Description
COMPOSITION AND METHOD FOR TREATING THE SURFACE OF
ALUMINIFEROUS METALS
FIELD OF THE INVENTION
This invention relates to a liquid composition, which may be either a work¬ ing composition suitable for direct use in treating metal (and if so may also be called a "bath" herein below even if not used by immersion) or a concentrate composition suitable for diluting with water and/or mixing with one or more other concentrate compositions to form a working composition, and to a method for treating the surface of aluminiferous metals, which are defined for this purpose to be aluminum and its alloys that contain at least 45 % by weight of aluminum. More particularly, this invention relates to a composition and/or method, for treating the surface of aluminiferous metals, that imparts thereto an excellent re¬ sistance to blackening by boiling water, an excellent paint adherence, and an ex¬ cellent lubricity, and which are therefore useful, for example, for creating surface conditions that are highly adapted for aluminum can fabrication. DESCRIPTION OF RELATED ART The manufacture of drawn-and-ironed (the phrase "drawn-and-ironed" and any grammatical variations thereof such as "drawing-and-ironing", "draw-and¬ iron", or the like being hereinafter usually abbreviated "Dl") aluminum cans typ¬ ically performed by a Dl process, followed by surface cleaning with an acidic cleaner in order to remove soil commonly called "smut" in the art, the smut being composed of aluminum microparticles, lubricant (coolant), metal soap, and the like, and then by a phosphate conversion coating treatment on the surface, with the goal of improving the corrosion resistance and paint adherence. These con¬ version coating treatments may be broadly classified into chromate treatments, which produce chromium phosphate coatings, and non-chromate treatments, which usually contain zirconium compounds such as fluozirconic acid and salts thereof and produce composite films of zirconium oxide, zirconium phosphate,, and the like.
Cleaning processes using non-chromate conversion reagents have re¬ cently come to account for approximately 80 % of the cleaning lines in Japan as
a consequence of environmental protection issues. After the conversion treat¬ ment, conversion-coated aluminum cans are generally subjected to a thorough rinse in a washer and drying in a water-draining oven, and, upon exiting the oven, are transported to a printing or painting process. Upon reaching the print- ing or painting process, the cans, which during previous process steps are typ¬ ically running in about five to thirty lines, are passed through a single filer to form a single line for transfer to a special-purpose conveyor. Can transport is imped¬ ed at this point by the contact occurring between the cans and guides and be¬ tween individual cans. The prevailing view is that the reason for this is the rela- tively high coefficient of static friction of cleaned and conversion-treated alumin¬ um cans. The recent increases in transport rates associated with increases in can manufacturing output have caused a proliferation in the sources of this prob¬ lem, and the resulting reduction in productivity has become an increasingly seri¬ ous problem. This has created a strong desire to reduce the coefficient of static friction of the external surfaces of aluminum cans without impairing the corrosion resistance.
For example, Japanese Patent Application Laid Open [Kokai or Unexam- ined] Number Sho 64-85292 [85,292/1989] teaches a method for imparting lu¬ bricity to aluminum cans and thereby raising the can transport efficiency. In this method, a water-soluble organophosphate ester, water-soluble derivative of a saturated fatty acid, or the like is sprayed onto the can surface between the final deionized water rinse in the can washer line and the draining-drying process. This spraying serves to form a lubricating organic film on the can surface.
However, when a cleaning unit is employed that recycles the deionized water from the final rinse using an active carbon adsorption treatment, compon¬ ents of the coating end up being adsorbed by the active carbon. This has nega¬ tive economic consequences because it accelerates deterioration of the active carbon and increases chemical consumption. In addition, when the shape of the workpiece is such that the bath tends to drain from one part of the workpiece sur- face into a pool over another part of the surface, the concentration of the residual bath in the pool zones during drying causes such problems as uneven blotches and paint film delamination.
Japanese Patent Application Laid Open [Kokai or Unexamined] Number Hei 5-239434 [239,434/1993] describes a method for forming a highly lubricating organic-inorganic composite coating. In this method, in the conversion coating process in the aforementioned can washer line the aluminiferous metal substrate is sprayed with or immersed in an acidic aqueous solution (pH adjusted to 2 to 5) that contains metal ions (Fe, Zr, Sn, Al, and/or Ce) and/or water-soluble or- ganophosphate esters or water-soluble derivatives of a saturated fatty acid. Ne¬ vertheless, the aluminiferous metal afforded by this method still does not exhibit an acceptable resistance to blackening. In sum, then, there is not yet available at the present time a composition and/or method for treating the surface of aluminiferous metals that is able to sim¬ ultaneously furnish an excellent corrosion resistance, excellent paint adherence, and excellent lubricity under all or almost all conditions of practical use of the treated aluminiferous metal substrates. DESCRIPTION OF THE INVENTION
Problems to Be Solved by the Invention The present invention seeks to solve the problems described above for the related art. In specific terms, the present invention introduces a novel sur¬ face-treatment composition and/or method that is able to form a very corrosion- resistant, strongly paint-adherent, and highly lubricating conversion coating on the surface of aluminiferous metals.
Summary of the Invention
It was discovered that very corrosion-resistant, strongly paint-adherent, and highly lubricating coatings can be formed on the surface of aluminiferous metals through the use of a water-based treatment bath containing particular quantities of phosphate ion, fluoride, water-soluble polyamide, and at least one selection from water-soluble zirconium and titanium compounds.
A composition according to the present invention, which may be either a working composition directly suitable for treating the surface of aluminiferous metals or a concentrate for making a working composition by dilution with water and/or mixing with other concentrates, comprises, preferably consists essentially of, or more preferably consists of, water and:
(A) phosphate ions;
(B) a component selected from water-soluble zirconium and titanium com¬ pounds, in an amount such that the ratio by weight of the stoichiometric equivalent as total zirconium and titanium metal to the weight of phosphate ions in the composition is from 0.01 to 50;
(C) a component selected from simple and complex fluoride anions, in an amount such that the ratio by weight of the stoichiometric equivalent as total fluorine to the weight of phosphate ions in the composition is from 0.01 to 200; and (D) a component selected from polyamides that include moieties selected from the group consisting of tertiary amino moieties and polyoxyalkylene moieties, in an amount such that the ratio by weight of the polyamides to the weight of phosphate ions in the composition is from 0.01 to 200.
A bath according to the present invention for treating the surface of aluminiferous metals is an aqueous solution, with a pH value in the range from
1.8 to 4.0, which comprises, preferably consists essentially of, or more preferably consists of water and:
(A) from 0.01 to 1.0 grams per liter (hereinafter usually abbreviated "g/L") of phosphate ions, (B) from 0.01 to 0.5 g/L, measured as its total stoichiometric equivalent as zirconium and/or titanium metal, of a component selected from the group consisting of water-soluble zirconium and titanium compounds;
(C) from 0.01 to 2.0 g/L, measured as its stoichiometric equivalent as fluorine, of a component selected from the group consisting of simple and complex fluoride anions; and
(D) from 0.01 to 2.0 g/L of a component selected from the group consisting of water-soluble polyamide molecules, each of which contains at least one moiety selected from the group consisting of tertiary amine moieties and polyoxyalkylene moieties. Finally, a method according to the present invention for treating a surface of aluminiferous metals characteristically comprises the formation of a conversion coating on a surface of aluminiferous metal by contacting the metal surface with
a surface-treatment bath according to the invention as described above, in order to form thereon a layer including material incorporated from the surface- treat¬ ment bath and, optionally but preferably, thereafter rinsing with water and drying by heating. 5 Brief Description of the Drawings
Figure 1 (A) is a top view showing cans to be tested for coefficient of fric¬ tion in place on a tiltable plate in testing apparatus. Figures 1(B) and 1 (C) are front and side views respectively of the same apparatus, with cans in place there¬ on, as is shown in Figure 1(A). ιo Description of Preferred Embodiments.
Aluminiferous metals which may be subjected to the present invention en¬ compass aluminum and aluminum alloys, wherein said aluminum alloys encom¬ pass aluminum/manganese alloys, aluminum/magnesium alloys, aluminum/cop¬ per alloys, and the like. The shape and dimensions of the aluminiferous metal is are not critical; for example, sheet, tubing, wire, and the like, may all be treated. A concentrate composition according to the present invention is a water- based mixture — and preferably an aqueous solution — containing the neces¬ sary ingredients already described above. The total solids concentration in such as concentrate composition is not critical, but in general preferably does not ex- 0 ceed 10 weight % and more preferably is 0.01 to 1 weight %.
The phosphate ions source can be, for example, phosphoric acid (H3P04), sodium phosphate (Na3P04), ammonium phosphate ((NH4)3P04), and/or the like. The phosphate ions concentration preferably ranges from 0.01 to 1.0 g/L and particularly preferably ranges from 0.02 to 0.40 g/L. The reactivity, with a surface 5 of aluminiferous metal, of a bath otherwise according to the invention but with phosphate ions concentrations below 0.01 g/L generally is inadequate, so that an acceptable coating will not be produced. Since no additional improvements in film-forming capacity are obtained at phosphate ions concentrations beyond 1.0 g L, the corresponding increase in the cost of the treatment bath is econom- o ically unjustified.
The water-soluble zirconium compounds and water-soluble titanium com¬ pounds can be selected, for example, from oxides such as zirconium oxide and
titanium oxide, hydroxides such as zirconium hydroxide and titanium hydroxide, fluorides such as zirconium fluoride and titanium fluoride, and nitrates such as zirconium nitrate and titanium nitrate; however, other water-soluble compounds of zirconium and titanium may be used. The concentration of this component 5 preferably ranges from 0.01 to 0.5 g/L, measured as the stoichiometric equiva¬ lent as zirconium and/or titanium metal, and particularly preferably ranges from 0.02 to 0.08 g/L as metal. The film-forming capacity of the surface-treatment bath is usually inadequate at concentrations below 0.01 g/L. On the other hand, no additional improvements in film-forming capacity are normally obtained at con- o centrations beyond 2.0 g/L, and the corresponding increase in the cost of the treatment bath is therefore economically unjustified.
The fluoride component can be obtained from acids such as hydrofluoric acid (HF), fluozirconic acid (HjZrFe), fluotitanic acid (H2TiF6), and the like, and from the salts of these acids (for example, ammonium salts, sodium salts, and s the like), but no specific limitations apply to the particular fluoride selected. (If flu¬ ozirconic and/or fluotitanic acids and/or salts thereof are used, these materials are sources of both the necessary metal content, as described in the paragraph immediately preceding this one, and the fluoride.) The fluoride concentration in the surface-treatment bath preferably ranges from 0.03 to 1.0 g/L, measured as o its stoichiometric equivalent as fluorine, and particularly preferably ranges from 0.03 to 0.6 g/L as fluorine. The poor reactivity occurring at concentrations below 0.03 g/L generally prevents the formation of an acceptable coating. At the other end of the range, concentrations above 1 g/L are undesirable due to the deteri¬ oration in appearance that results from the greater degree of etching of the alum- 5 iniferous metal surface. The most optimal fluoride concentration is determined by the concentration of aluminum that elutes from the metal and will therefore vary as a function of this aluminum concentration. This is due to the fact that the fluoride is required at least in part for the purpose of stabilizing, as aluminum fluoride, the aluminum eluted into the treatment bath. For example, approximate- ly 0.2 g/L of fluorine is required per 0.1 g/L of eluted aluminum.
One type of amino-functional water-soluble polyamides used by the pres¬ ent invention is exemplified by condensation polyamides from dicarboxylic acid
molecules (e.g., adipic acid, sebacic acid, etc.) and diamine molecules that con¬ tain a tertiary amino group in their main chains, such as N-(aminoethyl)pipera- zine, bis[N-(aminopropyl)piperazine], and the like, and by copolyamides of the preceding with lactams, including lactams that contain a pendant tertiary amino group, e.g., alpha-dimethylamino-epsilon-caprolactam.
A second type of polyamides, whose main chains contain polyoxyalkylene moieties, are exemplified by polyamides from dicarboxylic acid molecules (e.g., adipic acid, sebacic acid, etc.) and diamine molecules obtained from polyoxyeth¬ ylene with a molecular weight of approximately 200 to 4,000, optionally also in- eluding diamines such as hexamethylenediamine, and by copolyamides of the preceding with lactams. In general, polyoxyethylene moieties are preferred over those derived from higher molecular weight epoxides than ethylene oxide.
The surface-treatment bath concentration of water-soluble polyamide mol¬ ecules preferably ranges from 0.01 to 2.0 g/L and particularly preferably ranges from 0.05 to 0.5 g/L. When the polyamide concentration falls below 0.01 g/L, coating formation is impeded and any coating formed also usually will be poorly lubricating. No additional improvements in film-forming capacity are generally obtained at polyamide concentrations beyond 2.0 g L, and the corresponding in¬ crease in the cost of the treatment bath is therefore economically unjustified. The pH of a surface-treatment bath according to the present invention should be from 1.8 to 4.0. The stronger etching that occurs at pH values below 1.8 makes it difficult for a coating to form, while the formation of highly corrosion- resistant coatings is hindered at pH values in excess of 4.0. These factors re¬ quire that the pH be in the range of 1.8 to 4.0; the preferred pH range is 2.0 to 3.0. The pH of the surface-treatment bath can be adjusted through the use of acid, e.g., phosphoric acid, nitric acid, hydrochloric acid, hydrofluoric acid, and the like, or alkali, e.g., sodium hydroxide, sodium carbonate, ammonium hydrox¬ ide, and the like.
When treatment bath stability is substantially reduced by alloying metal ions, from alloying components such as copper, manganese, and the like, eluting from the workpiece, an at least difunctional organic acid such as gluconic acid, oxalic acid, etc. and/or other known chelating agent(s), may advantageously be
added to a bath according to this invention, in order to chelate this destabilizing component.
Surface-treatment methods according to the present invention will be ex¬ plained in detail in the following. While no narrow requirements apply to the treatment temperature and treatment time for the surface-treatment bath used in the invention method, treatment preferably uses the following conditions: (i) when the surface-treatment bath is applied to the aluminiferous metal sur¬ face by spraying, preferred conditions are contact for 15 to 40 seconds at temperatures of 25 °C to 50 °C, followed by water rinsing; (ii) when the metal workpiece is immersed in the surface-treatment bath, pre¬ ferred conditions are immersion for 15 to 60 seconds at 25 °C to 50 °C, followed by water rinsing.
More specifically preferred embodiments of the method according to the present invention are given below, Steps, in Order of Use, in Alternative Preferred Process #1 :
1. Degreasing the metal surface (e.g., Dl cans) at 40 °C to 80 °C by spraying an acidic or alkaline aqueous based or an organic solvent based degreas¬ ing composition on the surface for 25 to 60 seconds.
2. Water rinse. 3. Surface treatment, using a bath according to the present invention at 25 °C to 50 °C by spraying for 15 to 50 seconds.
4. Water rinse.
5. Rinse with deionized water
6. Drying. Steps, in Order of Use, in Alternative Preferred Process #2:
1. Degreasing the metal surface (e.g., Dl cans) at 40 °C to 80 °C by spraying an acidic or alkaline aqueous based or an organic solvent based degreas¬ ing composition for 25 to 60 seconds.
2. Water rinse. 3. Phosphate conversion coating treatment at 30 °C to 50 °C by spraying for 8 to 30 seconds. 4. Surface treatment, using a bath according to the present invention at 25
°C to 50 °C by spraying for 3 to 30 seconds.
5. Water rinse.
6. Rinse with deionized water
7. Drying. Steps, in Order of Use, in Alternative Preferred Process #3
1. Degreasing the metal surface (e.g., Dl cans) at 40 °C to 80 °C by spraying an acidic or alkaline aqueous based or an organic solvent based degreas¬ ing composition for 25 to 60 seconds.
2. Water rinse. 3. Phosphate conversion coating treatment at 30 °C to 50 °C by spraying for 8 to 30 seconds.
4. Water rinse.
5. Surface treatment, using a bath according to the present invention at 25 °C to 50 °C by spraying for 3 to 30 seconds. 6. Water rinse.
7. Rinse with deionized water.
8. Drying.
As specified above, 25°C to 50°C is the preferred range for the treatment temperature using a surface-treatment bath according to the present invention. Low reactivity at temperatures below 25 °C can lead to failure to form a high quality coating. Most zirconium compounds in the treatment bath according to this invention become unstable at temperatures above 50 °C, which leads to their partial precipitation and can lead to loss of treatment bath stability.
With regard to the treatment times given above, appropriate treatment times in the case of surface-treatment Alternative Preferred Process #1 are 15 to 50 seconds. Sufficient reaction does not reliably occur and a strongly corro¬ sion-resistant coating may therefore not be produced at treatment times below 15 seconds. Additional increases in performance become uncertain at treatment times in excess of 50 seconds. A particularly preferred treatment time range for surface-treatment Alternative Preferred Process #1 above is 20 to 30 seconds. Preferred treatment times for surface-treatment Alternative Preferred Pro¬ cesses 2 and 3 above are 3 to 30 seconds. Sufficient reaction does not reliably
occur and a strongly corrosion-resistant coating may therefore not be produced at treatment times below 3 seconds. Additional increases in performance be¬ come uncertain at treatment times in excess of 30 seconds. A range of 5 to 15 seconds is the particularly preferred treatment time range for surface-treatment Alternative Processes #2 and #3 above.
The known non-chromium conversion coatings for aluminum can be used as the phosphate conversion coating in the two-reactive-treatment sequences of Processes 2 and 3 above. These are specifically exemplified by the conver¬ sion coatings described in Japanese Patent Publication Numbers Sho 52-131937 [131,937/1977], Sho 58-30344 [30,344/1983], and Sho 57-39314 [39,314/1982]. When the conversion treatment bath does not contain a component (e.g., S04 ions) that is detrimental to the effects of the present invention, treatment with a bath according to the present invention can be executed immediately after con¬ version treatment without an intervening water rinse, as in Alternative Preferred Process 2 above. When the conversion treatment bath does contain such a component, treatment with a bath according to the present invention is preferably carried out following a water rinse after conversion coating.
This invention will be illustrated in greater detail hereinafter through work¬ ing examples, and the benefits of the invention will be illustrated by comparative examples.
General Conditions for Examples and Comparison Examples _L Substrate metal: Aluminum Dl cans
The aluminum Dl cans that were surface treated as described beiow were fabricated by Dl-processing of aluminum sheet and then cleaned with a hot aque- ous solution of PALKLIN® 500 acidic degreaser, commercially supplied by Nihon Parkerizing Company, Ltd. _ Evaluation methods
(1 ) Corrosion resistance: Corrosion resistance of the aluminum Dl cans was examined by evaluating the extent of blackening after immersion of the treated can in boiling water for 30 minutes. Absence of blackening is the desired result.
(2) Lubricity: Lubricity was evaluated based on the following test using the sliding tester depicted in Figures 1(A), (B), and (C). Three of the surface-treated
aluminum Dl sample cans were placed on the horizontally positioned tiltable plate 1 in the sliding tester. Two of the cans, designated as 2a, were loaded with their bottom ends facing to the front. The remaining single can, designated as 2b, was loaded with its open end facing to the front. The tiltable plate 1 was then tilted at a constant rate of 3° of angle per sec¬ ond by the action of the motor 3. The coefficient of static friction was calculated from the angle of inclination, determined from the time required until at least one can fell off. (3) Paint adherence: In order to evaluate the paint adherence, the surface of the treated can was coated with an epoxy-urea can paint to a paint film thick¬ ness of 5 to 7 micrometers, then baked for 4 minutes at 215 °C. Cellophane tape-peel testing was then carried out on a cross scribed in the evaluation sur¬ face using a knife cutter to determine primary adherence. The sample cans were subsequently immersed for 60 minutes in a boiling test solution with the composi- tion given below, after which cellophane tape-peel testing was again carried out to determine secondary adherence. The adherence was evaluated as the pres¬ ence/absence of paint film peeling.
Test solution (simulated juice) 5 g/L of sodium chloride 5 g/L of citric acid
Balance: deionized water Specific Examples
Example 1 The surfaces of cleaned aluminum Dl cans were subjected to the following treatment steps in the sequence given: spraying for 20 seconds with ALODINE® 404 zirconium phosphate based conversion coating bath for aluminum Dl can ap¬ plications heated to 35 °C (commercially supplied by Nihon Parkerizing Com¬ pany, Ltd.); spraying for 10 seconds with Surface-treatment Bath 1 having the composition shown below and heated to 35 °C; rinsing with tap water; spraying for 10 seconds with deionized water with a specific resistivity of at least 3,000,000 ohm-cm; and drying for 2 minutes at 200 °C in a hot-air drying oven. The corrosion resistance and paint adherence of the resulting Dl can were then
evaluated. (Note: In all the descriptions of the surface treatment baths below, "ppm" = parts per million by weight and the value shown for fluorine ["F"] is the total fluorine from both fluozirconic acid and hydrofluoric acids when both are present.) Surface-treatment Bath 1
75 % phosphoric acid (H3P04): 138 ppm (P04: 100ppm)
20 % fluozirconic acid (H2ZrF6): 1137 ppm (Zr: 100 ppm)
20 % hydrofluoric acid (HF): 235 ppm (F: 170 ppm) water-soluble polyamide #1 : 250 ppm pH: 2.5 (adjusted with nitric acid or aqueous ammonia)
The remainder of the Bath was water. Water-soluble polyamide #1 was a terpol- ymer of adipic acid, N-(aminoethyl)piperazine, and caprolactam.
Example 2 Cleaned aluminum Dl cans were subjected to the following treatments in the sequence given: spraying for 25 seconds with the same surface-treatment as was used in the first step in Example 1 ; immersion for 15 seconds in Surface- treatment Bath 2 having the composition shown below and heated to 30 °C; a water rinse and 10-second spray with de-ionized water as in Example 1 ; and drying for 2 minutes at 200 °C in a hot-air drying oven. The corrosion resistance and paint adherence of the resulting Dl cans were then evaluated. Surface-treatment Bath 2
75 % phosphoric acid (H3P04) 206 ppm (P04: 150ppm)
20 % fluozirconic acid (H2ZrF6) 455 ppm (Zr: 40 ppm)
20 % hydrofluoric acid (HF) 210 ppm (F: 90 ppm) water-soluble polyamide #1 150 ppm pH: 3.0 (adjusted with nitric acid or aqueous ammonia) The remainder of the Bath was water.
Example 3 The cleaned aluminum Dl cans were subjected to the following treatments in the sequence given: spraying for 20 seconds with the same surface-treatment as was used in the first step in Example 1 ; spraying for 5 seconds with Surface- treatment Bath (3) having the composition shown below and heated to 45 °C;
and a water rinse, de-ionized water rinse, and drying as in Example 1. The cor¬ rosion resistance and paint adherence of the resulting Dl cans were then evalu¬ ated.
Surface-treatment Bath 3 75 % phosphoric acid (H3P04) 413 ppm (P04: 300 ppm)
20 % fluotitanic acid (H2TiF6) 683 ppm (Ti: 40 ppm)
20 % hydrofluoric acid (HF) 262 ppm (F: 100 ppm) water-soluble polyamide #2 200 ppm pH: 2.5 (adjusted with nitric acid or aqueous ammonia) The balance of the Bath was water. Water-soluble polyamide #2 is a terpolymer of adipic acid; an amine terminated polyoxyethylene with the general formula H2N-(C2H40)n-NH2, where n represents a positive integer with a value such that the polyoxyethylene block represented by (C2H40)n has a molecular weight in the range from about 200 to 4,000; and caprolactam. Example 4
The cleaned aluminum Dl cans were subjected to the following treatments in the sequence given: spraying for 20 seconds with the same surface-treatment as was used in the first step in Example 1 ; immersion for 30 seconds in Surface- treatment Bath 4 having the composition shown below and heated to 50 °C; and a water rinse, deionized water rinse, and drying as in Example 1. The corrosion resistance and paint adherence of the resulting Dl cans were then evaluated. Surface-treatment Bath 4
75 % phosphoric acid (H3P04) 138 ppm (P04: 100 ppm)
20 % fluozirconic acid (H2ZrF6) 1137 ppm (Zr: 100 ppm) 20 % hydrofluoric acid (HF) 235 ppm (F: 170 ppm) water-soluble polyamide #2 100 ppm pH: 2.8 (adjusted with nitric acid or aqueous ammonia) The balance of the Bath was water.
Example 5 The cleaned aluminum Dl cans were subjected to the following treatments in the sequence given: spraying for 20 seconds with the same surface-treatment as in the first step of Example 1 ; spraying for 8 seconds with Surface-treatment
Bath 5 having the composition shown below and heated to 35 °C; and a water rinse, deionized water rinse, and drying as in Example 1. The corrosion resist¬ ance and paint adherence of the resulting Dl cans were then evaluated. Surface-treatment Bath (5 s 75 % phosphoric acid (H3P04) 138 ppm (P04: lOOppm)
20 % fluozirconic acid (H2ZrF6) 1137 ppm (Zr: 100 ppm)
20 % hydrofluoric acid (HF) 235 ppm (F: 170 ppm) water-soluble polyamide #3 100 ppm pH: 2.5 (adjusted with nitric acid or aqueous ammonia) o The balance of the Bath was water. Water-soluble polyamide #3 was a block terpolymer of blocks of (i) polycaproiactam, (ii) a copolymer of adipic acid and N-(aminoethyl)piperazine, and (iii) a copolymer of adipic acid and an amine ter¬ minated polyoxyethylene with the general formula H2N-(C2H40)n-NH2) where n represents a positive integer with a value such that the polyoxyethylene block s represented by (C2H40)n has a molecular weight in the range from about 200 to 4,000.
Example 6 The cleaned aluminum Dl cans were subjected to the following treatments in the sequence given: spraying for 30 seconds with PALCOAT® 3753 surface- o treatment, for aluminum Dl cans, commercially supplied by Nihon Parkerizing Company, Ltd. and heated to 50 °C; rinsing with water; spraying for 15 seconds with Surface-treatment Bath 6 having the composition shown below and heated to 35 °C; and a water rinse, deionized water rinse, and drying as in Example 1. The corrosion resistance and paint adherence of the resulting Dl cans were then 5 evaluated.
Surface-treatment Bath 6
75 % phosphoric acid (H3P04) 412 ppm (P04: 300 ppm)
20 % fluotitanic acid (H2TiF6) 683 ppm (Ti: 40 ppm)
20 % fluozirconic acid (H2ZrF6) 455 ppm (Zr: 40 ppm) 20 % hydrofluoric acid (HF) 157 ppm (F: 80 ppm) water-soluble polyamide #3 100 ppm pH: 3.0 (adjusted with nitric acid or aqueous ammonia)
The balance of the Bath was water. Example 7
The cleaned aluminum Dl cans were sprayed for 30 seconds with Sur¬ face-treatment Bath 7 having the composition shown below and heated to 25 °C, followed by a water rinse, de-ionized water rinse, and drying as in Example 1. The corrosion resistance and paint adherence of the resulting Dl cans were then evaluated.
Surface-treatment Bath 7 75 % phosphoric acid (H3P04) 69 ppm (P04: 50 ppm) 20 % fluozirconic acid (H2ZrF6) 455 ppm (Zr: 40 ppm)
20 % hydrofluoric acid (HF) 25 ppm (F: 55 ppm) water-soluble polyamide #3 50 ppm pH: 3.0 (adjusted with nitric acid or aqueous ammonia) The balance of the Bath was water. Example 8
The cleaned aluminum Dl cans were immersed for 35 seconds in Surface- treatment Bath 8 having the composition shown below and heated to 40 °C, fol¬ lowed by a water rinse, deionized water rinse, and drying as in Example 1. The corrosion resistance and paint adherence of the resulting Dl cans were then eval- uated.
Surface-treatment Bath 8
75 % phosphoric acid (H3P04) 110 ppm (P04: 80 ppm)
20 % fluotitanic acid (H2TiF6) 854 ppm (Ti: 50 ppm)
20 % hydrofluoric acid (HF) 10 ppm (F: 65 ppm) water-soluble polyamide #2 100 ppm pH: 3.0 (adjusted with nitric acid or aqueous ammonia) The balance of the Bath was water.
Comparative Example 1 The cleaned aluminum Dl cans were sprayed for 25 seconds with the same surface-treatment as in the first step of Example 1 , followed by a water rinse, deionized water rinse, and drying as in Example 1. The corrosion resist¬ ance and paint adherence of the resulting Dl cans were then evaluated.
Comparative Example 2 The cleaned aluminum Dl cans were subjected to the following treatments in the sequence given: spraying for 20 seconds with the same surface-treatment as in the first step of Example 1 ; spraying for 10 seconds with Surface-treatment Bath 9 having the composition shown below and heated to 35 °C; and a water rinse, deionized water rinse, and drying as in Example 1. The corrosion - resistance and paint adherence of the resulting Dl cans were then evaluated. Surface-treatment Bath 9 75 % phosphoric acid (H3P04) 138 ppm (P04: lOOppm) 20 % fluozirconic acid (H2ZrF6) 500 ppm (Zr: 44 ppm)
20 % hydrofluoric acid (HF) 210 ppm (F: 95 ppm) pH: 3.0 (adjusted with nitric acid or aqueous ammonia) The balance of the Bath was water.
Comparative Example 3 The cleaned aluminum Dl cans were subjected to the following treatments in the sequence given: spraying for 25 seconds with the same surface-treatment as in the first step of Example 1 ; spraying for 20 seconds with Surface-treatment Bath 10 having the composition shown below and heated to 35 °C; and a water rinse, deionized water rinse, and drying as in Example 1. The corrosion resist- ance and paint adherence of the resulting Dl cans were then evaluated. Surface-treatment Bath 10
75 % phosphoric acid (H3P04) 138 ppm (P04: 100ppm)
20 % hydrofluoric acid (HF) 210 ppm (F: 40 ppm) water-soluble polyamide #3 100 ppm pH: 3.0 (adjusted with nitric acid or aqueous ammonia) The balance of the Bath was water.
Comparative Example 4 The cleaned aluminum Dl cans were subjected to the following treatments in the sequence given: spraying for 25 seconds with the same surface-treatment as in the first step of Example 1 ; spraying for 15 seconds with Surface-treatment Bath 11 having the composition shown below and heated to 35 °C; and a water rinse, deionized water rinse, and drying as in Example 1. The corrosion reresist-
ance and paint adherence of the resulting Dl cans were then evaluated.
Surface-treatment Bath 11
20 % fluozirconic acid (H2ZrF6) 500 ppm (Zr: 44 ppm)
20 % hydrofluoric acid (HF) 26 ppm (F: 60 ppm) water-soluble polyamide #3 100 ppm pH: 4.5 (adjusted with nitric acid or aqueous ammonia)
The balance of the Bath was water.
Comparative Example 5 The cleaned aluminum Dl cans were sprayed for 20 seconds with Sur- face-treatment Bath 12 having the composition shown below and heated to 35
°C, followed by a water rinse, deionized water rinse, and drying as in Example
1. The corrosion resistance and paint adherence of the resulting Dl cans were then evaluated.
Surface-treatment Bath 12 75 % phosphoric acid (H3P04) 138 ppm (P04: 100ppm)
20 % fluozirconic acid (H2ZrF6) 500 ppm (Zr: 44 ppm)
20 % hydrofluoric acid (HF) 236 ppm (F: 100 ppm) water-soluble polyamide #3 100 ppm pH: 4.5 (adjusted with nitric acid or aqueous ammonia) The balance of the Bath was water.
The test results from Examples 1 to 8 and Comparative Examples 1 to 5 are reported in Table 1. In Examples 1 to 8, the surfaces of aluminiferous metal were treated with a surface-treatment bath according to the present invention by the surface-treatment method according to the present invention. As the corre- sponding results in Table 1 make clear, an excellent corrosion resistance, excel¬ lent paint adherence, and excellent lubricity were obtained in all cases. In con¬ trast to this, a poor lubrication performance in particular was obtained for the products in Comparative Examples 1 to 5, which used surface-treatment baths outside the scope of the invention. Application of the surface-treatment bath ac- cording to the present invention to aluminum Dl cans provides the surface of
Table 1
Identification RtBbB 1 Lubricity2 Paint Adhesion3
Primary Secondary
Example 1 + + + + no peeling no peeling
Example 2 + + + + no peeling no peeling
Example 3 + + + + no peeling no peeling
Example 4 + + + + no peeling no peeling
Example 5 + + + + no peeling no peeling
Example 6 + + + + no peeling no peeling
Example 7 + + + + no peeling no peeling
Example 8 + + + + no peeling no peeling
Comparative Example 1 + + X no peeling no peeling
Comparative Example 2 + + X no peeling no peeling
Comparative Example 3 + + + no peeling no peeling
Comparative Example 4 + + X no peeling no peeling
Comparative Example 5 X + no peeling no peeling
Footnotes for Table 1
1 "RtBbBW" = "Resistance to Blackening by Boiling Water" and was reported on the following scale: x: entire surface blackened
+: partial blackening
+ +: complete absence of blackening.
2Lubricity was evaluated on the following scale: x: coefficient of static friction greater than 1.3
+: coefficient of static friction of 0.9 to 1.3
+ +: coefficient of static friction below 0.9.
3Paint Adherence, both primary and secondary, was evaluated by the presence or absence of any detected paint film peeling.
aluminum Dl cans with an excellent corrosion resistance and lubricity prior to the painting or printing thereof. This makes possible the highly desirable effect of supporting an acceleration of the manufacturing line.