Note: Descriptions are shown in the official language in which they were submitted.
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N~OD FOR TR~A~ING AL~MINUN CON~AINING ~R~AC~8
TECHNICAL FIELD
This invention concerns a method of treating a surface
including metallic aluminum or an aluminum alloy that is
at least 45 % by weight, or preferably at least 85 % by
weight, aluminum, in order to form on the surface a film
which has excellent corrosion resistance, painting proper-
ties and electrodeposition painting properties. (Herein-
after, unless the context implies to the contrary, the term
"aluminum" is to be understood as including aluminum alloys
as specified above, and constitutions specified in percent-
ages are to be understood as percentages by weight unless
otherwise stated.) The process according to the invention
is particularly suited to surfaces in sheet or strip form.
In recent years, there has been a tendency to use
aluminum sheet for parts of an automobile body in order to
reduce the weight of automobiles. When this is done, the
aluminum sheet or press formed aluminum sheet forms a com
posite material in which it is joined by welding, bonding
or bolting to zinc alloy plated steel sheet, alloyed zinc
plated steel sheet, zinc plated steel sheet, or the like.
This pres~nt invention also concerns a method of forming
films which have excellent corrosion resistance and paint-
ing properties on these composite materials.
BACKGROUND ART
In the past, phosphate treatment liquids which con-
tained fluoride, especially in the form of silicofluoride,
were used in the main for forming phosphate films on alum-
inum sheets and formed and worked aluminum sheets. How-
ever, there was a disadvantage in that there was a marked
deterioration in the phosphate film forming properties due
to the build-up of Al3+ ion in the treatment liquid during
the treatment for the formation of the phosphate film.
Hence, with the conventional silicofluoride containing
treatment liquids, renewal of the treatment liquid was
required after a short period of time and there was a
problem in that the cost of forming a phosphate film was
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high. Furthermore, the treatment liquids of which the
forming properties for phosphate films had deteriorated
were waste materials and there was a problem in that the
disposal of the waste treatment liquids which contained
fluoride was undesirable from the viewpoint of pollution.
Acidic sodium fluoride and acidic potassium fluoride
have been added to phosphate treatment liquids as a means
of precipitating and removing the Al3+ ion as K2NaAlF6 com-
pounds in order to prevent the lowering of the forming
properties due to the admixture of A13~ ions as mentioned
above, but fluorine is contained in the precipitate and
this is undesirable from the viewpoint of pollution.
There are also methods in which a chromate film is
formed on the aluminum sheet, for preventing the dissolu-
tion of aluminum into the phosphate treatment liquid, be-
fore the aluminum sheet is joined with a steel sheet, a
zinc plated steel sheet or a zinc alloy plated steel sheet
or the like and subjected to a phosphate treatment, but
when these methods of treatment are used there are pollu-
tion problems with waste treatment liquids with Cr6+ and Fand this is undesirable.
DESCRIPTION_OF THE INVENTION
Problem to Be Solved by the Invention
This present invention takes as one of its objects the
provision of a method for the formation of phosphate films
with which the A13+ ion does not substantially increase in
the phosphate treatment liquid and with which there is no
deterioration of the phosphate film forming properties.
Furthermore, this present invention discloses a method
for the uniform formation of a phosphate film which has ex-
cellent corrosion resistance and painting properties on
composite materials in which a press worked aluminum sheet
and a steel sheet or a zinc based plated steel sheet are
combined.
Summary of the Invention
In this present invention, a primary film of Ni, Fe or
Co, or a composite of two or more of thesel is formed on
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the aluminum sheet and washed with water.
Pure aluminum and aluminum alloys of which aluminum is
the principal component, for example pure aluminum such as
lS and 2S, corrosion resistant aluminum and magnesium based
alloys such as 52S and 56S, aluminum and manganese based
alloys such as 3S, aluminum and magnesium alloys such as
61S and 63S, duralumin such as 14S, 17S and 24S, and extra
super duralumin such as 74S and 75S can be used for the
aluminum sheet in this present invention. Hence, sheets of
these aluminum materials are included among the aluminum
sheets of this present invention.
In this present invention, a primary film of Ni, Fe,
Co is formed on these aluminum sheets. This primary film
is obtained by coating Ni, Fe, Co on the aluminum sheet,
preferably in an amount calculated as metal of 5 - 100 mg/m2
using a non-electrolytic or cathodic electrolytic method.
This primary film can be formed using a simple method, as
described hereinafter, and moreover it is not lost on cold
forming and working or in the phospha~e forming treatment
and so it is desirable as a primary film.
An example of a method of forming a primary film of
Ni, Fe, Co or a compositie non-electrolytically is de-
scribed below. First of all the aluminum sheet is de-
greased and washed, using alkali for example. For example,
if the aluminum sheet is immersed for from 5 seconds to 2
minutes in a warm solution of 15 g/l of sodium carbonate,
25 g/l of sodium phosphate and surfactant, the oil and
grease and the oxide film are removed from the aluminum
sheet and a surface which is suitable for the deposition of
Ni, Fe, Co or a combination thereof is obtained. The de-
greased and washed aluminum film is washed with water, neu-
tralized with nitric acid, sulfuric acid or the like and
washed with water. The treatment liquid for forming the
primary film is an aqueous solution, used at a temperature
in the range from normal ambient temperature to 80 C,
which contains Fe2+, Fe3+, Ni2+, and/or Co2+, and, by
immersing the degreased and washed aluminum sheet in this
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aqueous solution, or by spraying the aqueous solution onto
the aluminum sheet, a primary film of Ni, Fe, and/or ~o can
be formed on the aluminum sheet.
Alternatively, when the primary film is formed using
a cathode electrolytic method, the aluminum sheet is im-
mersed in an aqueous solution which contains Fe2+, Fe3+,
Ni2+, and/or Co2+ and a thin film is formed on the aluminum
sheet, for example by cathode electrolysis at a current
density of 0.3 - 30 amps/dm2 with a quantity of electricity
of from 0.3 to 10 coulombs/dm2. For example, a solution in
which from 20 to 50 grams of iron chloride or nickel chlor-
ide or cobalt chloride and 100 milliliters ("ml") of in-
dustrial hydrochloric acid have been dissolved in l liter
of water can be used for the aqueous solution which con-
tains Fa2~, Fe3+, Ni2+, and/or Co2~. Furthermore, nitrates,
sulfates, phosphates and condensed phosphates are suitable,
non-exclusive counterions for the aforementioned metal
ions, and phosphoric acid, sulfuric acid, and nitric acid
are suitable, non-exclusive acids for ajusting the acidity
of the plating solution.
The immersion time or cathode electrolysis time in the
treatment liquid with which the primary film is formed is
selected appropriately according to the composition of the
aluminum sheet, but a metal primary film of Ni, Fe, and/or
Co of some 5 - 100 mg~m2 is formed on the aluminum sheet by
means of this procedure. The aluminum sheet is then washed
with water and rinsed, whereupon an aluminum sheet on which
a primary film of Ni, Fe or Co, or an alloy of two or more
of these, is obtained as part of this present invention.
A phosphate film is then formed on the aluminum sheet
on which the primary film has been formed, using a treat-
ment liquid which contains fluoride. Furthermore, when a
phosphate film is formed on an aluminum sheet on which the
primary film had been formed, the increase in Al3+ ion in
3~ the treatment liquid is prevented and excellent phosphate
film forming properties can be maintained over a long per-
iod of time. Furthermore, after the primary film has been
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formed on the aluminum sheet, the secondary phosphate film
has been formed and an anti-rusting oil has been applied,
the product can be obtained as a surface treated aluminum
sheet. Furthermore, the primary film is not lost even if
the aluminum sheet is press formed using the usual press
lubricating oils, and it is retained on the aluminum sheet
surface after press forming. Hence, aluminum sheet press
worked and formed products with which the primary film is
retained on the surface are obtained if a press lubricating
oil is applied to an aluminum sheet on which a primary film
has been formed and the sheet is then prPss formed and de-
greased, and when this formed product is subjected to a
phosphate treatment the dissolution of aluminum into the
phosphate treatment liquid which occurred in the past can
be prevented and it is possible to form good phosphate
films over long periods of time with no deterioration of
the phosphate film forming properties of the treatment
liquid.
Furthermore, the inventors have made composite mater-
ials comprised of aluminum sheets and zinc plated steel
sheets or plain steel sheets using aluminum sheets on which
a primary film of Ni, Fe, and/or Co had been formed in an
amount calculated as metal of 5 - 100 mg/m2, or an aluminum
sheet obtained by press forming such a sheet, by joining
with spot welding to the zinc based plated steel sheet or
steel sheet. A phosphate film was formed on these compos-
ite materials using a phosphate film treatment liquid which
contained fluorides of sodium and potassium, and good phos-
phate films could be formed on the aluminum sheet and on
the zinc plated steel sheet or steel sheet. Fur~hermore,
an attempt was made to form phosphate films on composites
of aluminum sheet and zinc based plated steal or plain
steel sheet using a treatment liquid which contained sili-
cofluoride which had been used in the past when forming
phosphate films on aluminum sheet and there was little dis-
solution of Al3+ into the treatment liquid and goo~ phos-
phate films could be formed on the aluminum sheet and the
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zinc based plated steel sheet or steel sheet.
Brief Explanation of the Drawinqs
Figure 1 is a drawing which shows the shape and size
of the pressed formed product in Examples 2, and Figure 2
is an explanatory drawing of the bonded composite work-
pieces in example 3.
Details of Some_Preferred Embodiments of the Invention
The invention may be further appreciated from the
following examples and comparison examples.
Examples 1.1 - 1.6 and Comparison Example 1.7
The inventors prepared in each case 100 aluminum
sheets on which a primary film had been formed as shown in
Table 1, using commercially pure aluminum sheet (Type 2S)
Table 1
AMOUNTS OF PRIMARY FILM AND CONDITIONS OF ITS FORMATION
Example No. Primarv Film Formation Conditions and Amount
Metal Con- Bath Tem- Contact Metal in Film,
centration perature, Time in mq/m2
in Bath C Seconds
1.13 g/L Ni+2 40 15 7
1.25 g/L Ni+2 45 30 23
1.35 g/L Fe~2 45 10 11
1.45 g/L Fe+2 60 90
~ 3 g/L Fe
1.55 g/L Co~2 70 5 15
1.65 g/L Fe+3 35 30 21 Ni
~ 5 g/L Ni + 13 Fe
1.7 ~ ----No primary metal layer-----------
Notes for Table 1
Test panels were initially degreased and cleaned by
immersion ~or 5 minutes in a solution of FINECLEANERTM 315,
comemrcially available from Nihon Parkerizing Co., Ltd., at
a temperature of 55 - 60 C. Panels were then treated
with 1 % aqueous hydrochloric acid solution as a neutral-
izing rinse before the treatments detailed above.
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with width of 300 mm, length of 300 mm, and thickness of
0.8 mm. These sheets were then subjected to the following
process steps: De-grease and wash -~ water waæh ~ neutral-
ization rinse ~ water wash ~ primary film formation ~ wash
~ dry ~ anti-rusting oil coating ~ left to stand for 1 week
indoors.
The de-greasing washing, neutralization and primary
film forming treatment conditions were as shown in table 1.
After primary film formation as shown in Table 1, the sam-
ples were phosphated. A volume of 100 liters of the phos-
phate treatment liquid composition shown in Table 2, which
contained silicofluoride, was housed in a treatment tank
and the aforementioned aluminum sheets on which a primary
film had been formed as shown in table 1 were de-greased
and washed with water and then immersed for 2.0 minutes/
sheet successively, using 50 sh~ets one after the other, in
the phosphate treatment liquid, so that a phosphate film
was formed. The phosphate film formation results are shown
in Table 3.
_ _ _ _
Table 2
COMPOSITION OF PHOSPHATING SOLUTION FOR (COMPARISON)
EX~MPLES 1
Zn2+ Concentration : 1O5 g/1
PO~3~ Concentration : 15 g/1
NO3 Concentration : 8 g/l
Ni2+ Concentration : 1.5 g/l
NO2 Concentration : 0.1 g/l
SiF62- Concentration : 1.0 g/l
Note for Table 2
The phosphating solution was used at a temperature of 43
C.
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Table 3
RESULTS OF PHOSPHATING IN (COMPARISON) EXAMPLES 1
Example No. Results for: _
Twentieth Sheet Fiftieth Sheet _
Areal Dens- Concen- Areal Dens- Concen~
sity of tratio~ sity of trati+o~
Phosphate of Al+ Phosphate of Al
Film, qLm2 Ions in Film, q/m2 Ions in
Treat- Treat-
ment ment
_iquid Li~uid
1.1 1.9 14 1.5 33
1.2 2.0 9 2,0 1~
1.3 1.9 11 1,7 25
1.4 1.8 13 1.4 30
1.5 2.3 8 1.8 30
1.6 2.2 7 2.1 16
1.7 1.5 27 0.2 48
Notes for Table 3
The samples were also subjected to a Filiform Corro-
sion Promotion Test Method, as follows: A specimen in
which scratches had been made in a cationically electrode-
posited paint film surface were immersed for 2 hours in
0.5N HCl aqueous solution which contained 1% H2O2 at 30C
and then washed with water and dried. Then, they were left
to stand for 240 hours in a room at 40C and 85% relative
humidity. and an assessment was made after six of these
cycles. The filiform corrosion length was less than 5 mm
for Experiments 1. 1 and 1.4, 5 - 10 mm for the remaining
Experiments 1.2, 1.3, 1.5, and 1.6, and more than 11 mm for
Comparison Experiment 1.7.
35The aluminum ion concentrations are given in parts per
million by weight.
It is clear from Table 3 that in all cases where an
aluminum sheet on which a primary film had been formed was
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used, a phosphate film of adequate thickness was formed in
a stable manner and, furthermore, as shown in the filiform
corrosion propagation test results column in table 3, phos-
phate films which had excellent performance can be formed.
Furthermore, even when 50 sheets were treated successively
the concentration of ~13+ ion in the phosphate treatment
liquid was low and there was little or no deterioration in
the coating forming power of the phosphate treatment li-
quid. However, as shown by the comparative example in Tab-
le 3, when an aluminum sheet on which no primary film had
been formed was used, the Al3+ ion concentration in the
phosphate treatment liquid increased on treating about 20
sheets and the phosphate film forming power deteriorated.
Consequently, the phosphate film became successively thin-
ner after the twentieth sheet and by the fiftieth sheet
essentially no phosphate film at all could be formed with
an immersion time of 2.0 minutes/sheet.
Examples 2.1 - 2.6
Ten of each of the aluminum sheets on which a primary
film had been formed, using the same method as in Experi-
ments 1.1 - 1.6 respectively, were press formed using the
process outlined below and the formed products were treated
with a phosphate film treatment liquid as shown in Table 2.
The process step sequence was: aluminum sheet on
which a primary film had been formed - coating with lubri-
cating oil ~ press forming ~ degreasing washing ~ water
washing ~ phosphate film ~orming treatment ~ water washing
The lubricating oil coating and degreasing washing
treatment conditions were as follows:
Lubrication Oil Coating: NOX-RUST550HNTM (made by
Parker Kosan Co.) was applied by coating with a brush.
Degreasing Washing: Immersed for 2.0 minutes in an
aqueous solution of FINECLEANERT~ L4460 (made by Nihon
Parkerizing Co.)
Furthermore, the press forming was carried out with
deep cylindrical pressing as shown in figure 1. Also, the
phosphate film forming treatment was carried out with the
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same immersion time (2.0 minutes/ sheet) using the same
treatment liquid as in table 2. The results of phosphate
film formation were as shown in Table 4. As shown in Table
4, the aluminum sheets on which a primary film of this
invention had been formed and which had been press formed
were such that a phosphate film could be formed in roughly
the same way as with aluminum sheets which had not been
subjected to press forming, as described in Table 3.
_ _ _ _ _ _ .
Table 4
RESULTS FROM PHOSPHATING PRESS FORMED PRIMARY METAL COATED
SHEETS ACCORDING TO THIS INVENTION
Example No. Weight of Phosphate Al3+ Ion Concentration
Film on 10t~ Sheetin Treatment Liquid
in a/m at 10th Sheet in ppm
2.1 2.0 7
2.2 2.1 5
2.3 2.1 6
2.4 2.0 7
2.5 2.4 5
2.6 2.3 4
Examples 3 1 3.6
Seams were formed by spot welding, at five points as
shown in Figure 2, a cold rolled steel sheet with a width
of 300 mm, length of 300 mm and thickness of 0.7 mm to each
of the aluminum sheets on which a primary film had been
formed using the same methods as in Examples 1.1 - 1.6 re-
spectively, and the resulting materials were treated in a
phosphate film treatment liquid. The treatment liquid
shown in Table 2 was used for the phosphate film forming
liquid and in each case the material was immersed for 2.0
minutes.
The results of phosphate film formation were as shown
in Table 5. It is clear from Table 5 that good phosphate
films were formed on the aluminum sheet and the cold rolled
steel sheet.
9 6 ~ 8
Seams were formed by spot welding formed hot dip gal-
vanized steel sheets which had been press formed and
worked, instead of the cold rolled steel sheet as noted in
the preceding paragraph, onto aluminum sheet on which a
primary film had been formed and a phosphate film forming
treatment was carried out using the same procedure, and in
this case again a good phosphate film was formed on the
zinc plated steel sheet and the aluminum sheet.
; .. _ . .................... , . . . _ _ . __ . ~_ .
Table 5
PHODSPHATE FILM WEIGHTS FOR SOME COMPOSITE SUBSTRATES
Example No. Phosphate Film Weiaht in g/m2 on:
~luminum Sheet Cold Rolled Steel Sheet
3.1 2.1 2.2
3.2 2.2 2.2
3.3 2.1 2.2
3.4 2.0 2.3
3.5 2.4 2.2
3.6 2.3 2.2
2~
Benefits of the Invention
As has been described above, when the invention is
employed a phosphate film which has excellent corrosion
resistance and painting properties is formed uniformly, in
a state in which the dissolution of aluminum into the phos-
phate treatment liquid is suppressed, on an aluminum sur-
face or a composite in which an aluminum surface, which may
be press worked, is combined with a steel or a galvanized
steel surface, which may or may not have been press worked.
