US3159558A - Process for electro-deposition of bituminous materials - Google Patents

Description

United Sta Pa en 9559*? asserts? t as Des 1 3,159,558 PROCESS FOR ELECTRfi-DEPQI'IHGN F BlTUMlNOUS MATERIALS Paul E. McCoy, Oakland, Calif, assignor to American Bitumuls 8: Asphalt Company, San Francisco, alif.,

a corporation of Delaware No Drawing. Filed Aug. 26,1960, Ser. No. 52,il64 8 Claims. ((11.204-481) This invention relates to a process of electro-depositing bituminous materials on metal surfaces so as to produce a uniform coating of bitumen thereon. More particularly, it relates to a process of electro-depositing bituminous materials such as asphalts, tars, pitches, and the like on the interior of metal tanks which serve to store water and other aqueous media, and of metal pipes which serve to conduct water and sewage and other kinds of aqueous eflluents, for the purpose of protecting these tanks and pipes against deterioration, corrosion, tuberculation, etc. It has been proposed in the past to rehabilitate and to protect internal surfaces of pipe-conduits and, in particular, of water mains and sewage lines by electro-depositing on their internal surfaces a thin coating or layer of a bituminous material, such as an asphalt, the metal surface to be coated forming the anode of the system. In such a system, a buried length of pipe to be reconditioned and coated constitutes the anode, while a metal (e.g., copper) electrode centered inside the pipe performs the function of the cathode by travelling through an anionic bituminous emulsion which fills the pipe and forms the electrolyte.

However, despite the relative effectiveness and speed of the aforementioned pipe rehabilitation treatment, certain disadvantages have been observed in its application. These disadvantages are ascribed to the particular nature of anionic type bituminous emulsions. It has been found that to effect a satisfactory coating with bitumen when employing anionic emulsions thereof, relatively high concentrations of certain inorganic and organic salts devoid of surface activity and acting as metal-sequestering agents, for instance, tetra-sodium pyrophosphate, ethylene diamine tetra-acetate and the like, have to be added to the bituminous emulsion medium. The presence of these high concentrations of salts insures a longer period for the electro-deposition of bitumen, and thus permits a heavier deposit thereof. Also, the coating or film which results from the application of anionic bituminous emulsions tends to have a sponge-like structure, filled with bubbles which are apparently caused by the high evolution and occlusion of gas during the electrolysis.

' pore-hour.

Eventually these bubbles become ruptured and bare metal spots appear on the internal bitumen-coated surface of the pipe.

I have now discovered that these drawbacks can be substantially eliminated and a uniform, smooth, adherent and strong coating of bitumen obtained on the surface of metal by employing cationic bituminous emulsions instead of anionic emulsions for depositing bitumen electrolytically onto metal surfaces, and, particularly, for coating interior surfaces of the metal pipes used to convey aqueous effluents. In cationic bituminous emulsions, as distinguished from anionic bituminous emulsions in which the emulsified droplets of bitumen bear a negative charge, the emulsified droplets of bitumen (the dispersed phase) carry a positive charge owing to the use of cation-active emulsifying agents, the oil-soluble portion of which is.

metal soaps as emulsifiers (of with alkali metal emulsifying bases if the bitumen is inherently acid).

According to my invention, it is now possible to produce efiiciently and economically a uniform, smooth, adherent, continuous, durable film of a bituminous material on a metal surface, which may be a plate, a rod or the interior surface of a buried pipe serving to transport Water or other aqueous eflluents by electro-depositing bitumen onto such surface from a cationic bituminous emulsion.

As a matter of fact, thermoplastic resins, for instance, polyvinylidene chloride, polystyrene, alkyd resins, acrylic resins and the like, so long as they can be emulsified to form a cationic emulsion, may be similarly electro-deposited onto metal surfaces in accordance with the process of the present invention.

The emulsion to be employed in the electro-deposition process of this invention is prepared in a known manner by emulsifying a bituminous material, for instance, an asphalt, in water with the aid of cation-active emulsifying agents. Preferably, these emulsions are diluted with water to contain from about 10 to about 30% by weight of the bitumen to assure economic operation of the electrodeposition process.

The cleaned metal surface to be treated is thoroughly contacted with such an emulsion by being immersed therein or, when the length of pipe intended for rehabilitation and coating is suitably sealed on one end, by filling its interior with the emulsion. The leads from a source of direct electrical current, such as a dynamo or a storage battery, are fastened: (l) the negative lead to the metal surface, or to a metal pipe, making it the cathode and (2) the positive lead to an appropriately designed metal electrode, for instance, one made of copper, which is immersed into the emulsion bath, or travels inside the pipe, and acts as the anode. An ammeter is inserted in the resulting electrical circuit, and the current is passed therethrough until the ammeters reading drops to zero, indicating that the coating of the metal surface with bitumen is complete. Voltages up to about volts are satisfactory for all practical purposes.

Quite significantly, employment of cationic bituminous emulsions according to the invention does not require addition of auxiliary salts, such as tetra-sodium pyrophosphate or ethylene diamine tetra-acetate, to assure deposition of an adequate coating of bitumen on the metal, and permits a higher rate of deposition per am- Thus, both the time and the quantity of electricity required for the coating treatment are considerably reduced. Furthermore, because the evolution of gas at the electrode is less than that occurring in the treatment with anionic emulsions, the resulting coating or film of bitumen is more uniform and smooth, so that less pitting, if any, takes place.

Any suitable bituminous material may be employed as the disperse phase in the cationic emulsions for use in coating metal surfaces according to the present invention,

and, although the operativeness of theinvention is illustrated in the present description by examples performed with emulsified asphalt which happened to be readily available for tests, other bitumens and thermoplastic resins, such as coal-tar, pitch, gilsonite, acrylic resins, alkyd resins, polystyrene, and the like, can be similarly electro-deposited. Asphalts and tars of all kinds, steam refined, air blown, etc., may be thus employed, provided they lend themselves to emulsification in water with the aid of cation-active emulsifiers, so as to impart an acid pH to the corresponding emulsion, namely, from about 2.0 to about 6.0, and preferably from about 3.0 to about 6.0. As already indicated, the concentration of the bituminous material in the emulsion employed as the electrolyte should preferably range from about 10 to about 30% by weight. This concentration is achieved either by virtue of original emulsification in water with a cationic emulsifier or by way of dilution of a more concentrated cationic emulsion, for instance, one containing from 55 to 70% of asphalt in the bituminous phase, to the aforementioned to 30% by weight range. In general, so long as a cationic emulsion, whether diluted or not, possesses adequate mechanical stability (i.e., while in storage and being handled prior to actual use), normally desired and displayed by conventionally prepared cationic bituminous emulsions, and remains stable at least one week after emulsification, and so long as it is capable of being pumped, it may be employed in the process of this invention.

The emulsified bitumen should have a sufiiciently fine particle size, preferably in the range from about 0.25 to 10.00 microns in order to facilitate pumping and to prevent settling on dilution with water.

Any cation-active material which would emulsify a bitumen in Water to form a pumpable emulsion of adequate mechanical stability, which emulsion, in turn, would provide at least from about 10 to about 30% by weight concentration of bitumen in the electrolyte fluid, may be employed as the emulsifier. Preferably, such emulsifiers are cation-active nitrogen-containing salts. Most desirable are cation-active salts of alicyclic and cyclic amines, salts of quaternary ammonium bases and salts of organosubstituted heterocyclic nitrogen bases, such as pyridinium salts, quinolinium salts, isoqu inolinium salts, piperidinium salts, imidazolinium salts, morpholinium salts and salts of other like quaternary nitrogen-containing bases. Specific examples of such emulsifiers are, for instance:

N,N-dimethyl-N-benzyl-N-octadecyl ammonium chloride N,N-dimethyl-N-hydroXyethyl-N-dodecyl ammonium chloride N,N-dimethyl-N-benzyl-N-octadecenyl ammonium chloride N,N-dimethyl-N-benzyl-N-dodecyl ammonium chloride N,N-dimethyl-N-hydroxyethyl-N-benzyl ammonium chloride Hexadecyl pyridinium chloride Hexadecyl triethyl ammonium bromide Octadecylbenzyl trimethyl ammonium methosulfatc Isopropylnaphthyl trimethyl ammonium chloride Octadecyl pyridinium bromide 1-(2-aminoethyl)-2-heptadecenyl imidazolinium chloride l- 2-hydroxyethyl -2-heptadecenyll- (4-chlorobutyl) imidazolinium chloride Hexadecyl methyl piperidinium methosulfate Dodecyl hydroxyethyl morpholinium bromide Particularly effective emulsification is obtained with those quaternary nitrogen-containing emulsifier salts, in which the active cationic component contains at least a long aliphatic hydrocarbon chain or other equivalent hydrocarbon radical of not less than 12 and not more than 24 carbon atoms.

The following examples are offered to illustrate the operation of the process of the present invention and to bring out with greater clarity the advantages thereof as contrasted with the prior practices of electro-depositing bitumens from anionic emulsions.

EXAMPLE 1 Short sections of 2 inch pipe'were subjected to the electro-deposition treatment in accordance with the invention. The bottom of each pipe has been sealed by a recessed rubber base. One lead from a source of direct electric current (a small dynamo) was fastened to the pipe, making the latter either the anode (in the case of anionic emulsion) or the cathode (in the case of cationic emulsion). The other lead was connected to a copper electrode placed in the center of the pipe filled with an Water /3 emulsion to /3 of water).

asphalt emulsion, diluted with water to /3 of its normal concentration. An ammeter provided indications as to the completeness of the treatment. The difference of potential between the electrodes was 40 volts. After the completion of the treatment, each pipe section was flushed with water to wash off any emulsion which was not completely deposited on the interior surface. In the run with anionic asphalt emulsion, this latter has been prepared by dispersing 200-250 penetration asphalt in water with the aid of a conventional alkali metal emulsifying base (KOl-l) which formed the necessary emulsifying soap with the asphaltogenic acids of the asphalt. The resulting emulsion was of the RS-l type and contained about 60% by weight of asphalt. It was diluted with water to A of its concentration, i.e., 20%. The film of asphalt which resulted from electro-deposition was, however, spongy and interspersed with bubbles. Bare metal spots appeared eventually, when these occluded gas bubbles ruptured. Gn flushing the pipe immediately after the electrodeposition treatment, a large amount of undeposited emulsion was observed to have been carried off by the flushing water.

In a parallel run, a cationic emulsion has been prepared by dispersing the same 200-250 penetration asphalt in water with the aid of a cation-active emulsifier salt, namely, N-dodecylbenzyl-N,N-diethyl-N-ethanol ammonium chloride (available in the trade under the trademark ADE-50), and diluting the resulting emulsion with In this instance, upon completion of the electro-deposition treatment, the interior of the pipe was found to be coated with a smooth, adherent continuous film. Only a slight discoloration could be noted in the water used to flush the pipe immediately after the treatment. Furthermore, the time which was required to coat the pipe was considerably less than the time required in the run with the anionic emulsion.

The results of similar comparison tests in which anionic and cationic bituminous emulsions were used to fiH longer lengths of pipe of large diameter (5") were equally conclusive of the superiority of cationic emulsions over the anionic ones for the process of the electro-deposition.

EXAMPLE 2 Another series of tests served to illustrate the operativeness of the process according to the invention and, furthermore, showed that this process is not limited to coating by electro-deposition of interior surfaces of pipe-conduits but can be equally successfully applied to any metal surfaces, such as panels and plates, including also metal rods and wires, such as are used for prestressed concrete work, for coating the interior of Water tanks, etc.

In this series, a weighed steel panel was immersed into a bath which contained an asphalt emulsion (anionic or cationic). In the runs with anionic emulsions, the positive Wire lead from a generator of direct electric current was clamped to the panel, while a metal plate connected to the negative lead was immersed into the emulsified asphalt electrolyte. After completion of the electrodeposition treatment, the panel was washed, dried and reweighed. Thereupon, a second metal panel was placed into the emulsion bath, and the treatment repeated. In the runs with cationic emulsions, the wire lead connectrons were reversed. The anionic emulsion used in this series had the following composition.

I presence of tetrasodium pyrophosphate.

The cationic emulsion had the following composition:

Percent Asphalt, 200-250 penetration of Venezuelan origin 20 N dodecylbenzyl N,N diethyl N ethanol ammonium chloride (ADE-50) Ammonium chloride 0.01 Water 79.66

Five runs were carried out with each of the two aforementioned emulsions, the cationic one at a pH of 3.0 and the anionic one at a pH of 9.2. In all runs, the difference of potential between the electrodes was 40 volts. In addition, a number of runs were carried out with the same kind of cationic emulsion but having pH values from 5.4 to 4.5. The results of this series of tests are shown in the following Table I.

Table 1 Maxi- Final Total Asphalt Emulsion Type pH mum Current Time Deposited Current (amps) (minutes) in g./sq. (amps) in./min.

Anionic 9. 2 1. 4 0. 25 3. 0. 034 9. 2 l. 0. 2. 75 0. 034 9. 2 1. 2 0. 3.0 0.036 9. 2 1. 3 0. 10 3. 0 0. 029 9. 2 1. 2 0. 10 2. 5 0.026 Cationic 5. 4 0. 10 0. 05 1. 0 0.082 5. 0 0. l0. 0. 10 2.0 0.070 4. 5 0.05 0. 01 5. 0 0. 048 Cationic 3.0 0. 30 0. 02 3.0 0. 076 i 3.0 0. 30 0. 01 3.0 0. 070 3. 0 0. 2O 0. 01 3.0 0. 067 3.0 0. 0. 01 3.0 0. 075 3. 0 O. 0. 01 3. 0 0. 073

It will be observed from the data in the table that the initial current required for the electro-deposition from the anionic emulsion is much higher than the current required for the deposition of asphalt from the cationic emulsion. The exact reason for this occurrence is not entirely clear, but the phenomenon probably reflects the fact of a greater concentration of ions in the anionic emulsion due to the Because more electricity was thus consumed and less asphalt was deposited per sqaure inch of the surface per minute, a

greater quantity of gas must have been evolved. In all runs, the-rate of asphalt deposition from the cationic emulsion is about twice as high as the rate observed with the anionic emulsion.

EXAMPLE 3 In still another series of tests, various cationic'asphalt emulsions were tested as electrolytes for the effective 6 emulsion at a fixed distance of separation between them. The surface area of the iron electrode was 2.19 sq. in. The voltage was so adjusted that the initial current passing through the system was 5.5 ma. In each run, the time during which the current intensity dropped to 1 ma. was recorded. If the intensity did not so drop after 30 minutes, the test was stopped, and the final current reading noted. The iron electrode on which the asphalt deposited itself Was weighed before the test. When the 10 deposition was terminated, the electrode was removed, washed in a gentle stream of water until the water was clear, dried on a hot plate and reweighed.

The emulsions employed, designated A, B, C, D, and E had the following compositions.

15 Emulsion A (anionic):

Asphalt, 200-250 penetration, of

Percent by weight Venezuelan origin 64 KOH 0.12 Pine-wood resins 0.025

20 Water Balance to 100.00

sion A 68 Octadecenyl methyl di-Z-hydroxyethyl ammonium chloride emulsifier 0.1 Water Balance to 100.00

The emulsifier is available in the trade under the trade mark Ethoquad 0-12. Emulsions D and E (both cationic) were similar to Emulsion B, except that the quantity of the imidazoline component, instead of 0.2%

by weight was 0.3% for Emulsion D and 0.4% for Emulsion E.

Table II Quantity Wt. of Wt. of Wt. of Time Average of Elec- Asphalt Asphalt Asphalt Emulsion (see) Current tricity per s per sq. in. per sq in (ma.) (ma-sec.) in. (g. per am per sec sec. (g. (g.)

Anionic 1, 800 3. 25 5, 850 0. 27 0. O5 0. 00015 Cationic-0.2% Nalcamine 28. 8 3. 25 93 0.03 0.32 0.0011 Cationic-0.3% Nalcamin 164. 8 3. 25 535 0. 22 0. 41 0. 0013 Cationic-0.4% Nalcamin 241 3. 25 783 0. 26 0. 33 0. 0011 OationieEtl1oquad 1, 800 3. 7 6, 660 2. 66 0. 40 0. 0015 The data in the table clearly show the superiority of cationic emulsions over the anionic ones. From six to eight times as much asphalt is deposited per ampereecond as in the case of anionic emulsions. Also, the rate of asphalt deposition is seven to ten times higher than in the case of anionic emulsions.

Although the invention as described is illustrated by examples and experimental data obtained in using asphalt emulsions, it is to be understood that cationic emulsionsof other bituminous materials, and thermoplastic resins, such as gilsonite, pitch, coal-tar, petroleum Wax, various acrylic and alkyd resins, and the like, can be similarly employed for electro-deposition onto metal surfaces, provided that these materials possess an adequate adhesion property to assure the permanency of the deposited film.

The aforegiven description and the experimental data point out convincingly that a new, effective and improved process for electro-deposition of bituminous materials and thermoplastic resins has been provided by the invention, permitting efiective deposition of bituminous or resinous: films from cationic emulsions on various metal surfaces, and, in particular, on the interior of pipeconduits and tanks for conveying and containing Water and other aqueous media.

Of course, the above description and examples servesolely to illustrate the invention, and, consequently, any variation thereof apparent to those skilled in the art are includible in the scope of the following claims.

I claim:

1. A process for electro-depositing on a metal surface an asphalt from a cationic emulsion thereof in water, containing a cation-active emulsifying halide salt of a quaternary nitrogen-containing base selected from the group consisting of quaternary ammonium bases and organo-substituted heterocyclic nitrogen bases and characterized by the presence of a long (Z -C aliphatic hydrocarbon chain in its cation-active portion, said emulsion having a pH from about 2.0 to about 6.0 and consisting essentially of from about to about 30% by weight of an asphalt, sufficient amount of said cation-active quaternary nitrogen-containing salt for emulsifying the asphalt in water and to form a pumpable, mechanically stable emulsion, and water in an amount to make up 100% by weight; the process comprising thoroughly contacting a metal surface with said emulsion and passing a direct electric current therethrough at an average density of at least about 2.5 milliamperes per square inch and in such a direction that the metal surface to be treated constitutes the cathode, whereby a uniform film of asphalt is deposited thereon.

2. A process for electro-depositing on a metal surface a bituminous material from a cationic emulsion thereof in water, said emulsion having a pH from about 2.0 to about 6.0, containing a cation-active emulsifying quaternary nitrogen-containing salt, and consisting essentially of from about 10 to about 30% by Weight of said bituminous material, a sufficient amount of said cation-active quaternary nitrogen-containing salt for emulsifying the bituminous material in water to form a mechanically stable, pumpable emulsion, and water in an amount to make up 100% by weight; said process comprising thoroughly contasting a metal surface with said emulsion, and passing a direct electric current therethrough at an average density of at least about 2.5 milliamperes per square inch and in such a direction that the metal surface to be treated constitutes the cathode, whereby a uniform film of bituminous material is deposited thereon.

3. A process for electro-depositing on a metal surface an asphalt from a cationic emulsion thereof in water, said emulsion having a pH from about 2.0 to about 6.0, containing a cation-active emulsifying quaternary nitrogen-containing salt, and consisting essentially of from about 10 to about by weight of an asphalt, sufficient amount of said cation-active quaternary nitrogencontaining salt for emulsifying the asphalt in water to form a mechanically stable, pumpable emulsion, and wa- 'ter in an amount to make up 100% by weight; said process comprising thoroughly contacting a metal surface with said emulsion, and passing a direct electric current through the emulsion at an average density of at least about 2.5 milliamperes per square inch and in such a direction that the metal surface to be treated constitutes the cathode, whereby a uniform film of asphalt is deposited thereon.

4. A process as defined in claim 3, wherein said cationic asphalt emulsion has a pH in the range from about 3.0

'to about 6.0.

5. A process as defined in claim 3, wherein said asphalt is characterized by an average particle size of from about 0.25 to about 10.00 microns.

6. A process for electrodepositing on a metal surface a bitumen from a cationic emulsion thereof in water, :said emulsion having a pH from about 2.0 to about 6.0, containing a cation-active emulsifying quaternary nitrogen-containing salt, and consisting essentially of from about 10 to about 70% by weight of a bitumen, a sufficient amount of said cation-active quaternary nitrogencontaining salt for emulsifying the bitumen in water to form a mechanically stable, pumpable emulsion, and water in an amount to make up 100% by Weight, said process comprising thoroughly contacting a metal surface with said emulsion, and passing a direct electric current through the emulsion at an average density of at least about 2.5 milliamperes per square inch and in such a direction that the metal surface to be treated constitutes the cathode, whereby a uniform film of asphalt is deposited thereon.

7. A process as defined in claim 6, wherein said bitumen is an asphalt.

8. A process as defined in claim 6, wherein said cationactive quaternary nitrogen-containing salt emulsifier is present in an amount from about 0.033 to 1.5% by weight,

. based on the finished emulsion.

References Cited in the file of this patent UNITED STATES PATENTS 1,294,627 Davey Feb. 18, 1919 1,807,563 Bennett May 26, 1931 2,068,424 Mark Jan. 19, 1937 2,206,090 Haggenmacher July 2, 1940 2,530,366 Gray Nov. 21, 1950 2,560,148 Arabian July 10, 1951 2,819,228 Dell Jan. 7, 1958 FOREIGN PATENTS 229,361 I Great Britain Feb. 19, 1925 230,177 Great Britain Mar. 5, 1925 OTHER REFERENCES Fink et al.: Deposition of Synthetic Resins, Transactions of the Electrochemical Society, vol. 94, 1948, pages 309-340.

Roehl: Metal Finishing, pages 313-316, May 1944.

Damerell et al.: Journal Phys. Chem, vol. 48, May 1944, pages 138-140.

Claims (1)

1. A PROCESS FOR ELECTRO-DEPOSITING ON A METAL SURFACE AN ASPHALT FROM A CATIONIC EMULSION THEREOF IN WATER, CONTAINING A CATION-ACTIVE EMULSIFYING HALIDE SALT F A QUATERNARY NITROGEN-CONTAINING BASE SELECTED FROM THE GROUP CONSISTING OF QUATERNARY AMMONIUM BASES AND ORGANO-SUBSTITUTED HETEROCYCLIC NITROGEN BASES AND CHARACTERIZED BY THE PRESENCE OF A LONG C12-C24 ALIPHATIC HYDROCARBON CHAIN IN ITS CATION-ACTIVE PORTION, SAID EMULSION HAVING A PH FROM ABOUT 2.0 TO ABOUT 6.0 AND CONSISTING ESSENTIALLY OF FROM ABOUT 10 TO ABOUT 30% BY WEIGHT OF AN ASPHALT, SUFFICIENT AMOUNT OF SAID CATION-ACTIVE QUATERNARY NITROGEN-CONTAINING SALT FOR EMULSIFYING THE ASPHALT IN WATER AND TO FORM A PUMPABLE, MECHANICALLY STABLE EMULSION AND WATER IN AN AMOUNT TO MAKE UP 100% BY WEIGHT; THE PROCESS COMPRISING THROUGHLY CONTACTING A METAL SURFACE WITH SAID EMULSION AND PASSING A DIRECT ELECTRIC CURRENT THEREGTHROUGH AT AN AVERAGE DENSITY OF AT LEAST ABOUT 2.5 MILLIAMPERES PER SQUARE INCH AND IN SUCH A DIRECTION THAT THE METAL SURFACE TO BE TREATED CONSTITUTES THE CATHODE, WHEREBY A UNIFORM FILM OF ASPHALT IS DEPOSITED THEREON.