin needed to provide sufficient material to form a resinous coating. The upper limit is dictated by the amount of resin particles which can be dispersed in the composition. In general, the higher the amount of resin particles in the composition, the heavier the coating formed, other factors being the same. Although coating ~
compositions can be formulated with about 5 to about 550 -grams/liter of resin solids, the amount of resin solids will tend to vary depending on the other ingredients comprising the composition and also on the specific latex or resin used.
Latices, dispersions of insoluble resin particles in water, for use in the composition of the present inven-tion are readily available commercially. Examples of such ~
commercially available latices are: ~;
Hycar LX 407* (manufactured by Nihon Geon Co., Ltd.~... styrene butadiene copolyme~
Goodrite 1800 x 72* (manufactured by Goodrich ChemicalCorp.)...styrene butadiene copolymer Pliolite 491* (manufactured by Goodyear Rubber and Chemical Corp.) ...styrene butadiene copolymer Hycar LX 814* (manufactured by Nihon Geon Co., Ltd.)...acrylic copolymer Synthemal 9404* (manufactured by Nihon Reichold Co. Ltd.)...acrylic copolymer . : . ' .. :
. .
106~2t~7 Polyol AP 300* (manufactured by Kobunshi Kagaku Kogyo Co., Ltd.) ...ethylene-vinyl acetate copolymer Poly-em 40* (manufactured by Gulf Oil Corp.) ...polyethylene Hycar 1870 x 4* (manufactured by Nihon Geon Co., Ltd.)...acrylonitrile Hycar 2600 x 112* (manufactured by Nihon Geon Co., Ltd.)...polyacrylaté
*(trade marks) As to other ingredients contained in the coating composition, U.S. Patent Nos. 3,585,084 and 3,592,699 dis-close the use of a variety of acids, for example, hydro-fluoric, nitric, phosphoric, and acetic, and the use of a variety of oxidizing agents, for example, hydrogen peroxide, dichromate, nitrite, and chlorate. The ingredients are present in amounts which are effective in dissol~ing metal from the metallic surface immersed therein to form in the composition ions in a sufficient amount to cause the resin particles to deposit on the metallic surface in a manner such that the resinous coating grows with time. Exemplary compositions disclosed in said patents are effective in dissolving at least about 25 mg/sq.ft. of an iron surface ~
within the first minute of time the surface is immersed -in the composition. For this purpose, the composition contains sufficient acid to impart a pH of less than 7 to the composition, and preferably a pH within the range of about 1.6 to about 3.8. The oxidizing agent is present in an amount sufficient to provide an oxidizing equivalent of at least about 0.01 per liter of the composition. The preferred composition described in the aforementioned :1060287 patents comprises about 5 to about 550 grams/liter of resin solids, hydrofluoric acid in an amount sufficient to impart to the composition a pll within the range of 1.6 to about 3.8 and equivalent to about 0.4 to about 5 grams/liter of fluoride, and an oxidizing agent preferably dichromate or hydrogen peroxide, in an amount to provide about 0.01 to about 0.2 of oxidizing equivalent per liter of composition.
United States Patent No. 3,709,743 discloses an aqueous acidic coating composition having a resin solids content of about 2 to about 65 wt. percent, preferably about 5 to about 20 wt. percent and nitric acid in an amount of about .1 to about 5 wt. percent, preferably about 0.5 to about 2 wt. percent with the preferred pH of the composi-tion being below about 2.
South African Patent No. 72/1146 discloses an aqueous acidic coating composition containing about 5 to about 550 grams/liter of resin solids, a soluble ferric-containing compound in an amount equivalent to about 0.025 to about 3.5 grams/liter ferric ion, preferably about 0.3 to about 1.6 grams/liter of ferric ion, and acid in an amount sufficient to impart to the composition a pH within the range of about 1.6 to about 5Ø Optionally an oxidizing agent may be used in an amount to provide from about 0.01 to about 0.2 oxidizing equivalent per liter of composition.
Examples of the aforementioned ferric-containing compounds are ferric fluoride, ferric nitrate, ferric chloride, ferric phosphate and ferric oxide. Examples of acids are sulfuric, hydrochloric, hydrofluoric, nitric, phosphoric, and organic -acids, including, for example, acetic, chloracetic and tri-chloracetic. Examples of oxidizing agents are hydrogen peroxide, dichromate, permanganate, nitrate, persulfate and .
106()287 perborate. The preferred composition is described as being prepared from about 5 to about 550 grams/liter of resin solids, about 1 to about 5 grams/liter of ferric fluoride trihydrate, and hydrofluoric acid in an amount sufficient to impart to the composition a pH within the range of about 1.6 to about 5Ø
Belgian Patent of Addition No. 811,841 discloses a coating composition containing about 5 to about 550 grams/liter of resin solids, a metal-containing compound which is soluble in the composition and acid to impart to the composition a pH within the range of about 1.6 to about 5Ø Examples of the soluble metal-containing com-pound are silver fluoride, ferrous oxide, cupric sulfate, cobaltous nitrate, silver acetate, ferrous phosphate, chromium fluoride, cadmium fluoride, stannous fluoride, lead dioxide, and silver nitrate. The metal compound is present in the composition in an amount within the range of about 0.025 to about 50 grams/liter. Examples of acids that can be employed are sulfuric, hydrochloric, hydro- ~ -fluoric, nitric and phosphoric and organic acids such as acetic, chloracetic and trichloracetic. The use of hydro-fluoric acid is preferred. Optionally, an oxidizing agent may be used in an amount sufficient to provide from about 0.01 to about 0.2 oxidizing equivalent per liter of composition. Examples of oxidizing agents are hydrogen peroxide, dichromate, permanganate, nitrate, persulfate and perborate.
British Patent No. 1,241,991 discloses an acidic aqueous coating composition containing an oxidizing agent and solid resin particles stabilized with an anionic sur-factant. The composition is substantially free of nonionic .
~L~6~287 ll767 surfactant. The resin particles comprise about 5 to about 60 wt. percent, preferably about 10 to about 30 wt.
percent, of the composition. The anionic surfactant com-prises about 0.5 to about 5 wt. percent, preferably about
2 to about 4 wt. percent based on the weight of the resin.
Examples of anionic surfactant are the alkyl, alkyl/aryl or naphthalene sulfonates, for example sodium dioctyl sulphosuccinate and sodium dodecylbenzene sulfonate. The oxidizing agent is described as being of the kind commonly known as a depolariser, and preferably is present in the composition in an amount of about 0.02 to about 0.2 N.
Examples of oxidizing agents are hydrogen peroxide, p-benzoquinone, p-nitrophenol, persulfate and nitrate. Acids such as phosphoric, hydrochloric, sulfuric, acetic, tri-chloracetic and nitric are used to impart to the composi-tion a pH of preferably less than 5, most preferably less than 3.5.
Various factors should be taken into account in determining whether the metallic surace should or should not be cleaned, and the extent of cleaning, prior to contact with the coating composition including, for example, the nature of foreign materials (if any) on the surface and the desired quality of the coating. F oreign materials which are present on the met~allic surface can lead to the forma-tion of coatings which are not uniform. Also, the adhesion and corrosion resistant properties of the resinous coating can be affected adversely as a result of the presence on the metallic surface of foreign materials during the coating step. Generally speaking, improved quality coatings can be consistently obtained the cleaner the surface. Excellent results can be achieved consistently by subjecting the _9_ ~ 11767 ~06028~
metallic surface to a cleaning operation which results in a surface on which there can be formed a water break-free film. The selection of the cleaning agent and mode of application thereof to the metallic surface will depend on the type of foreign materials present on the metallic surface. Available cleaning agents can be used in accord-ance with known technology. Thus, depending on the type of soil or foreign materials which are present, acidic, alka-line or other cleaning agents can be used. By way of example, dilute phosphoric acid can be used to clean lightly rusted parts and hot alkaline compositions can be used for the removal of oils, greases, fingerprints and other organic deposits.
After the metallic surface has been cleaned, it -~
may or may not be water rinsed prior to immersing the metallic surface in the coating composition. Water rinsing the surface removes therefrom foreign materials, for example, residual cleaning, agent, which may tend to adversely affect the coating operation. For example, foreign materials carried into the coating composition may ~-have adverse effects thereon. Whether or not a water rinse should be used in a particular application can be best determined by taking into account the quality of the coatings desired and observing whether or not unrinsed surfaces adversely affect the coating bath and coating quality. To avoid or minimize such adverse effects, it is recommended that the clean surface be rinsed with ~
deio~ed water for a sufficient period of time to remove ~-fore.ign materials therefrom and that most of the rinse water be removed from the surface (for example, by allowing -10-- ~
~60Z87 it to drain therefrom) before the surface is immersed in the coating bath.
As mentioned above, the longer the metallic surface is immersed in the coating composition, the greater the buildup in coating thickness. It is believed that for most applications, desired coating thicknesses can be obtained by immersing the metallic surface in the composition for a period of time within the range of about 30 seconds to about 3 minutes. However, it should be understood that longer or shorter periods of time can be used.
Agitating the composition aids in maintaining it uniform. Also, agitation of the composition is effec-tive in improving the uniformity of the coatings formed.
Other factors held constant, heating of the coating composition will result in heavier coatings. For example, a composition having a temperature of about 35F
formed a coating having a thickness of about 0.8 mil, whereas at a temperature of about 100F, the coating formed had a thickness of about 1.1 mils. Satisfactory results can be obtained by operating the coating process at ambient temperatures.
Once the metal surface has been contacted with the coating composition, it may or may not be rinsed with water before significant drying takes place. Water rinsing is effective in removing residuals such as acid --and other ingredients that adhere to the coated surface.
If such residuals are allowed to remain on the coated ';
surface, they may change or adversely affect the quality of the coating. For a specific application, a determi-nation can be made as to whether the residuals cause - : :
: ' ' . , , adverse affects which are not tolerable. If they do, they should be removed, for example by water rinsing with tap or deionized water. If they do not, this step of removing them can be avoided.
Following contact with the aqueous coating composition, and in certain instances the optional water rinse with tap or deionized water, the coated metal surface can then be treated according to the present invention.
The aqueous rinse composition for use in the practice of this invention comprises a coalescing agent.
The coalescing agent to be used can be selected from a wide variety of compounds. Examples of such compounds include:
a) alcohols having two or more hydroxy groups such as ethyleneglycol and triethylene glycol;
b) ketones having two or more carbonyl groups, such as acetonylacetone (methyl butoxyketone~; -c) alcohol esters having a hydroxy group and an ester group such as butyl lactate, isopropyl lactate, ethyl lactate;
d) ketone esters having a carbonyl group and an ester group such as ethyl aceto acetate;
e) alcohol ethers having a hydroxy group and an ether linkage such as diethylene glycol diethyl ether, 2-ethoxyethanol, 2-butoxy-ethanol, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethyl-ene glycol monobutyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, tripropylene glycol methyl ether;
'~~ 11767 ~0b;~)2~7 f) ketone ethers having a carbonyl group and an ether linkage such as acetonyl methanol ethyl ether; and g) ester ethers having an ester group and an ether linkage such as 2-ethoxy ethyl acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate.
It is noted that the compounds mentioned above contain two or more oxygen atoms in groups, or oxygen containing functional groups, such as hydroxyl, carbonyl, ester, and ether.
Compounds mentioned above are water miscible and have a lower evaporation rate than water. In addition, compounds among those mentioned above are generally effective in causing the resin particle to swell or soften, and in effect, tend to lower the minimum film formation ~;
temperature of the resin particles.
The preferred coalescing agents for use in the practice of the present invention are alcohol ethers and ester ethers and most preferably 2-butoxyethanol and diethyl-ene glycol monobutyl ether acetate. Although other means can be utilized to apply the coa~escing agent to the uncured coating, it is recommended and preferred that it be applied from an aqueous carrier. The selection of the particular coalescing agent to be employed will depend on its commercial availability and on its solubility properties.
It is noted that the above listed compounds are soluble in water, having a solubility of more than 3 percent by `;
weight in water. It is further noted that each of the above listed compounds have a boiling point of at least 134C. It is preferred that the coalescing agent have a - ~ .
, ~060~87 11767 solubility of more than 3 percent by weight in water and a boiling point above 140C., Thus, during the baking step, which is generally used to cure or fuse the coating, the water of the wet coating will tend to evaporate at a faster rate than the coalescing agent, , thereby tending to concentrate the coalescing agent in the resinous coating.
Generally, the mere presence of the coalescing agent in the aqueous rinse composition will be effective in reducing the tendency of the coating to crack, blister, and/or bridge. However, to realize a significant improve-ment, the amount of coalescing agent in the aqueous carrier should be at least about 10 gramstliter. Preferably, the aqueous rinse composition will contain from about 20 grams/liter to about 100 grams/liter of coalescing agent.
Optimum results have been obtained wherein there is from about 20 grams/liter to about 30 grams/liter of diethyl-ene glycol monobutyl ether acetate in the rinse composition.
Treatment of the uncured coating can be accom-plished by employing any of the contacting techniques knownto the art, for example immersion, mist spray, and shower-ing. Preferably, the uncured coating is rinsed with an aqueous solution comprising the coalescing agent by mist spray or immersion methods.
The coated surface is brought into contact with the aqueous rinse composition under suitable conditions of temperature and contact time. The time of treatment of the coated surface with the rinse composition need only be long enough to insure complete wetting of the coating. Preferably, the rinse composition can be applied to the coated surface for from about 30 seconds ~ 11767 10602~37 to about 5 minutes. In certain commercial operations, such as formed parts lines, it is beneficial to have longer contact time periods so that the entire metal workpiece is sufficiently contacted with the rinse composition. The uncured coating should not be con-tacted with the coalescing agent for lengthy periods of time such that adhesion of the coating to the under-lying metal surface is impaired. Rinsing can be accom-plished over a broad temperature range, for example, from about 10C to about 80C. Satisfactory results are obtained by utilizin-g a rinse composition at room temperature.
After treatment with the coalescing agent, the uncured coating can then be fused, for example by baking as will be discussed hereinbelow.
However, if desired, the corrosion resistant properties of the coated surface can be improved by contacting the uncured coated surface with an acidic rinse solution containing hexavalent chromium.~ Such chromium rinse solutions are prepared from chromium trioxide or water soluble dichromate or chromate salts, for example, ammonium, sodium, and potassium salts. There can also be used a chromium composition obtained by treating a concentrated aqueous solution of chromic acid with formaldehyde to reduce a portion of the hexavalent chromium. This type of rinse, which is described in U.S. Patent No. 3,063,877 to Shiffman, contains chromium in its hexavalent state and reduced chromium in aqueous soLution. By way of example, such an aqueous rinse solution can comprise a total chromium concentration within the range of about .15 grams/liter (expressed as .
,, 1060Z1~7 CrO3) to about 2 grams/liter, wherein from about 40-95 percent of the chromium is in its hexavalent state and the remainder of the chromium is in its reduced state.
A small amount of phosphoric acid can also be added to the rinse solution to prevent gel formation and as little as .05 ml of 75 percent H3P04 solution per gram of total chromium has been found effective.
The amount of hexavalent chromium or hexavalent chromium and reducedchromium will, in general, be governed by the corrosion resistant properties required for the specific application. It is preferred that at least about .01 grams/liter of hexavalent chromium be used and that the amount be adjusted upwardly as required, if neces-sary.
While the aqueous rinse composition of the present invention can be applied to the coated metal surface prior to or after contacting the coated surface with a rinse solution containing hexavalent chromium, it has been found that the aqueous rinse composition of the present invention can be prepared containing the hexa-valent chromium therein. Therefore, both the chromiumand the coalescing agent can be contacted with the coated metal surface simultaneously, thereby eliminating the necessity for multiple treating steps. Of course, the particular coalescing agent to be employed when the chromium is also incorporated in the aqueous rinse compo-sition must be selected so that it is stable in the composition at the operating parameters of the rinse composition. The preferred coalescing agent to be -employed along with chromium in the aqueous rinse composition is diethylene glycol monobutyl ether acetate.
r ~(~60287 Following contact with the aqueous rinse composition, the coating should be cured or fused.
Fusion of the resinous coating renders it continuous, thereby improving its resistance to corrosion and adherence to the underlying metallic surface. The drying of the coated surface can be accomplished under varying conditions dependent upon the type of resin or ' polymeric material employed in the coating process.
Generally, heating or baking will be required to fuse the resin coating. When a heated invironment or baking is employed, the drying or fusion step can be accomplished at temperatures from about 110C to about 250C. Most of the resin coatings require heated drying stages or ~
baking steps in order to fuse the resin and to insure ~ ;
that optimum corrosion resistant properties of the coating are obtained.
It is not fully understood why the use of the coalescing agent reduces the tendency of the cured coating to crack, blister and/or bridge. However, it is believed that during drying or curing, surface stresses arise in the coating as it contracts in volume. This volume contraction results in stresses which may be resolved in directions parallel to the surface. It is these stresses on a planar surface which, it is believed, causes visible cracks to open. On the underside of a surface, where the surface is non planar, such as where it is bent, curved or cornered, these stresses resulting from contraction, it is believed causes the coating to separ-ate from-the underlying metal surface to form bridges.
The cracks or bridges which form relieve the surface stresses, and it has been observed that cracks form perpendicularly to any surface stresses. The use of the ~ -.. ~ ., . ., ~ . .
` ~060287 11767 coalescing agent in the rinse composition appears to alleviate the effects of volume contraction, thereby reducing cracking and/or bridging. It is also believed that the use of the coalescing agent reduces formation of blisters by enhancing adhesion of the coating to the underlying metal surface.
The examples presented below are illustrative of this invention and are not considered as limiting for other materials and operating conditions falling within the scope of the invention that might be substituted.
In the examples cold-rolled steel panels were cleaned with an alkaline cleaner, rinsed with water, and immersed, as indicated in each example, in an aqueous coating composition to form an autodeposited coating.
Upon being withdrawn from the coating composition, the -~
autodeposited coating was formed on the surface and the panels thereafter underwent the particular treating steps indicated in each example- In some instances the coated panels were rinsed first with tap water then rinsed with the aqueous rinse composition, in some instances said aqueous rinse composition containing both coalescing agent and chromium. Thereafter, the coated panels were -placed in an oven at the specified temperatures and specified baking time. After being withdrawn from the oven the appearance of the coatings was observed visually for the purpose of evaluating the presence of cracking, ~;
blistering, and/or bridging.
EXAMPLE I ~;
An aqueous coating composition was prepared containing the following:
Parts by wei~ht styrene butadiene copolymer 200 (Nippol LX 407*- sold by Nippon Zeon) Chromate pigment (KiKu Jerushi 50 OEN 5G-3KB~sold by Kikuchi Kogyo) iron oxide pigment (Tenyo50 Bengara*sold by Tone Sangyo) anionic surfactant (Demol-P ^ 5 sold by Kao Atlas Co.) ferric fluoride (trihydrate) 10 hydrofluoric acid 3 tap water 692 The aqueous coating composition is prepared by adding lead chromate pigment, anionic surfactant, ferric fluoride trihydrate, iron oxide pigment and a portion of the tap water to a porcelain ball mill and mixed for 16 hours until dispersed to form a pigment paste. Thereafter the styrene butadiene copolymer is added to the pigment paste with mixing and thereafter, the remainder of tap water is added. Hydrofluoric acid is then added with stirring.
Cold Rolled Steel panels (Nos. 1-6) were immersed in the above aqueous ccating composi~ion at room temperature for 3 minutes. After being withdrawn from the aqueous coating composition each panel was per- -mitted to stand for 10 minutes and each was thereafter immersed in a particular composition comprising diethyl-ene glycol monoethyl ether acetate and water for specified time periods. The particular compositions comprising diethylene glycol monoethyl ether acetate in specified *(trade mark) 1~6~287 117G7 concentrations are listed in Table 1 below. The panels were withdrawn from the composition comprising diethylene glycol monoethyl ether acetate and thereafter were placed in an oven having a temperature of 180C and were baked for 5 minutes. The appearance of the coated panels was thereafter observed and the observations are noted in Table 1 below.
One set of control panels was immersed in the aqueous coating composition under the identical conditions as above and was permitted to stand after being withdrawn from the aqueous coating composition for a period of 10 minutes, thereafter placed in an oven having a temperature of 180C and baked for 5 minutes. The appearance of the control panels was observed and is noted in Table l below.
Table 1 _ . :-~
Concentratlon o~, diethylene glycol Immersior monoethyl ether Time Appearance of No. acetate (g/l) (min.) coated film 1 100 .5 Good - No cracking or blistering ;
2 100 2 Good - No cracking or blistering
Examples of anionic surfactant are the alkyl, alkyl/aryl or naphthalene sulfonates, for example sodium dioctyl sulphosuccinate and sodium dodecylbenzene sulfonate. The oxidizing agent is described as being of the kind commonly known as a depolariser, and preferably is present in the composition in an amount of about 0.02 to about 0.2 N.
Examples of oxidizing agents are hydrogen peroxide, p-benzoquinone, p-nitrophenol, persulfate and nitrate. Acids such as phosphoric, hydrochloric, sulfuric, acetic, tri-chloracetic and nitric are used to impart to the composi-tion a pH of preferably less than 5, most preferably less than 3.5.
Various factors should be taken into account in determining whether the metallic surace should or should not be cleaned, and the extent of cleaning, prior to contact with the coating composition including, for example, the nature of foreign materials (if any) on the surface and the desired quality of the coating. F oreign materials which are present on the met~allic surface can lead to the forma-tion of coatings which are not uniform. Also, the adhesion and corrosion resistant properties of the resinous coating can be affected adversely as a result of the presence on the metallic surface of foreign materials during the coating step. Generally speaking, improved quality coatings can be consistently obtained the cleaner the surface. Excellent results can be achieved consistently by subjecting the _9_ ~ 11767 ~06028~
metallic surface to a cleaning operation which results in a surface on which there can be formed a water break-free film. The selection of the cleaning agent and mode of application thereof to the metallic surface will depend on the type of foreign materials present on the metallic surface. Available cleaning agents can be used in accord-ance with known technology. Thus, depending on the type of soil or foreign materials which are present, acidic, alka-line or other cleaning agents can be used. By way of example, dilute phosphoric acid can be used to clean lightly rusted parts and hot alkaline compositions can be used for the removal of oils, greases, fingerprints and other organic deposits.
After the metallic surface has been cleaned, it -~
may or may not be water rinsed prior to immersing the metallic surface in the coating composition. Water rinsing the surface removes therefrom foreign materials, for example, residual cleaning, agent, which may tend to adversely affect the coating operation. For example, foreign materials carried into the coating composition may ~-have adverse effects thereon. Whether or not a water rinse should be used in a particular application can be best determined by taking into account the quality of the coatings desired and observing whether or not unrinsed surfaces adversely affect the coating bath and coating quality. To avoid or minimize such adverse effects, it is recommended that the clean surface be rinsed with ~
deio~ed water for a sufficient period of time to remove ~-fore.ign materials therefrom and that most of the rinse water be removed from the surface (for example, by allowing -10-- ~
~60Z87 it to drain therefrom) before the surface is immersed in the coating bath.
As mentioned above, the longer the metallic surface is immersed in the coating composition, the greater the buildup in coating thickness. It is believed that for most applications, desired coating thicknesses can be obtained by immersing the metallic surface in the composition for a period of time within the range of about 30 seconds to about 3 minutes. However, it should be understood that longer or shorter periods of time can be used.
Agitating the composition aids in maintaining it uniform. Also, agitation of the composition is effec-tive in improving the uniformity of the coatings formed.
Other factors held constant, heating of the coating composition will result in heavier coatings. For example, a composition having a temperature of about 35F
formed a coating having a thickness of about 0.8 mil, whereas at a temperature of about 100F, the coating formed had a thickness of about 1.1 mils. Satisfactory results can be obtained by operating the coating process at ambient temperatures.
Once the metal surface has been contacted with the coating composition, it may or may not be rinsed with water before significant drying takes place. Water rinsing is effective in removing residuals such as acid --and other ingredients that adhere to the coated surface.
If such residuals are allowed to remain on the coated ';
surface, they may change or adversely affect the quality of the coating. For a specific application, a determi-nation can be made as to whether the residuals cause - : :
: ' ' . , , adverse affects which are not tolerable. If they do, they should be removed, for example by water rinsing with tap or deionized water. If they do not, this step of removing them can be avoided.
Following contact with the aqueous coating composition, and in certain instances the optional water rinse with tap or deionized water, the coated metal surface can then be treated according to the present invention.
The aqueous rinse composition for use in the practice of this invention comprises a coalescing agent.
The coalescing agent to be used can be selected from a wide variety of compounds. Examples of such compounds include:
a) alcohols having two or more hydroxy groups such as ethyleneglycol and triethylene glycol;
b) ketones having two or more carbonyl groups, such as acetonylacetone (methyl butoxyketone~; -c) alcohol esters having a hydroxy group and an ester group such as butyl lactate, isopropyl lactate, ethyl lactate;
d) ketone esters having a carbonyl group and an ester group such as ethyl aceto acetate;
e) alcohol ethers having a hydroxy group and an ether linkage such as diethylene glycol diethyl ether, 2-ethoxyethanol, 2-butoxy-ethanol, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethyl-ene glycol monobutyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, tripropylene glycol methyl ether;
'~~ 11767 ~0b;~)2~7 f) ketone ethers having a carbonyl group and an ether linkage such as acetonyl methanol ethyl ether; and g) ester ethers having an ester group and an ether linkage such as 2-ethoxy ethyl acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate.
It is noted that the compounds mentioned above contain two or more oxygen atoms in groups, or oxygen containing functional groups, such as hydroxyl, carbonyl, ester, and ether.
Compounds mentioned above are water miscible and have a lower evaporation rate than water. In addition, compounds among those mentioned above are generally effective in causing the resin particle to swell or soften, and in effect, tend to lower the minimum film formation ~;
temperature of the resin particles.
The preferred coalescing agents for use in the practice of the present invention are alcohol ethers and ester ethers and most preferably 2-butoxyethanol and diethyl-ene glycol monobutyl ether acetate. Although other means can be utilized to apply the coa~escing agent to the uncured coating, it is recommended and preferred that it be applied from an aqueous carrier. The selection of the particular coalescing agent to be employed will depend on its commercial availability and on its solubility properties.
It is noted that the above listed compounds are soluble in water, having a solubility of more than 3 percent by `;
weight in water. It is further noted that each of the above listed compounds have a boiling point of at least 134C. It is preferred that the coalescing agent have a - ~ .
, ~060~87 11767 solubility of more than 3 percent by weight in water and a boiling point above 140C., Thus, during the baking step, which is generally used to cure or fuse the coating, the water of the wet coating will tend to evaporate at a faster rate than the coalescing agent, , thereby tending to concentrate the coalescing agent in the resinous coating.
Generally, the mere presence of the coalescing agent in the aqueous rinse composition will be effective in reducing the tendency of the coating to crack, blister, and/or bridge. However, to realize a significant improve-ment, the amount of coalescing agent in the aqueous carrier should be at least about 10 gramstliter. Preferably, the aqueous rinse composition will contain from about 20 grams/liter to about 100 grams/liter of coalescing agent.
Optimum results have been obtained wherein there is from about 20 grams/liter to about 30 grams/liter of diethyl-ene glycol monobutyl ether acetate in the rinse composition.
Treatment of the uncured coating can be accom-plished by employing any of the contacting techniques knownto the art, for example immersion, mist spray, and shower-ing. Preferably, the uncured coating is rinsed with an aqueous solution comprising the coalescing agent by mist spray or immersion methods.
The coated surface is brought into contact with the aqueous rinse composition under suitable conditions of temperature and contact time. The time of treatment of the coated surface with the rinse composition need only be long enough to insure complete wetting of the coating. Preferably, the rinse composition can be applied to the coated surface for from about 30 seconds ~ 11767 10602~37 to about 5 minutes. In certain commercial operations, such as formed parts lines, it is beneficial to have longer contact time periods so that the entire metal workpiece is sufficiently contacted with the rinse composition. The uncured coating should not be con-tacted with the coalescing agent for lengthy periods of time such that adhesion of the coating to the under-lying metal surface is impaired. Rinsing can be accom-plished over a broad temperature range, for example, from about 10C to about 80C. Satisfactory results are obtained by utilizin-g a rinse composition at room temperature.
After treatment with the coalescing agent, the uncured coating can then be fused, for example by baking as will be discussed hereinbelow.
However, if desired, the corrosion resistant properties of the coated surface can be improved by contacting the uncured coated surface with an acidic rinse solution containing hexavalent chromium.~ Such chromium rinse solutions are prepared from chromium trioxide or water soluble dichromate or chromate salts, for example, ammonium, sodium, and potassium salts. There can also be used a chromium composition obtained by treating a concentrated aqueous solution of chromic acid with formaldehyde to reduce a portion of the hexavalent chromium. This type of rinse, which is described in U.S. Patent No. 3,063,877 to Shiffman, contains chromium in its hexavalent state and reduced chromium in aqueous soLution. By way of example, such an aqueous rinse solution can comprise a total chromium concentration within the range of about .15 grams/liter (expressed as .
,, 1060Z1~7 CrO3) to about 2 grams/liter, wherein from about 40-95 percent of the chromium is in its hexavalent state and the remainder of the chromium is in its reduced state.
A small amount of phosphoric acid can also be added to the rinse solution to prevent gel formation and as little as .05 ml of 75 percent H3P04 solution per gram of total chromium has been found effective.
The amount of hexavalent chromium or hexavalent chromium and reducedchromium will, in general, be governed by the corrosion resistant properties required for the specific application. It is preferred that at least about .01 grams/liter of hexavalent chromium be used and that the amount be adjusted upwardly as required, if neces-sary.
While the aqueous rinse composition of the present invention can be applied to the coated metal surface prior to or after contacting the coated surface with a rinse solution containing hexavalent chromium, it has been found that the aqueous rinse composition of the present invention can be prepared containing the hexa-valent chromium therein. Therefore, both the chromiumand the coalescing agent can be contacted with the coated metal surface simultaneously, thereby eliminating the necessity for multiple treating steps. Of course, the particular coalescing agent to be employed when the chromium is also incorporated in the aqueous rinse compo-sition must be selected so that it is stable in the composition at the operating parameters of the rinse composition. The preferred coalescing agent to be -employed along with chromium in the aqueous rinse composition is diethylene glycol monobutyl ether acetate.
r ~(~60287 Following contact with the aqueous rinse composition, the coating should be cured or fused.
Fusion of the resinous coating renders it continuous, thereby improving its resistance to corrosion and adherence to the underlying metallic surface. The drying of the coated surface can be accomplished under varying conditions dependent upon the type of resin or ' polymeric material employed in the coating process.
Generally, heating or baking will be required to fuse the resin coating. When a heated invironment or baking is employed, the drying or fusion step can be accomplished at temperatures from about 110C to about 250C. Most of the resin coatings require heated drying stages or ~
baking steps in order to fuse the resin and to insure ~ ;
that optimum corrosion resistant properties of the coating are obtained.
It is not fully understood why the use of the coalescing agent reduces the tendency of the cured coating to crack, blister and/or bridge. However, it is believed that during drying or curing, surface stresses arise in the coating as it contracts in volume. This volume contraction results in stresses which may be resolved in directions parallel to the surface. It is these stresses on a planar surface which, it is believed, causes visible cracks to open. On the underside of a surface, where the surface is non planar, such as where it is bent, curved or cornered, these stresses resulting from contraction, it is believed causes the coating to separ-ate from-the underlying metal surface to form bridges.
The cracks or bridges which form relieve the surface stresses, and it has been observed that cracks form perpendicularly to any surface stresses. The use of the ~ -.. ~ ., . ., ~ . .
` ~060287 11767 coalescing agent in the rinse composition appears to alleviate the effects of volume contraction, thereby reducing cracking and/or bridging. It is also believed that the use of the coalescing agent reduces formation of blisters by enhancing adhesion of the coating to the underlying metal surface.
The examples presented below are illustrative of this invention and are not considered as limiting for other materials and operating conditions falling within the scope of the invention that might be substituted.
In the examples cold-rolled steel panels were cleaned with an alkaline cleaner, rinsed with water, and immersed, as indicated in each example, in an aqueous coating composition to form an autodeposited coating.
Upon being withdrawn from the coating composition, the -~
autodeposited coating was formed on the surface and the panels thereafter underwent the particular treating steps indicated in each example- In some instances the coated panels were rinsed first with tap water then rinsed with the aqueous rinse composition, in some instances said aqueous rinse composition containing both coalescing agent and chromium. Thereafter, the coated panels were -placed in an oven at the specified temperatures and specified baking time. After being withdrawn from the oven the appearance of the coatings was observed visually for the purpose of evaluating the presence of cracking, ~;
blistering, and/or bridging.
EXAMPLE I ~;
An aqueous coating composition was prepared containing the following:
Parts by wei~ht styrene butadiene copolymer 200 (Nippol LX 407*- sold by Nippon Zeon) Chromate pigment (KiKu Jerushi 50 OEN 5G-3KB~sold by Kikuchi Kogyo) iron oxide pigment (Tenyo50 Bengara*sold by Tone Sangyo) anionic surfactant (Demol-P ^ 5 sold by Kao Atlas Co.) ferric fluoride (trihydrate) 10 hydrofluoric acid 3 tap water 692 The aqueous coating composition is prepared by adding lead chromate pigment, anionic surfactant, ferric fluoride trihydrate, iron oxide pigment and a portion of the tap water to a porcelain ball mill and mixed for 16 hours until dispersed to form a pigment paste. Thereafter the styrene butadiene copolymer is added to the pigment paste with mixing and thereafter, the remainder of tap water is added. Hydrofluoric acid is then added with stirring.
Cold Rolled Steel panels (Nos. 1-6) were immersed in the above aqueous ccating composi~ion at room temperature for 3 minutes. After being withdrawn from the aqueous coating composition each panel was per- -mitted to stand for 10 minutes and each was thereafter immersed in a particular composition comprising diethyl-ene glycol monoethyl ether acetate and water for specified time periods. The particular compositions comprising diethylene glycol monoethyl ether acetate in specified *(trade mark) 1~6~287 117G7 concentrations are listed in Table 1 below. The panels were withdrawn from the composition comprising diethylene glycol monoethyl ether acetate and thereafter were placed in an oven having a temperature of 180C and were baked for 5 minutes. The appearance of the coated panels was thereafter observed and the observations are noted in Table 1 below.
One set of control panels was immersed in the aqueous coating composition under the identical conditions as above and was permitted to stand after being withdrawn from the aqueous coating composition for a period of 10 minutes, thereafter placed in an oven having a temperature of 180C and baked for 5 minutes. The appearance of the control panels was observed and is noted in Table l below.
Table 1 _ . :-~
Concentratlon o~, diethylene glycol Immersior monoethyl ether Time Appearance of No. acetate (g/l) (min.) coated film 1 100 .5 Good - No cracking or blistering ;
2 100 2 Good - No cracking or blistering
3 100 60 - Blistering and peeling
4 5 2 Cracking 2 Good - No cracking or blistering 6 500 2 Good - No cracking or blistering _ Control cracking EXAMPLE II
An aqueous coating composition was prepared containing the following:
~06()28~
styrene butadiene copolymerParts by Weight (Darex 673* sold by W. R. Grace) 200 hydrogen peroxide 3 hydrofluoric acid 4 tap water 800 The styrene butadiene copolymer is diluted with tap water to which the hydrogen peroxide and hydrofluoric acid is added with stirring.
Steel panels (Nos. 7-13) were immersed in the coating composition at room temperature for 3 minutes.
Thereafter the panels were withdrawn from the coating composition and permitted to stand for a period of 10 minutes. The panels were then immersed in particular aqueous rinse compositions, having constituent concentrations and for periods of time as indicated in Table 2 below. ~;
The panels were thereafter removed from the rinse compo-sitions and were placed in an oven having a temperature of 180C for a period of 5 minutes. The baked coatings were thereafter visually observed and their appearance ~ -is noted in Table 2.
*(trade mark) Table 2 Rinsing Condition Appearance- . .
Rinsin~ Solution Time ~ of coated .
No. Aqueous solvent Concentration (Min.) film 7 Ethylene glycol 500 1 Good - No ::
cracking or blistering 8 Diethylene glycol 200 2 , monoethyl ether 9 Diethylene glycol monobutyl ether acetate 100 3 Dipropylene glycol 50 4 methyl ether 11 Dipropylene glycol 100 5 methyl ether 12 Tr-propylene glycol 200 2 methyl ether 13 2-ethoxy ethyl acetate 500 3 .
: :
~06~)Z87 EXAMPLE III
An aqueous coating composition was prepared containing the following:
Ingredients Amounts styrene butadiene copolymer sold under the trademark Goodright 1800X73 (pH 3.5 ' surface tension 70 dynes/cm 48% solids) 180 grams black pigment dispersion 5 grams ferric fluoride 3 grams hydrofluoric acid 2.3 grams water to make 1 liter A steel panel was immersed in the above aqueous coating composition for 90 seconds at ambient temperature.
After withdrawal from the coating composition, the coated panel was allowed to stand in air for a period of 60 seconds and thereafter was rinsed with running tap water.
Thereafter the coated panel was immersed for a period of 30 seconds in a solution comprising about 9 g/l of Na2Cr207.2H20. The coated panel was then baked for 10 minutes in an oven at 170C. The cured coating was visually observed and blistering was evident.
A second steel panel was immersed in the above coating composition, thereafter removed and allowed to stand in air for a period of 60 seconds, and then immersed in an aqueous rinse composition comprising 9 g/l of Na2Cr207.2H20 and 18.06 g/l of 2-butoxyethanol for a period of 30 seconds. Thereafter the coated panel was baked for 10 minutes in an oven at 170C. The cured coating was visually observed and was virtually free of blisters.
The rinse composition comprising butyl 2-butoxyethanol and Na2Cr207.2H20 appeared to substantially eliminate blistering.
~602~7 11767 EXAMPLE IV
An aqueous coating composition was prepared containing the following:
Ingredients Amounts styrene butadiene copolymer (sold under the trademark Darex 637) 180 grams black pigment dispersion 5 grams -ferric fluoride 3 grams hydrofluoric acid 2.3 grams water to make 1 liter Steel panels were prepared for coating to measure any blistering, bridging, or cracking by forming conex deformations on each panel by impactlng the panel surfaces with a one inch ball with a measured force. The impacted test panels were immersed in the above coating composition -for two minutes at ambient temperature. After withdrawal from the coating composition, the coated panels were allowed to stand in air for a period of sixty seconds and thereafter rinsed by immersion in tap water.
Thereafter, the coated panels were immersed in compositions indicated in Table IV. Control panels were immersed for a period of thirty seconds in an aqueous composition comprising about 2 gramstliter hexavalent ~`-chromium, about .9 grams/liter trivalent chromium and .6 grams/liter phosphoric acid. The composition is prepared by combining an aqueous solution of partially reduced (with formaldehyde) hexavalent chromium having phosphoric acid therein with an aqueous solution of soluble dichromate salt, such as Na2Cr207.2H20, Na2CrO4, NH4Cr207, or LiCr207.2H20, thereafter adding sufficient water to give the desired concentration of constituents. Test panels `
were immersed in particular compositions comprising the above chromium containing composition and having added thereto the particular materials indicated in Table IV, present in the amounts as indicated in Table IV. There-after, the coated panels were baked for five minutes in :
an oven at 215.5C. The cured coatings were visually -observed and the results are listed in Table IV below.
TAsLE IV
Concentration (~/1) Appearance Control Blisters over planar surface and bridging around impacted area Propylene glycol S0 Blisters over planar monomethyl ether (100% surface and bridging soluble in water and around impacted area boiling point 121C) Triethylene glycol (100~/D 50 No blisters soluble in water and boiling point 290C.) ____________________________________________________________________ .
Control Two large blisters on planar surface Propylene glycol 50 Bridging around impacted nomethyl ether area Triethylene glycol 50 No blisters or bridging ____________________________________________________________________ Control Bridging around entire impacted area Propylene glycol 100 Bridging around 2/3 monomethyl ether of impacted area _____________________________________________________________________ .
Control Three separate bridges 4 cm around impacted area .
Triethylene glycol 10 1.5 X 1.5 cm blister inside impacted area Triethylene glycol 30 No blisters or bridging Triethylene glycol 50 No blisters or bridging - :
Control Four separate 1 cm bridges Triethylene glycol 10 Four separate small bridges ~:
Triethylene glycol 30 One small bridge Triethylene glycol 50 No blisters or bridging ______________________________________________________________________ 24.
`- 1060287 11767 EXAMPLE V
An aqueous coating composition was prepared containing the following:
Ingredients Amounts styrene butadiene copolymer180 grams (sold under the trademark Darex 637) black pigment dispersion 5 grams ferric fluoride 3 grams hydrofluoric acid 2.3 grams water to make 1 liter Steel panels were prepared for coating to measure cracking. Control panels were immersed in the above coating composition for one minute at ambient temperature. After withdrawal from the coating composition, the coated panels were allowed to stand in air for a period of 60 seconds and thereafter were rinsed by immersion in tap water for 30 seconds.
The control panels were then immersed, for a period of 30 seconds, in an aqueous composition comprising about 2 grams/liter hexavalent chromium, .9 grams per liter `
trivalent chromium and .6 grams/liter phosphoric acid. ~, The composition was prepared as set forth in Example 4 ;-;~
combining an aqueous solution of partially reduced hexa-valent chromium with an aqueous solution of soluble dichromate salt. After immersion in the aqueous chromium containing composition, the control panels were air dried.
Test panels were immersed in the above coating composition for a period of 60 seconds at ambient tempera-ture. Ater withdrawal from the coating composition, the coated test panels were allowed to stand in air for a period of 60 seconds. Thereafter each test panel under-went a separate processing sequence as follows:
25.
106~287 11767 Test Panel No. 1 - immersed in an aqueous rinse composition comprising 20 grams/liter of diethylene glycol monobutyl ether acetate for a period of 30 seconds. After withdrawal from said composition, the panel was immersed in the above chromium containing composition for a period of 30 seconds. Thereafter, the panel was air dried.
Test Panel No. 2 - immersed in an aqueous composition comprising 30 grams/liter diethylene glycol monobutyl ether acetate for a period of 30 seconds. After withdrawal from said composition, the panel was immersed in the above chromium containing composition for a period of 30 seconds. Thereafter, the panel was air dried.
Test Panel No. 3 - immersed in tap water for a period of 30 seconds. After withdrawal from the tap water, the panel was immersed in an aqueous composition -comprising the above chromium containing composition having added thereto 20 grams/liter of diethylene glycol monobutyl ether acetate for a period of 30 seconds.
Thereafter, the panel was air dried.
The control panel and the test panels were visually observed for cracking and the results are listed in Table V below.
TABLE V ~-Panels A~earance Control Severe cracking of entire surface Test Panel #l No Cracks Test Panel #2 No Cracks Test Panel #3 No Cracks , , , :
-106~87 11767 EXAMPLE VI
An aqueous coating composition was prepared containing the following:
Ingredients Amounts styrene butadiene copolymer (sold under the trademark Darex 637) 180 grams black pigment dispersion 5 grams ferric fluoride 3 grams hydrofluoric acid 2.3 grams water to make 1 liter Steel panels were prepared for coating to measure blistering. Control panels were immersed in the above coating composition for 5 minutes at ambient temperature. After withdrawal from the coating composi- ;
tion the coated panels were allowed to stand in air for a period of 60 seconds and thereafter were rinsed by immersion in tap water for a period of 30 seconds.
The control panels were then immersed for a period of 30 seconds in an aqueous composition comprising 9 grams/liter of Na2Cr207.2H20. After withdrawal from the chromium containing composition, the control panel was :
placed in an oven for 10 minutes at 210C. After with-drawal from the oven, the coating was visually observed and a heat blister was present over the entire surface of the panel. Upon attempting to peel the coating from the surface, mechanically by scraping, 100% of the coating was removed.
Test Panel No. 1 was immersed in the above coating composition for a period of 5 minutes at ambient temperature. After withdrawal from the coating composition, 27.
.
, 106028'~ 11767 the coated test panel was allowed to stand in air for a period of 60 seconds and thereafter was rinsed by immersion in tap water for a period of 30 seconds. The test panel was then immersed for a period of 30 seconds in an aqueous composition comprising 9 grams/liter of Na2Cr207.2H20 and 20 grams/liter of diethylene glycol monobutyl ether acetate for a period of 30 seconds.
After withdrawal from said chromium containing composition, the test panel was placed in an oven for 10 minutes at ~10C. After withdrawal from the oven, the coating was visually observed and a heat blister was present over about 50% of the surface. Upon attempting to remove the coating, mechanically by scraping, the coating was peeled from about 50% of the surface, corresponding to the area where the blister had been evident. ~ -Test Panel No. 2 was immersed in the coating composition for 5 minutes at ambient temperature. After withdrawal from the coating composition, the coated panel was allowed to stand in air for a period of 60 seconds and thereafter was rinsed by immersion in tap water for 30 seconds. The panel was then immersed for a period of 30 seconds in an aqueous composition comprising 9 gramstliter of Na2Cr207/2H20 and 30 grams/liter of diethylene glycol monobutyl ether acetate for a period of 30 seconds. After withdrawal from the chromium containing composition, the panel was placed in an oven for 10 minutes at 210~. After removal from the oven, the coating was visually observed and was found to be uniform in appearance with no blister-ing evident. An attempt was made to remove the coating mechanically by scraping, and none of the coating could be removed and no loss of adhesion was evident.
28.
An aqueous coating composition was prepared containing the following:
~06()28~
styrene butadiene copolymerParts by Weight (Darex 673* sold by W. R. Grace) 200 hydrogen peroxide 3 hydrofluoric acid 4 tap water 800 The styrene butadiene copolymer is diluted with tap water to which the hydrogen peroxide and hydrofluoric acid is added with stirring.
Steel panels (Nos. 7-13) were immersed in the coating composition at room temperature for 3 minutes.
Thereafter the panels were withdrawn from the coating composition and permitted to stand for a period of 10 minutes. The panels were then immersed in particular aqueous rinse compositions, having constituent concentrations and for periods of time as indicated in Table 2 below. ~;
The panels were thereafter removed from the rinse compo-sitions and were placed in an oven having a temperature of 180C for a period of 5 minutes. The baked coatings were thereafter visually observed and their appearance ~ -is noted in Table 2.
*(trade mark) Table 2 Rinsing Condition Appearance- . .
Rinsin~ Solution Time ~ of coated .
No. Aqueous solvent Concentration (Min.) film 7 Ethylene glycol 500 1 Good - No ::
cracking or blistering 8 Diethylene glycol 200 2 , monoethyl ether 9 Diethylene glycol monobutyl ether acetate 100 3 Dipropylene glycol 50 4 methyl ether 11 Dipropylene glycol 100 5 methyl ether 12 Tr-propylene glycol 200 2 methyl ether 13 2-ethoxy ethyl acetate 500 3 .
: :
~06~)Z87 EXAMPLE III
An aqueous coating composition was prepared containing the following:
Ingredients Amounts styrene butadiene copolymer sold under the trademark Goodright 1800X73 (pH 3.5 ' surface tension 70 dynes/cm 48% solids) 180 grams black pigment dispersion 5 grams ferric fluoride 3 grams hydrofluoric acid 2.3 grams water to make 1 liter A steel panel was immersed in the above aqueous coating composition for 90 seconds at ambient temperature.
After withdrawal from the coating composition, the coated panel was allowed to stand in air for a period of 60 seconds and thereafter was rinsed with running tap water.
Thereafter the coated panel was immersed for a period of 30 seconds in a solution comprising about 9 g/l of Na2Cr207.2H20. The coated panel was then baked for 10 minutes in an oven at 170C. The cured coating was visually observed and blistering was evident.
A second steel panel was immersed in the above coating composition, thereafter removed and allowed to stand in air for a period of 60 seconds, and then immersed in an aqueous rinse composition comprising 9 g/l of Na2Cr207.2H20 and 18.06 g/l of 2-butoxyethanol for a period of 30 seconds. Thereafter the coated panel was baked for 10 minutes in an oven at 170C. The cured coating was visually observed and was virtually free of blisters.
The rinse composition comprising butyl 2-butoxyethanol and Na2Cr207.2H20 appeared to substantially eliminate blistering.
~602~7 11767 EXAMPLE IV
An aqueous coating composition was prepared containing the following:
Ingredients Amounts styrene butadiene copolymer (sold under the trademark Darex 637) 180 grams black pigment dispersion 5 grams -ferric fluoride 3 grams hydrofluoric acid 2.3 grams water to make 1 liter Steel panels were prepared for coating to measure any blistering, bridging, or cracking by forming conex deformations on each panel by impactlng the panel surfaces with a one inch ball with a measured force. The impacted test panels were immersed in the above coating composition -for two minutes at ambient temperature. After withdrawal from the coating composition, the coated panels were allowed to stand in air for a period of sixty seconds and thereafter rinsed by immersion in tap water.
Thereafter, the coated panels were immersed in compositions indicated in Table IV. Control panels were immersed for a period of thirty seconds in an aqueous composition comprising about 2 gramstliter hexavalent ~`-chromium, about .9 grams/liter trivalent chromium and .6 grams/liter phosphoric acid. The composition is prepared by combining an aqueous solution of partially reduced (with formaldehyde) hexavalent chromium having phosphoric acid therein with an aqueous solution of soluble dichromate salt, such as Na2Cr207.2H20, Na2CrO4, NH4Cr207, or LiCr207.2H20, thereafter adding sufficient water to give the desired concentration of constituents. Test panels `
were immersed in particular compositions comprising the above chromium containing composition and having added thereto the particular materials indicated in Table IV, present in the amounts as indicated in Table IV. There-after, the coated panels were baked for five minutes in :
an oven at 215.5C. The cured coatings were visually -observed and the results are listed in Table IV below.
TAsLE IV
Concentration (~/1) Appearance Control Blisters over planar surface and bridging around impacted area Propylene glycol S0 Blisters over planar monomethyl ether (100% surface and bridging soluble in water and around impacted area boiling point 121C) Triethylene glycol (100~/D 50 No blisters soluble in water and boiling point 290C.) ____________________________________________________________________ .
Control Two large blisters on planar surface Propylene glycol 50 Bridging around impacted nomethyl ether area Triethylene glycol 50 No blisters or bridging ____________________________________________________________________ Control Bridging around entire impacted area Propylene glycol 100 Bridging around 2/3 monomethyl ether of impacted area _____________________________________________________________________ .
Control Three separate bridges 4 cm around impacted area .
Triethylene glycol 10 1.5 X 1.5 cm blister inside impacted area Triethylene glycol 30 No blisters or bridging Triethylene glycol 50 No blisters or bridging - :
Control Four separate 1 cm bridges Triethylene glycol 10 Four separate small bridges ~:
Triethylene glycol 30 One small bridge Triethylene glycol 50 No blisters or bridging ______________________________________________________________________ 24.
`- 1060287 11767 EXAMPLE V
An aqueous coating composition was prepared containing the following:
Ingredients Amounts styrene butadiene copolymer180 grams (sold under the trademark Darex 637) black pigment dispersion 5 grams ferric fluoride 3 grams hydrofluoric acid 2.3 grams water to make 1 liter Steel panels were prepared for coating to measure cracking. Control panels were immersed in the above coating composition for one minute at ambient temperature. After withdrawal from the coating composition, the coated panels were allowed to stand in air for a period of 60 seconds and thereafter were rinsed by immersion in tap water for 30 seconds.
The control panels were then immersed, for a period of 30 seconds, in an aqueous composition comprising about 2 grams/liter hexavalent chromium, .9 grams per liter `
trivalent chromium and .6 grams/liter phosphoric acid. ~, The composition was prepared as set forth in Example 4 ;-;~
combining an aqueous solution of partially reduced hexa-valent chromium with an aqueous solution of soluble dichromate salt. After immersion in the aqueous chromium containing composition, the control panels were air dried.
Test panels were immersed in the above coating composition for a period of 60 seconds at ambient tempera-ture. Ater withdrawal from the coating composition, the coated test panels were allowed to stand in air for a period of 60 seconds. Thereafter each test panel under-went a separate processing sequence as follows:
25.
106~287 11767 Test Panel No. 1 - immersed in an aqueous rinse composition comprising 20 grams/liter of diethylene glycol monobutyl ether acetate for a period of 30 seconds. After withdrawal from said composition, the panel was immersed in the above chromium containing composition for a period of 30 seconds. Thereafter, the panel was air dried.
Test Panel No. 2 - immersed in an aqueous composition comprising 30 grams/liter diethylene glycol monobutyl ether acetate for a period of 30 seconds. After withdrawal from said composition, the panel was immersed in the above chromium containing composition for a period of 30 seconds. Thereafter, the panel was air dried.
Test Panel No. 3 - immersed in tap water for a period of 30 seconds. After withdrawal from the tap water, the panel was immersed in an aqueous composition -comprising the above chromium containing composition having added thereto 20 grams/liter of diethylene glycol monobutyl ether acetate for a period of 30 seconds.
Thereafter, the panel was air dried.
The control panel and the test panels were visually observed for cracking and the results are listed in Table V below.
TABLE V ~-Panels A~earance Control Severe cracking of entire surface Test Panel #l No Cracks Test Panel #2 No Cracks Test Panel #3 No Cracks , , , :
-106~87 11767 EXAMPLE VI
An aqueous coating composition was prepared containing the following:
Ingredients Amounts styrene butadiene copolymer (sold under the trademark Darex 637) 180 grams black pigment dispersion 5 grams ferric fluoride 3 grams hydrofluoric acid 2.3 grams water to make 1 liter Steel panels were prepared for coating to measure blistering. Control panels were immersed in the above coating composition for 5 minutes at ambient temperature. After withdrawal from the coating composi- ;
tion the coated panels were allowed to stand in air for a period of 60 seconds and thereafter were rinsed by immersion in tap water for a period of 30 seconds.
The control panels were then immersed for a period of 30 seconds in an aqueous composition comprising 9 grams/liter of Na2Cr207.2H20. After withdrawal from the chromium containing composition, the control panel was :
placed in an oven for 10 minutes at 210C. After with-drawal from the oven, the coating was visually observed and a heat blister was present over the entire surface of the panel. Upon attempting to peel the coating from the surface, mechanically by scraping, 100% of the coating was removed.
Test Panel No. 1 was immersed in the above coating composition for a period of 5 minutes at ambient temperature. After withdrawal from the coating composition, 27.
.
, 106028'~ 11767 the coated test panel was allowed to stand in air for a period of 60 seconds and thereafter was rinsed by immersion in tap water for a period of 30 seconds. The test panel was then immersed for a period of 30 seconds in an aqueous composition comprising 9 grams/liter of Na2Cr207.2H20 and 20 grams/liter of diethylene glycol monobutyl ether acetate for a period of 30 seconds.
After withdrawal from said chromium containing composition, the test panel was placed in an oven for 10 minutes at ~10C. After withdrawal from the oven, the coating was visually observed and a heat blister was present over about 50% of the surface. Upon attempting to remove the coating, mechanically by scraping, the coating was peeled from about 50% of the surface, corresponding to the area where the blister had been evident. ~ -Test Panel No. 2 was immersed in the coating composition for 5 minutes at ambient temperature. After withdrawal from the coating composition, the coated panel was allowed to stand in air for a period of 60 seconds and thereafter was rinsed by immersion in tap water for 30 seconds. The panel was then immersed for a period of 30 seconds in an aqueous composition comprising 9 gramstliter of Na2Cr207/2H20 and 30 grams/liter of diethylene glycol monobutyl ether acetate for a period of 30 seconds. After withdrawal from the chromium containing composition, the panel was placed in an oven for 10 minutes at 210~. After removal from the oven, the coating was visually observed and was found to be uniform in appearance with no blister-ing evident. An attempt was made to remove the coating mechanically by scraping, and none of the coating could be removed and no loss of adhesion was evident.
28.
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for treating a coated metal surface having thereon an uncured autodeposited coating formed by contacting said surface with an aqueous acidic coating composition containing a water dispersible resi-nous material which comprises contacting said uncured autodeposited coating with a coalescing agent with the result that blistering, bridging and cracking of said coating, after curing, is reduced.
2. A method as defined in Claim 1 wherein the coalescing agent is one having two or more oxygen containing functional groups selected from the group consisting of ester groups, ether linkages, hydroxy groups, and carbonyl groups.
3. A method as defined in Claim 2 wherein the coalescing agent is present in water in a concen-tration of at least 10 g/l.
4. A method as defined in Claim 2 wherein the coalescing agent is an alcohol having two or more hydroxy groups.
5. The method as defined in Claim 2 wherein the coalescing agent is a ketone having two or more carbonyl groups.
6. The method as defined in Claim 2 wherein the coalescing agent is selected from the group consisting of alcohol esters, ketone esters, ketone ethers and ester ethers.
7. The method as defined in Claim 6 wherein the coalescing agent is diethylene glycol monobutyl ether acetate.
29.
29.
8. The method as defined in Claim 6 wherein the coalescing agent is diethylene glycol monoethyl ether acetate.
9. The method as defined in Claim 6 wherein the coalescing agent is 2-ethoxy ethyl acetate.
10. A method for forming a corrosion resistant resinous coating on a metal surface comprising:
(a) contacting the surface with an aqueous acidic coating composition containing a water dispersible resinous material with the result that resin is deposited on the surface while said surface is contacted with the composition, the amount of resinous coating increasing during at least a portion of the time the surface is contacted with the composition.
(b) withdrawing the resinous coated surface from the aqueous acidic coating composition and treating the resinous coating with an aqueous rinse composition containing a coa-lescing agent wherein the amount of coalescing agent in said rinse composition is sufficient to reduce cracking, blistering, and bridging of said coating, after curing.
(a) contacting the surface with an aqueous acidic coating composition containing a water dispersible resinous material with the result that resin is deposited on the surface while said surface is contacted with the composition, the amount of resinous coating increasing during at least a portion of the time the surface is contacted with the composition.
(b) withdrawing the resinous coated surface from the aqueous acidic coating composition and treating the resinous coating with an aqueous rinse composition containing a coa-lescing agent wherein the amount of coalescing agent in said rinse composition is sufficient to reduce cracking, blistering, and bridging of said coating, after curing.
11. A method as defined in Claim 10 wherein said resinous coating is water rinsed prior to being contacted with a coalescing agent.
30.
30.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10403574A JPS5130245A (en) | 1974-09-09 | 1974-09-09 | METARUKOOTEINGUHOHO |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1060287A true CA1060287A (en) | 1979-08-14 |
Family
ID=14369960
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA235,044A Expired CA1060287A (en) | 1974-09-09 | 1975-09-09 | Metal coating method |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5130245A (en) |
| CA (1) | CA1060287A (en) |
| DE (1) | DE2540068C3 (en) |
| FR (1) | FR2283936A1 (en) |
| GB (1) | GB1498144A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6033492A (en) * | 1995-07-25 | 2000-03-07 | Henkel Corporation | Composition and process for autodeposition with modifying rinse of wet autodeposited coating film |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8411890D0 (en) * | 1984-05-10 | 1984-06-13 | Albright & Wilson | Dyeing processes |
| US4800106A (en) * | 1987-06-19 | 1989-01-24 | Amchem Products, Inc. | Gloss enhancement of autodeposited coatings |
| US4946711A (en) * | 1987-10-14 | 1990-08-07 | Desoto, Inc. | Masking compositions and method for applying the same |
| US4806390A (en) * | 1987-10-14 | 1989-02-21 | Desoto, Inc. | Masking compositions for chemical milling and method for applying the same |
| US5248525A (en) * | 1991-01-24 | 1993-09-28 | Henkel Corporation | Treating an autodeposited coating with an alkaline solution containing anions of multifunctional organic acids |
| US5164234A (en) * | 1991-01-24 | 1992-11-17 | Henkel Corporation | Treating an autodeposited coating with an alkaline solution containing organophosphonate ions |
| US6451383B2 (en) | 1996-08-06 | 2002-09-17 | The University Of Connecticut | Polymer-coated metal composites by dip autopolymerization |
| US6355354B1 (en) * | 1996-08-06 | 2002-03-12 | The University Of Connecticut | Polymer-coated metal composites by dip autopolymerization |
| US5807612A (en) | 1996-08-06 | 1998-09-15 | The University Of Connecticut | Method for coating metals by dip autopolymerization |
| AU3373600A (en) | 1999-04-28 | 2000-11-10 | Ecolab Inc. | Polymer surface coating made by coalescing polymer particulate with a coalescingagent |
| CN105086647A (en) * | 2015-08-03 | 2015-11-25 | 苏州舒而适纺织新材料科技有限公司 | Polystyrene multi-color coating |
-
1974
- 1974-09-09 JP JP10403574A patent/JPS5130245A/en active Pending
-
1975
- 1975-09-09 CA CA235,044A patent/CA1060287A/en not_active Expired
- 1975-09-09 DE DE19752540068 patent/DE2540068C3/en not_active Expired
- 1975-09-09 FR FR7527624A patent/FR2283936A1/en active Granted
- 1975-09-09 GB GB3694975A patent/GB1498144A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6033492A (en) * | 1995-07-25 | 2000-03-07 | Henkel Corporation | Composition and process for autodeposition with modifying rinse of wet autodeposited coating film |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2540068C3 (en) | 1980-02-21 |
| GB1498144A (en) | 1978-01-18 |
| DE2540068A1 (en) | 1976-04-08 |
| FR2283936B1 (en) | 1978-08-18 |
| JPS5130245A (en) | 1976-03-15 |
| DE2540068B2 (en) | 1979-06-21 |
| FR2283936A1 (en) | 1976-04-02 |
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