Methods and compositions for removing copper and copper oxides from surfaces

Methods and compositions for removing copper and copper oxide deposits from metal surfaces including surfaces formed of austenitic, nickel-chromium and other similar alloys without adversely affecting such surfaces are provided. The copper and copper oxide deposits are dissolved in an aqueous ammoniacal cleaning solution which includes one or more alkali metal or ammonium perborate oxidizing agents.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to methods and compositions for removing copper and 
copper oxides from surfaces, and more particularly, to methods and 
compositions for dissolving copper and copper oxide deposits whereby alloy 
surfaces contacted by the compositions are not adversely affected thereby. 
2. Description of the Prior Art 
In process equipment such as steam boilers, feed water heaters, heat 
exchangers and pressure vessels in which water is circulated, water 
insoluble salts commonly deposit on the interior metal surfaces of such 
equipment. The formation or deposition of scale deposits can markedly 
reduce the heat transfer and/or the capacity of flow passages in the 
equipment. 
In process equipment which includes or is associated with components 
constructed of copper alloys, the scale produced on internal surfaces is 
frequently found to contain copper and copper oxides. A variety of methods 
and compositions have been developed and used heretofore for removing such 
copper and copper oxide deposits. For example, one method which has been 
employed for removing copper and copper oxide scale deposits from ferrous 
metal surfaces is to initially contact the surfaces with an ammoniacal 
oxidant wash, such as an ammoniacal solution containing ammonium 
persulfate or sodium bromate to remove part of the copper deposits 
followed by contacting the surfaces with a cleaning solution containing an 
acid plus a copper complexing material. The copper complexing material 
functions to tie up the remaining copper so that it is dissolved and held 
in the cleaning solution. While such multi-stage cleaning procedures have 
been used successfully, they are generally expensive to carry out. 
Another method of removing copper and copper oxides from ferrous metal 
surfaces is disclosed in U.S. Pat. No. 4,452,643 issued June 5, 1984. That 
method comprises contacting copper and copper oxide deposits with an 
aqueous composition having a pH of from about 3 to about 6 comprised of an 
oxidizing agent, preferably hydrogen peroxide, a compound selected from 
the group consisting of oxalic acid and the alkali metal and ammonium 
salts of oxalic acid and an ingredient selected from the group consisting 
of citric acid, polyaminocarboxylic acid, the ammonium and alkali metal 
salts of citric acid and polyaminocarboxylic acids and mixtures thereof. 
While the above described methods have been utilized successfully in 
removing copper and copper oxide deposits from ferrous metal surfaces, in 
some process equipment such as nuclear steam generators, some of the 
internal surfaces are formed of alloys such as austenitic steel alloys, 
alloys of nickel, iron and chromium, alloys of nickel and chromium and 
other similar alloys. It has been found that when these alloys are 
contacted with copper and copper oxide scale removal cleaning solutions 
containing strong oxidizing agents, e.g., sodium bromate and ammonium 
persulfate, the alloys can be adversely affected such as by the occurrence 
of stress corrosion cracking. That is, sodium bromate is believed to cause 
cracking of austenitic stainless steel and other alloys due to the 
presence of bromide in the spent solution. Ammonium persulfate is believed 
to cause intergranular attack of nickel-chromium alloys due to the 
presence of sulfur. In addition, ammonium persulfate is unstable at 
temperatures above about 110.degree. F., sodium bromate contains a form of 
the element bromine which can cause personnel hazards and hydrogen 
peroxide is unstable in some cleaning solutions. 
By the present invention an improved copper and copper oxide cleaning 
solution is provided which does not adversely affect surfaces of formed of 
austenitic, nickel-chromium and other similar alloys when contacted 
therewith. In addition, the cleaning solution, and particularly the 
oxidizing agent utilized therein, is more economical than heretofore used 
solutions and oxidizing agents. 
DESCRIPTION OF PREFERRED EMBODIMENTS 
The method of the present invention for removing copper and copper oxide 
deposits without adversely affecting austenitic, nickel-chromium and other 
similar alloy surfaces is comprised of the steps of contacting the 
deposits with an aqueous ammoniacal cleaning solution for a period of time 
sufficient to dissolve the deposits therein followed by the removal of the 
cleaning solution containing the dissolved deposits from the surfaces. The 
aqueous ammoniacal cleaning solution contains one or more water soluble 
perborate oxidizing agents, e.g., alkali metal and ammonium perborates, 
which do not adversely affect austenitic, nickel-chromium and other 
similar alloys. The perborate oxidizing agent or agents function in the 
ammoniacal cleaning solution to oxidize free copper in contacted deposits 
whereby copper oxide is formed. Copper oxide originally contained in the 
deposits and the newly formed copper oxide are readily dissolved in the 
ammoniacal solution. 
While the aqueous ammoniacal solution of this invention can contain a 
variety of components in addition to the water soluble perborate oxidizing 
agent or agents, such as chelating or complexing agents, e.g., ammonia, 
ethylenediaminetetracetic acid (EDTA) or ethylenediamine (EDA), a 
particularly preferred cleaning solution is comprised of an aqueous 
solution containing ammonia, ammonium bicarbonate and one or more water 
soluble perborates. 
A particularly preferred and suitable cleaning solution of the present 
invention for removing copper and copper oxide deposits without adversely 
affecting alloy surfaces contacted therewith is comprised of water, 
ammonia present in the solution in an amount in the range of from about 
0.05% to about 15% by weight of the solution, ammonium bicarbonate present 
in the solution in an amount in the range of from about 0.04% to about 10% 
by weight of the solution and one or more water soluble perborates, 
preferably sodium perborate, present in the solution in an amount in the 
range of from about 0.05% to about 5% by weight of the solution. 
The most preferred such aqueous cleaning solution has a pH of about 10.5 
and contains ammonia in an amount of about 9.7% by weight of the solution, 
ammonium bicarbonate in an amount of about 10% by weight of the solution, 
and sodium perborate in an amount of about 1% by weight of the solution. 
The ammoniacal-perborate solution can be used for dissolving copper and 
copper oxide deposits without adversely affecting austenitic stainless 
steel and nickel-chromium alloys at temperatures from ambient up to about 
150.degree. F. The preferred temperature range at which the cleaning 
solution is brought into contact with copper and copper oxide deposits to 
be dissolved is between about 120.degree. F. and about 150.degree. F. At 
these temperatures and the component concentrations set forth above, the 
aqueous ammoniacal cleaning solution is non-corrosive to ferrous metal 
surfaces and surfaces formed of the alloys mentioned above. 
The aqueous cleaning solutions of this invention are brought into contact 
with copper and copper oxide deposits and the surfaces containing such 
deposits using any suitable technique, e.g., static soaking, pouring, 
spraying or circulating. Preferably, the cleaning solution is circulated 
over the surfaces to be cleaned at the preferred temperatures mentioned 
above, the circulation being continued until the copper and copper oxide 
deposits are dissolved in the solution. 
The quantity of cleaning solution required and the time the solution should 
remain in contact with the copper and copper oxide deposits depends on the 
quantity of the deposits to be removed. In cleaning vessels, heat 
exchangers and the like, to insure adequate contact with all surfaces to 
be cleaned, sufficient cleaning solution is introduced into the vessel, 
exchangers, etc., whereby they are filled. The solution is then preferably 
slowly circulated by pumping to insure continuous contact with all 
surfaces to be cleaned. From time to time additional amounts of the 
cleaning solution can be added to the original quantity placed within the 
equipment so that the capacity of the cleaning solution for dissolving the 
copper and copper oxide deposits will be sufficient. The circulation of 
the cleaning solution is generally carried out at a pressure slightly in 
excess of atmospheric pressure and after the copper and copper oxide 
deposits have been dissolved, the cleaning solution is drained from the 
equipment being cleaned and the equipment is flushed with fresh water. 
The ammoniacal cleaning solutions of this invention can be prepared in any 
suitable manner with care being taken to prevent spillage or contact with 
personnel or oxidizable materials. If concentrates of the cleaning 
solution are prepared, they should be contained in containers lined with 
non-metallic corrosion resistant material in that in concentrated form, 
the solutions can decompose on ferrous metal surfaces. To prevent 
decomposition, the concentrates should not be mixed in advance of their 
intended use. In a preferred technique for preparing the cleaning 
solutions, fresh water at a temperature in the range of from about 
120.degree. F. to about 150.degree. F. is first mixed with ammonium 
bicarbonate such as by agitating or circulating the water in a tank while 
adding the ammonium bicarbonate thereto. After the ammonium bicarbonate 
has dissolved in the water, the alkali metal perborate oxidizing agent or 
agents utilized are added to the solution while continuing to agitate the 
solution in the tank. Once the ammonium bicarbonate and perborate oxidant 
are dissolved, ammonia, preferably in the form of an aqueous solution 
containing about 30% by weight ammonia is added to the tank while 
agitating or circulating the tank. The resulting concentrated solution is 
diluted with hot water as it is pumped into the vessel or system to be 
cleaned. 
As mentioned above, when the vessel or system to be cleaned is filled to 
operating level, the cleaning solution can be slowly circulated or it can 
be allowed to contact the interior surfaces and the deposits to be removed 
therefrom in a static or relatively static condition. Provision should be 
made to allow any gases formed during the dissolution of the deposits to 
escape from the system. In static treatments, intermittent agitation is 
recommended, either by circulation, drain-back or injection of air or 
nitrogen. During the treatment, the copper content of the cleaning 
solution can be monitored to assure the solution remains active, and when 
the copper content stops increasing, additional active solution can be 
circulated into the system if required or the treatment will be completed. 
If during the treatment, the pH of the cleaning solution falls below about 
9.5, more ammonia should be added to the cleaning solution to assure 
continued copper dissolution and to prevent replating of dissolved copper. 
Once the treatment has been completed and the copper and copper oxide 
deposits removed, a fresh water flush is carried out in the cleaned 
equipment to prevent copper ions remaining therein from being replated 
during subsequent cleaning stages or operation of the equipment. 
In order to facilitate a clear understanding of the methods and 
compositions of this invention, the following examples are given.

EXAMPLE 1 
In order to compare sodium perborate (NaBO.sub.3.4H.sub.2 O) to sodium 
bromate (NaBrO.sub.3) and ammonium persulfate [(NH.sub.4).sub.2 S.sub.2 
O.sub.8 ] when present in ammoniacal copper solvents, a series of tests 
are performed using various copper and copper oxide cleaning solutions. 
The solutions are prepared by blending the various components thereof 
including the particular oxidizing agent utilized with water. The 
solutions are placed in plastic or glass beakers and one copper and one 
mild steel corrosion coupon are added to each of the beakers. The coupons 
are prepared as follows: 
Coupon Preparation Procedure 
1. Stamp coupon for identification; 
2. Degrease coupon in acetone; 
3. Bead blast coupon with 35 psig. air pressure to remove any corrosion 
products present on the coupon surface; 
4. Rinse coupon in acetone and allow to air dry; and 
5. Weigh coupon to nearest 0.001 gram and record this weight as initial 
weight. 
After placement of the coupons in the test cleaning solutions, the beakers 
are capped with a self-venting lid in all tests not involving air blows. 
In tests involving air blows of the solution, a two-hole stopper is used 
as a cap for the beakers. A sintered glass air sparger is inserted through 
one hole and air is introduced at this point while the other hole serves 
as a vent. The beakers are placed in thermostated water baths for test 
time periods after which the coupons are removed and cleaned according to 
the following procedure: 
Post-Test Coupon Cleaning Procedure 
1. Scrub coupon lightly with steel wool pad and mild soap; 
2. Rinse coupon in tap water; 
3. Rinse coupon in deionized water; 
4. Rinse coupon in acetone and allow to air dry; and 
5. Weigh coupon to nearest 0.001 gram and record this weight as final 
weight. 
The results of these tests are shown in Tables I and II below. In the 
Tables, the corrosion rates are calculated using the following formulas: 
##EQU1## 
TABLE I 
______________________________________ 
A Comparison of the Copper Dissolving Capabilitites of 
Ammoniacal Solutions Containing Sodium Perborate 
with Solutions Containing Sodium Bromate 
______________________________________ 
Temperature: 150.degree. F. 
Coupon Surface Area: 4.37 in..sup.2 
Velocity: static 
Volume: 10 ml. 
Test Length: 6 hours 
______________________________________ 
Test mpl. Mild Steel Corrosion 
No. Solvent Cu Rate (lb./ft.sup.2 /day) 
______________________________________ 
1 0.2 wt. % sodium perborate 
1163 0.0001 
+ 0.16 wt. % ammonium 
bicarbonate 
+ 0.75 wt. % ammonia 
2 0.2 wt. % sodium bromate 
1000 Wt. Gain 
0.16 wt. % ammonium 
bicarbonate 
+ 0.75 wt. % ammonia 
______________________________________ 
TABLE II 
______________________________________ 
A Comparison of the Copper Dissolving Capabilities of 
Ammonium Bicarbonate Solutions Containing Sodium Perborate 
with Solutions Containing Ammonium Persulfate 
______________________________________ 
Solvent Volume: 100 ml. 
Velocity: static 
Coupon Surface Area: 4.37 in..sup.2 
______________________________________ 
Mild Steel 
Corrosion 
Test Rate 
No. Solvent mpl. Cu (lb./ft..sup.2 /day) 
______________________________________ 
1 10 wt. % ammonium bicarbonate + 
1,963 0.0014 
9.67 wt. % ammonia + 
1 wt. % sodium perborate at 
150.degree. F. for 6 hours 
2 Repeat Test No. 1 with 
4,056 0.0026 
2 wt. % sodium perborate 
3 Repeat Test No. 1 with 
4,900 0.0014 
3 wt. % sodium perborate 
4 10 wt. % ammonium bicarbonate + 
.sup. 98,375.sup.1 
0.0121 
9.67 wt. % ammonia + 
0.5 wt. % sodium perborate 
at 150.degree. F. for 24 hours with 
airblow 
5 10 wt. % ammonium bicarbonate + 
98,375 0.0014 
9.67 wt. % ammonia + 
0.5 wt. % sodium perborate 
at 100.degree. F. for 24 hours with 
airblow 
6 10 wt. % ammonium bicarbonate + 
102,550 &lt;0.001 
9.67 wt. % ammonia + 
1 wt. % ammonium persulfate 
at 100.degree. F. for 24 hours with 
airblow 
______________________________________ 
.sup.1 Large quantities of copper oxides were present on the copper 
coupons upon test conclusion. A coating of copper oxides was also present 
on the mild steel coupons. 
.sup.2 All airblows at 5 c.c/min. 
As shown by Tables I and II, sodium perborate functions as an oxidizing 
agent in ammoniacal cleaning solutions equivalently to sodium bromate 
and/or ammonium persulfate. All of the various cleaning solutions tested 
functioned well in dissolving copper while being relatively non-corrosive 
to mild steel. 
EXAMPLE 2 
Pilot tests are conducted utilizing a pot boiler circulation system 
consisting of a large carbon steel vessel through which solvents can be 
circulated under controlled conditions. The solvent volume used in each 
test is 45 liters and solvent circulation is maintained at 4 liters per 
minute during the course of each test. 
An aqueous solution containing about 3% by weight citric acid, ammonia in a 
quantity such that the pH of the solution is adjusted to 3.5, 0.376% by 
weight copper sulfate and 0.1% of a corrosion inhibitor (OSI-1 sold by 
Halliburton Services of Duncan, Oklahoma) is injected into the pot boiler 
and circulated at 200.degree. F. to produce a copper plating on the 
internal surfaces of the boiler. The plating represents about 67 grams of 
copper and following the plating, the boiler is rinsed with deionized 
water. The copper solvents tested are circulated through the boiler after 
plating in each test. The results of these tests are present in Table III 
below. 
TABLE III 
______________________________________ 
Comparison of an Ammoniacal Copper Solvent Utilizing 
Sodium Perborate as an Oxidant with an Equivalent 
Solvent Containing Sodium Bromate 
______________________________________ 
Solvent: 0.15 wt. % oxidant + 0.12 wt. % 
ammonium bicarbonate + 
0.61 wt. % ammonia 
Temperature: 150.degree. F. 
Solvent Volume: 
45 liters 
Circulation Rate: 
4 liters per minute 
______________________________________ 
Oxident 
Time sodium perborate 
sodium bromate 
(hrs.) mpl. Cu mpl. Cu.sup.1 
______________________________________ 
2 460 835 
4 587 500 
6 640 525 
8 675 450 
10 775 430 
12 795 405 
14 957 385 
16 910 255 
18 1157 365 
20 1222 225 
22 1390 390 
24 1430 430 
26 1510 -- 
______________________________________ 
.sup.1 Heavy deposits of CuO were present on all metal surfaces in contac 
with the solvent following this test. 
The data presented in Table III shows that sodium perborate dissolved in 
excess of 0.15 wt.% copper after 24 hours of contact time. The interior 
surfaces of the pot boiler were inspected after the test and were 
determined to be free of copper with no rusting or precipitation. 
EXAMPLE 3 
An actual boiler tube section containing scale deposits is obtained and the 
scale analyzed. The results of the analysis are given in Table IV below. 
TABLE IV 
______________________________________ 
Analysis of Deposit in Boiler Tube Section 
______________________________________ 
X-ray Diffraction Analysis 
Copper (Cu): Major 
Cuprous Oxide (Cu.sub.2 O): 
Moderate 
Magnetite (Fe.sub.3 O.sub.4): 
Moderate 
Cupric Oxide (CuO): 
Small 
X-ray Fluorescence Analysis 
Magnesium 1-3 
Aluminum &lt;1 
Silicon 1.5-4.5 
Phosphorous 1.5-4.5 
Sulfur 0.4-1.2 
Calcium 1.5-4.5 
Chromium &lt;0.05 
Manganese 0.05-0.15 
Iron 17-25 
Nickel 2-6 
Copper 35-45 
Zinc 0.1-0.3 
______________________________________ 
The boiler tube section is cut into smaller pieces which are subjected to 
cleaning treatments consisting of contact with an aqueous ammoniacal 
oxidant solution for copper removal followed by contact with an aqueous 
hydrochloric acid solution for iron oxide removal followed by a second 
contact with an aqueous ammoniacal oxidant solution for the removal of 
residual copper. 
In one test the oxidant used is sodium bromate and in a second test the 
oxidant used is sodium perborate. The results of these tests are given in 
Table V below. 
TABLE V 
______________________________________ 
Results of Solvent Tests on Boiler Tube Pieces 
All Tests Conducted with 200 ml. of Solvent 
Under Static Conditions at 150.degree. F. for 6 Hours 
Test 
No. Treatment Results 
______________________________________ 
1 0.1 wt. % Ammoniacal Bromate 
435 mpl. Cu 
Solution.sup.1 followed by 5 wt. % 
Hydrochloric Acid + 0.1 wt. % 
Corrosion Inhibitor.sup.2 
3320 mpl. Fe 
followed by 0.1 wt. % 
Ammoniacal Bromate Solution.sup.1 
217 mpl. Cu 
Tube Clean 
2 0.1 wt. % Ammoniacal 390 mpl. Cu 
Perborate Solution.sup.3 
followed by 5 wt. % 
Hydrochloric Acid + 3230 mpl. Fe 
0.1 wt. % Corrosion 
Inhibitor.sup.2 237 mpl. Cu 
followed by 0.1 wt. % 
Tube Clean 
Ammoniacal Perborate 
Solution.sup.3 
______________________________________ 
.sup.1 Ammoniacal bromate solution is comprised of 0.1 wt. % sodium 
bromate + .078 wt. % ammonium bicarbonate + 0.3 wt. % ammonia. 
.sup.2 Rodine 213 corrosion inhibitor sold by Amchem Products, Inc. of 
Ambler, Pennsylvania. 
.sup.3 Ammoniacal perborate solution is comprised of 0.1 wt. % sodium 
perborate + .078 wt. % ammonium bicarbonate + 0.3 wt. % ammonia. 
As shown in Table V, sodium perborate is an equivalent oxidizing agent in 
aqueous ammoniacal copper solvent to sodium bromate. 
EXAMPLE 4 
In the pot boiler system described in Example 2, a simulated sludge deposit 
is produced by mixing 900 grams of technical grade copper powder with 300 
grams of technical grade magnetite (Fe.sub.3 O.sub.4) powder. The 
simulated sludge is placed in the bottom of the boiler and an aqueous 
ammoniacal cleaning solution is injected into the pot and circulated at a 
rate of 1 gpm. The solvent is heated to 150.degree. F. and maintained at 
such temperature for the first 20 hours of the test. 
The cleaning solution is analyzed periodically throughout the test, the 
results of which are given in Table VI below. 
TABLE VI 
______________________________________ 
Analysis of First Copper Stage 
______________________________________ 
Solvent: 1 wt. % Sodium Perborate + 10 wt. % 
Ammonium Bicarbonate + 
9.67 wt. % ammonia 
Solvent Volume: 
45 liters 
Temperature: 150.degree. F. 
Circulation Rate: 
4 liters per minute 
Pot Loading: 900 gm. Cu Powder and 300 gm. 
Fe.sub.3 O.sub.4 Powder 
______________________________________ 
Elapsed 
Time, mpl. Grams Cu 
Hours Cu Removed Remarks 
______________________________________ 
0 0 0 Sodium perborate = 1.0 wt. % 
2 925 41 Sodium perborate = 0.02 wt. %, 
add 0.5% Sodium perborate 
3 -- -- Sodium perborate = 0.04 wt. %, 
begin airblow at 2 liters 
minute 
4 1,355 60 
8 2,535 114 
12 3,050 137 
16 4,500 202 
20 5,225 235 Reduce temperature to 100.degree. F., 
Reduce airblow to 1 liter 
minute 
30 6,400 288 
50 7,375 331 
86 10,300 463 
122 10,400 468 
158 10,900 490 Add 4 lb of 30% Ammonium 
Hydroxide + 0.5% sodium 
perborate at 166 hours 
190 12,200 549 
214 12,200 549 
______________________________________ 
Approximately 1 wt.% copper is dissolved in the cleaning solution during 
the first 100 hours of contact with the solution. 
After the test described above is completed, the pot boiler is filled with 
a cleaning solution for removing iron oxide, namely, an aqueous solution 
containing 10 wt.% ethylenediaminetetracetic acid (EDTA), 0.5 wt.% 
hydrazine, ammonium hydroxide in an amount to adjust the pH to 6.0, and 
0.6 wt.% corrosion inhibitor (OSI-1 sold by Halliburton Services of 
Duncan, Oklahoma). This solvent is circulated at 200.degree. F. for 44 
hours and dissolves approximately 3200 mpl. iron. This iron concentration 
represents 198 grams of dissolved magnetite. 
A deionized water rinse is injected into the pot boiler following the iron 
removal stage. This rinse is circulated through the boiler for 30 minutes 
and then drained to waste. A fresh solution of copper cleaning solution is 
prepared at ambient temperatures and circulated through the boiler in the 
same manner as in the first stage. The results of the second copper 
removal test are given in Table VII below. 
TABLE VII 
______________________________________ 
Analysis of Second Copper Stage 
______________________________________ 
Solvent: 1 wt. % Sodium Perborate + 10 wt. % 
Ammonium Bicarbonate + 
9.67 wt. % Ammonia 
Solvent Volume: 
45 liters 
Temperature: 100.degree. F. 
Circulation Rate: 
4 liters per minute 
Pot Loading: 900 gm. Cu Powder and 300 gm. 
Fe.sub.3 O.sub.4 Powder 
______________________________________ 
Elapsed Time, Grams Cu 
Hours mpl. Cu Removed Remarks 
______________________________________ 
2 475 21 Gas evolution almost nil 
3 -- -- Initiate 2 liters/minute 
airblow 
4 710 31 
8 900 40 
16 1,355 60 
32 2,030 91 
48 2,825 127 
64 3,675 165 
80 4,200 189 
96 5,225 235 
112 5,550 249 
128 5,725 257 
142 5,875 264 
146 5,875 264 
______________________________________ 
The three-stage treatment removes 90 wt.% of the copper and 66 wt.% of the 
magnetite. Table VIII below sets forth a summary of the entire test 
sequence. 
TABLE VIII 
______________________________________ 
Summary of Deposits Removed During Entire Test Sequence 
______________________________________ 
Boiler Loading: 900 gm. Cu & 300 gm. Fe.sub.3 O.sub.4 
System Volume: 45 liters 
Circulation Rate of All Solvents: 
1 gm. 
______________________________________ 
Stage Deposit 
No. Solvent Removed 
______________________________________ 
1 1 wt. % Sodium Perborate + 10 wt. % 
549 gm. Cu 
Ammonium Bicarbonate + 9.67 wt. % 
Ammonia, at 150.degree. F. with 2 liters/min. 
airblow for 20 hours followed by 
100.degree. F. and 1 liter/min. airblow for 
194 hours 
2 10 wt. % EDTA + 0.5 wt. % hydra- 
198 gm. Fe.sub.3 O.sub.4 
Zine + Ammonia + 0.6 wt. % 
Corrosion Inhibitor.sup.1 at 200.degree. F. for 
44 hours 
3 1 wt. % Sodium Perborate + 10 wt. % 
264 gm. Cu 
Ammonium Bicarbonate + 9.67 wt. % 
Ammonia, at 100.degree. F. with 2 liters/min. 
airblow for 146 hours 
TOTAL 813 gm. Cu 
198 gm. Fe.sub.3 O.sub.4 
______________________________________ 
.sup.1 OSI1 sold by Halliburton Services of Ducan, Oklahoma