U.S. patent number 3,803,047 [Application Number 05/300,936] was granted by the patent office on 1974-04-09 for organic phosphonic acid compound corrosion protection in aqueous systems.
This patent grant is currently assigned to W. R. Grace & Co.. Invention is credited to Chih Ming Hwa.
United States Patent |
3,803,047 |
Hwa |
April 9, 1974 |
ORGANIC PHOSPHONIC ACID COMPOUND CORROSION PROTECTION IN AQUEOUS
SYSTEMS
Abstract
The invention disclosed relates to organo-phosphonic acid
compounds in combination with azole compounds and zinc salts for
use to inhibit metal corrosion in aqueous systems. The
organo-phosphonic acid compounds include alkylene polyphosphonic
acids, and the water-soluble salts and esters thereof.
Inventors: |
Hwa; Chih Ming (Palatine,
IL) |
Assignee: |
W. R. Grace & Co. (New
York, NY)
|
Family
ID: |
27404778 |
Appl.
No.: |
05/300,936 |
Filed: |
October 26, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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645600 |
Jun 13, 1967 |
|
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|
581151 |
Sep 22, 1966 |
3431217 |
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Current U.S.
Class: |
252/389.22;
106/14.13; 252/181; 252/391; 507/237; 106/14.12; 106/14.16;
252/390; 252/392; 507/939 |
Current CPC
Class: |
C23F
11/08 (20130101); C23G 1/066 (20130101); Y10S
507/939 (20130101) |
Current International
Class: |
C23G
1/02 (20060101); C23F 11/08 (20060101); C23G
1/06 (20060101); C23f 011/16 (); C23f 011/14 () |
Field of
Search: |
;252/389A,389R,181,86,8.55E ;21/2.7A,2.7R,2.5A,2.5R ;106/14
;260/502.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Quarforth; Carl D.
Assistant Examiner: Gluck; Irwin
Attorney, Agent or Firm: Bond; Eugene M.
Parent Case Text
This application for United States Letters patent is a continuation
of U.S. Pat. application Ser. No. 645,600 and now abandoned, filed
June 13, 1967, which in turn is a continuation-in-part of U.S. Pat.
application Ser. No. 581,151, filed Sept. 22, 1966, and now U.S.
Pat. No. 3,431,217.
Claims
1. A composition useful for inhibiting corrosion in aqueous
systems, said composition consisting essentially of one part by
weight zinc in the form of a water-soluble zinc salt; from 0.02 to
about 300 parts by weight of a water-soluble organic phosphonate
compound having the formula ##SPC14##
where R.sub.1 is independently selected from the group consisting
of alkyl groups up to four carbon atoms, and phosphonate groups,
and R.sub.2 is selected from the group consisting of alkyl groups
having up to four carbon atoms, when R.sub.1 is a phosphonate
group; and ##SPC15##
where n is 0 to 6, when R.sub.1 is an alkyl group, and
water-soluble salts and esters thereof; and corrosion inhibiting
amounts of a copper corrosion inhibitor selected from the group
consisting of 1,2,3-triazoles, thiazoles, oxazoles, imidazoles,
isoxazoles, isothiazoles and pyrazoles.
2. The composition of claim 1 in which the water-soluble zinc salt
is zinc
3. The composition of claim 1 in which the phosphonate compound is
ethanol
4. A method of inhibiting corrosion in aqueous systems comprising
maintaining therein an amount of the composition of claim 1 to
provide up to about 100 ppm. copper corrosion inhibitor.
Description
This invention relates to a method and composition for preventing
corrosion of metal surfaces in contact with aqueous systems.
In summary the corrosion inhibiting composition of this invention
consists essentially of from 1 to 80 weight percent of an alkylene
polyphosphonic acid having one of the following formulae A, B or C:
##SPC1##
or ##SPC2##
Or ##SPC3##
Wherein m is an integer from 1 to 10, R.sub.1 is hydrogen, or an
alkyl group having from 1 to 4 carbons and R.sub.2 is hydroxyl,
hydrogen, or an alkyl group having from 1 to 4 carbons, R.sub.3 is
an alkyl group having 1 to 10 carbons, benzyl or phenyl, R' is an
aliphatic radical having from 1 to 10 carbons, and the
water-soluble salts and esters thereof; or mixtures thereof, and
from 1 to 80 weight percent of an azole compound selected from a
group consisting of triazoles, pyrazoles, imidazoles, isoxazoles,
oxazoles, isothiazoles, thiazoles and mixtures thereof, and/or from
1 to 95 weight percent of a water-soluble zinc salt. Aqueous
solutions of 1 to 70 weight percent of this composition are also
encompassed within this invention.
In summary, the method of this invention for preventing corrosion
of metals in contact with an aqueous liquid comprises maintaining
in the aqueous liquid from 1 to 10,000 ppm. of the alkylene
polyphosphonic acid, salts or esters thereof, and from 1 to 10,000
ppm. of the azole compound and/or from 1 to 10,000 ppm. of a
water-soluble zinc salt.
Water-soluble inorganic chromates are widely used to treat
industrial water systems to prevent corrosion of metal parts in
contact therewith. When these chromates are employed alone, they
are used in concentrations as low as 200 ppm. and as high as 10,000
ppm., depending upon the protection needed and the permissible
cost. When these chromates are used in combinations with
molecularly dehydrated inorganic phosphates such as disclosed in
U.S. Pat. No. 2,711,391, chromate concentrations as low as 20 ppm.
have been found adequate in mild corrosive systems. Therefore,
combinations of chromates and molecularly dehydrated phosphates are
widely used.
Although chromates are highly effective corrosion inhibitors, their
use is subject to several difficulties. Chromates cause serious
skin and eye irritations, and chromates cannot be used in aqueous
systems such as cooling towers or air-wash units where the
resulting spray will contact people. Chromate solutions, because
they are toxic, often require chemical treatment before being
discharged to waste systems. Furthermore, chromates degrade organic
compounds mixed therewith, limiting the types or organic compounds
which can be mixed with the chromates in dry mixtures and aqueous
solutions.
The use of molecularly dehydrated inorganic phosphates in aqueous
systems causes serious problems because the polyphosphates
hydrolyze to form alkaline earth metal orthophosphates, causing
scaling and fouling of the aqueous systems treated. Because of this
hydrolysis, excess quantities of the polyphosphates must be
employed.
It is an object of this invention to provide a nontoxic composition
for treating aqueous systems to prevent corrosion of metal surfaces
in contact therewith which does not introduce orthosphophates to
the aqueous systems. The composition contains an organic phosphonic
acid compound in combination with an azole compound and/or a
watersoluble zinc salt.
The compositions of this invention are useful for treating a
variety of aqueous systems, that is, any aqueous system corrosive
to metal surfaces in contact therewith. Suitable systems which can
be treated according to this invention include water treatment
systems, cooling towers, water circulating systems, and the like
wherein fresh water, brines, sea water, sewage effluents,
industrial waste waters, and the like are circulated in contact
with metal surfaces. These compounds are useful in acid pickling
baths, radiator coolers, hydraulic liquids, antifreezes, heat
transfer mediums, and petroleum well treatments. The process of
this invention is suitable for reducing the corrosion of iron,
copper, aluminum, zinc and alloys containing these metals such as
steel and other ferrous alloys, brass, and the like which are in
contact with corrosive aqueous systems.
All concentrations are given herein as weight percents unless
otherwise specified.
The compositions of this invention contain from 1 to 80 percent of
an organo-phosphonic acid compound. The preferred organo-phosphonic
acid compound for use in the composition of this invention is an
alkylene diphosphonic acid having the foregoing Formula A, such as
those disclosed in U.S. Pat. Nos. 3,214,454 and 3,297,578, the
entire disclosures of which are incorporated herein by reference.
Also suitable is an alkylene diphosphonic acid having the foregoing
Formula B or Formula C such as those disclosed in U.S. Pat. No.
3,303,139, the entire disclosure of which is incorporated herein by
reference. Suitable acids of this type include
methylenediphosphonic acid; ethylidenediphosphonic acid;
isopropylidenediphosphonic acid; 1-hydroxy, ethylidenediphosphonic
acid; hexamethylenediphosphonic acid; trimethylenediphosphonic
acid; decamethylenediphosphonic acid; 1-hydroxy,
propylidenediphosphonic acid; 1,6-dihydroxy, 1,6-dimethyl,
hexamethylenediphosphonic acid; 1,4-dihydroxyl, 1,4-diethyl,
tetramethylenediphosphonic acid; 1,3-dihydroxy, 1,3-dipropyl,
trimethylenediphosphonic acid; 1,4-dibutyl,
tetramethylenediphosphonic acid; dihydroxy, diethyl,
ethylenediphosphonic acid; 4-hydroxy, 6-ethyl,
hexamethylenediphosphonic acid; 1-hydroxy, butylidenediphosphonic
acid; butylidenediphosphonic acid; 1-aminoethane-1,1-diphosphonic
acid; 1-aminopropane-1, 1-diphosphonic acid;
1-aminobenzyl-1,1-diphosphonic acid;
1,6-diaminohexane-1,1,6,6-tetraphosphonic acid;
1-aminoethane-1,1-diphosphonic acid monethyl ester, and 1-amino - 2
- phenylethane -1,1-diphosphonic acid. The water-soluble salts of
these acids such as the alkali metal, alkaline earth metal, zinc,
cobalt, chromium, lead, tin, nickel, ammonium, or amine and lower
alkanol amine salts can be used. Also, esters of these acids with
an aliphatic alcohol having from 1 to 4 carbons, or mixtures of the
above acids, salts or esters can be used. Use of mixtures of any of
the general types of organo-phosphonic acid compounds described
above is also contemplated within the scope of this invention.
It will be seen from the foregoing listing of acid compounds within
the scope of Formula A and a number of the examples which follow,
as well as the like compounds disclosed in U.S. Pat. No. 3,214,454
and 3,297,578, that a number of these can be described as methanol
phosphonic acid derivatives having the following Formula D:
##SPC4##
where R.sub.4 is independently selected from the group consisting
of an alkyl group up to four carbon atoms and phosphonate groups,
and R.sub.5 is selected from the group consisting of alkyl groups
having up to 4 carbon atoms, when R.sub.4 is a phosphonate group
and ##SPC5##
where n is 0 to 6, when R.sub.4 is an alkyl group; and
water-soluble salts thereof.
Specific methanol phosphonic acid compounds thus disclosed include,
for example, 1-hydroxy, ethylidene diphosphonic acid (i.e.,
ethanol, or methyl methanol, 1,1-diphosphonic acid); 1-hydroxy,
propylidene diphosphonic acid (i.e., ethyl methanol diphosphonic
acid); 1,6-dihydroxy-1,6-dimethyl, hexamethylene diphosphonic acid
(i.e., tetramethylene bis (methyl methanol phosphonic acid)) and
its sodium salt (Examples 44 and 110); 1,4-dihydroxy-1,4-diethyl,
tetramethylene diphosphonic acid (i.e., dimethylene
bis(ethylmethanol phosphonic acid)); 1,3-dihydroxy-1,3-dipropyl
trimethylene diphosphonic acid (i.e., methylene bis (propylmethanol
phosphonic acid)) and its sodium salt (Examples 46 and 112);
dihydroxy, diethyl, ethylene diphosphonic acid (i.e.,
bis(ethylemethanol phosphonic acid)) and its sodium salt (Examples
52 and 118); and 1-hydroxy butylidene diphosphonic acid (i.e.,
propyl methanol diphosphonic acid).
The compositions of this invention also contain from 1 to 80 and
preferably from 25 to 45 percent of an azole compound and/or from 1
to 95 and preferably from 25 ti 45 percent of a water-soluble zinc
salt. Preferably, both the azole compound and zinc salts are used
in the composition of this invention is the stated concentrations.
It will be seen that the use of the more common water-soluble zinc
salts such as zinc nitrate (Zn(NO.sub.3).sub.2, molecular weight
189) zinc chloride (ZnCl.sub.2, molecular weight 136.29) and zinc
sulfate (ZnSO.sub.4 or ZnSO.sub.4.sup.. H.sub.2 O, molecular weight
161.44 and 179.44, respectively) in the aforesaid concentrations
will provide zinc ion (Zn.sup.+.sup.2) concentrations from as
little as 0.345 weight percent (as 1 percent Zn(NO.sub.3).sub.2) to
as high as 45.5 weight percent (equivalent to 95 percent
ZnCl.sub.2). Thus the weight ratio of zinc (in the form of one of
said water-soluble salts) to phosphonic acid compound may range
from about 0.345:80 to about 45.5:1 or, in other words, from about
1:232 to about 1:0.022. At the preferred concentrations of zinc
salt the weight ratio of zinc ion may range from about 8.64:80
(Zn.sup.+.sup.2 equivalent in 25 weight percent of
Zn(NO.sub.3).sub.2) to about 21.5:1 (Zn.sup.+.sup.2 equivalent in
45 weight percent of ZnCl.sub.2); or in other words, from about
1:9.27 to about 1:0.0465. As seen in the following specific
Examples 5 and 7, a typical zinc to phosphonic acid compound weight
ratio is 1:1.
Azoles are nitrogen containing heterocyclic 5-membered ring
compounds, and azoles which are suitable in the composition of this
invention include triazoles, pyrazoles, imidazoles, isoxazoles,
oxazoles, isothiazoles, thiazoles and mixtures thereof as disclosed
in U.S. Pats. No. 2,618,608, No. 2,742,369, and No. 2,941,953.
The triazoles which can be employed in the composition of this
invention are any water-soluble 1,2,3-triazoles such as
1,2,3-triazole itself or a substituted 1,2,3-triazole where the
substitution takes place in either the 4 or 5 position (or both) of
the triazole ring as shown here by the structural formula:
##SPC6##
Suitable triazoles include benzotriazole (the preferred triazole);
4-phenyl-1,2,3-triazole; 1,2-napthotriazole; and
4-nitrobenzotriazole; and the like.
The pyrazoles which can be used in the composition of this
invention include any water-soluble pyrazoles such as pyrazole
itself or a substituted pyrazole where the substitution takes place
in the 3, 4, or 5 position (or several of these positions) of the
pyrazole ring as shown by the structural formula: ##SPC7##
Suitable pyrazoles include pyrazole; 3,5-dimethyl pyrazole;
6-nitroindazole; 4-benzyl pyrazole; 4,5-dimethyl pyrazole; and
3-allyl pyrazole; and the like.
The imidazoles which can be used in the composition of this
invention include any water-soluble imidazoles such as imidazole
itself or a substituted imidazole where the substitution takes
place in the 2,4 or 5 position (or several of these positions) of
the imidazole ring as shown here by the structural formula:
##SPC8##
Suitable imidazoles which can be employed in the composition of
this invention include imidazole; adenine; quanine; benzimidazole;
5-methyl benzimidazole; 2-phenyl imidazole; 2-benzyl imidazole;
4-allyl imidazole; 4-(betahydroxy ethyl)-imidazole; purine;
4-methyl imidazole; xanthine; hypoxanthene; 2-methyl imidazole; and
the like.
Isoxazoles which can be employed in the composition of this
invention include any water-soluble isoxazole such as isoxazole
itself or a substituted isoxazole where the substitution takes
place in the 3, 4 or 5 position (or several of these positions) of
the isoxazole ring as shown here by the structural formula:
##SPC9##
Suitable isoxazoles include isoxazole; 3-mercaptoisoxazole;
3-mercaptobenzisoxazole; benzisoxazole; and the like.
The oxazoles which can be employed in the composition of this
invention include any water-soluble oxazoles such as oxazole itself
or a substituted oxazole where the substitution takes place in the
2, 4 or 5 position (or several of these positions) of the oxazole
ring as shown here by the structural formula: ##SPC10##
Suitable oxazoles include oxazole; 2-mercaptoxazole;
2-mercaptobenzoxazole; and the like.
The isothiazoles which can be employed in the process of this
invention include any water-soluble isothiazoles such as
isothiazole itself or a substituted isothiazole where the
substitution takes place in either the 3, 4 or 5 position (or
several of these positions) of the isothiazole ring as shown here
by the structural formula: ##SPC11##
Suitable isothiazoles include isothiazole, 3-mercaptoisothiazole;
3-mercaptobenzisothiazole; benzisothiazole; and the like.
The thiazoles which can be used in the composition of this
invention include any water-soluble thiazole such as thiazole
itself or a substituted thiazole where the substitution takes place
in the 2, 4 or 5 position (or several of these positions) of the
thiazole ring as shown here by the structural formula:
##SPC12##
suitable thiazoles include thiazole; 2-mercapthothiazole;
2-mercaptobenzothiazole; benzothiazole; and the like.
In the above azole compounds, the constituents substituted in the
azole rings can be alkyl, aryl, aralkyl, alkylol, and alkenyl
radicals so long as the substituted azole is water-soluble.
The zinc salts which can be employed in the composition of this
invention include water-soluble zinc salt such as zinc sulfate,
zinc chloride, zinc nitrate, alkali metal-zinc phosphate glasses,
crystalline alkali metal-zinc polyphosphates, and the like.
Aqueous systems can be treated with aqueous solutions containing
from 1 to 70 percent and preferably from 1 to 10 percent of the
compositions of this invention. These solutions can be made by
premixing the ingredients of this composition and then adding the
mixture to water, or by adding the individual ingredients of the
composition of this invention separately to water. These aqueous
feed solutions are stable and can be stored prior to use.
In the methods of this invention for preventing corrosion of metals
in contact with aqueous liquids, from 1 to 10,000 ppm. and
preferably from 1 to 100 of the organophosphonic acid compounds,
and from 1 to 10,000 ppm. and preferably from 1 to 100 ppm. of the
azole compounds and/or from 1 to 10,000 and preferably from 2 to
200 ppm. of the water-soluble zinc salts are maintained in aqueous
liquid. Preferably, both the azoles and zinc salts are maintained
in the systems in the stated concentrations.
The aqueous corrosion resistant solutions of this invention are
solutions of at least 1 and preferably from 5 to 200 ppm. of the
compositions of this invention. The ingredients can be added to the
aqueous solutions either in premixed solid or solution or
individual solids or solutions to form this aqueous solution
composition.
The compositions of this invention are non-toxic and prevent
corrosion of metals in contact with aqueous liquids. These
compositions can be substituted for chromate base corrosion
inhibitors previously used where the toxicity of the chromate makes
its use undesirable or where disposal of corrosion inhibiting
solutions containing chromates raises serious water pollution
problems requiring extensive pretreatment to remove the chromates
prior to disposal of such solutions. The compositions of this
invention in aqueous solutions prevent corrosion of metal parts
such as heat exchangers, engine jackets, and pipes and particularly
prevent metal loss, pitting, and tuberculation of iron base alloys,
copper alloys, and aluminum alloys in contact with water.
This invention is further illustrated by the following specific but
non-limiting examples.
EXAMPLE 1
This example demonstrates the synergistic reduction in corrosion
rates obtained with the compositions of this invention.
In this test, circulating water having the following composition
was used:
Calcium sulfate dihydrate 445 ppm. Magnesium sulfate heptahydrate
519 ppm. Sodium bicarbonate 185 ppm. Calcium chloride 136 ppm.
During the test, the circulating water was fed to a closed
circulating test system at a rate of 5 gallons per day, the
overflow from the test system being discharged to waste.
In the closed circulating system, circulating water having a
temperature of 130.degree. F. and pH of 6.5-7.0 was fed at a rate
of 1 gallon per minute to a coupon chamber containing test coupons
for the corrosion test. Water from the coupon chamber was then
passed through an arsenical admirality brass tube surrounded by a
jacket through which a heating fluid having an initial temperature
of 240.degree. F. was countercurrently passed. The circulating
water was then cooled to 130.degree. F. and recirculated through
the system. The total circulating time for each test was 10
days.
Mild steel, brass (33 wt. percent zinc), copper and aluminum
coupons having an average area of 26.2 cm..sup.2 were used in the
test chamber. The coupons were carefully cleaned and weighed before
use. Following the test, each coupon was cleaned with inhibited
hydrochloric acid, rinsed, dried and weighed to deterine the
corrosion rate in mils per year. A comparison of the corrosion
rates of the individual ingredients of the composition of this
invention with combinations of these ingredients according to this
invention were found to be as shown in Table A. ##SPC13##
As shown in Table A, Examples 5, 6 and 7 corresponding to the
compositions of this invention provide a corrosion protection far
greater than would be expected in view of the effects of the
individual components thereof.
EXAMPLE 8
The corrosion rates in mils per year of aluminum in contact with
liquid containing 10 ppm. Zn.sup.+.sup.+ and 10 ppm. of
benzotriazole according to the above test procedure was found to be
1.1.
Examples of other compositions according to this invention are
shown in Table B.
TABLE B
Example No. Ingredients - wt.% 9 Zinc sulfate -- 70.0%;
benzotriazole 30.0% 10 Zinc chloride -- 40.0%; hydroxy ethylidene
diphosphonic acid -- 60.0% 11 Benzotriazole -- 35.5%; hydroxy
ethylidene diphosphonic acid -- 64.5% 12 Zinc nitrate -- 70.0%;
benzotriazole -- 15.0%; hydroxy ethylidene diphosphonic acid --
15.0% 13 Sodium trimethylenediphosphonate -- 15%; pyrazole -- 15%;
zinc sulfate monohydrate -- 70% 14 Decamethylenediphosphonic acid
-- 15%; 3,5-dimethyl pyrazole -- 15%; zinc sulfate monohydrate --
70% 15 Sodium 1,6-dihydroxy,1,6-dimethyl,
hexamethy-lenediphosphonate -- 15%; imidazole -- 15%; zinc sulfate
monohydrate -- 70% 16 1-amino-2-phenylethane-1,1-diphosphonic acid
-- 15%; 2-benzyl imidazole -- 15%; zinc sulfate monohydrate -- 70%
17 Sodium 1,3-dihydroxy,1,3-dipropyl, trimethylenediphosphonate --
15%; isoxazole -- 15%; zinc sulfate monohydrate -- 70% 18 Zinc
1-aminoethane-1,1-diphosphonate -- 15%; benzisoxazole -- 15%; zinc
sulfate monohydrate -- 70% 19 1-aminoethane-1,1-diphosphonic acid
monoethyl ester -- 15%; 2-mercaptobenzoxazole -- 15%; zinc sulfate
monohydrate -- 70% 20 Tin methylenediphosphonate -- 15%;
isothiazole -- 15%; zinc sulfate monohydrate -- 70% 21
Butylidenediphosphonic acid -- 15%; 1,2-naphthotriazole -- 15%;
zinc sulfate monohydrate -- 70% 22 1-aminobenzyl-1,1-diphosphonic
acid -- 15%; 4-nitrobenzotriazole -- 15%; zinc sulfate monohydrate
-- 70% 23 Sodium dihydroxy, diethyl, ethylenediphosphonate -- 15%;
benzotriazole -- 15%; zinc sulfate monohydrate -- 70% 24 Magnesium
methylenediphosphonate -- 50%; 1,2,3-triazole -- 50% 25 Zinc
isopropylidenediphosphonate -- 50%; benzotriazole -- 50% 26 Sodium
trimethylenediphosphonate -- 50%; pyrazole -- 50% 27
Decamethylenediphosphonic acid -- 50%; 3,5-dimethyl pyrazole -- 50%
28 Sodium 1,6-dihydroxy, 1,6-dimethyl, hexamethylenediphosphonate
-- 50 %; imidazole -- 50% 29
1-amino-2-phenylethane-1,1-diphosphonic acid -- 50%; 2-benzyl
imidazole -- 50% 30 Sodium 1,3-dihydroxy, 1,3-dipropyl,
trimethylenediphosphonate -- 50%; isoxazole -- 50% 31 Zinc
1-aminoethane-1,1-diphosphonate -- 50%; benzisoxazole -- 50% 32
1-aminoethane-1,1-diphosphonic acid monoethyl ester -- 50%;
2-mercaptobenzoxazole -- 50% 33 Tin methylenediphosphonate -- 50%;
isothiazole -- 50% 34 Butylidenediphosphonic acid -- 50%;
1,2-naphthotriazole -- 50% 35 1-aminobenzyl-1,1-diphosphonic acid
-- 50%; 4-nitrobenzotriazole -- 50% 36 Sodium dihydroxy, diethyl,
ethylenediphosphonate -- 50%; benzotriazole -- 50% 37 Magnesium
methylenediphosphonate -- 30%; zinc sulfate monohydrate -- 70% 38
Zinc isopropylidenediphosphonate -- 30%; zinc sulfate monohydrate
-- 70% 39 Sodium trimethylenediphosphonate -- 30%; zinc sulfate
monohydrate -- 70% 40 Decamethylenediphosphonic acid -- 30%; zinc
sulfate monohydrate -- 70% 41 Sodium 1,6-dihydroxy, 1,6-dimethyl,
hexamethylenediphosphonate -- 30%; zinc sulfate monohydrate -- 70%
42 1-amino-2-phenylethane-1,1-diphosphonic acid -- 30%; zinc
sulfate monohydrate -- 70% 43 Sodium 1,3-dihydroxy, 1,3-dipropyl,
trimethylene-diphosphonate -- 30%; zinc sulfate monohydrate -- 70%
44 Zinc 1-aminoethane-1,1-diphosphonate -- 30%; zinc sulfate
monohydrate -- 70% 45 1-aminoethane-1,1-diphosphonic acid monoethyl
ester -- 30%; zinc sulfate monohydrate -- 70% 46 Tin
methylenediphosphonate -- 30%; zinc sulfate monohydrate -- 70% 47
Butylidenephosphonic acid -- 30%; zinc sulfate monohydrate -- 70%
48 1-aminobenzyl-1,1-diphosphonic acid -- 30%; zinc sulfate
monohydrate -- 70% 49 Sodium dihydroxy, diethyl,
ethylenediphosphonate -- 30%; zinc sulfate monohydrate -- 70% 50
1-hydroxy ethylidene diphosphonic acid -- 40%; zinc chloride --
30%; benzotriazole -- 30% 51 1-hydroxy propylidene diphosphonic
acid -- 30%; zinc sulfate monohydrate -- 50%; benzotriazole -- 20%
52 1-hydroxy ethylidene diphosphonic acid -- 25%; zinc nitrate --
55%; mercaptobenzothiazole -- 20% 53 1-hydroxy butylidene
diphosphonic acid -- 20%; zinc sulfate monohydrate -- 50%;
mercaptobenzothiazole -- 30%
* * * * *