Note: Descriptions are shown in the official language in which they were submitted.
1~)7~636
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The present lnventlon relate~ to a method of forming a
coloured anodic oxide coating on the ~ur~ace of aluminum or an
alumlnum-based alloy meterlal.
It 1~ known that coloured anodic oxlde fllms can be form-
`5 od on the surface ~f aluminum or an alumlnum alloy (hereinafter
~, ,
-~ roforrod to a~ aluminum-ba~ed metal) by first anodlzlng the
aluminum-ba~ed metal to produce an anodically oxldized film
, . . .
~ thoroon and then subJectlng lt to an electrolytlc process ln
~, . .--
~hich the anodlzed metal i~ placed ln a bath of an eloctrolyte
contalning a metal Jalt. In thls electrolytlc proce~s, tho
nodlzed metal and metal~ serve as an anode or as both of an
.,, ~ . ;
anode and a cathode. Consequently, the anodlc oxlde fllm on
the ~ur~ace o~ the metal i8 provlded wlth a colour ln accordance
~ .~
~lth the type o~ the metal salt contalned ln the bath.
~15 For example, Unlted State~ Patent No. 3,382,160 to T.
A~ada di~close~that an anodic oxlde fi~lm produced on the
~urface of an alumlnum-ba~ed metal 1~ coloured by sub~ectlng
.. , ~ . .. .
tho anodlzed aluminum-based metal to an electrolytlc proce~s ln
whlch an alternatlng current 18 passed through an acldlc bath
-~ 20 contalnlng a metal lon ~uch a-q nlckel, cobalt, chromlum, copper
or cadmium lons. Unlted States Patent No. 3,669,856 to O.C.
Gedde dlscloses that a colour of an anodized fllm can be easlly
controll-d by suO~ectlng the anodized fllm to an alternatlng
current wlth an asymmetrlc voltage pattern ln an anodic bath
contalnlng metal ion~.
In these electrolytlc colouring processes, it has been
thought that the anodic oxlde rllms may be coloured wlth the
etal~lonJ whlch are flrst depo~lted on the walls of pores ln
the anodlc oxlde ~llms when the negatlve voltage i8 applied
and thon~dl~solved there~rom when the positlve voltage is applled.
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1070636
It 18 known that tho colour~ thus produced on the anodlc oxide
rllms may depend on the location~ and amo ~ of the metal ions
dissolvlng from the pores of the films. These conventional
- processe~ cannot provide a positlve control of such locatlons
;-~ 5 and amountJ Or the metal lons disJolvlng rrom the pores of the
; rilms. Control therefor i8 carried out by ad~ustlng the bath
temperatur~ and the processlng time in accordance with a desired ~-
amount of the metal lons to be dissolved. However, the ad~ust-
.: ment is not sati~factorr to provide uniform colours on the apo-
~10 dized oxide layera. Particularly, it ha~ been found thereinthat e~en ~ery small ~arlations in the processing time may ai?i~ect
tho colour~ o~ the S~lm~. For example, even ~light changes~,
.
- ~ though sometlmea unavoidable, in the bath temperature and the
proce8sing time ln a single bath may provlde the anodlc oxide
. .
!~.... 15 rllm wlth coloura lncluding from a brlght amber color to a dark
; ~ blacklsh bronze colour.
It 1~ therefore an ob~ect of the present inventlon to pro-
vlde a process oS produclng coloured anodic oxlde films on p!,,~
~lu~inum-based metals wlth minimum variations ln colour.
Another ob~ect o~ the present invention is to provide a
process of applylng colours to anodic oxido fllm~ on aluminum-
.
ba~ea ~et d~ in a bath of electrolyte havlng a given composition.
~ A further ob~ect Or the present lnvention i~ to provlde a
;~ proceJs of producing coloured anodlc oxide films on aluminum-
based metals by applylng alternatlng voltage pulses having
negative pulffo duration longer than po~itlve pulse duration to
tho metals in a bath of el~ctrolyte containing a water-soluble
~ lckel salt and borlc acid.
''~ . " ` ! ~ me method of-producing coloured anodic oxlde films on
~ 30 ~ alumlnum-based metals ac¢ordlng to tho present inventlon compri~es
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1070636
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~- the steps of producing anodlc oxide films on the metals, lm-
mersing the metals in a bath of electrolyte containlng a water-
- oolublo nickel salt and boric acid and applying to the metal~
--~ alternatlng voltage pulse~ having negative pulse duration whlch
~- 5` 1~ at least the aame as or longer than positive pulse duration.
- According to th~ method of the present invention, it may
~; bo noted that boric acid contained in thc electrolyte may ~erve
.
- ~ ao produclng a complex of a water-soluble nickel salt and boric
~` acld ln the viclnlty of the previou~ly formed anodic films and
~0 ~ that the actlve sites of pores in the anodic oxide film may be
oaturated with the metallic ions as coloring factors for a short
:, .
i ~ perlod because of the action of high level energy at the ris~ng
and decreaolng periods o~ each pulse on the aluminum-bas~ed metal,
thcreby keeping the metallic lons from dissplution after a
predetermined period of tlm~ ~or electr~lyJis and consequently
prorlding a uniform color.
: . .
~ ~ The process of the present invention is carried out as fol-
~ . ~
~ lowo. An aluminum-baqed material to be colored i8 first provided
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~ wlth an anodlc fllm accordlng to conventional anodizlng treat-
. ~ - , . ; ~ . .
;~ 20- mont.
,~ . .
~ The anodized material ls then dlpped into a bath of electro-
,. . . .
lyto containing borlc acid and a water-baluble nickel salt. In
; ~ thls procels, the anodized material or materials serve as one or
both Or electrodes, The bath~contain from about 10 to 50 grams
~25 of boric acid per liter of water. Preferably, the boric acid may
be di~sol~ed ~p to its upper linit. me amount of the water-
ooluble nickel salt may be from about 15 to 150 grams per liter
;~ of water. Preferred examples of the water-~oluble nickel salts
aro nickel acetate, nickol sulfate and nickel chloride; other
-~ 3~ nickol oalto ~ay bo used as long ao they aro ooluble in water.
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10~0636
e aluminum-based material 1s placed in a bath through
whlch a pulsating altornating current is passed, the current
h~lng negatl~e pul~e voltago greater than the posltive one and
ha~lng longer duratlon than that of tho positlve pul~e voltage.
~: - 5 me voltage thus applied to the material may comprise al-
` t~rnating po~iti~e and noatlvo pulses or a plurallty of positi~e
pulse~ which are followed by a plurality of negative pulses.
Pul8~ting voltages of any wave rorm may be used as long as they
c n apply ~lgh le~el energy to the materials to be treated.
- lO According to the prosent lnventionj the anodlc oxide fllm
~ ,:
-~ on the materlal is glven with bronze based colours which are
; lnherent to nlckel ions and which may be selected ln the range
lncluding relati~ely bright amber through relatively dark
blackish colour ~imply by determining the values of the al-
lS ternating voltage pui9es. It i8 posslble to provlde a substantial-
ly unifor color on the anodic oxlde fllms over a wlde range
; evon ~fter the treatment waJ ptrformed beyond a certaln requlred
~. .
time. There may be substantially no colour varlatlons ln ac-
oordance with a change ln proco~lng time and/or temperature.
~; :. ;: 20 : Examples
An alu~minum-based alloy (llOO) was flrst subJected to a
con~entlonal anodizing process to form thereon an oxlde film.
Then, the material is dlpped ln a bath Or colouring electrolyte
.: ~. ; . .
containing SO grams of boric acid and lOO grams of (CH3C00)2-
Ni4H20 per liter of water. Thereafter, a colouring electrolytic
proce~ was performed by applying to the materlal for ~ to lO
minutes such voltage pulses that comprise aiternating po~itive
and negativo pulses. me bath wa~ maintained at a temperature
of 20 to 22C. me results are shown ln Table l wherein the
30~ chur~oter~ X, Y and Z designate Munsell notations.
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1070636
It ~111 be noted i~rom Table 1 that an amber-like colour
can be produced by applying to the material alternatlng voltage
- pulse~ comprislng alteraatlng negatlve voltage pulses of 13
~ volt~ and 3 second duration and positlve voltage pulses of 13 `,~,~ 5 ` volt~ and l aecond duration. As far as the treatment was per-
for~od iPor at least 7 mlnute~, the proce~slng tlme did not have
-,` any ei?~ect on the colour.
An alumlnu~-based alloy member~ having anodic oxide films
were dlpped a~ the electrode~ ln a bath of electrolyte having
'"`''~;10~ a composltlon a~ Jhown in Table 2 and havlng a bath temperature
' ;'` ' ,o~ 20 to 22VC. Alternating voltage pulses were then passed bst-
,' ; ween the members for i?lve mlnute~. The alternatlng voltage
-''' ';~ pul~eJ comprl~ed negative pulses o~ 12,5 volts Or average voltage
' and duratlon o~ 3 ~oconds, and posltlve pulses of 5.5 volts Or
-~"~-15 a~erage voltage~nad,~duratlon of l seco~d. me results are ~hown
~' ln Table 2. me M~nsell notation~ in Tablo 2 are average values
o~ those obtained upon several experiments. Visual observations
, proved very llttle variatlons ln coloùr particularly wlth the
bath containlng 100 g/l Or nickel salt and 50 g/l of boric acid.
~ me lnvention ha~ thus been shown and described with refe-
' renoe to ~pecific example~ however, it ~hould be noted that the
!; ",~ i m entlon is no way llmited to the detalls of the described ex-
, ample~ but changes and modirications may,be made without depart- '
g rrc- the ~Cop- Or the appended clalma.
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~070636
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107~636
. Tsble.2
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: : ~ . . Electrolyte (gll) Colour Tone
r
Nl S~lt Borlc Acld Y X Z,,`,`.,,;,, ~ ~: ' : :
;-- ~ 20 ~ 4 . 4 3 . 7 4 . 4
. 10 35 3 . 5 2 . 8 3 . 8
. `.i~: _ 50 ~ 3 . 3 2 . 9 3 . 6
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3 . 0 2 . 3 3 . 6 .
;: 20 35 2 . 7 2 . 2 3 . 3
~ :~: ~ . 50 ." : 2 . 5 2 . Q 3 . O
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~- 30 35 2 . 6 2 . 1 3 . 3
. . . ~ 50 2 . 2 1 . 7 2 . 8
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. 20 2 . 5 2 . 0 3 . 4
`` `. ~0 : . 35 2 . 7 2 . 1 3 . 5
:~ 50 2 . 2 1 . 7 3 . 0
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`-: 20 2 . 7 2 . 1 3 . 5
~70 35 2 . 5 . 1 . 9 3 . 2
: ~ ~ 50 2 . 2 1 . 7 2 . 9
- : 20 . 2 . 8 2 . 3 3 . 5
. ~ 1,00 35 2 . 2 1 . 8 2 . 8
-~ . . _ . 2 . 2 I ~ 2 . 9
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