US3565782A

US3565782A - Electrocoating process

Info

Publication number: US3565782A
Application number: US635977A
Authority: US
Inventors: Felix Wehrmann
Original assignee: Stollack AG
Current assignee: Stollack AG
Priority date: 1966-05-03
Filing date: 1967-05-02
Publication date: 1971-02-23
Anticipated expiration: 1988-02-23

Abstract

A PROCESS FOR THE TRANSFER OF COATING MATERIAL INTO AN ELECTROCOATING BATH WHEREIN A COATED, SO-CALLED "TRANSFER ELECTRODE" IS IMMERSED IN AN ELECTROCOATING BATH AND THE COATING MATERIAL IS REMOVED FROM THE TRANSFER ELECTRODE AND APPLIED ONTO AN OPPOSITELY CHARGED ELECTRODE.

Description

' Fe 23, 19 1 F. WEHRMANN ELECTROCOATING PROCESS 3 Sheets-Sheet 1 Filed May 2, .1967

INVENTOR FELIX WEHRMANN av I ATTORNEYS Feb. 23, 1.971 F. WEHRMANN ELECTROCOATING} PhocEss 3 Sheets-Sheet 2 Filed May. 2. 1967 INVENTOR FELIX WEHR MANN BY HWWJM/M ATTORNEYS Filed May 2. 1967 $.Sheets-Sheet 8 INVENTOR FELI X WEHRMANN BY HIM xz'za ATTORNEYS United States Patent 3,565,782 ELECTRO0ATING PROCESS Felix Wehrmanu, Vienna, Austria, assignor, by mesne assignments, to Stollaek Aktiengesellschaft, Guntramsdorf, near Vienna, Austria, a corporation of Austria Filed May 2, 1967, Ser. No. 635,977 Claims priority, application Austria, May 3, 1966, A 4,180/ 66; Mar. 13, 1967, A 2,352/ 67; Apr. 28, 1967, A 4,002/67 Int. Cl. B0lk 5/02; C23b 13/00 US. Cl. 204-181 Claims ABSTRACT OF THE DISELOSURE A process for the transfer of coating material into an electrocoating bath wherein a coated, so-called transfer electrode is immersed in an electrocoating bath and the coating material is removed from the transfer electrode and applied onto an oppositely charged electrode.

PRIOR ART Up to now, automatically or semi-automatically controlled metering devices have been used to keep the solids content of electrocoating baths as constant as possible. However, these operations have not been sufficiently accurate because coating material to replenish that consumed are highly viscous pastes which have to be diluted with the bath liquor after metering thereof and before addition to the electrocoating bath. The amount of the coating material to be metered has to be readjusted each time to conform to the analysis of the solids content of the electrocoating bath and the resulting difiiculties and inaccuracies cannot guarantee a satisfactory operation. Moreover, such metering devices have a high initial cost and a high operating cost and call for exact chemical and physical analysis methods to ascertain the quantities of coating agent needed to regenerate the coating bath. Great analysis difficulties particularly arise in maintaining constant composition in electrocoating baths having a low solids content.

Another problem in electrocoating processes arises in the losses which occur in the washing step. When any type of article, such as an automobile body is lifted from the immersion electrocoating bath, a liquid film of the coating emulsion or dispersion adheres to the surface of the said article on to the coating applied to the article. This film has to be washed off before the drying and annealing process and the washing is usually accomplished in a wash tank equipped with overhead shower heads to facilitate the rinsing process. However, the rinsed off film contains all of the lacquer ingredients, pigments and coating agents used for the preparation of the electrocoating bath. Up to now, these wash waters were discarded into drains since the coating material was believed to be too greatly diluted for economical recovery thereof. The loss of these valuable, expensive ingredients not only considerably increases the cost of operation of an electrocoating plant, but the wash waters become so heavily soiled because the coating materials amount to about 2% by weight thereof that the main drains become clogged.

OBJECTS OF THE INVENTION It is an object of the invention to provide a novel process for introducing coating material into an electrocoating bath by means of a transfer electrode.

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It is another object of the invention to provide a novel process maintaining the solids content of an electrocoating bath constant in a simple manner.

It is a further object of the invention to provide a novel economical electrocoating process wherein excess coating material is recovered from the wash water.

It is an additional object of the invention to provide novel apparatus for maintaining the solids content of electrocoating baths constant without expensive metering devices.

It is another object of the invention to provide novel apparatus for recovering excess coating material from wash waters for reuse in the electrocoating process.

These and other objects and advantages of the invention will become obvious from the following detailed description.

THE INVENTION The novel process of the invention for transferring coating material into an electrocoating bath comprises immersing a transfer electrode coated with the coating material in an electrocoating bath and removing the coating agent from the transfer electrode and applying it to a counter electrode. With an anodically depositable coating material, the transfer electrode acts as a cathode in the electrocoating bath and with a cathodically depositable coating material, the transfer electrode acts as an anode in the electrocoating bath.

When using the process of the invention to maintain the solids content constant in an electrocoating bath without the use of metering devices the transfer electrode, which may be one or several electrodes, is immersed in a supply vessel containing additional coating material, an electric charge is applied to the transfer electrode so that the coating material is deposited on the transfer electrode, the transfer electrode is then immersed in the elec trocoating bath wherein the electrocoating material is removed from the transfer electrode and deposited on an oppositely charged electrode which may be the objects to be coated or a stationary electrode in the electrocoating bath. The surface area of the transfer electrode is such that the amount of the coating material transferred is sufficient to coat a predetermined number of articles.

The process may be effected in an anhydrous and/ or aqueous medium depending upon the type of coating material being employed. Therefore, both the supply bath and the electrocoating bath may be aqueous or anhydrous solutions, suspensions or dispersions of the coating material or one bath may be aqueous and the other bath may be anhydrous.

The composition of the coating material in the supply bath is selected so that the coating material removed from the transfer electrode in the coating bath has the same composition as that required as a feed solution. The solids content of the liquid coating compositions may be the same in both baths but a higher solids content is preferably maintained in the supply bath than that in the electrocoating bath. In the electrocoating bath, the solids content may be 0.1 to 45% by weight of the bath, but the solids content in the supply bath may be 0.1 to by weight. The transfer electrode may also be coated by various physical and chemical methods, such as immersion.

This process makes it possible for the first time to operate the electrocoating bath at a very low solids content since the composition thereof can be accurately controlled which reduces any loss of coating material during the rinsing process to a minimum not previously possible. An additional great advantage of the low solids content in the electrocoating bath is that it is constantly recycled whereby no decomposition reactions of the synthetic resin binders and the like will occur. Because fresh coating material equal to that applied to the oppositely charged electrode is being continuously supplied to the electrocoating bath, the pH value of the bath adjusts itself to an equilibrium due to the simultaneous addition and consumption of acids or bases present therein. Also, no care of the electrocoating bath or the replenishment of water or solvent is required. When a high content of organic solvent is used, it is possible to employ a coating material additive wtih a solids content of 70%.

The electrical circuits for the electrocoating bath and the supply bath for coating the transfer electrode may be operated separately or in series or parallel relation to each other. The voltages may range from 0.1 to 100,000 volts.

When using the process of the invention to recover coating material from the wash waters used to rinse the electrocoated objects before drying, a direct current is passed through the Wash waters having immersed therein a transfer electrode whereby coating material in the wash Water is deposited thereon and the coated transfer electrode is passed to the electrocoating bath wherein the voltage on the counter electrode is greater than that on the transfer electrode and the coating material is removed from the transfer electrode, and combines with the bath liquor. Again in this process, the transfer electrode acts as an anode or cathode in wash water and in the reverse sense in the electrocoating bath depending on whether the coat-' ing material is anodically or cathodically deposited. The opposite electrode in the electrocoating bath may be in the articles to be coated or a stationary electrode in the electrocoating bath.

The transfer electrodes in this process preferably have as large a surface area as possible due to the great dilution of the coating materials in the Wash water. The dimension of the transfer electrodes is more or less adapted to the width of the baths and the electrodes preferably have a grooved or corrugated net-like roughened surface. The transfer electrodes can be one or a series of plate electrodes or may be a continuous electrode with one loop of the electrode in the wash waters and a second loop of the electrode in the electrocoating bath.

This variation of the process of the invention has the advantage that all of the coating material is recovered from the wash water so that the discarded wash water is not polluted and otherwise lost coating material is recovered which greatly reduces the cost of the electrocoating operation.

When using a continuous transfer electrode, the applied voltages are selected so that the lowest voltage is applied to the 'wash bath or a counter electrode in the wash bath and the highest voltage is applied to the article to be coated which acts as the counter electrode in the electrocoating bath while the continuous moving electrode has a voltage between the two baths so that it will act as an anode in the wash bath and as a cathode in the electrocoating bath. Preferably, the voltage difference between the counter electrode in the wash tank and the continuous moving electrode and between the continuous moving electrode and the article to be coated is within the range of 150 to 200' volts. Therefore, the voltage on the counter electrode in the wash bath may be 0, the voltage on the moving electrode may be +150 to 200 volts and the voltage on the article to be coated may be +350 to 400 volts. However, by varying the circuit, the voltage on the counter electrode in the wash bath may be .15O to 200 volts, the voltage on the moving electrode may be and the voltage on the article to be coated may be +150 to 200 volts depending upon the requirement of the operation.

When using one or more individual transfer electrodes,

the application onto and removal of the coating material from the transfer electrode is preferably effected at the same voltage although a different voltage may be used to apply the coating material to the transfer electrode and preferably a lower voltage than that used to remove the coating material from the transfer electrode. Again, advantageous voltages are of the order of to 200 volts.

The apparatus of the invention for transferring coating material into an electrocoating bath is comprised of a coating bath, a washing device and a supply bath and at least one continuous transfer electrode which in cycles is coated with coating material in the supply bath and deposits the coating material in the coating bath. Preferably, there is a plurality of transfer electrodes.

The transfer electrodes may be grounded and the counter electrodes in the supply bath and in the coating bath are oppositely polarized and have a potential greater than zero, or the article to be coated in the coating bath may be attached to one pole of a direct current source, the transfer electrode may be fed by voltage division and the counter electrode in the supply vessel has a zero potential.

In one embodiment of the invention, the individual members of the apparatus are constructed or installed so that the full cross-sectional area of the immersion bath may be used for the coating of the various articles. The said apparatus is characterized in that it consists of two grounded suspension trolleys forming a common branch across two switch points which leads into the coating bath and across the said common branch, the articles to be coated and the large surface area electrodes which have been coated in the wash water collecting bath are individually conveyed into the coating tank. For technical reasons, the wash and rinsing baths should be disposed immediately adjacent to the coating bath to prevent the liquid film which adheres to the article after having been lifted out of the coating tank, from drying on the surface of said article. The gradually accumulating rinsing or wash water is pumped into a water collecting bath, after a certain concentration has been attained. One loop of the suspension trolley is guided into this tank which may be set up at any desired location, and the large surface area transfer electrodes are immersed in the wash water collecting tank by this loop.

The two switch points of the apparatus are constructed as pole selector switches, which has the effect that while passing the article to be coated across the first switch point, the electric selector switches of both switch points and the insulated electrodes in the coating bath are connected with one pole, for example, the negative pole of the rectifier aggregate. When the coated article leaves the immersion tank and passes over the second switch point, the electric selector switches of both switch points connect the electrodes with the other pole, for example, the positive pole of the rectifier aggregate. When immediately thereafter, a second article is to be coated, the process of switching will be repeated. However, when an electrode which has been coated in the wash water collecting tank is guided across the first switch point onto the common branch of the suspension trolley, the insulated electrodes present in the coating tank remain connected with the same pole, for example, the positive pole of the rectifier aggregate, so that the coating on the electrode can be removed in the coating tank and thus is recovered. When the large surface area transfer electrode, freed of the coating film, leaves the coating tank and passes across the second switch point the electrodes present in the coating vessel become connected again with the first pole, for example, the negative pole of the rectifier aggregate by means of the selector switches of the two switch points.

By this electrical switch operation, simple conductive suspension rods, in contrast to the previously used susgension rods equipped with insulating means, can be used for the conveyance of articles to be coated as well as of large surface area transfer electrodes. This means an additional, substantial simplification of the apparatus while at the same time guaranteeing absolute safety against electrical shocks by accidentally touching any of the individual elements of the apparatus.

To conduct the removal process in the wash water collecting bath in a static-free manner, the counter electrodes present therein, are enclosed in a well known manner in diaphragm cells. A further modification of the invention is not only to ground the two suspension trolleys, but also both baths as well as the neutral point of the rectifier aggregate of the alternating current. It is also advantageous to insulate, in the usual manner, the coating and the wash water collecting baths by coating the interior walls of these tanks in order to prevent any deposits of the coating material along these walls. Because of the very low concentration of the coating materials in the rinsing water, electrodes of the largest possible surface area are used for the recovery of the coating material. The dimension of the electrodes is adapted more or less to the dimension of a cross-section of the coating bath and these electrodes may have a corrugated, grooved, mesh-like roughened surface. These electrodes act in reverse sense to those in the coating tank.

Referring now to the schematic drawings:

FIG. 1 illustrates an embodiment of the invention in which the solids content of the electrocoating bath is maintained constant and the transfer electrode and article to be coated are immersed simultaneously in the electrocoating bath.

FIG. 2 illustrates an embodiment wherein the solids content of the electrocoating bath is maintained constant in which a counter electrode is employed in the electrocoating bath.

FIG. 3 illustrates an embodiment of the invention wherein the coating material from the wash waters is transferred to the electrocoating bath by means of a moving, continuous electrode.

FIG. 4 illustrates an embodiment of the invention wherein the coating material is transferred from the wash water to the electrocoating bath by transfer electrodes which pass alternatively into the electrocoating bath with the article to be coated.

In the embodiment of FIG. 1, the apparatus is comprised of an electrocoating bath 3 and a supply bath which are connected by a continuous suspension trolley 1 which conveys transfer electrodes 2 on insulated suspension rods. The transfer electrodes 2 are movably spaced at such a distance from one another that when one uncoated transfer electrode 2 is immersed in supply bath 4 provided with counter electrode 4a, a coated transfer electrode 2 is immersed in electrocoating bath 3 and a third coated transfer electrode 2 is simultaneously washed in a rinsing device 6. Simultaneous with the immersion of transfer electrodes 2 in the supply and electrocoating baths, an article 5 to be coated is conveyed by suspension trolley 7 for immersion of the article 5 in the electrocoating bath. The electric current is applied so that the uncoated transfer electrode 2 in the supply bath 4 acts as an anode with counter electrode 4a acting as the cathode whereby the said transfer electrode is coated with the coating material while the coated transfer electrode '2 in the electrocoating bath 3 acts as a cathode with the article 5 to be coated acting as an anode. This permits the same amount of coating material to be added to the electrocoating bath from transfer electrode 2 as is being removed therefrom by deposit on the article 5 to be coated. By regulating the removal of the coating material from the transfer electrode 2, the transfer electrode 2 can supply to the electrocoating bath a sufficient amount of coating material to coat one or more articles 5 to be coated. If more than one article 5 is to be coated by one transfer electrode 2, the transfer electrodes 2 are preferably provided with a serrated, net-shaped or roughened surface so that the surface area of the electrode 2 is large.

In the embodiment of FIG. 2, the transfer electrode 2 is not immersed in the electrocoating bath simultaneously with the article 5 to be coated and the electrocoating bath is provided with counter electrodes 8. The transfer electrodes 2 again are transported on insulated suspension rods on suspension trolley 1 from supply bath 4 through rinsing device 6 to electrocoating bath 3. The coating material is removed from a coated transfer electrode 2 in the electrocoating bath 3 and transferred to stationary counter electrodes 8. After removal of transfer electrode 2 from the electrocoating bath 3, the article 5 to be coated is conveyed by suspension trolley 7 to electrocoating bath 3. The direction of the electric current in the electrocoating bath is reversed whereby the coating material is transferred from stationary electrodes 8 onto the article 5. The number of transfer electrodes 2 may be greater or less than the three shown in FIGS. 1 and 2 and the transfer electrodes may be coated by a con venient means, such as, electrocoating baths, immersion means and other chemical and physical coating means.

In the apparatus of FIG. 3, the article 11 to be coated is immersed in the coating composition 10 in elcctro coating bath 9 by means of trolley 11a whose guide rail is connected to the positive pole of the direct current source supplying 400 volts. After the coating operation is completed, the article 11 is removed from the electrocoating composition and passed through wash tank 12 where under currentless conditions it is freed of any still adhering coating composition by being passed under sprayer 18. The rinsed off coating composition accumulates in wash waters 13 in wash bath 12 and the wash waters 13 have to be drained off after a short period of operation.

A continuous metal electrode in the form of a band, chain or mesh is guided by means of guide pulleys 14 and 15 so that one loop 16 of the electrode is immersed in wash bath 12 while the loop 17 is immersed in the electrocoating bath 9 and the continuous electrode is driven by operating pulley 15. In this illustration, the continuous electrode is fed with a R-R positive direct current of about 200 volts by a voltage divider, whereas the wash tank or a counter electrode present in the said tank shows the zero potential. The voltage difference between zero and 200 volts is adequate to deposit the valuable coating material present in wash waters 13 on the continuous moving electrode. When this coating material arrives in the electrocoating bath, the voltage difference in relation to the article to be coated, which is again about 200 volts, which causes the coating material to become detached. These detached coating materials then become dispersed in the electro-immersion bath and are conveyed from these onto the article to be coated.

In the embodiment of FIG. 4, the coating bath 19 is provided with a common branch 2122 of two grounded suspension trolleys 21 and 22 leading into the said tank 19. The two switch points 25 and 25' are developed as pole selector switches which are circuit connected in a synchronized manner. One branch of the suspension trolley 21 leads into the wash water collecting bath 20 wherein electrodes 29 are arranged in diaphragm cells. When an article 24 to be coated is conveyed via the trolley '22 across the first point 25 the insulated electrodes 28 present in the coating tank 1 are, by means of the pole selector switches of the two switch points 25 and 25, connected via the circuit 31 with the negative pole 33 of the rectifier aggregate of the alternating current, whereby the grounded article 24 acts as an anode and is coated. 'When the coated article 24 leaves the immersion bath 19, the electrodes 28 in the coating bath 19 are, while passing the second switch point 25', connected by means of the pole selector switches via the circuit 31 with the positive pole 32 of the rectifier aggregate of the alternating current. Now, either the next article 24 to be coated can be conveyed into the coating bath 19 with a repeating of the switching operation as described, or a large surface area electrode 23 which has been coated in the wash water collecting bath 20, can be moved across the first switch point 25 into the coating bath 20. The two pole selector switches leave the electrodes 28 connected with the positive pole 32 of the rectifier. When the electrode 23, 23 has been freed of the adherent coating material and has left the said bath 19 and has crossed the second switch point 25, then the electrodes 28 are connected With the negative pole 33 by the pole selector switches.

The articles 24, upon leaving the coating bath 19, are freed of any adherent liquid coating film by passing under the water jets 30 disposed above rinsing bath 26. After a predetermined concentration of the coating material is attained in the wash water, this 'water is conveyed by pump 27 into wash water collecting bath 20, wherein the large surface area electrodes 23 are coated, to recover the coating materials. When using cathodically removable binding agents, the circuit arrangement may be effected so that the article 24 to be coated acts as an anode in immersion bath 19 and so that the large surface area electrodes 23 act as anodes in immersion bath 19 and as cathodes in wash water collecting bath 20.

In the following examples there are described several preferred embodiments to illustrate the invention. However, it should be understood that the invention is not intended to be limited to the specific embodiments.

EXAMPLE I A coating composition concentrate was prepared from 34 parts by weight of aluminum silicate pigment, 13 parts by weight of barium chromate, 45 parts by weight of titanium dioxide, 3 parts by weight of talc and 420 parts by weight of Resydrol E 450 (83% water-soluble, heathardenable electrophoresis resin). The said concentrate was diluted with water to a solids content of 10% by weight and was used in the supply bath and the coating bath of FIG. 1 with a voltage of 15 volts in both baths.

EXAMPLE II 15 parts by weight of acrylamide were dissolved in 70 parts by weight of butanol and then 8 parts by weight of acrylic acid, 25 parts by weight of styrene, 25 parts by weight of butyl acrylate, 27 parts by weight of ethyl acrylate, parts by weight of dodecyl mercaptan and 1 part by weight of di-tert.-butyl peroxide were added there to. One portion of the mixture was heated to effect polymerization and when reflux temperatures were reached, the rest of the mixture was added over a period of 2 to 3 hours. The degree of polymerization was controlled by the solids content. After polymerization \was complete, 12.7 parts by weight of formaldehyde were added to the clean, viscous solution and the reaction mixture was maintained at reflux until no more water of reaction was formed (2 to 3 hours). A portion of the butanol was removed by vacuum distillation and the solution was concentrated as much as possible. The resulting resin, after neutralization with dimethyl ethanolamine was watersoluble and was diluted with water to a concentration of 60%.

A coating composition was prepared from 835.0 gm. of a 60% solution of the said resin, 57.0 gm. of aluminum silicate, 19.4 gm. of molybdate orange, 15.1 gm. of Permanent violet MR, 5.8 gm. of iron oxide red, 3.6 gm. of titanium dioxide and 64.1 gm. of water. The concentrate wate diluted with a 70:30 mixtures of ethanol and isopropyl glycol. In the coating bath of FIG. 1, the solids content of the coating composition was 20% and the voltage was 140 volts and the solids content in the supply bath was 50% and the voltage was 90 volts.

EXAMPLE III The concentrate of Example I was diluted with water to a solids content of 20% by weight for the coating composition in the supply bath of FIG. 1 operated at a voltage of 60 volts and to a solids content of 1% by weight in the electrocoating bath operated at a voltage of 180 volts.

EXAMPLE IV A concentrate consisting of 3.5 parts by weight of carbon black, 11 parts by weight of barium sulfate, 3 parts by weight of talc, 19.0 parts by weight of butyl glycol, 4 parts by weight of nonanol, 12 parts by weight of water and 40.8 parts by weight of Resydrol P 410 (a watersoluble plasticized, heat hardenable phenol resin) was diluted with a 20:80 mixture of ethylene glycol and ethanol. The supply bath of FIG. 1 had a solids content of 40% and was operated at volts while the electrocoating bath had a solids content of 80% and was operated at a voltage of 280 volts.

EXAMPLE V A coating material concentrate consisting of 35 parts by weight of lithopone, 3 parts by weight of tale, 9 parts by weight of butyl diglycol, 3 parts by weight of ethylene glycol, 9 parts by Weight of water and 34 parts by weight of Resydrol M 490 (a water-soluble, plasticized, heathardenable melamine resin) was diluted with ethanol. The supply bath of FIG. 1 had a solids content of 5% by weight and was operated at volts while the electrocoating bath had a solids content of 0.5 by weight and was operated at 150 volts also.

EXAMPLE VI A coating bath concentrate consisting of 3 parts by weight of carbon black, 2 parts by weight of strontium chromate, 6 parts by weight of butyl glycol, 7 parts by weight of methylene glycol, 0.2 part by weight of diethylamine, 20 parts by weight of water and 60 parts by weight of Resydrol P 410 (water-soluble, plasticized, heathardenable phenol resin) was diluted with ethanol to a solids content of 40% for use in the supply bath of FIG. 1 operated at 80 volts. The same concentrate without strontium chromate resin was diluted with water to a solids content of 10% for the electrocoating bath operated at 150 volts. The excess coating material in the rinse water could be removed using the process exemplified by FIGS. 3 and 4 and the solids content in the rinse water bath should be about 0.2 to 5.0%.

Various modifications of the process and apparatus of the invention may be made without departing from the spirit or scope thereof.

I claim:

1. A process for transferring non-conductive coating including a non-ionizable, electrophoretic, polymeric material into an electrocoating bath comprising substantially the same polymeric material which comprises immersing a transfer electrode coated with said coating into an electrocoating bath and removing said coating from the transfer electrode and applying it to a counter-electrode.

2. The process of claim 1 wherein the transfer electrode is coated in a supply bath.

3. The process of claim 2 wherein the transfer electrode acts as anode in one of the baths and as a cathode in the other bath.

4. The process of claim 3 wherein the deposit onto and removal of the coating material from the transfer electrode is eifected at a voltage of 0.1 to 100,000 volts.

5. The process of claim 3 wherein the coating material is deposited on a continuous electrode as it passes through the supply bath and is removed from the continuous electrode as it passes through the electrocoating bath.

6. The process of claim 3 wherein there is at least one transfer electrode which is conveyed via a suspension trolley from the supply bath into the electrocoating bath and back again.

7. The process of claim 3 wherein the articles to be coated in the electrocoating bath act as counter-electrodes to the transfer electrode.

8. The process of claim 3 wherein stationary electrodes in the electrocoating bath act as counter-electrodes to the transfer electrode.

1 2,453,757 11/1948 Renzoni 2o4-49 9. The process of claim 3 wherein the solids content of the coating composition in the electrocoating bath is between 01-45% by Weight.

10. The process of claim 3 wherein the solids content of the coating composition in 'the supply bath is between 0.170% by Weight.

References Cited UNITED STATES PATENTS 8/1965 Burnside et al 204-181 US. Cl. X.R.