Note: Descriptions are shown in the official language in which they were submitted.
~QS~7~32
- _C G~OUND
A number of different metal cleaners are known to
the art for cleaniny and proces~ing aluminum and other alloys.
Such materials are usually based primarily on sodium hydroxide,
sodium carbonate and/or sodium bicarbonate. Such cl~aners,
however, suffer from the disadvantage of being very sensitive
to a lower pH range, exposure of aluminum thereto causes
instability and a short lived cleaning bath. A high pH, on the
~ other hand, favors a sometimes undesirable strong etching effect.
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This is particularly true as it later becomes difficult to lay
down a uniform intermediate blocking layer. Control of the pH
is further complicated in the use of cleaning compositions by
the fact that additives such as detergents and corrosion
inhibitors such as arsenic and antimoney salts can also create
environmental or toxicological problems.
It is an object of an aspect of the present invention
to easily and cheaply clean metal surfaces without over-etching
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- and to remove spontaneously formed oxides therefrom.
; It is an object of an aspect of the present inventi3n ;~
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to obtain an environmentally safe partly decomposible cleaning
composition or bath capable of removing both porous and non-
` porous oxide layers from metal surfaces such as aluminum,
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aluminum alloys or aluminum coated alloys so that a controlled
~; electronically useful oxide barrier layer can be subsequently
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generated thereon and durable adhexent photoconductive coats -
successfully applied thereto as desired.
` THE INVEN~ION - ~-
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In accordance with one aspect of this invention there
is provided a method for cleaning and removing oxide layers -~
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from aluminum or alumunum alloy surfaces comprising
contacting the oxide-coated metal surface with a cleaning
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bath at a temperature up to about 90C. for a period o not
less than about 1/2 minute, and thereafter washing the
treated metal surface, said cleaning bath comprising about
0.5% - 15% by weight of at least one component providing
carbonate ions, about 0.5% - 15~ by weight of at least one
polyphosphate component, and up to about 0~ - 1% by weight
of at least one surfactant, the balance of the bath compris~
~ ing water or an alcohol solution, said carbonate ion
; providing component being at least one member selected from
10 the group consisting of an alkali metal carbonate, alkali
metal bicarbonate, an ammonium carbonate, corresponding
hydrate salts thereof and mixed salts thereof, and the
polyphosphate component being one or more of an alkali metal
polyphosphate.
Active metal cleaning baths within the present
invention preferably include, for instance, a total of about
.5~-15% by weight and preferably 1-5% of carbonate ion-providing
component(s) such as at least one alkali metal carbonate,
alkali metal bicarbonate, ammonium carbonate, corresponding
20 hydrate salts thereof, and mixed salts thereof. Especially
favored are corresponding sodium or potassium salts comprising
a total of about 1-3% by weight of the cleaning bath. Such
can include, for instance, about 1~ by weight sodium bicarbonater
~:,
about 1-2~ by weight sodium carbonate.
The polyphosphate component can include a total of
about 1-5% by weight and preferably 1-3% by weight of one or
more alkali metal polyphosphate components inclusive of
corresponding hydrates and mixed salts thereof. Most preferred,
for this purpose, is about 1-3% by weight of one or more of
30 sodium tripolyphosphate (STPP), tetrasodium pyrophosphate (TSPD),
sodium hexametaphosphate also corresponding higher phosphate
salts and hydrates thereof. ~-
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~()5763'~
In addition, cleanlng baths within the present
invention also optionally contain at least one surfactant
component such as an organic sodium sulfate or a branched
chain alcohol. Suitable materials are obtainable commercially
from chemical suppliers and include, for instance, tertiary
acetylenic glycols such as those ~sold under the trade marks
"Tergitol 08"*, "Surfynol 82"**, also substances sold under
the trade marks "Aerosol GPG", and "Aerosol OT"***, etc. in
amounts up to about 1% by weight.
lQ The cleaning bath, as above described, can be use-
fully maintained within a p~ range of about 7-11 (preferably
pH 8-10) by buffering where needed and will remain stable for
long periods at temperatures up to about 90 C.
Option~lly, the best method for cleaning and remov~
ing oxide layers from oxide-forminy metal surfaces such as
; aluminum comprises contacting the metal surface with a suit-
able cleaning bath as above described at a temperature up to
about 90 C. for a period of not less than about one-half min-
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ute, followed by rinsing and drying of the treated surface. -
It is recognized, however, that the period and method of
, exposure to the bath, the bath temperature, exposure time,
et~., can be usefully varied, depending upon what constitutes
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an acceptable amount of metal etching, and depending upon the
thickness and exact type of oxide layer to be removed, etc.
Generally speaking, however, relatively thin meta~ plates or
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*Union Carbide Chemicals -~
**Air Products and Chemicals Inrorporated
***American Cyanamid Co. ~ ~
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~ S7632
drums of aluminum; aluminum alloys with copper, manganeser
magnas ium, chromium, etc., such as Alcoa (trade mark) Alloys
ANSl**** #6061, 1100, 1175, 2014, 3003; 1175 over 1100; other
aluminum clad alloys; bra~s or even
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****American ~ationai Standard Aluminum Alloy Designation
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1~)5763~
nickel ~for cleaning purpos~s3 can be successfully bath
treated at about 60-9QC. for a period of not ~ess than
about one-half minute and usually not more than (although
not limited to) about five min~tes. When so treated~ the
; desired objects are achieved with a minimal etching ef~ect~
Where aluminum containing metal surfaces are being
c~eaned, a bath temperature of about 75C.-85C. and immersion
for a period o about 1-3 minute~ are particularly preferred.
This invention is further demonstrated although
o not limited, ~y the following examples,
EX~MPLE I
Five 2" x 6" stain-free aluminum test strips of
about 80 mil thickness are degreased with trichloroethylene.
~he strips are then separately dipped into a 1 percent
, i . .
~S equimolar sodium carbonate/sodium phosphate bath, water
- rinsed and then air dried and aged in an oven for about 1/2
-hour at 200OC, ihen immersea in boiling deionized water for
60 minutes to obtain a thick external coating (about 100 ~) ;
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~ of undesixed porous hydrated aluminum oxide on each strip.
~he dried test strips, identified as T-l throu~h T-5, are
then initially tested and observed wit~ respec~ to surface
wettability~ light reflectivity (i.eO relative etching
,
effect) and with respect to the area and thickness of the
$ oxide coating. The tes~ samp}es are, thereafter, individually
dipped into cleaning Bath A identified below, the dip time ~
; and bath tcmperature being varied. ~hc test strips are then - ~ -
~ rinsed twice with d~ionized water, air dried, and then -
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reobser~ed and retested as beforo to do~ermine the amount
~i of oxide remo~7al, wettability chan~es and etching effect
- 30 o~ the bath. The results are reported in Tablc I b~low.
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~05~632
~ or test purposes in each case th~ xel~tive
wettability is best determined by exposing each strip at
room temperature to a stream of deionized water and observing
the drainage patterns on the strip surface. The etching
; effect of the bath is obtained by detennining percent loss
; in reflectivity. The later determination is vbtained in
routine manner with an Edward's Modulated Beam Photometer
Mo~el MBP2B. Direct observation of the amount of oxide
; layer i5 effected by the routine use of Transmission Electron
Microscopy techniques using a P~ilips EM 200 model. A
convenient alternative method for obtaining an average oxide
thickness, howe~er, is by routine voltage breakdown determinations.
' . BATH A
!',. 50 g. sesquicarbonate of soda (~A2C03 ~aHC03 o 2H20),
50 g. sodium tripolyphosphate,
10 gO '!Tergitol 08"* with~ .
deionized water to 1 liter volume.
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~A ssdium salt of mono(2-ethyl-hexyl) sulfatc obtained from
~:Union Carbidc Chemicals Divi.s~on
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Oxidf~**
Sample Elath TempDip Time Wettability* Reflectivity Removal
C.(Minutes) (Before and After) (Observed)
Tl 90 1 Pass 7 ~x
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T2 90 1/2 Pass 8~
~1?3 80 3 Pass 87 ' EX
T~ 75 1 Pass 85 EX
T5 70 5 Pas s 86
.
i *Pass = sur~ace film observed
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** P = poor (less than 49% oxide removed)
:. F = fair ( 50%~74% oxide removed)
i G = good ( 7 5%~84% oxide removed) - . :.
, tl ' VG = very yood (85%-9~% oxide removed) :
I EX = excellent (95/O-all oxide re~oved) -~:
EX~MPLE I I
Five ~" x 6" stain ree aluminum test strips
~ identified as T6-T10 of the same type and composition
'20 . used in Example I are degreased, pretreated and observed :~
i as before, then dipped into Bath B as hereinafter described,
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~ and ~hen washed, dried and tested in ~he same manner as
:', Example I. The results are reported in Table ~I below.
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BAT~l B
30 g~ sesquicarbonate of soda~
30 g. tetrasodium pyrophosphate,
10 g. "Tergitol 08" surfactant, and
deionized water to 1 liter volume.
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Oxiae** '
R~fle~tivityRemoval
Sampl~ Bath Temp Dip Time Wettability* (~efore and After) (O~.~erved~
C. (Minutes)
:~ T6 90 1 Pass 85 Ex
~7 9~ 1~2 Pass 85 EX
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T8 80 1 Pass 84 Ex .
~ 83
`~ T9 70 2 Pass ~6 Ex
81.
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T10 60 2 Pass : 25 EX
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~i *Pass - surface film observed
~ail - no filming observed ~:
:,~ ** P = poor (less than 49% oxide removed)
'l F - fair (50~0-74% oxide removed)
I G - good (75/'-84% oxide removed)
VG a very good (85%~94% oxide removed)
,- EX = excellent (950/a-all oxide removed)
EXAMPLE III ~:
; Six 2" x 6" s~ain free test strips identified as
Tll-T16 consisting of an ~lcoa aluminum alloy ANSl 1175 having
essentially the same dimensions as the strips used in ~ -
~ Examples I and II are degrcased, obserYed dipping into ~.
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:30 cleaning Bath C (s~e below) and ther~after washed, air dried
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~i763Z
and retested as in Example I. The r~sults are reported
in Table III below.
BAq~I C
~ 5 g. sodium bicarbon~te,
: 5 g. sodium carbonate,
10 g. sodium tripolyphosphate (Na5P3010),
2.5 g. "Tergitol 08'~,
` 2.5 gO "Surfanol 82" plus
deionized water to 1 liter volume. ~
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Oxide**
R~fle~tivity Removal.
Sample Bath Temp Dip Time Wettability* (sefore and A~ter) (Observed)
. C. (Minutes3 ,~
Tll 90 1 ~ass 84 EX -~
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, T12. 90 1/2 Pass 85 Ex. ;:~
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T13 80 1~ Pass 87 ~x
T14 BO 3 IPass 84 Ex
T15 70 4 Pass 84 ~G .
`, ~16 ~0 5 Pass 84 VG `~
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,l *Pass = surface film observed
.~ Fail = no filming observed
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. ' I ** P = poor ( less than 49% oxide removed) ~:
.' . F - fair (50,'~,-74% oxide removed) : ~ ;
G = good (75e~o~84~ oxide removed~ .
l :YG = very ~ood ~85h-94% oxi~e removed)
,., EX 8 e*cellent (95,'-aIl oxide removed) -
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