CA2035048A1 - Phosphate coating composition and method of applying a zinc-nickel-manganese phosphate coating - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
This invention relates to a method of coating metal surfaces including zinc-coated steel with zinc, nickel and manganese phosphate crystals for the purposes of improving paint adhesion, corrosion resistance, and resistance to alkali solubility. Potassium, sodium, or ammonium ions present as a phosphate salt are combined with zinc ions and nickel and manganese ions in relative proportions to cause the nickel and manganese ions to form a crystalline coating on the surface in combination with the zinc and phosphate.

Description

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PHOSPHATE COATING COMPOSITION AND METHOD OF

Field of the Invention The present invention relates to a composition and method of applying an alkali-resistant phosphate coating on metal substrates 12 which include zinciferrous coatlngs. More particularly, the present invention relates to nlckel-manganese-zinc phosphate conversion 14 coating composicions prepared rom concentrates wherein a substantially saturated solution, having a balance of monovalent 16 non-coating metal ions and divalent coating metal ions, such as zinc nickel and manganese form a coating upon the metal substrates.

Backg~ound o~ the Invention Conversion coatings are used to promote paint adhesion and improve the reaistance of painted substrates to corrosion. One type 22 of conversion coating is a zinc phosphate conversion coatlng which is compo~ed primarily of hopeite [Zn3(PO4)2]. Zinc phosphate coatings 24 f ormed primarily of hopeite are soluble ln alkali solutions. Such conversion coatings are generally painted which prevents the 26 conversion coating from dissolving. However, if the paint coating is chipped or acratched, the zinc phosphate coating is then exposed and 28 subject to attack by alkaline solutions such as salt water. ~hen the conversion coating is dissolved, the underlying substrate is subject 30 to corrosion.
In the design and manufacture of automobiles, a primary 32 objective is to produce vehicles which have more than five-year cosmetic corrosion resistance. To achieve this objective, the 34 percentage of æinc-coated steels used in the manufacture of vehicle bodies has continually increased. The zinc-coated steels currently 36 uaed include hot-dip galvaniæed, galvanneal~ electro~inc and - 2 ~ a ~ !~ g electrozinc-iron coated steels. Such zinc coating present problems 2 relating to maintaining adequate paint adhesion. Adhesion to zinc-coated steel, uncoated steel and aluminum substrates can be improved 4 by providing a phosphate converslon coating. To be eEfective in vehicle manufacturing applications, a conversion coating must be 6 effective on uncoated steel, coated steel and aluminum substrates.
An improved zinc phosphate conversion coating for steel is 8 disclosed in U.S. Patent No. 4,330,345 to Miles et al. In the Miles patent, an alkali metal hydroxide is used to suppress hopeite crystal 10 formation and encou~age the formation of phosphophyllite [FeZn2(P04)2]
crystals, or zinc-iron phosphate, on the surface of the steel panels.
12 The phosphophyllite improves corrosion resistance by reducing the alkaline solubility of the coating. The alkaline solubility of the 14 coating is reduced because iron ions from the surface of the steel panels are included with zinc in the conversion coating.
16 The formation of a zinc-iron crystal in a phosphate conversion coating is possible on steel substrates by providing a 18 high ratio of alkali metal to zinc. The alkali metal suppresses the formation of hopeite crystals and allows the acld phosphate solution 20 to draw iron ions from the surface of the substrate and bond to the iron ions in the boundary layer or reaction zone formed at the 22 interface between the bath and the substrate. This technique for creating a phosphophyllite-rich phosphate conversion coating is not 24 applicable to substrates which do not lnclude iron ions.
The predomlnance of zinc-coated metal used in new vehicle 26 designs interferes wlth the formation of phosphophylllte in accordance with the Miles patent. Generally, the zlnc-coated panels do not 28 provide an adequate source of iron ions to form phosphophyllite. It i6 not practical to form phosphophyllite crystals by the addition of 30 iron ions to the bath solution due to the tendency of the iron to precipitate from the solution causing unwanted sludge in the bath. A
32 need exists for a phosphate conversion coating process for zinc-coated substrates which yields a coating having reduced alkaline 34 solubility.

- 3 - ~ ~3~8 In U.S. Patent No. 4,596,607 and Canadian Patent No.
2 lyl99,588 to Zurilla et al., a method of coating galvanized substrates to improve resistance to alkali corrosion attack i8 disclosed wherein 4 high levels of nickel are incorporated into a zinc phosphate conversion coating solution~ The Zurilla process uses high zinc and 6 nlckel levels in the zinc phosphating coating composition to achieve increased resistance to alkaline corrosion attack. The nickel 8 concentration o the bath, as disclosed in Zurilla, is 85 to 94 mole percent of the total zinc-nickel divalent metal cations with a minimum 10 of 0.2 grams per liter, i.e., 200 parts per million (ppm), zinc ion concentration in the bath solution. The extremely high levels of 12 nickel and zinc disclosed in Zurilla result in high material costs on the order of three to five times the cost of prior ~inc phosphate 14 conversion coatings for steel. Also, the high zinc and nickel levels result in increased waste disposal problems since the zinc and nickel 16 content of the phosphate coating composition results in higher levels of such metals being dragged through to the water rinse stage 18 following the coating stage. Reference is also made to U.S. Patent No. 4,595,424.
It has also been proposed to incl~de other divalent metal ions in phosphate conversion coatings such as manganese. However, 22 one problem with the use of manganese is that it is characterized by multiple valence states. In valence states other than the divalent 24 state, manganese tends to oxldize and precipitate, forming a sludge in the bath instead of coating the substrate. The sludge must be 26 filtered from tbe bath to prevent contamination of the surface.
A primary objective of the present invention is to increase 28 the alkaline corrosion resistance of phosphate conversion coatings applied to ~inc-coated metals. By lncreasin~ the resistance of the 30 phosphate coating to alkaline corrosion attack, it is anticipated that the ultimate objec~ive of increasing corrosion resistance of 3Z vehicles to more than five years will be achieved.

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Another objective is to improve the control of the phosphate 2 coating process so that an eiEective coating, which is both corrosion-resistant and adhesion-promoting, can be consistently 4 applied to steel, aluminum and zinc-coated panels. As part of this general ob~ective, the control of a phosphate coating process 6 including manganese is desired wherein sludge formation is minimized.
A further objective of the present invention is to reduce 8 the quantity of metal ions transferred to a waste disposal system servicing the rinse stage of the phosphate conversion coating line.
10 By reducing the quantity of metal ions transferred to waste disposal, the overall environmental impact of the process is minimized.
12 Another important objective of the present invention i9 to provide a conversion coating which satisfies the above objectives whlle not 14 unduly increasing ~he cost of ~he conversion coating process.

16 Summarv of the Invention This invention relates to a method forming a phosphate 18 conversion coating on a metal substrate in which a coating composition comprising zinc, another divalent cation such as nickel, 20 and manganese, and a non--coating, monovalent metal cation. The invention improves the alkaline solubility o~ conversion coatings 22 applied to zinc-coated substrates and produces a coating having a favorable crystal structure and good paint adhesion characteristics.
24 According to the method of the present inventlon, three essentlal components of the conversion coating ~ath are maintained 26 within relat~ve proportions to obtain a preferred crystal structure, referred to as "Phosphonicollite" [Zn2Ni(P04)2] or "Phosphomangollite"
28 [Zn2Mn(P04)2], which are considered ~rademarks of the assignee. A
Phosphonicollite~ is a zinc-nickel phosphate which has superior 30 alkaline solubility characteristics as compared to hopeite crystals characteristic o~ other phosphate conversion coatings, the essential 32 constituents being grouped as follows:

A - potassium, sodium, or ammonium ions present as a 2 phosphate;
B - zinc ions; and 4 C - nickel or nickel and manganese.
The quantity of zinc ions in the coating composition at bath dilution 6 is between 300 and 1000 ppm. The ratios in which the essential constituents may be combined may range broadly from about 4-40 parts 8 A : two parts B : 2-13 parts C. A preferred range of the ratios of essential ingredients is 8-20 parts A : two parts B : 2-3 parts C
10 with the preferred quantity of zinc being between 500 and 700 ppm.
Optimum perfoxmance has been achieved when the essential constituents 12 are combined in the relative proportions of about 16 parts A : 2 parts B : 3 parts C. All refsrences to parts are to be construed as 14 parts by weight unless otherwise indicated.
The method is preferably performed by supplementing the 16 essential constituents with accelerators, complexing agents, surfactants and the like and is initially preparad as a two-part 18 concentrate as follows:

TAB~E I - CONCENTRATE_A

Most 24 Preferred Preferred Broad ~aw Materlal Rangq ~9 _ Range % Ra~e %

1. Water 20% 10-50% 0-80%

2. Phosphoric Acid (75~)3870 20-4570 10-60 3. N-ltric Acid 21% 5-25~ 2-35%

4. Zinc Oxide 5% 4-9% 2-15%

5. Nickel Oxide 8% 3-18% 1.5 25%

6. Sodium Hydroxide 4% 0-6% 0-10%

7. Ammonium Bifluoride 2% 0.2-5% 0-10%

8. Sodium salt of 2 ethyl 42 hexyl sulfate 0.3% 0.2-0.5% 0.1%
44 9. Nitro Ben~ene Sulfonic Acid trace % O-trace % O-trace %

~ 6 - ~ ~3 TABLE II - ~ONCENTRATE B

4 Most Chemical Preferred Preferred Broad 6 Raw M~-t-ç~l-al FamilyRan~e % Ran~e % Ran~
8 l. Water Solvent 34% 30-60~ 30-80%
10 2. Phosphoric Acid (75~) Acid 28% 20-35% 10-35%
12 3. Nitric Acid Acid 5% 0-10% 0-15%
14 4. Sodium ~ydroxlde (50~) Alkali 13% 0-30% 0-30 16 5. Potassium Hydroxide (45%) Alkali 20% 0-45~ 0-45%

As used herein? all percentages are percent by weight and "trace" is 20 about 0.05 to 0.1%.
According to the present invention, a phosphate coating bath 22 comprising a substantially saturated solution of zinc, nickel and alkali metal or other monovalent non-coating ions results in the 24 formation of a nickel-enriched phosphate coating having improved alkaline solubility characteristics. The surprising result realized 26 by the method of the present invention is that as the zinc concentration of the coating bath decreases, the nickel content of 28 the r~sulting coating i8 increased without increasing the concentration of the nickel. This surprising effect is particularly 30 evident at higher nickel concentrations. If the concentratlon of ~inc is maintained at a high level of more than 1000 ppm ? the 32 increase in nickel in the coating per unit of nickel added to the bath is less than in baths wherein the zinc concentration is in the 34 range of 300 to 1000 ppm.
While not wishing to be bound by theory, it i9 believed that 36 the inclusion oE nickel in the coating depends on the relative proportion of nickel and other divalent metal ions available for 38 precipitation on the metal surface. The inclusion of nickel in the coating may be controlled by controlling the concentration of the 40 divalent metal ions at the boundary layer. The relative proportion . . .

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of ionæ must be controlled since different divalent metal ions have 2 different precipitation characteristics. At the boundary layer, the zinc concentration i8 higher than the zinc bath concentration by an 4 amount which can be approximated by calculation from the nickel to zinc ratio in the bath and the resultant coating composition. It has 6 been determined that low zinc/hlgh nickel phosphate coating solutions produce a higher nickel content in the phosphate coating than either 8 high z~nc/higher nickel or low zinc/low nickel coating solutions.
According to another aspect of the present invention, a 10 third divalent metal ion may be added to the coating solution to further improve the alkaline solubility characteristics of the 12 resultine coating. The third divalent metal ion is preferably manganese. When manganese is lncluded in the bath, the nickel 14 content of the coating drops because the presence of manganese in the boundary layer competes with nickel for inclusion in the phosphate 16 coating. Manganese is considerably less expensive than nickel and, therefore, a manganese/nickel/æinc phosphate coating solution may be 18 the most cost-effective method of improving resistance to alkaline solubility. Alkaline solubility of manganese/nickel/phosphate 20 coatings is improved to the extent that the ammonium dichromate stripping process generally used to strip phosphate coatings is 22 ineffective to remove the manganese/nickel/zinc phosphate coating completely. i , 24 Prior attempts to manufacture a manganese phosphate concentrate encountered a serious problem o unwanted precipitation 26 that formed sludge which, in turn, must be removed. adding manganese alkali, such as MnO, MN(OH)2 or MnCO3 to phosphoric acid results in 28 the formation of a brownish sludge. ~ccording to the preser~t invention, nitrogen-containing reducing agents such as sodium 30 nitrite, hydrazine sulfate, or hydroxylamine sulfate eliminates the unwanted precipitation. The precise quantity of reducing agent 32 required to eliminate precipitation depends upon the purity of the manganese alkali. The reducing agent must be added prior to the 34 manganese and prior to any oxidizer~ Hence, manganese can be 203~

employed in amounts that are significantly higher than employed 2 heretofore and the manganese and nickel ion concentrations, in accordance with this invention can be above 1500 ppm.

Brie~ ~ç,,scription of the D~awi~s 6 Figure 1 graphically represents data from Table IV relating the nickel content o~ a phosphate coating to the nickel concentration 8 in the corresponding phosphate bath. Two types of phosphate baths are compared. One has low zinc levels and the other has high zinc 10 levels. The coatings are applied to steel panels such as used by the automotive industry for body panels.
12 Figure 2 graphically presents test data as in Figure 1 as applied to hot-dip galvanized panels.
14 Figure 3 graphically presents test data as in Figure 1 as applied to electroæinc panels.
16 Figure 4 graphically presents test data as in Figure 1 as applied to galvanneal panels.
18 Figure 5 graphically presents test data as in Figure 1 as applied to electrozinc-iron panels.
Figure 6 graphically presents test data from Tables V and VII relating the ratio of nickel to zinc in the boundary layer to the 22 percentage of nickel in the coating as applied to steel panels.
Figure 7 graphically pregents test data as in Figure 6 as 24 applied to hot-dip galvani~ed panels.
Figure 8 graphically present6 test data as in Figure 6 as 26 applied to electrozinc panels.
Figure 9 graphically presents test data as in Figure 6 as 28 applied to galvanneal panels.
Fi~ure 10 graphically presents test data as in Figuxe 6 as 30 applied to electrozinc-iron panels.
Figure 11 graphically presents test data showing the 32 improvement in alkaline solubility realized by increasing the nickel concentration in a phosphate bath as applied to steel panels.
34 Figure 12 graphically presents test data as in Figure 11 as applied to hot dip galvanized panels.

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Figure 13 graphically presents test data as in Figure 11 as 2 applied to electrozinc panels.
Figure 14 graphically presents test data as in Figure 11 as 4 applied to galvanneal panels.
Figure 15 graphically presents test data as in Figure 11 as 6 applied to electrozinc-iron panels.
Figure 16 graphically presents the dependence of corrosion o and paint adhesion on the nickel to zinc ratio in the boundary layer as applied to steel panels.
Figure 17 graphically presents test data as in Figure 16 as applied to hot-dip galvanized panels.
12 Figure 1~ graphically presents test data as in Figure 16 as applied to electrozinc panels.
14 Figure 19 graphically presents test data as in Figure 16 as applied to galvanneal panels.
16 Figure 20 graphically presents test data as in Figure 16 as applied to electrozinc-iron panels.
18 Figure 21 graphically represents data from Tables XXVI to XXX relating the nickel content of a phosphate coating relative to 20 the manganese concentration in the corresponding bath. The coatings are applied to cold rolled steel panels.
22 Figure Z2 graphically represents test data as in Figure 21 as applied to electrozinc and hot d~p galvanized steel panels.
24 ~igure 23 graphically represents test data as in Figure 21 as applied to electrozinc-iron and galvanneal panels.
26 Figure 24 graphically represents test data as in Flgure 21 as derived from a five-substrate average of the panel.

DetaIled Description of the Preferred Embodiments The method of the present invention is generally referred to as phosphate conversion coating wherein a zinc phosphate solution is 32 applied to metal substrates by spray or immersion. The metal substrate is first cleaned with an aqueous alkaline cleaner solution.
34 The cleaner may include or be followed by a water rinse containing a titanium-conditioning compound. The cleaned and conditioned metal substrate is then sprayed or immersed in the phosphate bath solution 2 of the present invention which is preferably maintained at a temperature between about 100F and 140F. The phosphate coating 4 solution preferably has a total acid content of between about 10 and 30 points and a free acid content of between about 0.5 and 1.0 6 points. The total acid to free acid ratio is preferably between about 10:1 and 60:1. The pH o the solution is preferably maintained 8 between 2.5 and 3.5. Nitrites may be present in the bath in the amount of about 0.5 to about 2.5 points.
Following application of the phosphate solution, the metal substrate is rinsed with water at an ambient temperature to about 12 100F for about one minute. The metal substrate is then treated with a sealer comprising a chromate or chromic acid-based corrosion 14 inhibiting sealer at a temperature of between ambient and 120F for about one minute which is followed by a deionized water rinse at 16 ambient temperature for about thirty seconds.
One benefit realized according to the present invention over 18 high zinc phosphate baths is a reduction of the quantity of divalent metal ions transferred from the phosphate treatment step to the water 20 rinse. A quantity of phosphating solution is normally trapped in openings in treated objects such as vehicle bodies. The trapped 22 phosphating solution is preferably drained off at the rinse stage.
According to the present lnvention, the total quantity of divalent 2~ metal ions is reduced, as compared to high zinc phosphate baths, by reduc~ng the concentration of zlnc ions. As the concentration is 26 reduced, the total quantity of ions transferred from the phosphate stnge to the rinse stage i8 reduced. The water run-off is then 28 processed through a waste treatment system and the reduction in divalent metal ions removed at the rinse stage results in waste 30 treatment savings.
The pri~ary thrust of the present invention is an 32 improvement in the coating step of the above process.

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EXAMPLES

4 Example 1 6 A phosphating bath solution was prepared from two concentrates as follows:

CONCENTRAT~ CONCENTRATE
10 Name o~ Raw ~_erial Al B

12 Water 29% 34%
14 Phosphoric Acid (75%)36~ 28%
16 Nitric Acid (67%) 18% 5%
18 Zinc Oxide 10% ---20 Nickel Oxide 4% ---22 Sodium Hydroxide (50%) --- 13%
24 Potassium Hydroxide (45%) --- 20%
26 Sodium Salt of 2 ~thyl ~exyl Sulfate <1% ---Ammonium Bifluoride 2% ---Ammonium Hydroxide <0.1% ---Nitro Benzene Sulonic Acid <0.1% ---36 The above concentrates were diluted to bath concentration by adding 5 liters of Concentrate Al to 378.5 liters of water to which was added 38 a mixture of 10 llters of Concentrate B. The above concentrates, after dilution, were combined and a sodium nitrite solution comprising 40 50 grams sodium nitrite in 378.5 liters of water which is added to the concentrate as an accelerator. The coating was spray-applied for 42 30 to 120 seconds or immersion-applied for 90 to 300 seconds in a temperature oP 115F to 130F. When no B concentrate is used, a 44 total of 7 liters of concentrate is added to 378.5 liters of water.
All the rest of the procedure is the same.

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The use of an alkali metal phosphate ln preparation of a zinc 2 phosphate bath involves addition of a less acidic alkali metal phosphate concentrate to a more acidic bath prepared from a standard 4 zinc phosphate concentrate. The higher pH of the alkali metal phosphate concentrate will cause precipitation of zinc phosphate 6 during periods of inadequate mixing. The phosphate bath will have a lower zinc concentration when the alkali metal phosphate is added at 8 a faster rate than when it is added at a slower rate. Variation in degree of precipitation will affect the free acid in that more 10 precipitation will lead to higher free acid. Examples 7, 7a, 12, and 12a demonstrate that one concentrate can produce baths that react 12 dlfferently.

14 Exam~les 2-16 The following examples have been prepared in accordance with the 15 method described in Example 1 above. Examples 3, 4 and 11 are control examples having a high zinc concentration which does not 18 include Concentrate B, a source of alkali metal ions.
Examples including manganese are prepared by adding the specified 20 quantity of the nitrogen-containing reducing agent to a phosphoric acid/water mixture. To this solutlon, a manganese-containing alkali, 22 such aq MnO, Mn(OH)2 and Mn(CO3) is added. If an oxidizerg such as nitric acid, is added to the bath, it is added subsequent to the 24 addition of the manganese-containing alkali.
Examples 2 through 16 were prepared in accordance with ~xample 1 26 above. However, the coating compositions were changed in accordance with the following tables:

Exam~le 2 CONCENTR~TECONCENTRATE
32 Name of Raw ~aterial A2 B
34 Water 35% 34%
36 Phosphoric Acid (75%) 39% 28%
38 Nitric Acid (67%) 12% 57O

- 13 - 2~ 3~0 ~ 8 Zinc Oxide 5~
Nickel Oxide 4% ---Sodium Hydroxide (50%) 2% 13%

Potassium Hydroxide (45%) --- 20%

Sodium Salt of 2 Ethyl 10 Hexyl Sulfate <1%
12 Ammonium Bifluoride 2%

14 Ammonium Hydroxide <0.1%
16 Nitro Ben7.ene Sulfonic Acid <0.1%

ExamRle 3 22 CON~ENTRATE
Name of Raw Material A3 Water 29%

Pho6phoric Acid (75~) 39%

Nitric Acid (6770) 15%
Zinc Oxide 1170 Nickel Oxide 3%

Sodium Hydroxide (5070) Potas 8 ium Hydroxide (45%) ---3~
Sodium Salt of 2 Ethyl Hexyl Sulfate ~1~
42 Ammonium Bifluoride 2%
44 Ammonium Hydroxide <0.1%
46 Nitro Benæene Sulfonic Acid <0~1%

3~8 ~ 14 -xample 4 CONCENTRATE CONCENTRATE
4 Name o~_~aw Material A4 B
6 Water 24% 34%
8 Phosphoric Acid (75%) 35% 28%
10 Nitric Acid (677~)2370 5%
12 Zinc Oxide 1070 --~
14 Nickel Oxide 5% ---16 Sodium Hydroxide ~50%) ~~~ 1370 18 Potassium Elydroxide (45%) ~~~ 20%
20 Sodium Salt of 2 Ethyl Hexyl Sulfate <1% ---Ammonium Bifluoride 2% ---Ammonium Hydroxide<0~1% ---Nitro Benzene Sulfonic Acid <0.170 ---Example 5 CONCENTRATE CONCENTRATE
34 Name of Raw Material A5 B
36 Water 20~ 34%
38 Phosphorlc Acid ( 75%) 39% 28%
40 Nitric Acid (6770)21% 5%
42 Zinc Oxide 5% ~~~
44 Nickel Oxide 8% ---46 Sodium Hydroxide (50%) 4% 13%
48 Potassium Hydroxide (45%) --- 20%
50 Sodium Salt of 2 Ethyl Hexyl Sulfate <1% ---- 15 - 2 ~ 3 ~

Ammonium Bifluoride270 ---Ammonlum Hydroxide<0.1% ---Nitro Benzene Sulfonic Acid <0.1% ---E~ample 6 CONCENTRATE CONCENTRATE
12 Name of Raw Material A6 B
14 Water 31% 34%

16 Phosphoric Acid (75%) 36% 2870 18 Nitric Acld (6770)17% 5%
20 Zinc Oxide 4% ---22 Nickel Oxide 9% ---24 Sodium Hydroxide (507~) 170 13%
26 Potassium Hydroxide (45%) --- 20%
28 Sodium Salt of 2 Ethyl Hexyl Sulfate~1% ---Ammonium Bifluoride 1% ---Ammonium Hydroxide<0.1% ---Nitro Benzene Sulfonic Acid <0.1% --- :

Exa.m~l.ç.Z
CONCENTRATE CONCENTRATE
42 Name o~ Raw Material A7 ~
44 Water 35% 34%
46 Phosphoric Acid (75%) 38% 28%
48 Nitric Acid (67%)12% 5%

50 Zinc Oxide 4% ~--~ 16 ~

Nickel Oxide 6% ---Sodium ~ydroxide (50%)3% 13%
Potassium Hydroxide (45%) --- 20%

Sodium Salt of 2 Ethyl 8 He~yl Sulfate ~1% ---10 Ammonium Bifluoride 1% ---12 Ammonium Hydroxide<0.1% ---14 Nitro Benzene Sulfonic Acid <0.170 ---18 E~amRle 8 CONCENTRATE CONCENTRATE
Na~e o~ Raw ~aterial A8 B

Water 36% 34%

Phosphoric Acid (75%)39% 28%

Nitrlc Acid (67%) 10~ 5%

Zinc Oxide 5% ---Nickel Oxide 570 ---Sodlum Hydroxide (50%)3% 13%

Potas8ium Hydroxide (45%) --- 20%

Sodium Salt of 2 Ethyl 38 Hexyl Sulfate c170 ---40 Ammonium Bifluoride 1% ---42 Ammonium Hydroxide<0.1% ---44 Nitro Benzene Sulfonic Acid <0.1% --~-- 17 - , ~03~0~8 Example 9 CONCENTRATE
4 Na,me ~f Raw Matçr,,ial A9 6 Water 35%
8 Phosphoric Acid (7570~ 33%
10 Nitric Acid (6770) 1670 12 Zinc Oxide 8%
14 Nickel Oxide 4%
16 Sodium Hydroxide (50%) ---18 Potassium Hydroxide (45%) ---20 Sodium Salt of 2 Ethyl Hexyl Sulfate <1%

Ammonium Bifluoride L%

Ammonium Hydroxide~0.170 Nitro Benzene Sulfonic Acid <0.1%

Example 10 CONCENTRAI'E CONCENTRATE
34 ~ame of Raw ~aterialA9 , B ~ :
36,Water 35% 34%
38 Phosphoric Acid (7570) 33% 28%
40 Nitric Acid (67%) 16% 570 42 Zinc Oxide 8% ---44 Nickel Oxide 4% ---46 Sodium Hydroxide (50%) --- 13%
48 Potassium Hydroxide (45%) --- 20%
50 Sodium Salt of 2 Ethyl Hexyl Sulfate ~1% ---- 18 - 2B3~8 Ammonium Bifluoride 1% ---Ammonium Hydroxide <0.1% ---Nitro Benzene Sulfonic Acid <0.1%

~mple 11 CONCENTRATE
12 Na~e ~f R~_Material A10 14 Water 36%
16 Phosphoric Acid (75%) 39%
18 Nitric Acid (67%) 11%
20 Zînc Oxide 11%

22 Nickel Oxide 1%
24 Sodium Hydroxide (50%) ---26 Potassium ~ydroxide (4570) ---28 Sodium Salt of 2 Ethyl Hexyl Sulfate <1%
Ammonium Bifluoride 1%

Ammonium Eydroxide<0.1%

Nitro Benzene Sulfonic Acid <0.1%

Example 12 4~
CONCENTRATE CONCENTRATE
42 Name of Raw ~aterial A10 B
44 Water 36% 34% '-46 Phosphoric Acid (7570) 39% 28%
48 Nitric Acid (67%) 11% 5%
50 Zinc Oxide 11% ---19- 2~3~

Nickel Oxide 170 ---Sodium Hydroxide (50%) --- 13%
Potassium Hydroxide (4570) --- 20%

Sodium Salt of 2 Rthyl 8 Hexyl Sulfate <1% ---10 Ammonium Bifluoride 170 ---12 Ammonium Hydroxide<O. l~o ~~~
14 Nitro Benzene Sulfonic Acid <0.1% ---18 Ex~mple 13 CONC~NTRATE CONC~NTRATE
Name of Raw MaterialA10 B

Water 36% 34%

Phosphoric Acid (75%)39%0 28%

Nitric Acid (67%~ 11% 5%

Zinc Oxide 11% ---3~
Nickel Oxide 1% ---Sodium Hydroxide (50%) --- 13%

Potassi~m ~ydroxide (45%) --- 20%

Sodium Salt of 2 Ethyl 38 Hexyl Sulfate <1% ---40 Ammonium Bifluoride 1% ___ . s 42 Ammonium Hydroxide<0.1% ---44 Nitro Benzene Sulfonic Acid <0.1~ ---- 20 - ~ ~ 3~ ~ ~ 8 Example 14 CONCENTRATE CONCENTRATE
4 Name of Raw.M.ater.i.alA12 B
6 Water 35% 34%
8 Phosphoric Acid (757O)337O 28%
10 Nitric Acid (6770) 16% 5%
12 Zinc Oxide 8% ---14 Nickel Oxide 4% ~~~
16 Sodium Hydroxide (50~) --- 13%
18 Potassium Hydroxide (45%) --- 2070 20 Sodium Salt of 2 Ethyl Hexyl Sulfate <1% ---Ammonium Bifluoride --- ---Ammonium Hydroxde <0.1% ---Nitro Benzene Sulfonic Acid ~0.1% ---2~
As the bath is used on a commercial basis, the phosphate bath is replenished after a series of coatings. The bath will become enriched 32 with nickel after a series of coatings because more zinc ~han nickel is contained in the phosphate coating. The replenishment solution 34 should be formula~ed to maintain the desired monovalent metal ion to: 1 ~i zinc ion to nickel lon concentration~
36 The above examples, when diluted to bath concentration, yield the following approximate ratios of alkali metal to zinc to nickel ions.

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TABLE III

4 Alkali Metal Ion: Zinc Ion: Nickel Ion ~xQmple ~o. Ratis Table 1 ~.5:1:0.80 2 4.9:1:0.92 3 0~1:1:0.30 4 5.2:1:0.97 7.8:1:1.24 6 6.0:1:1.39 7 6.4:1:1.35 8 5.8:1:0.88 9 0.1:1:0.57 11 0.1:1-0.20 12 5.0:1:0.27 12a 9.4:1:0.55 Example 15 CONCENTRATE CONCENTRATE
36 Na~e of ~aw Mater~JDL_____ ~B
38 Water 29% 34%
.

40 Phosphoric Acid 175%) 36% 2870 42 Nitric Acid (67%) 19% 5%
44 Zinc Oxide 10% --~
46 Nickel Oxide 1%
48 Manganese Oxide 4æ ---50 Sodium Hydroxide (50%) --- 13%
52 Potas~ium Hydroxide (45%) --- 1973 - 22 - ~ Q 3 ~Q ~ 8 Hydroxylamine Sulfate <1% ---Sodium Salt of 2 Ethyl 4 Hexyl Sulfate <1% ---6 Ammonium Blfluoride --- 1%
8 Am~onium Hydroxide<0.1% ---10 Nitro Benzene Sulfonic Acid <0.1% ---14 Example 16 Name o~ Raw MaterialM2 MB

Water 24% 34%
Phosphorlc Acid (75%) 36% 28%

Nitric Acid (67%) 23% 5%

Zinc Oxide 9% ~~~

Nickel Oxide 3% --- ~ , Manganese Oxide 47O ---Sodium Hydroxide (507O) --- 13%

Pot~ssium Hydroxide (45%) --- 19%

Hydroxylamine Sulfate <1% ---Sodium Salt o~ 2 Ethyl 38 Hexyl Sulfate <1% ---40 Ammonium Bifluoride --- 1%
42 Ammonium Hydroxide<0.1% ---44 Nitro Benzene Sulfonic Acid <0.1% ---- 23 - ~ 8 TESTING
2 A series of test panels were coated with combinations of two-part coating solutions. The tests panels included uncoated steel panels, 4 hot-dip galvanized, electrozinc, galvanneal, and electrozinc-iron.
The test panels were processed in a laboratory by alkaline cleaning, 6 conditioning, phosphate coating, rinsing, sealing and rinsing to simulate the prevlously described manufacturing process. The panels 3 were dried and painted with a cationic electrocoat primer paint. The panels were scribed with either an X or a straight line and then 10 subjected to four different testing procedures, the General Motors Scab Cycle (GSC), Ford Scab Cycle (FSC), Automatic Scab Cycle (ASC), 12 Florida ~xposure Test, and the Outdoor Scab Cycle (OSC).

14 TEST MET~OD5 The GSC, or 140F indoor scab test, is a four-week test with each 16 week of testing conslsting o~ five 24-hour cycles comprising immersion in a 5% sodium chloride solution at room temperature followed by a 18 75-minute drying cycle at room temperature followed by 22.5 hours at 85% relative humidity at 140F. The panels are maintained at 140F
20 at 8570 relative humidity over the two-day period to complete the week.
Prior to testing, the test panels are scribed with a carbide~tipped 22 scribing tool. After the testing cycle is complete, the scribe is evaluated by simultaneously scraping the paint and blowing with an 24 air gun. The test results were reported as rated from 0, indicating a total paint loss, to 5, indicating no paint loss.
26 The FSC test is the same as the GSC test except the test i9 for ten weeks7 the temperature during the humidity exposure portion of 28 the test is set at 120F and the scribe is evaluated by applying Scotch Brand 898 tape and removing it and rating as above.
The ASC test is comprised of 9~ 12-hour cycles wherein each cycle consists of a 4-3/4 hour 95 to 100 humidity exposure followed by a 32 15-minute salt fog followed by seven hours of low humidity (less than 50 percent humidity) drying at 120F. The ASC test is evaluated in 34 the same way as the FSC test.

-- 24 - 2 0 3 ~ ~ ~ 8 The Florida expos~re test is a three-month outdoor exposure facing 2 the south and oriented at 5 from horizontal at an inland site in Florida. A salt mist is applied to the test panels twice a week.
4 Panels are scrlbed per ASIM D-1654 prior to exposure and soaked in water for 72 hours following exposure. The panels are crosshatched 6 after soaking and tested according to ASTM D-3359 Method B.
The most reliable test i9 the OSC test wherein a six-inch scribe 8 i8 made on one-half of a panel and the other half is preconditioned in a gravelometer in accordance with SAE J 400. The panel is then 10 exposed to salt spray for 24 hours which is followed by deionized water immersion for 48 hours. The panel is then placed outside at a 12 45 angle southern exposure. A steel control panel, treated with the same conversion process except for the final rinse which was chrome 14 (III) final rinse, is treated simultaneously in the same manner.
When the control panel exhibits a corrosion scab of about six 16 mlllimeters, the panels are soaked for 24 hours. The OSC is evaluated according to the same procedure used for the FSC and ASC
18 tests as described previously.
The panels scribed with a crosshatch grid were used to evaluate 20 adhesion performance. After cyclical testing, the panels were contacted by an adhesive tape which is removed and qualitatively 22 evaluated depending upon the degree of removal of non-adhering film by the tape. The numerical rating for this test is based upon a 24 five-point scale ranging from a rating of 0 or no adhesion to 5 for perfect adhesion.
26 The above examples were tested ~or corrosion resistance and adhesion by the above-described test method.
28 Table IV shows the relationship of the percentages of nickel in the baths, the zinc level in the baths, the percentage of nickel 30 contained in the coatings for si~ different phosphate bath compositions as applied to steel, hot-dip galvanized, electrozinc, 32 galvanneal, and electrozinc-iron by both the spray and immersion methods.

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- 26 ~ 8 Referring to the above table, examples that are low zinc/high 2 nickel phosphatss yield the highest percentages of nickel in the phosphate coatings~ Example 11, which is a low zinctlow nickel 4 phosphate, has a lower percentage of nickel incorporated in the phosphate coating. Even lower levels of nickel incorporation are 6 achieved when a high zinc/low nickel composition is used as shown in Example 10. The use of a high zinc/high nickel phosphate bath results 8 in only slightly moxe nickel in the phosphate coating than in the low zinc/low nickel bath and considerably less than any of the low 10 zinc/high nickel baths. Thus, to obtain more nickel in the coating, the bath concentration of nickel should be high and the bath lZ concentration of zinc should be low. The results are graphically presented in Figures 1-5 which clearly show that with either immersion 14 or spray appl~cation methods, the low zinc formulations are more efficient in increasing nickel content of the phosphate coating than 16 high zinc formulations. Figures 1-5 each relate to a different substrate material and the results acheived indicate that the low 18 zinc formulations are preferable for all substrates.
For each of the above examples, tbe percentage of nickeL in the 20 phosphate coatings is sho~n in Table V be:Low for the five tested substrates after immersion phosphating.

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- - 28 - 2 ~ 3 ~ ~ ~ g Again, the percentage of nickel in the phosphate coating is 2 increased most effectively by the use of low zinc/high nickel formulations such Examples 19 2, 4, 5, 6, 7, 7a and 8. The low 4 nickel/high zinc is the least effective and the low nickel/low zinc or the high nickel/high zinc are only slightly more effective.
NICKEL/ZINC RATI0 IN T~E BOUNDARY LA~ER
8 The proportion of nickel in the phosphate coating is proportional to the nickel/zinc ratio available for precipitation. Unfortunately, 10 the ratio available for the precipitation is not the overall bath ratio but rather the ratio at the boundary layer between the metal 12 surface and the bulk of the bath. For all substrates tested, high metal ion concentration in the boundary layer resulting from acid 14 attack on the metal surface tended to lower the proportion of nickel available for precipitation. While it is not practical to measure 16 metal ion concentrations at the boundary layer directly, the boundary layer concentrations can be calculated based on the linear correlation 18 between the proportion of nickel in the coating and the nickel/zinc ratio. As the zinc concentration increases, the linear correlation 20 coefficient is maximiæed at the boundary layer concentration.
Furthermore, as the concentration of zinc is increased, the 22 y-intercept should approach zero. These two criteria will be met only half the time each for application o~ this change to random 24 dsta. Whether they follow the expected changes or not constitutes a test of the accuracy o the theory. For both criteria to be met for 26 all five materials, there is a 99~9 percent chance that the theory is correct. In fact, all five materials met these criteria. The 28 increase in metal ions in the boundary layer and the correlation coefficients are given in Table VI.

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For hot~dip galvanized and electrozinc, the extra metal ions are 2 zinc and hence can be added directly to the zinc concentration in the bath to obtaln the zinc concentration in the boundary layer. However, 4 for steel, the increase in concentration relfects an increase in the iron concentration. Since iron ions have a greater tendency to cause 6 precipitation, the concentration of additional metal ions in the boundary layer of 1600 ppm iB somewhat distorted. The ferrous ions 8 compete more effectively than zinc ions for inclusion i.n the coating because phosphophyllite has a lower acid solubility than hopeite.
10 This means that the determined concentration increase of loOO ppm is greater than the actual ferrous ion concentration. The 1600 ppm 12 represents the amount of zinc that would compete as effectively as the ferrous ions actually present and, therefore, can also be added 14 directly to the bath concentration of zinc. A similar argument can be made for galvanneal and electrozinc-iron. The boundary layer 16 ratios can be calculated by the following equation:

18 Nickel/zinc ratio Nickel in Bath =

In the boundary layer (7inc in bath + Extra metal ions in the boundary layer) 2~
24 Using this equation, nickel/zinc ratios in the boundary layers are calculated with the results shown in Table VII below:

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- 32 ~ 8 Figures 6-10 show the correlation between the nickel/zinc ratio in 2 the boundary layer and the percentage nickel in the coating.

4 FORM~TION OF PHOSPHOPHYLLITE
WTTH A HIGH NICKEL PHOSPHAT~
6 It has been previously established that higher phosphophyllite phosphate coating improves the painted corrosion resistance and paint 8 adhe6ion on steel. In the previous section, it was shown that nickel competes with zinc for inclusion in the phosphate coatlng. It is 10 critical to this invention that the inclusion of high phosphophyllite on iron-containing substrates is maintained at the high levels 12 obtained with low zinc/low nickel baths. Data in Table VIII below shows that hlgh nickel/low zinc phosphates have a phosphophyllite 14 content equivalent to that of low nickel/low zinc phosphates. Notice that high zinc baths have lower phosphophyllite contents than the low 16 zinc baths, even for the zinc-iron alloys, AOl galvanneal and electrozinc-iron. This will have important repercussions in the 18 painted corrosion testing o~ these baths.

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-- 34 - ~ ~ 3 CORRGSION AND ADHESION TEST R~SUI,TS

INDOOR SCAB TEST RESULTS
4 Table IX below shows the 140F indoor scab test results on five substrates with spray and immersion application processes. The low 6 zinc/high nickel baths show improved corrosion and adhesion results when applied by the immersion process. The adhesion and corrosion 8 test results are superior for Examples 1, 2 and 4 as compared to the hlgh zinc/high nickel composition of Example 3 and the low zinc/low 10 nickel composition of Example 12 for electrozinc and hot-dip galvanized. This difference is ascribed to the higher nickel content.
12 Steel, AOl galvanneal and electrozinc-iron showed worse performance with Example 3 only. This difference can be ascribed to lower 14 phosphophyllite contents.

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_ 5~ _ In Table X below, the automotive scab test results for the same 2 examples are ~hown~ The automatic scab test shows improvement in corrosion resistance with high nickel/low zinc baths as compared to 4 the other two for hot-dip galvanizéd and electrozinc. Steel and electrozinc-iron show decreased performance from the high zinc bath, 6 undoubtedly because of lower phosphophyllite. On galvanneal, paint adhesion is adversely affected by high z~nc baths but low nickel 8 levels adversely affect corrosion resistance for all coated samples and equivalent results with uncoated steel. Variations from the 10 general trend are believed to be unrelated to the expected effectiveness of the low zinc/high nickel compositions.

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- 38 - ~03~8 A second automatic scab test was conducted for Examples 5-9 and 2 12a as shown in Table Xl below. The test results showed improvement in adhesion ~or galvanneal and electrozinc-iron substrates for the 4 low zlnc/high nlckel compositions as compared to the low zinc/low nickel and high zinc/high nickel compositions. The corrosion test 6 results indicated substantial improvement for hot-dip galvanized and electrozinc with the low zinc/high nickel formulations. Steel showed slight lmprovement with high nickel baths. The results of this test will be discussed in more detail in the section on alkaline 10 solubility.
:

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_ 40 - 2~3~

Examples 1-4 and 12 were tested in Florlda exposure with the 2 results shown in Table XII below.

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~3~8 The Florida exposure test results show increased corrosion 2 resistance or paint adhesion of the low zinc/high nickel composition on electrozinc, galvalmeal, and hot-dip galvanized when compared to 4 the low zinc/low nickel or high zinc/high nickel compositions.
Superior corrosion resistance and paint adhesion was observed on 6 electrozinc-iron and steel for low zinc as compared to high zinc/high nickel. In particular, Examples 2 and 4 showed excellent corrosion 8 resistance and adhesion when compared to the other formulations when spray applied.
In summary, hot-dip galvanized and electrozinc show consistent imprGvement with low zinc/high nickel phosphate baths over either low 12 nickel/high nickel phosphate baths over either low nickel/low zinc or high nickel/high zinc baths. This is because of the increased nickel 14 content in the phosphate coating. Electrozinc-iron and steel show an inconsistent or slight improvement related to the level of nickel in 16 the phosphate coating, but a large improvement related to the level of phosphophyllite in the coating. Galvanneal does not clearly show 18 improvement related to Phosphonicolite or phosphophyllite levels in the coating.
In the following section, this data w:ill be related to the solubility of the phosphate coating in an alkaline media.

ALK~ S~UB~ITIES OF PHOSPHAT~ COATI~LGS
24 Table XIII (below) and Figures 11-15 show that low zinc/high nickel compositions are represented by Example 5 are superior to low 26 zinc/low nlckel compositions when tested for solubility in alkali solutions. No real improvement in resistance to alkaline attack was 28 shown on steel panels; however, resistance to alkaline attack on pure zinc substrates, such as hot-dip galvanized and electrozinc, is 30 substantially increased with higher nickel content bath. Galvanneal shows no increase in the resistance to alkaline attack based upon the 32 nickel content. Electrozinc-iron shows a slight increase in resistance.

~3~0~
- ~3 -TABLE XIII
Alkaline Solubilitles of Phosphate Coatings 6 Percentage Qf Coatin~ Insoluble in Alkali*
Tvpe of PhosphateLow Zinc / Hi~h Nickel Low Zinc / Low Nickel Concentrate UsedE~ample 5 Example 12 Steel 27% 24%

Hot Dip Galvanized 28% 15 Elec~rozinc 38% 17%

A01 Galvanneal 36~ 37 ~lectrozinc-Iron 32% 26%
2~
22 * Solubilities of the galvanized products are higher than expected because of a redeposition of white powder associated with attack 24 on the substrate. Spray phosphate coatings.

Figures 16-20 show that higher nickel/zinc ratios in the boundary 28 layer can be correlated with decreased corroslon andlor paint adhesion lo~s. Electrozinc, hot-dip galvanized and, to a lesser 30 extent, electrozinc-iron all show a decrease in alkaline solubility at higher nickel/zinc ratios, and all show a decrease in corrosion 32 and/or paint 10s6. A01 galvanneal does not show a decrease in alXaline solubility or a decrea6e in corrosion and paint loss due to 34 a higher nickel to zinc ratio in the boundary layer. No significant changes are noted in the alkaline aolubility because there is such 36 æmall change in the nickel/zinc ratio in the boundary layer. It is interesting to note that the data available suggests that if the 38 nickel/zinc ratio for steel were raised, then it would improve the painted corrosion resistance or paint adhesion.

~3~8 ~CCELERATÆD T~STING FOR NICYEL AND FLUORIDE
2 The coating compositions of E~amples 13 and 14, having different levels of ammonium bifluoride, were applied to a cold-rolled steel 4 and hot-dip gal~anized as well as electroæinc substrates. The test results show that high nickel phosphate baths based on low zinc/high 6 nickel are superior to phosphate baths having low zinc/low nickel for steel, hot-dip galvanized and electrozinc. Tables XIV and XV (below) 8 show that fluoride does not substantially affect the quality of the phosphate coating for a high nickel bath over the range of 0-400 ppm.

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ZINC M~NGANESE NICKEL PHOSPHATE COMPOSITIONS
2 Additional testing has been conducted to determine the effectiveness of adding manganese and nickel to zinc phosphate 4 coating solutions having preferred ratlos of zinc to nickel. Also, formulations incorporating nitrite, hydra7.ine, and hydroxylamine have 6 the effect of reducing the manganese precipitation and producing a clearer bath solution of the concentrate.
8 The compositions were tested as previously described and are listed above as Examples 15 and 16.
TEST RESULTS OF MANGANESE ZINC PHOSPHATES
12 Examples 10, 12, 15 and 16 were compared to determine the e~fect of the addition of manganese to both a low zinc/low nickel composition 14 as represented by Example 12 and a low zinc/high nickel composition as represented by Example 10. The nickel and manganese contents of 16 manganese-containing zinc phosphate coatings and comparable panels from non-manganese baths are shown in Table XVI below:

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When manganese is included in the bath, the nickel content of the 2 coating drops. This is because the manganese in the boundary layer also competes with the nickel for inclusion in the phosphate coating.
4 As will be shown below, the addition of manganese to the bath does not cause a drop ln performance, but in some instances actually shows 6 improvements. Since manganese is generally less expensive than nickel, a manganese/nickel/zinc phosphate bath may be the most 8 cost-effective method of improving resistance to alkaline solubility.
Quantitative testing of the alkaline solubility of manganese/nickel/
10 zinc phosphate coatings is not possible since the ammonium dichromate stripping method was not eEfective in removlng the coating. However, 12 qualitatively the decrease in alkaline solubility of manganese/nickel/
zinc phosphate is clearly shown by the increased resistance to the 14 alkaline stripping method that was effective on nickel/zinc phosphate coatings.

C~RRO$ION ~ND AD~ES_QN TEST RES~2-18 The manganese/nickel/zinc phosphate coatings were tested by the indoor scab test witll the results shown in Table ~VII below:

.

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NITROGEN-REDYCING AGENTS
Substantially equivalent phosphate concentrate having manganese oxide were prepared using a reducing agent to limit precipitation 12 during manufacture. Some effective reducing agents were nitrite, hydrazine, and hydroxylamine when added in the proportions shown 14 below in Table XVIII:

18Effect of Nitrogen-Reducing Agents on Manganese Phosphate _Q~ Nitrlte HvdrazineHvdroxylamin~

Water 46.4% 46.4% 46.0% 46.2%

Phosphoric Acid 40.2% 40.2% 39.9% 40.0%

Sodium Nitrite ---- 0.38% ---- ----Hydrazine Sulfate ---- ---- 0.75% ----Hydroxylamine Sulfate ---- ---~ 0.75%

Manganese Oxide 9.10% 9.10% 9.03% 9.06%

Nitric Acid 3.7Z% 3.49% 3.76% 3.47%

Nickel Oxide 0.45% 0.45% 0.45% 0.45%

Solution Clarity muddy brown slightly cloudy clear clear Precipitate heavy brown slightly brown none none - 54 - 2~3~

Table XVIII and all other concentrates in this section show the 2 ingredients in the order added.
The results of the above comparative test indicates that the 4 hydrazine and hydroxylamine reducing agents were completely effective ~-in obtaining a clear solution and eliminating precipitation from the 6 baths. The sodium nitrite was moderately ef~ective in clarifying the solution and partially effective in that it reduced the degree of 8 precipitation. Therefore, the addition of sufficient amounts of nitrogen containing reducing agents can eliminate or greatly reduce 10 the precipitation and clarity problems. The ~uantity of reducing agent required is expected to be dependent upon the purity of the 12 manganese alkali. The quantity of reducing agent is limited primarily by cost considerations. The reducing agent is preferably 14 added prior to the manganese and prior to any oxidizing agent.
Another key factor is the ratio of manganese to phosphoric acid.
16 Table XIX shows the effect of variations of the manganese/phosphoric acid ratio on the clarity of the concentrate.

TABLE XIX
EFFECT OF MANGANESE: PHOSPHORIC ACID RATI~Q

ExampleExample Example Example 24 Name of Raw Material XVII XVIII XIX
26 Water 41.1%42.3% 43.5% 46.5%
28 Phosphoric Acid (7570) 48.0% L~6.8% 45.570 42.3 30 Hydroxylamine Sulfate 0.52% 0.52% 0.52% 0.53%
32 Manganese Oxide 10.4%10.4% 10.5% 10.7%
34 Clarity ClearSlightly CloudyVoluminous Cloudy White ppt.

Mn:H3P04 Molar Ratio 0.378:1 0.388:1 0.403:1 0.441:1 - 55 - _ ~ V ~ ~ Q ~ 8 Clearly, the manganese:phosphoric acid molar ratio should be 2 between 0.388:1 and 0.001:1. As in all concentrates, the less water added the better as long as no precipitate is formed. Table XX shows 4 the effect of increasing the concentration of the concentrate. One of the traits of manganese phosphate concentrates is that they form 6 moderately stable supersaturated solutions. Thus, in order to determine whether or not a solution has been formed that will not 8 precipitate during storage9 the concentrates must be seeded.

TABLE XX
12 EFFECT OF C~NCENTRATION

Example Example Example 16 Name of Raw Material XXI ~XII XXIII
18 Water 31.8% 36.4% 41.1%
20 Phosphoric Acid (75%) 55.6% 51.8% 48.0%
22 Hydroxylamine Sulfate 0.60% 0.56% 0.52%
24 Manganese Oxide 12.0% 11.2% 10.4%
26 Manganese Concentration 2.42 m/l2.24 m/l 2.06 m/l 28 Mn:H3PO4 Molar Ratlo 0.388:1 0.388:1 0.388:1 30 Initial SolubilityAll Soluble All SolubleAll Solublè
32 Solubility after Seeding MassiveAll Soluble All Soluble Precipitation 36 Thus, the concentration of manganese should be 2.24 M/L or below.

- 56 - ~ ~ 3 ~ s ADDITIONAL EXAMPL~S
2 The followiDg illustrates the incorporation of high level of manganese into a coating to form a nickel-manganese-zinc conversion 4 coating and the comparison thereof to art-related compositions. As afore-stated, in theo~y, the inclusion of nickel in a coating may be 6 controlled by controlling the concentration of the divalent metal ion at the boundary layer. When manganese is included in the bath, it 8 has been believed that nickel content of the bath drops.
Surprisingly, it has been found that in certain concentrations the 10 nickel content is not so ad~ersely affected.
An lmproved coating composition of this invention was prepared by 12 using Concentrates A and B, hereinbelow, followed by the addition of a manganese concentxate as shown in Example ~XII followed by addition 14 o~ more manganese to constitute a bath having from 800 to 1300 ppm manganese.

CONC NTRATE A

l. Water 20~o 2. Phosphoric Acid (75%) 38%

3. Nitric Acid 21%

4. Zinc Oxide 5%

5. Nickel Oxide 8%

6. Sodium Oxide 47O
7. Ammonium Bifluoride 2%

8. Sodium salt of 2 ethyl 34 hexyl sulfate 0.3%
36 9. Nitro Benzene Sulfonic Acid trace %

~ 57 ~ ~ ~3~0~8 CONCENTRAT~ B

1. Water 34%
2. Phosphoric Acid (7570) 28 3. Nitric Acid 5%
4. Zinc Oxide 13 5. Mickel O~ide 20%

14 As used herein, all percentages are percent by weight and "trace" is about 0.05 to 0 1%.
16 Tables XXVI to XXXI hereinbelow illustrate the composition of the improved phosphate coatings of this invention and their performance 18 properties in comparison with art-related compositions. The coatings with increasing levels of manganese were applied to five types of 20 substrates. Decrease in corrosion was observed at manganese concen~rations of about 800 to 1300 ppm. Surprisingly, i~ has been 22 found that the higher levels of manganese do not adversely affect the formation of Phosphonicollite~. At the high levels, manganese can be 24 employed at about 15 to 50 percent, preferably above 20 percent and typically from about 35 to 50 percent (on cold rolled steel) based on 26 the welght of the divalent metals.

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Claims (8)

1. A method of phosphate conversion coating metallic substrates selected from the group consisting of steel, zinc-coated steel, and aluminum comprising the steps of:
cleaning the surface of the substrates with an alkali cleaner;
conditioning the surface of the substrates with a titanium-containing aqueous solution;
coating the surface of the substrates with a solution consisting essentially of an aqueous solution of the constituents A, B and C combined in the ratio of about 4 to 40 parts by weight A:2 parts by weight B:2 to 13 parts by weight C, and B is provided at a concentration of between about 300 and 1,000 ppm, wherein:
A is selected from the group consisting of potassium, sodium and ammonium ions present as a phosphate salt;
B is zinc ions; and C is nickel and manganese;
applying said coating composition to the surface of the substrates at a temperature of between about 100°F and 140°F for between 30 and 300 seconds;
rinsing said substrate and applying a chromate rinse to the substrate and rinsing the substrate with water.

2. The method of claim 1 wherein the constituents are combined in a ratio of 4 to 40 parts by weight B:4 to 13 parts by weight C
wherein manganese is at least 15 percent by weight.

3. The method of claim 1 wherein said constituents are combined in a ratio of from about 8 to 20 parts by weight A:2 parts be weight B:6 to 10 parts by weight C, and the concentration of B is between about 500 to 700 ppm.

4. The method of claim 1 wherein said constituents are combined in a ratio of about 10 parts by weight A:2 parts by weight B:8 parts by weight C, and the concentration of B is between about 500 and 700 ppm.

5. A method of coating substrates selected from the group consisting of steel, zinc-coated steel, and aluminum comprising the steps of:
cleaning the substrates with an alkali cleaner;
conditioning the surface of the substrates with an aqueous solution of Jernsted salts;
preparing a coating composition by diluting in an aqueous bath first and second concentrates;
said first concentrate consisting essentially of in weight percent:
Water 0-80%
Phosphoric Acid (75%) 10-60%
Nitric Acid (67%) 2-20%
Zinc Oxide 1-5%
Nickel Oxide 1-13%
Manganese Oxide 1-12%
Sodium Hydroxide (50%) 0-10%
Potassium Fluoride 0-20%
Surfactant 0-1%
Organic Nitro Compound 0-1%
said second concentrate consisting essentially of in weight percent:
Water 30-80%
Phosphoric Acid (75%) 10-35%
Nitric Acid 0-15%
Sodium Hydroxide (50%) 0-30%
Potassium Hydroxide (45%) 0-45%

said aqueous bath having a zinc ion concentration of between about 300 and 1,000 ppm, an alkali metal ion concentration from an alkali metal phosphate of between about 600 and 20,000 ppm, and a nickel ion and a manganese ion concentration of between about 1500 to 3000 ppm, characterized in that the manganese ion concentration is about 400 to 1600 ppm;
applying said coating composition to the surface of the substrates at a temperature of between about 100°F and 140°F for between 30 and 300 seconds;
rinsing said substrates;
applying a chromate rinse to the substrates; and rinsing said substrates with water.

6. A method of coating a substrate selected from the group consisting of steel, zinc-coated steel, and aluminum comprising the steps of:
cleaning the substrates with an alkali cleaner;
conditioning the surface of the substrates with an aqueous solution of Jernsted salts;
preparing a coating composition by diluting in an aqueous bath first and second concentrates;
said first concentrate consisting essentially of in weight percent:
Water 10-50%
Phosphoric acid (75%) 20-45%
Nitric Acid (67%) 5-15%
Zinc Oxide 2-5%
Nickel Oxide 3-11%
Manganese Oxide 3-11%
Sodium Hydroxide (50%) 0-6%
Potassium Fluoride 0.2-5%
Surfactant 0.2-0.5%
Organic Nitro Compound 0-1%

said second concentrate consisting essentially of in weight percent:
Water 30-60%
Phosphoric Acid (75%) 20-35%
Nitric Acid 0-10%
Sodium Hydroxide (50%) 0-30%
Potassium Hydroxide (45%) 0-45%
said aqueous bath having a zinc ion concentration of between about 500 and 700 ppm, an alkali metal hydroxide ion concentration of between about 2000 and 7000 ppm, and a nickel and manganese ion concentration of between about 1000 to 2000 wherein the manganese ion concentration is about 700 to 1300 ppm;
applying said coating composition to the surface of the substrates at a temperature of between about 100°F and 140°F for between 30 and 300 seconds;
rinsing said substrates;
applying a sealing rinse to the substrates; and rinsing said substrates with water.

7. A method of coating a substrate selected from the group consisting of steel, zinc-coated steel, and aluminum comprising the steps of:
cleaning the substrates with an alkali cleaner;
conditioning the surface of the substrates with an aqueous solution of Jernsted salts;
preparing a coating composition by diluting in an aqueous bath first and second concentrates;
said first concentrate consisting essentially of in weight percent:
Water 20%
Phosphoric Acid (75%) 38%
Nitric Acid (67%) 21%
Zinc Oxide 4%
Nickel Oxide 8%

Manganese Oxide 8%
Sodium Hydroxide (50%) 4%
Potassium Fluoride 4%
Surfactant 0-1%
Organic Nitro Compound 0-1%
said second concentrate consisting essentially of in weight percent:
Water 34%
Phosphoric Acid (75%) 28%
Nitric Acid 5%
Sodium Hydroxide (50%) 13%
Potassium Hydroxide (45%) 20%
said aqueous bath having a zinc ion concentration of between about 500 and 700 ppm, an alkali metal hydroxide ion concentration of between about 2000 and 7000 ppm, and a nickel and manganese ion concentration of between about 1500 to 3500 ppm; wherein the manganese ion content is about 35 to 50 weight percent of B and C;
applying said coating composition to the surface of the substrates at a temperature of between about 100°F and 140°F for between 30 and 300 seconds;
rinsing said substrates;
applying a chromate rinse to the substrates; and rinsing said substrates with water.

8. The invention or inventions substantially as herein described and with reference to any of the preceding claims.