close

Вход

Забыли?

вход по аккаунту

?

Патент USA US2407544

код для вставки
2,401,543V f
Patented Sept. 10, 1946l
UNITED _*sTATEs" PATENT olfl'ilclë:¥
METHOD 0F ANODICALLY POLISHIÑG
BRASS
‘
Charles L. Faust, Columbus, Ohio, assignor to
Battelle Memorial Institute, Columbus, Ohio, a
corporation of Ohio
_ Application November? .6, 1939, serial No. 302,952
11 claims.
(c1. coi-14o) `
1
'I'his invention relates to a method of and an
, In order toget the best polishing results, how
ever, I have found that the range of proportions
of phosphoric acid, chromic acid and water
electrolyte for anodically polishing brass. More
particularly the invention relates to an aqueous
electrolyte comprising chromic acid» and water,
or chromic acid, phosphoric acid and water, and
should be kept within certain narrowe;` limits,
to the use of such an electrolyte in the anodic
accompanying diagram by the separate, lesser
polishing of brass.
areas defined by the solid line AE, dot and dash
line ELF, solid line FM, dot and dash lines MG
and GH, and the solid line HA, and by the solid
and these narrower limits are represented on th'e
f
I4 have now found that an aqueous electrolyte
comprising chromic acid and water, or prefer
ably chromic and phosphoric acids and water, 10 line IK and dot and dash line KJI. The pre
ferred compositions of electrolyte, with respect
can be very satisfactorily used in the anodic
to the relative proportions of phosphoric acid,
polishing of brass. If the relative proportions of
the principal ingredients of the bath be keptl
chromic` acid and water, lie within the two dis- connected areas just described, both of which are
within certain limits, which I have determined,
surfaces can be produced that have relativelyl
wh'olly enclosed within the broader area ñrst
superior characteristics to those obtainable by
defined.
mechanical polishing or bufñng operations.
The reading of a trìaxial diagram such as the
It is therefore an important object of my in- i
accompanying one is well understood but the
vention to provide an electrolyte containing phos
following will be given for purposes of illustra
phoric acid, chromic acid and water within cer 20 tion. The point on the diagram represented by
tain limits as to their relative proportions, for
the letter A, for instance, indicates a composition
use in the anodic polishing `of brass to impart
comprising 0% of phosphoric acid, 65% of chro
thereto a highly lustrous surface.
mic acid and 35% of water; the point indicated
It is a further important object of this inven
by the reference letter B a composition compris
tion to provide a method of anodically polishing
ing 85% of phosphoric acid, a small but signifi
brass and using an electrolyte of novel composi
cant proportion, say 0.1% of chromic acid and
tion that'is operative through a wide range of
the balance, somewhat less than 15%, water; the
anode current densities and temperatures.
point represented by the reference letter C a. com»
Other and further important objects of this
position comprising 5% of phosphoric acid, about
invention will become apparent from the dis 30 0.1% of chro-mic acid and the balance, somewhat
closures in the specification and the accompany
less than 95%, Water; and the point indicated by
ing drawing.
`
the reference letter D a composition comprising
This invention (in its preferred form) is illus
l0% of phosphoric acid, 5% of chromic acid and
trated in the drawing and hereinafter more fully
95% of water.
described.
It will be seen that the maximum phosphoric
-On the drawing:acid content is 85% and the minimum 0%; the
'I'he figure represents a triaxial diagram show
maximum chromic -acid content about 65% and
ingfthe relative proportions of phosphoric acid,
the minimum about 0.1%; and the maximum
chromic acid and water for compositions of elec
- water content 95% and the minimum about 13%.
trolytes coming within the scope of my invention.
The preferred composition limits are from 0 to
In the accompanying diagram, the respective
v85% phosphoric acid, from 2 to' 65% CrOa, and
sides of the >triangle indicate the percentages o_f
from 13 to 92% water. These relative percent
phosphoric acid (HsPOt), of water (H2O), and
ages of the ingredients of my bath, however, are
of chromic acid (CrOs), from 0 to 100%. On
interdependent, so that in order to insure an
the basis of experimental data, I have deter 45 operative bath. its composition should be selected
mined the relative proportions of phosphoric acid,
by reference to- the triaxial diagram and the
chromic acid and water that give compositions
areas defined thereon.
of electrolyte that are operative for the anodic
The triaxial diagram thus shows the relative
polishing of brass. The area representing opera
proportions of chromic acid and water in a two
tive compositions of electrolyte is defined on the 50 component system (the phosphoric acid being
accompanying diagram by the solid lines AB,
0%), or the relative proportions of chromic acid,
BC, CD and DA. Within the area so deñned,
phosphoric acid and water in a three component
any composition selected will be found to be op
system. Suitable baths of these two or three
component systems may nevertheless also include
erative inthe method hereinafter described for
the anodic polishing of brass.
>
55 other ingredients, such as other acids and/or
2,407,543
.
4
3 .
salts. From the diagram, however, th‘e relative
proportions that chromic acid and water, or that
chromic acid, phosphoric acid and water, should
ily obtained. ’I‘he highly lustrous surface ob
tainable by my method, using an electrolyte lof
preferred composition, is an important feature
bear to each other may be determined for opera
of my invention and one that sharply distin
guishes it from prior art ñnishes produced in the
tive and preferred ranges of composition, re
gardless. of what other non-essential ingredients
may be present in the bath.
'
-
electrolytic cleaning of brass.
The formation of highly polished and lustrous
surfaces is undoubtedly associated with the pres
Thus, for instance, in making up an electro
lyte for the anodic polishing of brass, one might
ence of la polarizing film over the surface of the
select the point X on the triaxial diagram as 10 metal during-the process of anodic dissolution.
being a bath of preferred composition. The com
The nature ‘of this ñlm is such that selective
position represented by the point X would be
attack on the various phases present in the brass
is minimized. Anodic dissolution apparently
58% of phosphoric acid, 12% of chromic acid and
takes place _at a relatively high rate and at a
30% of water. During the continued use of suchk
a bath in the electropolishing of brass, the bath 15 high anodic polarization value, with the result
composition would necessarily change, owing to
that anodic dissolution of the metal acts to level
the anodic dissolution into the bath of copper
the crystal surfaces thereof` and to vproduce a
and zinc from the brass undergoing polishing.
mirror-like finish. `These conditions do not pre
There might also be some change in the water f vail in the simple electrolytic cleaning treatment
content, such as an increase due to absorption 20 known to the prior art. . `
,
by the bath of moisture from the air, or a de
In order to obtain the best results in a reason
crease due to evaporation of water from the sur
able length of time, it is preferable to use rela
face of the bath,Í to decomposition of water by
tively high current densities, such as those of
electrolytic action, or to loss of Water from the
the order of magnitude of from 100 to 1000 arn
bath by entrainment thereof in gases given off 25 peres per sq. ft. It will be understood, however, „
from the bath.
that lower current densities, even as low as l0
Notwithstanding such changes in its composi
amperes per sq. ft., may be employed with con
tion as may occur during continued use, if the
sequent prolongation of the time of treatment.
relative percentages of phosphoric acid, chromic
Higher current densities, up to as high as 2000
acid and water, expressed as percentages by 30 or 3000 amperes per sq. ft., may also be used,
weight of the total weight of only these three
but such high current densities imply, in gen
ingredients in the bath composition, remain with
eral, larger currents, which require more expen
sive equipment. The length of time to eñ‘ect the
desired results depends upon the magnitude of
factorily. Preferably, however, the bath compo 35 the current densities employed and to some ex
sition should be maintained within the preferred
tent upon the particular analysis of the brass,
areas of composition, which have been defined
and also upon the character of the surface of
the brass initially. Rough surfaces, of course,
Consequently, where the relative percentages of
require a longer time to polish than relatively
phosphoric acid, chromic acid and water in a 40 smooth ones.
' given bath composition lie within either the pre
With any of the compositions of electrolyte
ferred or less preferred areas defined on the ac
lying within the preferred areas defined by the
companying triaxial diagram, such bath compo
solid line AE, dot and‘dash line ELF, solid line
Qsition is intended to come within the scope of
FM, dot and dash lines MG and GH, and solid ,
my invention, even though it may contain othen 45. line HA, or by the solid line ZIK and dot and dash
acids> than phosphoric and chromic and even
line KJI on the accompanying triaxial diagram,
though it may ,contain a substantial quantity of>
excellent polishes are obtained on brasses of any
in the area defined by the solid lines AB, BC, CD
and DA, the bath will continue to operate satis
'
above.
metallic salts.
'
~
of the usual compositions.
‘
Instead of chromic acid, soluble chromates and
The term “brass” is intended to cover‘copper
bichromates may be substituted therefor and are 50 zinc alloys of varying compositions, some of which
to be considered the equivalent of chromic acid
may contain small percentages of lead, tin,
on a stoichiometric basis. Thel term ‘.‘chromic
and/or other metals. With the more ordinary
acid equivalent,” as used in this specification and
brasses, such as -those containing around '70%
in the claims, is therefore intended to include
copper, 29% zinc and up to 1% tin, I prefer to
chromic acid itself (CrOs) and stoichiometrically 55 employ anode current densities of about 500 am
equivalent weights of , soluble chromates and bi
peres per sq. ft., a bath temperature lying within
chromates.
the range of 80 to 175° F., and a time of treat
Similarly, in `place of orthophosphoric acid,
ment varying from`11/2 to 12 minutes. In gen
other phosphoric acids, such as meta-_ and pyro
eral, the temperature may be maintained at any
phosphoric acids, may be used and are to be con 60 point between room temperature and the boiling
sidered as included within the term “phosphoric
point of Water, but temperatures of around 100°
acid.”
F. are found very satisfactory.
In the method of anodically- polishing brass,
From the foregoing description of my inven
using a bath of a composition indicated to be
tion, it will be apparent that I have provided
suitable by reference to the accompanying tri
a novel composition of electrolyte and a method
axial diagram, the brass, or an article having a
whereby the same may be used to produce highly
lustrous polishes on brass. My electrolyte and
surface of brass, is made the anode in a bath
of the selected composition and an electric cur
method avoid the disadvantages of the old meth
rent is passed therethrough of sufficient density
ods of mechanically polishing brass and enable
and for a suñicient length of time to produce the 70 the production of brass articles having surfaces
desired high degree of luster, or polish, on the
that are free from mechanical strain, Vdragging
brass. By employing an electrolyte having a
and “pilingf’ and which are superior to'those
composition within the preferred areas, as de
obtainable by mechanical polishing methods.
fined on the accompanying triaxial diagram, a
It Will, of course, be understood 4that various
highly lustrous, mirror-like surface can be read 75 details of the process may be varied through a
2,407,543
7. The method of anodically 'polishing brass
-wide range without departing from the principles
which comprises making brass the Aanode in a
of this invention and it is, therefore, not the
purpose to limit the patent granted hereon other
wise than necessitated by the scope of the ap
pended claims.
solution comprising essentially av composition
lying within the area defined in the accompany
ing diagram by the lines IJK and KI, and passing
,
an electric current therethrough at a current
I claim as my invention:
1. The method of anodically polishing brass,
density of from one hundred to three thousand
3. The method of anodically polishing brass
ing diagram by the solid line AE, the dot-dash
line ELF, the solid line FM, the straight dot-dash
line MG, the dot-dash line GH, and the straight
amperes per square foot at a temperature be
which comprises making brass the anode in a
tween 80° and_212° F. for a sufiicient period of
solution comprising from 5 to 65% CrOa, the
balance comprising essentially water, and at a 10 time to eiîect the polishing of said brass.
8. The'method of anodically polishing brass
temperature below 212° F. and a current density
which comprises making brass the anode in a
not in excess of three thousand amperes per
solution comprising essentially a composition.
square foot passing an electric current there
lying within the area deñned in the accompany
through of sufficient density and for a suiiicient
ing diagram by the line AB, the straight line BC,
period of time 'to eifect the polishing of said
the straight line CD and the straight line DA,
brass.
and at a temperature below 212° F. and a current
2. The method of anodically polishing brass, e
density not in excess of three thousand amperes
which comprises making brass the anode in a
per square foot passing an electric current there
solution comprising from 42% to 65% CrOa, the
balance comprising essentially water, and at a 20 through of suiiicient density and for a suñlcient
period of time to eiîect the polishing of said brass.
temperature below 212° F. and a current density
9. The method of anodically polishing brass
not in excess of three thousand amperes per
which comprises making brass the anode in a
square foot passing an electric current- there
solution comprising essentiallyl a composition
through of sufiicient density and for a sufficient
25 lying within the area deiined in the accompany
period to effect the polishing of said brass.
which comprises making brass the anode in a
solution comprising from 24% to> 34% CrOa, the
solid line HA, and at a temperature below 212° F.
balance comprising essentially water, and at a
temperature belowv 212° F. and a current density 30 and a current density not in excess of three
thousand amperes per square foot passing an
not in excess of three thousand amperes per
electric current therethrough of sufllcient density
square foot passing an electric current there-v
and for a suiiicient period of time to effect the
through of suiiicient density and for a. suiiicient
polishing of said brass.
« period of time to effect the polishing of said brass.
4. The method of anodically polishing brass 35
which comprises making brass the anode in a .
solution comprising essentially a composition
~
10. The method of anodically polishing brass
which comprises making brass the anode in a
, solution comprising essentially a composition
lying within the area defined on the accompany
lying within the area defined in the accompany
ing diagram by the line AB, the straight line BC,
ing diagram by thelines IJK and KI and at a
temperature below 212° F. and a current density 40 the straight line CD, and the straight line DA,
and passing an electric current therethrough at
not in excess of three thousand amperes per
a current density of from one hundred. to three
square foot passing an electric current there
thousand amperes per square foot at a tempera
through of sufûcient density and for a suillcient
ture between 80° and 212° F. for a suiiicient period
period of time to effect the polishing of said brass.
of time to eilîect the polishing of said brass.
45
5. The method of anodically polishing brass
‘ 11. The method of anodically polishing brass
which comprises making brass the anode in a
which comprises making brass the anode yin a
` solution comprising from 5% to 65% CrOa, the
solution comprising essentially a composition
balance comprising essentially water, and pass
lying within the area deilned on the accompany
ing an electric current therethrough at a current
density of from one hundred to three thousand 50 ing diagram by the solid line AE, the dot-dash
line ELF, the solid line FM, the straight dot-dash
amperes per square foot at a temperature be
line MG, the dot-dash line GH, and the straight
tween 80° and- 212° F. for a sufficient period of
solid line HA, and passing an electric current
time to ei‘rect- the polishing of said brass.
therethrough at a current density of from one
6. The method of anodically polishing brass
which comprises making brass the anode in a 55 »hundred to three thousand amperes per square
foot at a temperature between 80° and 212° F. for
solution comprising from 42% to 65% CrOa, the
a suiiicient period of time to eiîect the polishing
balance comprising essentially water, and passing
an electric current therethrough at a current
density of from one hundred 'to three thousand
amperes per square foot at a temperature between
80° and 212° F. for a sufñcient period of time to
effect the polishing oi' said brass.
'
l
of said brass.
CHARLES L. FAUST.
Документ
Категория
Без категории
Просмотров
0
Размер файла
530 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа