US2899367A

US2899367A - Method of preparing surfaces for

Info

Publication number: US2899367A
Authority: US
Publication date: 1959-08-11
Anticipated expiration: 1976-08-11

Description

NETHOD F PREPARING SURFACES FOR ELECTROPLATING Lloyd N. Veeder, Norwalk, Califl, assignor to North American Aviation, Inc.

'10 Claims. (Cl. 20432) This invention relates to processing metal and alloy surfaces. More particularly this invention relates to a method for preparing metal and alloy surfaces for nonaqueous electroplating processes.

Anti-corrosion protection is often provided for metals such as iron and steel by covering with a coat of non-corrosive metal or alloy. For example, cadmium is electroplated on steel to provide such an anti-corrosion coating. The cadmium provides good protection up to the temperature of about 550 F., at which temperature the cadmium alloys with the steel. This results in embrittlement of the steel which causes a serious reduction in its tensile strength. A better anti-corrosion protective metal is aluminum which offers greater protec tion than cadmium does. An advantage to the use of aluminum is its higher melting point as compared to cadmium. However, difiiculties have been encountered in trying to electroplate adhering aluminum on different steels in an organic aluminum plating bath. The difii culty, presumably, is due to the presence of impurities on the surface of the metal being plated. Often this impurity consists of an oxide film on the surface of the metal. Prior to the electroplating, the metal on which the protective coating is to be plated is subjected to a cleaning cycle, usually aqueous in nature. If the clean metal surface is thoroughly dried before immersing in the organic non-aqueous electroplating bath, it is found that the cleaned surface readily oxidizes. The oxide film thus formed interferes with the deposition of an adherent electroplated coating. This is found to be the case in the electro deposition of aluminum on steel. If, on the other hand, in order to prevent exposure of the clean surface to the oxygen of the atmosphere, a film of water is allowed to remain on the surface when the metal workpiece to be plated is immersed in electroplating bath, the water interferes with the electro deposition process so that an adherent coating cannot be obtained. The problem, therefore, is to develop a method for preparing the surface of the metal for non-aqueous electroplating which will provide a clean and active surface.

It is, therefore, an object of this invention to provide a composition suitable for forming a protective film on metal surfaces. Another object is to provide a method for preparing the metal-containing surface of a workpiece for electroplating with a metal in a non-aqueous electroplating bath. It is also an object of this invention to provide a method for obtaining an impurity-free active metal-containing surface suitable for receiving a deposit by electroplating in a non-aqueous medium. Another object of this invention is to provide a method for the introduction of a metal workpiece into a non-aqueous electroplating medium without the introduction of water as a contaminant. It is also an object to provide a method for the electrodeposition of an adherent coating of one metal or alloy onto a second metal or alloy.

rates Patent 0 The objects of this invention are accomplished by providing a composition, suitable for forming a protective coating on metal surfaces, comprising (1) 5-95 weight percent of at least one compound selected from the class consisting of organic acids having from about 9 to about 36 carbon atoms, and organic ether compounds having from about 8 to about 22 carbon atoms, and (2) 95-5 weight percent of a ketone having from 3 to 4 carbon atoms. The amount of the organic acids and/or organic ether compounds in the composition can vary from about 5 to about 95 weight percent, while the amount of the ketone having from 3 to 4 carbon atoms can vary from about 95 to about 5 weight percent. An example of the composition is one made up of an organic acid and acetone. For example, a composition made up of 75 weight percent oleic acid and 25 weight percent acetone can be used to provide a good protective coating.

The objects of this invention are also accomplished by providing a method of preparing a metal-containing surface of a workpiece for electroplating with a metal in a non-aqueous electroplating bath, comprising cleaning said surface with an aqueous cleaning solution in a manner so as to leave an aqueous film on said surface, applying an organic composition composed of (1) at least one compound selected from the class consisting of organic acids having from about 9 to about 36 carbon atoms, and organic ether compounds having from about 8 to about 22 carbon atoms, and (2) a ketone having from 3 to 4 carbon atoms, said composition being applied so as to form a coating on said surface and thereby displacing said aqueous film, and immersing said composition-coated workpiece in a non-aqueous plating bath.

The acids employed in the process of this invention are aliphatic, that is, paraflinic and olefinic acids. In general, the acids are non-aromatic, organic carboxylic acids in which a non-aromatic hydrocarbon group has one or more carboxylic COOH groups attached thereto. Non-limiting examples of these acids include saturated fatty acids such as pelargonic acid which has 9 carbon atoms, decanoic acid, dodecanoic acid, palmitic acid and stearic acid; unsaturated fatty acids such as oleic acid, linoleic acid, and the dimer of linoleic acid which has two carboxylic groups and has the general formula C H O etc. When employing fatty acids having a melting point above room temperature, such as saturated acids having from about 10 to about 18 carbon atoms, it is advantageous to use them in admixture with other so as to provide liquid rather than solid films on the protected surface.

The ethers which are employed in the instant process have from about 8 to about 22 carbon atoms and have the general formula R OR in which R and R can be the same or different and are hydrocarbon groups having from one to about 16 carbon atoms. These hydrocarbon groups can be aliphatic groups which are either saturated or unsaturated and either cyclic or non cyclic, aromatic groups, aliphatic substituted aromatic groups, and aromatic substituting aliphatic groups. Thus the groups can be alkyl, cycloalkyl, alkenyl, aryl, aryalkyl and alkaryl. Non-limiting examples of these ethers are dibutyl ether, ethyl hexyl ether, ethyl heptyl ether, hexyl cetyl ether, butyl benzyl ether, propyl tolyl ether, alyl tolyl ether, butyl phenyl ether, heptyl phenyl ether, cetyl phenyl ether, etc. Cyclic ethers such as dioxane may also be used. In this case the R and R in the formula given above would be combined to form a divalent hyfrom the discussion which follows.

drocarbon group which may be designated by R; as in a general formula 3v wherein R, can have from about 6 to about 22 carbon atoms.

It is preferred to employ ethers which have not more than one six-membered hydrocarbonraromaticring-groupingin its molecular structure. The examples giveninrthe previous paragraph include such ethers.

water will'be displaced'from the surface of the metal and because of its greater density will tend to collect at the bottom of the container.

balance of the-solution is'kept to a minimum;

The ketones that are employed: in the process of this inveniton'are acetone and methyl ethyl ketone. These ketones have a high degree of'miscibility with water:

Hence, whena solution composed of an acid and/or ether together with a'ketone is applied to the surface of a metal.

workpiece which contains an aqueous film, the water of the film readily mixes with the ketone with the result that it is removed fromthe surface. of the metal; The more viscous acid and/ or ether is then permitted to come in contact with that part of the surface fromwhich the water has been removed. The action of water removal from the surface and subsequent replacement by'the acid and/ or ether continues until all the water which had been absorbed as a film on the surface of the metal has been replaced. The surface is then protected by a non-aqueous organic compound, namely, the acid and/or the ether..

In this manner an aqueous film has been replaced by a protective non-aqueous film without exposing the cleaned: surface to the oxygen of the atmosphere. The organic film-protected workpiece can then be immersed in a nonaqueous plating bath with the assurance that a coatingcan be plated on its surface having maximum adherent qualities.

The amount of ketone in the organic composition which is used to replace water from the metal surfacecan vary from to about 95 weight percent. That is, the organic composition is composed of ('1) 5-95. weight percent of at least one compound selected from the class consisting of organic acids having from about 9 to about 36 carbon atoms, and organic ether compounds having from about 8 to about 22 carbon atoms, and (2) 95-5 weightpercent of a ketone having from 3 to 4 carbon atoms. When the composition contains less than 5% by weight of the acid and/or ether is found to be difiicult to obtain a satisfactory non-aqueous organic film on the metal surface. On the other hand, when the composition contains less than about 5 weight percent ketone, it is founddifficult t'o satisfactorily remove all the water which may be absorbed on the surface of the metal. Hence, itis found that each of the components can vary from 5 to about 95 weight percent based on the total weight of the composition.

A preferred organic composition for forming an aqueous film on the surface of metal is one composed of acids and ketones of the type described hereinabove; An especially preferred combination is found to be oleic acid and acetone. For example, a composition containing 75 weight percent oleic acid and 25 weight percent acetone is found to be very satisfactory in the replacement of an aqueous film with an oleic acid film.

The organic composition employed in this process is readily prepared by mixing the ketone with the organic acidand/or ether until a homogeneous composition is obtained. The components are simply added to a vessel equipped with the-means for agitation and then subjected to agitation such as, for example, stirring, shaking, etc., until the composition is homogeneous throughout; The order of addition of the components to the-vessel is immaterial. For example, the ketone may be added first and then the acid added, followed by the addition of the ether, if any. Changing the order, the acid may be added The ethers; of this kind have a density lower than'thatofwaterso that when a metal workpiece covered with an aqueoustfilm. is immersed in a solution of a ketone and anether, the

Such collected water can be" easily withdrawn and thus the water contaminationofthe;

to the vessel first and this followed by the addition of the ketone and lastly by the addition of the ether, if any. Alternatively, the ether may be added before the ketone. Likewise the ether, if used, may be added first followed by the addition of either the acid or the ketone or a combination of the two, etc. For example, 25 parts by weight of acetone was added to 75 parts by weight of oleic acid in a container equipped with means for agitation, and the two components were agitated until a homogeneous mixture was obtained. In like manner compositions are obtained containing parts by weight pelargonic acid and 5 parts by weight of methyl ethyl ketone; 5 parts by weight of cetyl phenyl ether and 95 parts by weight of acetone; 50 parts by weight of n-butyl ether and 50 parts by weight of acetone; 2 parts by weight stearic acid, 60 parts by weight of ethyl hexyl ether, 20 parts by weight of acetone and 18 parts by weight of methyl ethyl ketone. The above arenon-lii'niting examples of various compositions that. serve the purpose of. this-invention.

In general the surface of a. metal workpiece which is to be electroplated with another metal is first cleaned by subjecting the workpiece to a cleaning cycle. The cleaning material is thenusually removedby rinsing with water. This leavesan aqueous film on the surface of. the metal which momentarily protects the cleaned and highly active surface from coming in contact with oxygen of the air. To replace the film with an organic non-aqueous film, the acetone and organic acid and/or ether composition is applied to-the surface. The composition may be applied by a brush. or a spray technique, allowing the excess to drain off. More than one application may be necessary insome instances to effectively remove all of the water from thesurface of the metal. The number of such applications is not critical, however, and one skilled in the art will soon be able to determinewhat number of applications are required for a particular metal surface, depending on the ketone content of the organic composition and the type of surface involved. For example, a smoothly polished surface may require but one application while a rough or pitted surfacemay require more than one application. Alternatively the workpiece containing the aqueous film on its surface may be dipped into a solution of a ketone and acid and/or ether solution. If desired, the solution may be agitated to hasten the solution of the water in the ketone and the replacement of the aqueous film with an organic non-aqueous film. The length of time of immersion is not critical. The composition may be used over and over for many immersions of water coated metal surfaces. If the acids and/or ethers employed have a specific gravity of less than one, it will be found that the water removed from the metal surface collects in a layer at the bottom of the container from whence it can be removed. The organic composition in the container can be brought up to strength from time to time by the addition of appropriate amounts of the ketone and the acid and/or ether.

It is often found that after the replacement of the water film, the subsequent organic non-aqueous film which adheres to the surface is of considerable depth. Since it is desirable to introduce as little extraneous organic material as possible to the plating bath, the organic coated workpiece may be sprayed or brushed with, or dipped in a low molecular weight ether solution such as an ethyl ether or propyl ether solution containing about 5-15 weight percent of the organic acid and/or ether. This will tend to reduce the amount of organic material adhering to the surface of the metal and yet provide sulficient thickness of said material to protect the surface from attack by oxygen of the air. The organic-coated metal-surfaced workpiece may then be immersed in a non-aqueous plating bath and the process of plating metal thereon can be carried out to provide a workpiece having an electroplated material of enhanced adhering quality on its surface.

The presence of the ketone in the organic composition used to replace the aqueous film on the metal workpiece is very important since in the absence of the ketone, the organic substance. namely, the organic acid and/ or ether, does not effectively displace the water from the aqueous film on the metal workpiece. In fact, the acid and/or ether when used without the ketone tend to trap minute quantities of water on the surface in the form of minute droplets under the organic film. Hence, when such a workpiece is immersed in a non-aqueous electroplating bath in which the organic coating dissolves, the trapped water droplets on the surface of the metal interfere with the deposition of the electroplate causing the formation of a coating which readily chips and peels off.

The process of this invention is further illustrated in the following examples:

Example I An SAE 4130 alloy steel fastener containing chromium and carbon which may be described as a 3% inch bolt having a diameter of 0.75 inch, and having a /8 inch head at one end and a threaded portion at its opposite end, was first subjected to a cleaning process. This consisted of immersing the fastener in a solution containing 3 ounces of sodium carbonate, 3 ounces of sodium phosphate, 1 ounce of sodium silicate and 2 ounces of sodium hydroxide per gal. of solution. The fastener was made the anode in an electrolytic cell set-up in this solution and an electric current having a density of 20 amps per square foot was passed through the solution for a period of about two minutes. The fastener was then removed from this solution and rinsed with Water. The electrolytic procedure described above was then repeated in an aqueous cyanide solution containing about 6 ounces of sodium cyanide per gallon of water. The fastener was then rinsed with water again. This was then followed by dipping in an aqueous hydrochloric acid solution. Finally it was rinsed once more with water completing the cleaning cycle. The fastener, containing a film of water on its surface, was then immersed in an organic solution composed of 75 weight percent oleic acid and 25 weight percent acetone where it was kept for approximately two minutes while keeping the organic composition in agitation and at a temperature of substantially 22 C.

The fastener was then removed from this organic composition and found to contain a non-aqueous organic film. The organic-material coated fastener was exposed to the atmosphere for substantially 5 minutes to allow time for the ketone and any ketone and water mixture to evaporate. Following this it was immersed in a nonaqueous plating bath. This bath was composed of a mixture of diethyl ether solution containing four mols per liter of aluminum trichloride and saturated with lithium hydride (approximately 0.25 mol LiH per liter). The steel fastener was made the cathode and a sheet of 99.96% pure aluminum was made the anode of an electrolytic cell set-up in this solution. Direct current was passed through the cell at a density of 10 amps. per square foot. This provided for a rate of deposition of aluminum on the steel fastener of substantially 0.4 mil (.004 of an inch) per hour. The current was passed through the cell so as to provide a cycle in which aluminum was deposited on the steel fastener for a period of 30 seconds, followed by a reversal of the current and hence a removal of aluminum from the fastener for a period of 5 seconds. This process was maintained for one hour providing an aluminum plating on the fastener of approximately 0.3 mil in thickness. The passage of the current was then discontinued, the fastener removed from the plating bath, rinsed with water and dried. A highly adherent aluminum coating was found on the fastener.

Following the process of Example I, a steel strip made of 4130 steel which contains 0.30 weight percent carbon, 0.50 weight percent manganese, 1.0 weight percent chormium and measuring 6" x 0.5" x 0.04" was processed with the modification that the organic coated strip was aluminum had been deposited substantially 0.0003 inch in thickness on the steel strip.

Example I] The procedure of Example I was followed with the modification that after the removal of the steel fastener from the oleic acid acetone composition, it was immersed in a solution composed of ethyl ether containing 10 weight percent oleic acid for a period of substantially one minute. Upon removal from this ether oleic acid solution, the fastener was found to have a much thinner film of acid On its surface. Upon subjecting it to aluminum plating as in Example I, a highly adherent aluminum coating was obtained.

Following the procedure of Example II, aluminum was plated on a 4130 steel strip having the dimensions of 6" x 0.5" x .04" to a thickness substantially 0.3 mil.

Example III The process of Example I was followed with the excep: tion that the organic composition used for displacing the aqueous film from the surface of the metal was composed of weight percent pelargonic acid and 5 weight percent methyl ethyl ketone. The aqueous film on the metal surface was effectively displaced by the acid and a good aluminum coating 0.003 inch in thickness was obtained in the plating process.

Example IV The procedure of Example II was followed with the exception that the organic composition employed for displacing the aqueous film on the metal was composed of 5 weight percent cetyl phenyl ether and 95 weight percent acetone. The plating bath used in this instance was composed of ethyl pryidinium bromide and aluminum trichloride in the molar ratio of 1:2, respectively, in 68 weight percent toluene as a solvent. The current density was 20 amps. per square foot with a cycle of five minutes plating and one minute reversal of current, for a period of one hour. In this procedure, the aqueous film on the metal surface was effectively displaced by the acid and a good and adherent aluminum coating was obtained in the plating process.

Example V The procedure of Example II was followed with the exception that the organic composition employed for displacing the aqueous film on the metal was composed of 15 weight percent dilinoleic acid dimer, 35 Weight percent benzyl butyl ether, and 50 weight percent acetone. The aqueous film on the metal surface was effectively displaced by the acid and a good aluminum coating was obtained in the plating process.

Example VI A steel strip having the dimension of 6 x 0.5" x 0.04 was subjected to a cleaning cycle as described in Example I. The water-coated steel strip was then immersed in pure oleic acid and maintained therein for a period of substantially two minutes while keeping the acid in agitation. The steel strip was then removed from the oleic acid and found to contain a film of this acid. The steel strip was then removed from the oleic acid and with an adhering film of this acid was then immersed in an aluminum plating bath of the type described in Example I. It was then subjected to the plating procedure described in Example I until a coating of aluminum plate of substantially 0.3 mil in depth had been deposited.

To determine the degree of the adherence of the aluminum plating to the steel specimen, the aluminum plated steel strips were bent at the mid point through a small radius followed by straightening out and bending in the opposite direction through an equally small radius. Several such operations causedthe steel strip to break into two pieces. The cross section of the steel st:ip displaying thelinner core of steel and the outer coating of aluminum plate was then examined under a microscope. In the case of steel strips on which the aluminum had been deposited as in Examples I-V, the aluminum coating was found to adhere tightly to the metal even though the steel strip had been twisted out of its original shape at the break. The aluminum coating on the strip processed as in Example VI was found to have peeled away from the surface of the metal at the break. This indicates that the aluminum deposit when the surface was processed as in Example VI was not as adherent as when the surface was prepared for electroplating by the process of Examples I-V. The only difference in the procedure of Example VI to that of the other examples was that in Example VI the water film was replaced by merely immersing the strip with an aqueous layer on its surface in pure oleic acid, whereas in Examples I-V, the metal strip with the aqueous film on it was immersed in a solution of a ketone together with an acid and/or ether. It is thus seen that the process of this invention provides a method for obtaining an aluminum plating of superior adherent qualities when deposited on metal surfaces.

The above is true whether the aluminum is being plated on stainless steel, carbon steel, steel alloys, nickel, copper, molybdenum or silver.

The resistance to corrosion of a metal workpiece protected by a coating of aluminum applied by a method using the processes of this invention is illustrated in the following example.

Example VII A 4130 steel strip coated with 0.3 mil of aluminum by the process described in Example I was subjected to an accelerated salt spray test according to the method described by the American Society for Testing Materials in their bulletin ASTM Bl17-49T. In this procedure the concentrated salt solution containing 20% sodium chloride was continuously sprayed onto the aluminum coated strip for a period of 75 hours at a temperature of '-2 C. At the end of this period the workpiece was rinsed with clear water and examined for evidence of corrosion. No corrosion was observed indicating that the aluminum coating applied by the process of this invention adequately protects the steel workpiece.

While in the examples above the process of preparing a metal surface for electroplating in a non-aqueous bath has been illustrated in the case of aluminum plating on steel, it is not to be construed to be so limited. The process is applicable wherever a metal surface is to be cleaned and subsequently subjected to a plating process in a non-aqueous medium, especially when the metal on which an electroplate is to be deposited is readily oxidized upon exposure to the oxygen of the atmosphere. For example, the process is also applicable in the plating of aluminum on chromium and chromium alloys.

The cleaning process to which the metal surface is subjected prior to the treatment with a composition composed of a ketone together with an acid and/ or ether of the type described above, is likewise not critical. Most cleaning processes employ chemicals and compounds which are not compatible with non-aqueous electroplating compositions. Therefore, transition may be made from the surface covered with components of a cleaning solution to a surface covered with a film of a material which is cmpatible with the cleaning solution by the process of this invention. The cleaning solution on the surface of the metal regardless of its nature, may usually be replaced by an aqueous film by any series of steps wellknown to one skilled in the art, the final one of which is usually the rinsing or washing of the surface with water. Once having obtained a workpiece whi 11 has a surface coated with an aqueous film, the latter may be replaced with an organic film compatible with a non-aqueous electroplating solution by the process of this invention as described hereinabove. The workpiece having its metal surface covered with a compatible film is then immersed in a non-aqueous electroplating solution and secured in position to make one of the electrodes in an electroplating cell, usually the cathode, and the electroplating carried out. The process of electroplating is well-known in the art and will not be described further here.

The temperature of theketone and acid and/or ether composition, at the time the aqueous film-coated metal is immersed into it, is not critical. Usually its temperature is that of the surrounding atmosphere and hence is from about 20 to about 25 C. However, the organic ketone and acid and/or ether composition readily displaces the aqueous film with an organic film at temperatures ranging from 0 to about 50 C In carrying out the process of this invention so as to provide an uncontaminated reactive metal surface for plating in a non-aqueous electroplating bath, it is only necessary that once the cleaning of the metal surface has been initiated the surface is thereafter continuously protected agaist contact with oxygen of the atmosphere by an aqueous or organic film. Thus when a metal-surfaced workpiece is subjected to a cleaning cycle, the change from one kind of cleaning solution to another is accomplished in a manner such that the surface remains coated with an aqueous film during the changeover. In other Words, the surface is never allowed to become dry so as to come in contact with the oxygen of the air. The same precaution is taken when washing the cleaning solution off with water and in applying the ketone and acid and/or ether composition to the washed metal surface. In other words, the cleaned metal surfaced workpiece is subjected to a water rinse while the surface to be plated is completely covered with a film of the cleaning solution. In this way the cleaning solution film is replaced by a film of water. The ketone and acid and/or ether solution is then applied to the surface while the surface is still completely covered with an aqueous film. The latter is thus replaced by an organic film without allowing the surface to come in contact with oxygen of the air. The organic film-coated metal surfaced workpiece is then exposed to the atmosphere for about 2 to 10 minutes to allow the ketone and any water-ketone mixture to evaporate from the organic film and it is then immersed in a non-aqueous electroplating bath. It is seen, therefore, that the time intervals between the various steps of the process of this invention are not critical. The process is merely carried out in a manner such that the metal surface, once having been cleaned is not thereafter exposed to the oxygen of the atmosphere. Consequently, the electroplate may be deposited on an uncontaminated surface. The time intervals between successive cleaning steps, the washing step, and the coating with the organic composition may thus vary from about a matter of seconds to ten or more minutes so long as the aqueous film is not allowed to evaporate or dry. The time interval between the application of the organic coating material and the immersion in the electroplating bath may be much longer than between the successive steps in the cleaning and washing procedure since the organic film has a much lower vapor pressure and will not evaporate or dry so readily. Hence, the organic film-coated metal surfaced workpiece may remain exposed to the atmosphere for ten or more hours without any ill effect. In most cases, however, the time interval between successive steps in the process is a matter of seconds or minutes and seldom exceeds ten to fifteen minutes.

Although the invention has been described and illustrated in detail, it is to be clearly understood that the same isby way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.

I claim:

1. A method of preparing a metal-containing surface of a workpiece for electroplating with a metal in a nonaqueous electroplating bath, comprising cleaning said workpiece with an aqueous cleaning solution in a manner so as to leave an aqueous film on said surface, applying an organic composition consisting essentially of (1) -95 weight percent of at least one compound selected from the class consisting of organic acids having from about 9 to about 36 carbon atoms, and organic ether compounds having from about 8 to about 22 carbon atoms, and (2) 95-5 weight percent of a ketone having from 3 to 4 carbon atoms, said composition being applied so as to form a coating on said surface and thereby displacing said aqueous film, and immersing said compositioncoated workpiece in a non-aqueous plating bath.

2. A method of preparing a metal-containing surface of a workpiece for electroplating with a metal in a nonaqueous electroplating bath, comprising cleaning said workpiece with an aqueous cleaning solution in a manner so as to leave an aqueous film on said surface, applying an organic composition consisting essentially of (1) 5-95 weight percent of an organic acid having from about 9 to about 36 carbon atoms, and (2) 95-5 weight percent of a ketone having from 3 to 4 carbon atoms, said composition being applied so as to form a coating on said surface and thereby displacing said aqueous film, and immersing said composition-coated workpiece in a nonaqueous plating bath.

3. The method of claim 2 in which said acid is oleic acid and said ketone is acetone.

4. The method of claim 2 in which said organic composition consists essentially of (1) 75 weight percent oleic acid, and (2) 25 weight percent acetone.

5. A method of preparing a metal-containing surface of a workpiece for electroplating with a metal in a nonaqueous electroplating bath, comprising cleaning said workpiece with an aqueous cleaning solution in a manner so as to leave an aqueous film on said surface, applying an organic composition consisting essentially of (1) 5-95 weight percent of at least one compound selected from the class consisting of organic acids having from about 9 to about 36 carbon atoms, and organic ether compounds having from about 8 to about 22 carbon atoms, and (2) 95-5 weight percent of a ketone having from 3 to 4 carbon atoms, said organic composition being applied so as to form a coating on said surface thereby displacing said aqueous film, immersing said composition-coated workpiece in an ethyl ether solution containing oleic acid, removing said workpiece from said ether solution, and immersing said workpiece in a non-aqueous plating solution.

6. A method of preparing a metal-containing surface of a workpiece for electroplating with a metal in a nonaqueous electroplating bath, comprising cleaning said workpiece with an aqueous cleaning solution in a manner so as to leave an aqueous film on said surface, applying an organic composition consisting essentially of (1) 5- 95 weight percent of an organic ether compound having from about 8 to about 22 carbon atoms, and (2) 95-5 weight percent of a ketone having from 3 to 4 carbon atoms, said composition being applied so as to form a coating on said surface and thereby displacing said aqueous film, and immersing said composition-coated workpiece in a non-aqueous plating bath.

7. A method of preparing a metal-containing surface of a workpiece for electroplating with a metal a nonaqueous electroplating bath, comprising cleaning sald workpiece with an aqueous cleaning solution in a manner so as to leave an aqueous film on said surface, applying an organic composition consisting essentially of (1) 5-95 weight percent of at least one compound selected from the class consisting of organic acids having from about 9 to 36 carbon atoms, and organic ether compounds having from about 8 to about 22 carbon atoms, and (2) -5 weight percent of a ketone having from 3 to 4 carbon atoms, said composition being applied so as to form a coating on said surface and thereby displacing said aqueous film, immersing said composition-coated workpiece in a lower alkyl ether solution containing from about 5 to about 15 weight percent of at least one compound selected from the class consisting of said organic acids and said organic ether compounds, removing said workplece from said ether solution, and immersing said workpiece in a non-aqueous plating solution.

8. A method of preparing a metal-containing surface of a workpiece for electroplating with a metal in a non aqueous electroplating bath, comprising cleaning said workpiece with an aqueous cleaning solution in a manner so as to leave an aqueous film on said surface, applymg an organic composition consisting essentially of (1) 5-95 weight percent of at least one compound selected from the class consisting of organic acids having from about 9 to 36 carbon atoms, and organic ether compounds having from about 8 to about 22 carbon atoms, and (2) 95-5 weight percent of .a ketone having from 3 to 4 carbon atoms, said composition being applied so as to form a coating on said surface and thereby displacing said aqueous film, immersing said compositioncoated workpiece in a lower alkyl ether solution containing from about 5 to about 15 weight percent of said organic acid, removing said workpiece from said ether solution, and immersing said workpiece in a non-aqueous plating solution.

9. A method of preparing a metal-containing surface of a workpiece for electroplating with a metal in a nonaqueous electroplating bath, comprising cleaning said workpiece with an aqueous cleaning solution in a manner so as to leave an aqueous film on said surface, applying an orgamc composition consisting essentially of (1) 5-95 weight percent of at least one compound selected from the class consisting of organic acids having from about 9 to 36 carbon atoms, and organic ether compounds having from about 8 to about 22 carbon atoms, and (2) 95-5 weight percent of a ketone having from 3 to 4 carbon atoms, said composition being applied so as to form a coating on said surface and thereby displacing said aqueous film, immersing said compositioncoated workpiece in an ethyl ether solution containing from about 5 to about 15 weight percent oleic acid, removing said workpiece from said ether solution, and immersmg said workpiece in a non-aqueous plating solution.

10. A method of preparing a metal-containing surface of a workpiece for electroplating with a metal in a nonaqueous electroplating bath, comprising cleaning said workpiece with an aqueous cleaning solution in a manner so as to leave an aqueous film on said surface, applying an organic composition consisting essentially of (1) 5-95 weight percent of at least one compound selected from the class consisting of organic acids having from about 9 to 36 carbon atoms, and organic ether compounds having from about 8 to about 22 carbon atoms and (2) 95-5 weight percent of a ketone having froni 3 to 4 carbon atoms, said composition being applied so as to form a coating on said surface and thereby displacmg sa1 d aqueous film, immersing said composition-coated workpiece in a lower alkyl ether solution containing from about 5 to about 15 weight percent of said organic ether compounds, removing said workpiece from said ether solution and immersing said workpiece in a non-aqueous plating solution.

References Cited in the file of this patent UNITED STATES PATENTS 725,002 Miller A 7 1,801,629 Kenaga Apn 21: OTHER REFERENCES Campbell: Transactions Faraday Society vol (1915),pages 91-101. 11

Claims

1. A METHOD OF PREPARING A METAL-CONTAINING SURFACE OF A WORKPIECE FOR ELECTROPLATING WITH A METAL IN A NONAQUEOUS ELECTROPLATING BATH, COMPRISING CLEANING SAID WORKPIECE WITH AN AQUEOUS CLEANING SOLUTION IN A MANNER SO AS TO LEAVE AN AQUEOUS FILM ON SAID SURFACE, APPLYING AN ORGANIC COMPOSITION CONSISTING ESSENTIALLY OF (1) 5-95 WEIGHT PERCENT OF AT LEAST ONE COMPOUND SELECTED FROM THE CLASS CONSISTING OF ORGANIC ACIDS HAVING FROM ABOUT 9 TO ABOUT 36 CARBON ATOMS, AND ORGANIC ETHER COMPOUNDS HAVING FROM ABOUT 8 TO ABOUT 22 CARBON ATOMS, AND (2) 95-5 WEIGHT PERCENT OF A KETONE HAVING FROM 3 TO 4 CARBON ATOMS, SAID COMPOSITION BEING APPLIED SO AS TO FORM A COATING ON SAID SURFACE AND THEREBY DISPLACING SAID AQUEOUS FILM, AND IMMERSING SAID COMPOSITIONCOATED WORKPIECE IN A NON-AQUEOUS PLATING BATH.