GB1579760A

GB1579760A - Compositions aqueous solutions and processes for cleaning metal surfaces

Info

Publication number: GB1579760A
Application number: GB5422177A
Authority: GB
Original assignee: Union Carbide Agricultural Products Inc
Current assignee: Union Carbide Agricultural Products Inc
Priority date: 1976-12-30
Filing date: 1977-12-29
Publication date: 1980-11-26
Also published as: AU518757B2; IT1126796B; JPS53102309A; AU3204377A; DE2758629B2; DE2758629C3; JPS6017831B2; DE2758629A1

Description

(54) COMPOSITIONS, AQUEOUS SOLUTIONS AND PROCESSES FOR CLEANING METAL SURFACES (71) We, UNION CARBIDE AGRICULTURAL PRODUCTS COMPANY INC., formally, Amchem Products, Inc., a Corporation organized under the Laws of the Commonwealth of Pennsylvania, United States of America, of Brookside Avenue, Ambler, State of Pennsylvania, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to compositions, aqueous solutions and processes for cleaning metal surfaces.It is especially concerned with the cleaning of tin-plated ferrous metal surfaces above all prior to subsequent pre-treatments designed to enhance the corrosion resistance of the surface and to promote the adhesion thereto of later-applied organic, sanitary lacquer, siccative finishes or the like.

Containers used in the food stuff industry can be made of tin-plated ferrous metal. These containers are ordinarily formed through a process referred to as "drawing and ironing", that is the tin-plated metal sheeting is drawn and intentionally thinned to form a drawn sheet providing uniform wall thickness and producing a.thin-walled, thick-bottomed container. Due to the high cost of tinplate, only a thin layer of tin-plating is employed.

During the fabrication and forming of the tin-plated ferrous metal container, lubricants are employed to facilitate the drawing and ironing operation. The lubricants which are deposited on the metal surface usually contain various types of mineral and vegetable-based oils, emulsifiers and corrosion inhibitors.

In recent years, improved lubricant compositions have been developed and employed on tin-plated cans for drawing and ironing operations. These recentlyintroduced compositions create a lubricant layer on the metal surface which has been found to be very difficult to remove. If the lubricant layer is not removed completely from the metal surface in a cleaning operation, the metal surface is dewetted, and is found to be unsuitable for subsequent treatment to enhance corrosion resistance or decorative appearance.

It has also been found that when these recently-introduced lubricants are employed for drawing and ironing operations, the cleaning solution employed can be rendered ineffective and/or difficult to handle due to the build-up therein of these lubricants, which causes the lubricating oils to be saponified, resulting in increased foaming.

Attempts to increase the efficiency of the cleaning solutions employed to remove these recently-introduced lubricants, either by increasing the alkalinity or by increasing the temperature of the cleaning solution, tend to result in excessive etching of the metal surface.

A serious general problem with drawn and ironed tin-plated containers is that the drawing operation stretches the interior tin-plate surface, and thereby increases the size-of existing pores and produces new ones, thus leaving the underlying ferrous metal surface exposed. In order to clean the surface and remove the lubricant therefrom, cleaners have been employed which not only remove the lubricant but etch the tin-plated ferrous surface. This etching aggravates the problem of corrosion of the exposed steel surface through the pores, and leaves unsightly rust marks. Moreover, conditions on the processing line, such as line stoppage, can lead to corrosion of the exposed ferrous surface as the containers are processed during manufacture, after the drawing and ironing step and the cleaning step.Any corrosion and blemishes formed on the surface will adversely affect the adhesion of any subsequent conversion coating or sanitary lacquer coating which is applied thereafter, making the containers unacceptable for use.

A variety of cleaning compositions have been employed in the art to treat tinplated ferrous metal surfaces in order to remove lubricants and forming oils from the surface. Cleaning compositions which not only remove the lubricants but also etch the surface are unsuitable, due to the acceleration of corrosion of the surface.

In addition, cleaning compositions known to the art have not provided protection of the tin-plate surface subsequent to the cleaning step and prior to any further treatment such as conversion coating or sanitary lacquer coating and still remove the new and improved cleaning lubricants while controlling foaming to an acceptable level.

Cleaning solutions which are used for the removal of lubricants and oils from metal surfaces are generally mildly to strongly alkaline. Such known aqueous cleaning solutions include for instance those described in United States Patent No.

3,888,783, which contain a condensed phosphate, an alkaline metal meta-silicate and borax, and are utilized for cleaning tin-plated ferrous metal surfaces, allegedly without etching the surface. Further examples of known aqueous cleaning solutions are those described in United States Patents No. 3,145,178 and No.

3,145,180, which describes cleaning compositions containing alkali metal hydroxides, phosphates, silicates and carbonates, together with at least one each of a sulphonated and a non-sulphonated tertiary carbonamine with from 12.5 to 17.5 polyoxyethylene units.

While these various known cleaners are suitable for a number of purposes, they are frequently found to be deficient for the intended purpose because they cannot produce a completely water break-free surface and/or because they produce excessive etching or foaming and/or because they are incapable of producing a surface suitable for a subsequent treatment to enhance corrosion resistance or the adhesion of later-applied organic, sanitary lacquer or siccative finishes. Furthermore, many of these known cleaning compositions have been found to be ecologically undesirable, for example those containing borates.

We have however now found that certain compositions, solutions and processes, hereinafter described in detail, may be used to remove lubricants from metal surfaces on which they have been employed during forming operations; specifically from tin-plated ferrous metal surfaces, so as to provide an acceptably clean, usually waterbreak-free metal surface suitable for subsequent passivating and/or finishing treatments such as conversion coating or organic or sanitary lacquer or other siccative coating operations, yet with little or no foaming and without any significant etching of the metal surface, thus minimizing corrosion of any areas of ferrous metal which may be exposed for prolonged periods prior to the previously-mentioned passivating and/or finishing treatments.

According to one aspect of this invention there is provided a cleaning composition comprising: (a) an alkali metal meta-silicate; (b) an alkali metal condensed phosphate; (c) an alkali metal carbonate; and (d) an alkali metal bicarbonate; wherein for each part by weight of the alkali metal meta-silicate in the cleaning composition there is from 0.1 to 1.5 parts by weight of alkali metal condensed phosphate, from 0.3 to 2.5 parts by weight of the alkali metal carbonate, and up to 1.5 parts by weight of the alkali metal bicarbonate.

According to another aspect of the invention there is also provided an aqueous cleaning solution comprising: (a) an alkali metal meta-silicate in an amount of from 0.5 grams/litre to 13 grams/litre; (b) an alkali metal condensed phosphate; (c) an alkali metal carbonate; and (d) an alkali metal bicarbonate; wherein for each part by weight of the alkali metal meta-silicate in the solution there is from 0.1 to 1.5 parts by weight of alkali metal condensed phosphate, from 0.3 to 2.5 parts by weight of the alkali metal carbonate, and up to 1.5 parts by weight of the alkali metal bicarbonate.

According to yet another aspect of the present invention there is also provided a process for cleaning a metal surface to remove lubricants therefrom, in which the surface is contacted with an aqueous cleaning solution of the invention, whereby the lubricants are removed from the metal surface without significant etching of the metal surface.

It should be understood that the term "ferrous metal" as used herein includes iron, iron alloys, and a wide variety of steels.

The term "tin-plated" as used herein refers to a metallic coating consisting substantially of tin. The metallic coating can be continuous or have discontinuities wherein the substrate is exposed.

The term "lubricants" as used herein means deposits formed on a metal surface during its formation, and particularly during drawing and ironing, which deposits generally contain various types of animal oils, mineral oils, vegetable oils, emulsifiers and corrosion inhibitors.

The cleaning compositions of the invention will normally be simple dry admixtures of their constituents. When dissolved in water so that the alkali-metal meta-silicate is present in the resulting solution in an amount of from 0.5 grams/litre to 13 grams/litre, the compositions of the invention form the aqueous cleaning solutions of the invention. The cleaning solutions will normally contain from 2.0 grams/litre to 30 grams/litre, and preferably from 2.5 grams/litre to 20 grams/litre, of a cleaning composition of the invention.

The alkali-metal meta-silicate employed in the present invention will normally either be sodium or potassium meta-silicate. the silicate contributes to the detergency of the cleaning solutions of the invention (thus rendering them more effective in removing the lubricants) and also helps protect the treated surface from corrosion. It is also an excellent saponifying agent for the lubricants and any residual loose dirt on the metal surface.

In the preferred practice of the present invention, anhydrous sodium metasilicate is employed since it is easily dissolved in water and offers the properties of high alkalinity and good detergency.

The alkali metal condensed phosphate employed is preferably either a tripolyphosphate or a pyrophosphate. Sodium tripolyphosphate and sodium pyrophosphate are advantageously employed, and of these sodium tripolyphosphate is preferred. The alkali metal condensed phosphates are valuable for their water softening, detergent and emulsifying properties. When added to water the alkali metal condensed phosphates are alkaline in nature, thereby aiding in preparing an alkaline aqueous cleaning solution.

The alkali metal carbonates and the alkali metal bicarbonates to be employed are preferably sodium carbonate and sodium bicarbonate. The pH of the cleaning solutions of the invention should normally be at least 10, and preferably should be from 11 to 12.5, and alkali metal carbonates and alkali metal bicarbonates are valuable in the control of pH, since when dissolved in water they are hydrolyzed and form alkaline solutions. Control of the alkalinity of the cleaning solution is more flexibly obtained at lower cost by utilizing alkali metal carbonates and alkali metal bicarbonates than, say, alkali metal hydroxides. Further, when the alkali metal carbonates and bicarbonates are dissolved in water, the alkali metal cation is available for the saponification of the lubricating oils.

In general it may be said that the alkali metal cation for the compounds employed in this invention is preferably sodium or potassium, and most preferably sodium.

The preferred amounts of alkali metal condensed phosphate, alkali metal carbonate and alkali metal bicarbonate for each part by weight of the alkali metal meta-silicate in the cleaning compositions and aqueous cleaning solutions of this invention are as follows: (a) from 0.2 to 0.7 parts by weight of alkali metal condensed phosphate; (b) from 0.45 to 1.7 parts by weight of alkali metal carbonate; and (c) from 0.2 to 0.55 parts by weight of alkali metal bicarbonate.

As specified hereinabove, the alkali metal meta-silicate employed is preferably sodium meta-silicate and the alkali metal condensed phosphate is preferably sodium tripolyphosphate. Pyrophosphate may however be substituted for the tripolyphosphate thereby producing a substantially equivalent cleaning composition or cleaning solution, in which case the concentrations of this material should correspond to that specified hereinabove when sodium tripolyphosphate is employed. The foregoing concentration parameters are calculated on the basis of the sodium form of meta-silicate and the sodium form of tripolyphosphate.

Surfactants, both high and low foaming, defoaming agents, and mixtures thereof are desirably included in the cleaning compositions and cleaning solutions of this invention. Such materials enhance cleaner performance and/or minimize fo;lming. Typical examples of surfactants and wetting agents which can be employed in the cleaning composition are ethoxylated straight chain alcohols and octyl or nonyl phenoxy polyethoxyethanol. Preferably, non-ionic surface active agents should be employed, and it is highly desirable to utilize at least one nonionic surfactant which has been modified in such a manner so as to have a lowfoaming characteristic -- that is a low foaming surfactant.

Preferably for each part by weight of alkali metal meta-silicate present in the cleaning composition or solution there is present a total of from 0.05 to 0.5 parts by weight of non-ionic surfactant.

Typical examples of cleaning compositions suitable for dilution with water to make effective cleaning solutions of the invention are as follows: Formula I Weight Ratio to alkali metal % by weight meta-silicate Sodium meta-silicate 26. 1.0 Sodium tripolyphosphate 9. .35 Sodium carbonate 44. 1.69 Sodium bicarbonate 11. .42 Non-ionic surfactant TritonN-100 5. .19 Onyx Defoamer#4 5. .19 Formula ll Weight Ratio to alkali metal /, by weight meta-silicate Sodium meta-silicate 29. 1.00 Sodium tripolyphosphate 10. .34 Sodium carbonate 45 1 55 Sodium bicarbonate 12. .41 Non-ionic surfactant TritonN-100 2. .07 Tergitol Min-Foam l-X 2. .07 Formula III Weight Ratio to alkali metal % by weight meta-silicate Sodium meta-silicate 35.0 1.0 Sodium tripolyphosphate 20.0 .57 Sodium carbonate 18.5 .53 Sodium bicarbonate 13.2 .38 Non-ionic surfactant Tergitol Min-Foam l-X 8.3 .24 Triton N-100 5.0 .14 Formula IV Weight Ratio to alkali metal /" by weight meta-silicate Sodium meta-silicate 39. 1.0 Sodium tripolyphosphate 9. .23 Sodium carbonate 21. .54 Sodium bicarbonate 21. .54 Non-ionic surfctant - Triton N- 100 5. 13 Tergitol Min-Foam l-X 5..13 Formula V Weight Ratio to alkali metal /" by weight meta-silicate Sodium meta-silicate 39.0 1.0 Sodium tripolyphosphate 22.5 .58 Sodium carbonate 20.7 .53 Sodium bicarbonate 14.8 .38 Non-ionic surfactant Tergitol Min-Foam l-X 1.8 .05 Triton N-100 1.2 .03 Formula VI Weight Ratio to alkali metal /n by weight meta-silicate Sodium meta-silicate 39.0 1.0 Sodium tripolyphosphate 22.5 .58 Sodium carbonate 20.7 .53 Sodium bicarbonate 14.8 .38 Non-ionic surfactant Tergitol Min-Foam l-X 3.0 .08 Formula VII Weight Ratio to alkali metal O/, by weight meta-silicate Sodium meta-silicate 35. 1.0 Sodium tripolyphosphate 20. .57 Sodium carbonate 20. .57 Sodium bicarbonate 15.

Non-ionic surfactant - Tergitol Min-Foam l-X 5.0 .14 .Triton N-100 5.0 .14 Formula VIII Weight Ratio to alkali metal /,} by weight meta-silicate Sodium meta-silicate 43.3 1.0 Sodium tripolyphosphate 23.3 .53 Sodium carbonate 23.3 .53 Sodium bicarbonate 10.1 .23 "Triton N-100" is the trademark of Rohm & Haas Corp. for a nonylphenoxy polyethoxy ethanol; "Onyx Defoamer &num;4" is the trademark of Onyx Chemical Co.

for a sulfonated oil based surfactant and "Tergitol Min-Foam l-X" is the trademark of Union Carbide Corp. for a modified linear alcohol ethoxylate.

Other surfactants (identified by trademark) which may be utilized in the cleaning compositions, with equal or improved efficacy, are Makon NF-12, Surfonic LF-17, Neodol 25-7 and 25-9, Min-Foam 2-X, Petroulf F-100-5F, Alkawet B, Triton X-102, Anti-Bubble Agent-D and the chemical compound tributyl phosphate.

In the process of this invention for cleaning metal surfaces, the cleaning solution may be applied to the substrate metal utilizing any conventional contacting technique. Preferably application will be effected by conventional spray or immersion methods. As indicated hereinbefore, the process of this invention is intended principally for application to tin-plated ferrous metal surfaces.

The time of treatment of the metal surface by the cleaning solution need only be long enough to insure complete wetting of the surface, although it can be for as long as 20 minutes. Preferably the surface should be treated for a time of from 15 seconds to 60 seconds.

The cleaning solution can be operated at temperatures as high as 90"C (1940F), although a temperature of from 57"C (1350F) to 800C (176"F) is preferred. Within this range cleaning is enhanced and foaming is minimized. In any event, temperatures of at least 54"C (1300F) should normally be employed since foam ins can be excessive below that temperature, particularly when the spray method of application is utilized.

During the process, depletion of the constituents in the cleaning solution will occur due to factors such as dragout and the action of the constituents on the lubricants and loose dirt. For example, the silicate will be expended during its saponifying and detergent action. Simple titration methods can be employed to determine the make up of the cleaning solution and the necessity for the addition of any replenishment composition. For example, the cleaning bath is maintained within its prescribed operating parameters with either suitable additions of the constituents therein by separate additions of each constituent, or by addition of a replenishing composition having the same make-up as the original cleaning composition.

The cleaning process can be accomplished by treating the tin-plated ferrous metal surface directly or a short time after the drawing and ironing step. In general, it is not necessary that the surface undergo any preliminary treatment prior to contact with the cleaning solution. However, it has been found that the life of the cleaning solution may be extended if there is a pre-wash step for the removal of excess lubricant. It has additionally be found that addition of a small amount of cleaning composition to the pre-wash solution can aid in the removal of excess lubricant from the surface prior to contacting the metal surface with the cleaning solution. In this way the overflow and discard of the cleaning solution during the cleaning operation are minimized. The cleaning process may be performed directly, or a short time after the pre-wash step.

While, as previously stated, the cleaning solutions of this invention may be utilized for the removal of many types of lubricants, they are particularly advantageous in the removal of difficult-to-remove mineral oil based lubricants used in drawing and ironing operations on tin-plated ferrous metal. Some of these mineral oil based lubricants have been found to be particularly troublesome to remove using the prior art cleaning solutions.

The difficult-to-remove lubricants are exemplified by Prosol 174 and 522 (Mobil Oil Corp.), Solvac 800, Quakerol 539 (Quaker Chemical Corp.), Technalube 174 (Techno Lube Products, Inc.), and Texaco 591 (Texaco, Inc.). "Prosol", "Solvac", "Quakerol" and "Texaco" are Registered Trade Marks.

The cleaning solutions of this invention can surprisingly remove such difficultto-remove lubricants, and tolerate a greater concentration of such lubricants than prior art cleaning solutions (thus reducing replenishment requirements and effluent) without excessive foaming and etching.

Following the application of the cleaning solution, the surface should be completely water break-free - that is completely free from lubricants, soil and other contaminants so that a continuous film of water may be formed on the surface. Such a clean and water break-free surface appears highly polished and has improved corrosion resistance. Indeed, a tin-plated ferrous metal surface which has been cleaned in accordance with the invention will not suffer corrosive attack when subjected even to prolonged exposure to air prior to application of a subsequent coating.

Subsequent to the cleaning process, the metal surface will normally be rinsed with water, since this removes any cleaning residues remaining on the metal surface after the cleaning step.

As noted hereinbefore, the cleaning process of this invention is primarily intended to be used as a preliminary step prior to conventional pre-treatments designed to increase corrosion resistance and enhance the adhesion of later applied organic, sanitary lacquer, siccative finishes or the like. For example, excellent corrosion resistance and sanitary lacquer adhesion has been obtained when an aqueous coating solution of the following formula is applied to the surface: /" by weight Monosodium monophosphate .65- .85 Disodium monophosphate .65.85 Hydroxylammonium acid sulphate .61-1.22 Ammonium bifluoride .03- .05 Water up to 100 An especially effective overall method of treating a tin-plated ferrous metal surface comprises the following steps.

(a) cleaning the surface to remove lubricants therefrom by contacting the surface with an aqueous cleaning solution of the invention having a pH value of from 11 to 12.5 and having for each part by weight of alkali metal meta-silicate in the solution amount from 0.2 to 0.7 parts by weight of alkali metal condensed phosphate, from 0.45 to 1.70 parts by weight of alkali metal carbonate, and from 0.2 to 0.55 parts by weight of alkali metal bicarbonate, whereby the lubricants are removed from the surface without significant etching of the surface; (b) rinsing the thus-cleaned surface with water; (c) contacting the rinsed surface with a coating solution which consists of or essentially contains monosodium monophosphate, disodium monophosphate, hydroxylammonium acid sulphate, ammonium bifluoride and water; (d) rinsing the thus-coated surface with water; and (e) applying a sanitary lacquer to the surface.

It will be noted that the cleaning solution employed in step (a) is a preferred cleaning solution of the invention.

Certain aspects of the present invention will now be described, though only by way of illustration, in the following Examples.

EXAMPLE I Drawn and ironed tin-plated steel cans were contacted in a production line for 40 seconds at various temperatures with an aqueous cleaning solution containing various concentrations of the cleaning composition of Formula IV above.

The pH of the cleaning solution was always between 11 and 12.

Quakerol 539 oil was added in various concentrations to the cleaning solution in addition to the Quaker 539 oil which was present from the forming operation.

The following observations were made on each run: Cleaning Additional Composition Quakerol 539 Concentration Concentration Temperature Run (grams/liter) (grams/liter) "C "F Observations 1 5.23 0 70.0 (158) Water break-free, no etching, foaming acceptable 2 5.23 .28 71.7 (161) Water break-free, no etching, foaming acceptable 3 7.48 .56 71.1 (160 Water break-free, no etching, foaming acceptable 4 11.22 1. 72.8 (163) Water break-free, slight etching of outside can walls, foaming acceptable 5 11.22 1.5 68.3 (155) Water break-free, no etching, foaming acceptable 6 11.22 1.5 70.0 (158) Water break-free, no etching, foaming acceptable The slight etching in Run 4 was caused by cleaning temperatures which were higher than necessary for the particular cleaning composition utilized.

Prior art cleaners, as exemplified by U.S. Patent No. 3,888,783, under the identical conditions, produced dewetting of side walls and domes of the cleaned drawn and ironed cans and produced excessive foaming in the cleaner tanks.

This example indicates that the cleaning solutions of this invention remove mineral oil based lubricants without etching and with only a minimum of foaming even when the cleaning solution contains an added lubricant.

EXAMPLE II Drawn and ironed tin-plated steel cans were contacted in a pilot plant for various times at a temperature of 71"C (160"F) with an aqueous cleaning solution containing 14.98 grams/liter of the cleaning composition of Formula IV above.

The pH of the cleaning solution was between 11 and 12.

Quakerol 539 was added in various concentrations to the cleaning solutions in addition to the Quakerol 539 oil which was present from the forming operation.

The following observations were made on each run: Additional Quakerol 539 concentration Time Run (grams/liter) (secs) Observations 0 0 60 Water break-free, no etching, foaming acceptable 2 .02 60 Water break-free, no etching, foaming acceptable 3 .04 60 Water break-free, no etching, foaming acceptable 4 .10 60 Water break-free, no etching, foaming acceptable 5 .23 60 Water break-free, no etching, foaming acceptable Two runs were then performed with an aqueous cleaning solution containing 22.47 grams/liter of the cleaning composition of Formula IV, and the following observations were made:: Additional Quakerol 539 concentration Time Run (grams/iiter) (secs) Observations 6 .63 60 Water break-free, no etching, foaming acceptable 7 .76 60 Water break-free, no etching, foaming acceptable This Example indicates that the cleaning solutions of this invention can tolerate buildup of lubricants and still remove mineral oil based lubricants without etching and with only a minimum of foaming.

EXAMPLE 111 Tin-plated drawn and ironed steel containers were employed in this Example.

A cleaning solution was prepared by adding 15 grams of the composition of Formula IV above to 1 liter of water, with stirring such that complete dissolution of the composition was achieved. The pH of the solution was between 11 and 12.

The containers were contacted by spraying the resulting solution for 60 seconds at 710C (160"F). After treatment, the containers were rinsed with cold water and visually observed for etching, gloss, and detinning. The test containers had a bright, rust free appearance with no tin loss or etching. During the cleaning process, it was observed that the metal surface was water break-free.

EXAMPLE IV Tin-plated steel containers were treated in the same manner as in Example I with the various solutions described below.

A base batch of solution was prepared by adding to water in the amount of 15 grams/liter a cleaning composition of the following mixture: , by weight Sodium meta-silicate (anhyd.) 29.9 Sodium tripolyphosphate (light) 9.5 Sodium bicarbonate 55.6 Onyx Defoamer &num;4 .5 The solution had a pH of 10.0 and is designated as Comparison Solution A.

To a portion of the above solution was added sufficient sodium hydroxide to react with half of the sodium bicarbonate, forming sodium carbonate and raising the pH to 10.7. This solution is designated as Invention Solution B, and is a cleaning solution of this invention. Invention Solution B contains, about, 27.8 /n sodium bicarbonate and 27.8 /n sodium carbonate.

To an additional portion of Comparison Solution A was added sufficient sodium hydroxide to convert all of the sodium bicarbonate present in the solution to sodium carbonate. The pH was 12.2. This solution is designated as Comparison Solution C, and contains about 55.6 sodium carbonate.

For comparison to Solutions A, B and C, a prior art cleaning solution was prepared having silicate, tripolyphosphate, a non-ionic surfactant and borax. This prior art cleaning composition, described in U.S. Patent 3,888,783, had the following formula: /n by weight Sodium meta-silicate (anhy. beads) 60 Sodium tripolyphosphate (anhy. powder) 14 Borax pentahydrate 21 Triton N-100 5 pH=l 1.9 The prior art cleaning composition was added to water in the amount of 10 g/l to form Prior Art Cleaning Solution D.

Solutions A, B, C and D were contacted respectively with tin-plated steel containers for 60 seconds at a temperature of 71"C (160"F) by spraying. The containers had residual lubricant oil. Quakerol 539, which is a difficult-to-remove mineral oil base lubricant, remaining on the surface from the drawing and ironing operation. After contacting the containers with the respective solutions, the cleaning solutions were observed for foaming action and the container surfaces were inspected for water-break, detinning and etching.

TABLE 1 Cleaning Solutions pH Observation Comparison Solution A 10 Gellation of solution, strong foaming action Invention Solution B 10.7 Water break-free sur face, some foam, no etching, no detinning Comparison Solution C 12.2 Slight etching and de tinning, water break free surface, no foam Prior Art Solution D 11.9 Medium etching, water break-free surface The Prior Art Cleaning Solution D resulted in unacceptable etching.

EXAMPLE V Drawn and ironed tin-plated steel cans were contacted for 60 seconds at 71 0C with an aqueous cleaning solution having the ingredients of phosphate, carbonate, bicarbonate, and silicate, to which were added various surfactants.

The basic cleaning composition to which surfactants were added had the following formula: /n by weight Sodium tripolyphosphate 10.0 Sodium carbonate 48.8 Sodium bicarbonate 12.2 Sodium meta-silicate (Metso anhyd. 2048 bead) 28.8 The cleaning composition was added to water in the amount of 13.5 grams/liter to form the Base Cleaning Solution.

One or more surfactants were then added to the Base Cleaning Solution.

From time to time additions were made to the cleaning solution of Quakerol 539, a drawing and ironing lubricant. The lubricant was added to the respective solutions in the form of a 100 oil-in-water emulsion, and the additions were made in 50 ml increments. An addition of a 10 n oil-in-water emulsion to a 6 liter bath (as used herein) resulted in .833 gramYliter increase in content of lubricant in the cleaning solution.

After contacting the can surface with the cleaning solution for 60 seconds, the surface was evaluated for cleanliness.

A thoroughly cleaned and water break-free surface was rated as 2. If the surface was substantially dewetted a rating of 0 was given. Numbers and fractions between 0 and 2 represent the amount of water break-free surface. These numbers are added together resulting in a "Total Cleanliness Rating" wherein 0 is a substantially dewetted surface and 8 is a thoroughly cleaned and water break-free surface.

After treating a number of cans, after which a sample can was taken for evaluation, the solution was observed for foaming. The table below gives the results of tests performed.

TABLE 2 Total Concentration Surfactant in Total Quakerol 539 Base Cleaning Surfactant in Cleaning Total Foam Solution Concentration Solution Cleanliness Height'2' (Tradenames) (g/l) (g/i) Rating" (inches) ( 1) Tergitol Min-Foam l-X 1.0 0 7 0 (2) Tergitol Min-Foam l-X(+) 2.0 0 8 0 Triton N-l00(l:l) (3) Tergitol Min-Foam l-X(+) 2.0 0 8 0 Triton No100(1:1) (4) Tergitol Min-Foam l-X(+) Triton N-100(2:1) 3.0 .833 8 T (5) Triton N-100 (+) MakonNF-12(1:1) 2.0 0 8 0 (6) Surfonic LF-17 1.0 0 6+ 0 (7)Surfonic LF-17(+) TritonN-100(1:1) 2.0 0 8 0 (8) Surfonic LF-17 (+) Triton N-100(1::1) 2.0 .833 6T (9)Neodol 25-7 1.0 0 8 1 (l0)Neodol 25-7(+) Tergitol Min-Foam l-X (1:1) 2.0 0 7T a (Il) Neodol 25-7 (+) Tergitol Min-Foam l-X(+) Triton N-100 (1:1:1) 3.0 .833 7 + (12) Neodol 25-7 (+) MakonNF-12(1:1) 2.0 0 8 (13) Surfonic LF-17 (+) Neodol 25-7(1:1) 2.0 0 8 + (14)Neodol 25-9 1 0 8 + (15) Neodol 25-9 (+) Tergitol Min-Foam l-X(l:l) 2.0 0 7T - (16) Neodol 25-9 (+) Tergitol Min-Foam l-X (1::1) 3. 0 7T (17)Neodol 25-9(+) Surfonic LF-17 2.0 0 8 (1) Foam height over 2+ inches is unsatisfactory.

(2) Total Cleanliness rating of less than 6 is unsatisfactory.

EXAMPLE VI Drawn and ironed tin-plated steel cans were contacted for 60 seconds at 71 0C with an aqueous cleaning solution having the ingredients of phosphate, carbonate, bicarbonate, and silicate, to which were added various surfactants.

The basic cleaning composition to which surfactants were added had the following formula: % by weight Sodium tripolyphosphate 10.1 Sodium carbonate 23.3 Sodium bicarbonate 23.3 Sodium meta-silicate (Metso anhyd. 2048 bead) 43.3 The cleaning composition was added to water in the amount of 13.5 grams/liter to form the Base Cleaning Solution.

One or more surfactants were then added to the Base Cleaning Solution.

From time to time additions were made to the cleaning solution of Quakerol 539, a drawing and ironing lubricant. The lubricant was added to the respective solutions in the form of a 10% oil-in-water emulsion, and the additions were made in 50 ml increments. An addition of a lY oil-in-water emulsion to a 6 liter bath (as used herein) resulted in .833 grams/liter increase in content of lubricant in the cleaning solution.

TABLE 3 Total Concentration Surfactant in Total Quakerol 539 Base Cleaning Surfactant in Cleaning Total Total Solution concentration Solution Cleanliness Height121 (Tradenames) (g/l) (g/l) Rating111 (inches) (1)None O 0 7s T (2) Tergitol Min-FoamlX 1.0 0 7+ + (3) Tergitol Min-Foam l-X (+) Triton N-100(1:1) 2.0 0 8 3, (4) Tergitol Min-Foam l-X (+) TritonN-100(1:1) 2.0 .833 8 1+ (5) Tergitol Min-Foam l-X (+) TritonN-100(1: :1) 2.0 1.666 6+ 2 (6) Tergitol Min-Foam l-X (+) Triton N-100 (+) Surfonic LF-17(1:1:1) 3.0 1.666 7+ + (7)SurfonicLF-l7 1.0 0 7 0 (8) Surfonic LF-17 (+) Triton N-100(1:1) 2.0 .833 8 < ]r (9) Triton N-100 (+) OnyxDefoamer#4 (1:1) 2.0 0 8 (10) Onyx Defoamer#4 (+) Triton N-100 (+) Surfonic LF-17 (1:1:1) .. . . a (1) Foam height over 2+ inches is unsatisfactory.

(2) Total Cleanliness rating of less than 6 is unsatisfactory.

Claims

WHAT WE CLAIM 15: I. A cleaning composition comprising: (a) an alkali metal meta-silicate; (b) an alkali metal condensed phosphate; (c) an alkali metal carbonate; and (d) an alkali metal bicarbonate; wherein for each part by weight of the alkali metal meta-silicate in the cleaning composition there is from 0.1 to 1.5 parts by weight of alkali metal condensed phosphate. from 0.3 to 2.5 parts by weight of the alkali metal carbonate, and up to

1.5 parts by weight of the alkali metal bicarbonate.

2. A cleaning composition as claimed in Claim 1, wherein the alkali metal condensed phosphate is an alkali metal tripolyphosphate or an alkali metal pyrophosphate.

3. A cleaning composition as claimed in Claim 1 or Claim 2, wherein the alkali metal condensed phosphate is or includes sodium tripolyphosphate.

4. A cleaning composition as claimed in any of the preceding claims, wherein the alkali metal carbonate is sodium carbonate.

5. A cleaning composition as claimed in any of the preceding claims, wherein the alkali metal bicarbonate is sodium bicarbonate.

6. A cleaning composition as claimed in any of the preceding claims, wherein the alkali metal meta-silicate is sodium meta-silicate.

7. A cleaning composition as claimed in any of the preceding claims, wherein substantially all the alkali metal cations are sodium and/or potassium.

8. A cleaning composition as claimed in any of the preceding claims, wherein substantially all the alkali metal cations are sodium.

9. A cleaning composition as claimed in any of the preceding claims, wherein the alkali metal meta-silicate is sodium meta-silicate, the alkali metal condensed phosphate is sodium tripolyphosphate, the alkali metal carbonate is sodium carbonate and the alkali metal bicarbonate is sodium bicarbonate.

10. A cleaning composition as claimed in any of the preceding claims, wherein for each part by weight of the alkali metal meta-silicate in the cleaning composition there is from 0.20 to 0.70 parts by weight of the alkali metal condensed phosphate, from 0.45 to 1.70 parts by weight of the alkali metal carbonate, and from 0.20 to 0.55 parts by weight of the alkali metal bicarbonate.

11. A cleaning composition as claimed in any of the preceding claims, which also comprises a non-ionic surfactant.

12. A cleaning composition as claimed in Claim 11, wherein for each part by weight of alkali metal meta-silicate present in the cleaning composition there is a total of from 0.05 to 0.5 parts of non-ionic surfactant.

13. A cleaning composition as claimed in Claim 11 or Claim 12, wherein the non-ionic surfactant is or includes at least one low-foaming surfactant.

14. A cleaning composition as claimed in any of the preceding claims and substantially as herein described.

15. An aqueous cleaning solution comprising: (a) an alkali metal meta-silicate in an amount of from 0.5 grams/iitre to 13 grams/litre; (b) an alkali metal condensed phosphate; (c) an alkali metal carbonate; and (d) an alkali metal bicarbonate; wherein for each part by weight of the alkali metal meta-silicate in the solution there is from 0.1 to 1.5 parts by weight of alkali metal condensed phosphate, from 0.3 to 2.5 parts by weight of the alkali metal carbonate, and up to 1.5 parts by weight of the alkali metal bicarbonate.

16. An aqueous cleaning solution as claimed in Claim 15, wherein for each part by weight of the alkali metal meta-silicate in the solution there is from 0.20 to 0.70 parts by weight of the alkali metal condensed phosphate, from 0.45 to 1.70 parts by weight of the alkali metal carbonate, and from 0.20 to 0.55 parts by weight of the alkali metal bicarbonate.

17. A solution as claimed in Claim 15 or Claim 16, having a pH of at least 10.

18. A solution as claimed in Claim 17, having a pH of from 11 to 12.5.

19. A solution as claimed in any of Claims 15 to 18. which further comprises a non-ionic surfactant.

20. A solution as claimed in Claim 19, wherein the non-ionic surfactant is or includes at least one low-foaming surfactant.

21. A solution as claimed in any of Claims 15 to 20, wherein the alkali metal meta-silicate is sodium meta-silicate; the alkali metal carbonate is a mixture of sodium carbonate and sodium bicarbonate; and the alkali metal condensed phosphate is sodium tripolyphosphate.

22. An aqueous cleaning solution as claimed in any of Claims IS to 21 and substantially as herein described.

23. A process for cleaning a metal surface to remove lubricants therefrom, in which the surface is contacted with a cleaning solution according to Claim 15, whereby the lubricants are removed from the metal surface without significant etching of the metal surface.

24. A process as claimed in Claim 23, wherein the metal surface is a tin-plated ferrous metal surface.

25. A process as claimed in Claim 24, wherein the metal surface is a drawn and ironed tin-plated ferrous metal surface.

26. A process as claimed in any of Claims 23 to 25, wherein the alkali metal meta-silicate is sodium meta-silicate.

27. A process as claimed in any of Claims 23 to 26, wherein the alkali metal condensed phosphate is sodium tripolyphosphate.

28. A process as claimed in any of Claims 23 to 27, wherein the alkali metal carbonate and alkali metal bicarbonate are, respectively, sodium carbonate and sodium bicarbonate.

29. A process as claimed in any of Claims 23 to 28, wherein the surfaces are contacted with the cleaning solution by spraying them therewith for a period sufficient to ensure complete wetting of the surfaces.

30. A process as claimed in any of Claims 23 to 29, wherein the surfaces are contacted with the cleaning solution by spraying theni therewith for a period not exceeding 20 minutes.

31. A process as claimed in Claim 30, wherein the surfaces are sprayed for a period of from 15 to 60 seconds.

32. A process as claimed in any of Claims 23 to 31, wherein the metal surfaces are contacted with the cleaning solution at a temperature which does not exceed 90"C.

33. A process as claimed in Claim 32, in which the temperature of the cleaning solution is from 57"C to 800C.

34. A process as claimed in any of Claims 23 to 33, wherein the cleaning solution further comprises a non-ionic surfactant.

35. A process as claimed in Claim 34, wherein the non-ionic surfactant is or includes at least one low foaming surfactant.

36. A process for cleaning a metal surface to remove lubricants therefrom, as claimed in any of Claims 23 to 35 and substantially as herein described.

37. A method of treating a tin-plated ferrous metal surface, which comprises the steps of: (a) cleaning the surface to remove lubricants therefrom by contacting the surface with an aqueous cleaning solution of the invention having a pH value of from 11 to 12.5 and having for each part by weight of alkali metal meta-silicate in the solution from 0.2 to 0: :7 parts by weight of alkali metal condensed phosphate, from 0.45 to 1.70 parts by weight of alkali metal carbonate, and from 0.2 to 0.55 parts by weight of alkali metal bicarbonate, whereby the lubricants are removed from the surface without significant etching of the surface; (b) rinsing the thus-cleaned surfaces with water; (c) contacting the rinsed surfaces with a coating solution which consists of or essentially contains monosodium monophosphate, disodium monophosphate, hydroxylammonium acid sulphate, ammonium bifluoride and water; (d) rinsing the thus-coated surfaces with water; and (e) applying a sanitary lacquer to the surface.

38. A method as claimed in Claim 37 wherein the alkali metal meta-silicate is sodium meta-silicate, the alkali metal condensed phosphate is sodium tripolyphosphate, the alkali metal bicarbonate is sodium bicarbonate.

39. A method of treating tin-plated ferrous metal surfaces as claimed in Claim 37 or Claim 38 and substantially as herein described.