INTRODUCTION- Puckorius & Associates, Inc. were requested by AS Inc. to determine the effective dosages of AS-8310 in controlling mild steel corrosion under laboratory conditions typical of closed/chilled water systems.. This is the final report including all test data.
AS-8310 TIN-BASED CORROSION INHIBITOR- This product is a specialty formulation containing a proprietary tin-based compound formulated with an azole, dispersant and stabilizers designed for use as a closed cooling/chilled water complete multimetal corrosion inhibitor. It is to be used to replace nitrite, molybdate, and typical closed cooling water treatments. Specific product composition information may be obtained from AS Inc.
TEST CONDITIONS-The laboratory tests were performed at temperatures of 60-70*F, with period stirring, and using low hardness city water with zero chlorination. The periodic stirring introduced oxygen as well as duplicating stagnant water often occurring in these closed water systems. These conditions were chosen since they represent the most operating conditions of closed cooling/chilled water systems.
MILD STEEL CORROSION SPECIMENS- The use of mild steel nails of a 1010-1020 grade that were degreased and dried were employed as the initial specimens to determine the dosage/effectiveness of the AS- 8310. A small portion of the mild steel nail was above the water level in the test bottle to determine if any protection would be obtained when periodically “wetted” with the treated water. No actual weight measurements were made. Physical inspection of the specimens were made as well as the appearance of the treated water. The presence of “rusty” water indicated corrosion, while clarity of the water indicated no corrosion.
Typical mild steel corrosion coupons, also 1010-1020 grade were also used to determine the corrosion rates in separate tests under the same water quality and test conditions as the nails.
COPPER CORROSION COUPONS- The final corrosion testing included copper corrosion coupons that represent the alloy commonly found in the chillers and heat exchangers of closed water systems. They were tested under the same water quality and test conditions as the mild steel coupons and nails but in separate glass vessels.
WATER QUALITY- The water used in this laboratory evaluation was city well water that did not contain any chlorine or any other treatment . The composition prior to treatment was:
Conductivity 600 microhms
Total Hardness 100 ppm
Calcium Hardness (as CaCO3) 60 ppm
Total Alkalinity 130 ppm
Chlorides ( as NaCl ) 15 ppm
Sulfates ( as Na2SO4) 10 ppm
Silica (as SiO2) 5 ppm
No iron or suspended solids
TEST CONTAINERS- The use of 175 ml glass bottles were used that were capped with plastic inserts in covers to prevent any other metal contamination. The bottles were filled to 125 ml of city water and the dosage of AS-8310 was added to provide the varying concentrations.
TEST CONTAINER SETUP PROCEDURE- The city water was initially added to the 125 ml level, then the specific dosage of AS-8310 added and mixed. The steel specimens were then added, capped, and inverted several times to assure good mixing. The specimens were allowed to lean in the bottle so that about 10% was exposed above the treated water level. Mixing by inverting occurred every several days as well as opening the lid to introduce air.
The corrosion coupon tests were a duplicate of the same conditions except the coupons were totally immersed in the treated water.
TEST RESULTS- Four ( 4 ) separate tests were performed , each for a duration of 30 days, with the first to identify the approximate range of effectiveness , then at a more definitive dosage to determine the most effective dosage of the AS-8310, the third with an AS-8310 formulation without the tin-based compound. But including all other ingredients. The forth test done at the most effective dosage of the tin-based AS-8310 product. In the first three tests an untreated water was used as the blank test. This was not needed for the corrosion coupons tests. Photos were taken to illustrate the appearance of the test vessels and are attached to this report.
TEST #1 RESULTS-.This test was done at dosage levels of 1000 to 3500 ppm of the AS-8310 tin-based formula with mild steel nails. It showed essentially no mild steel corrosion control at dosages less than 750 ppm of product and excellent corrosion protection at and above 1500 ppm. Photos of these are shown in the appendix.
TEST #2 RESULTS- This test showed the following mild steel corrosion protection of the AS-8310
DOSAGE( as AS-8310 product) RESULTS-MILD STEEL
Less than 750 ppm poor but some protection
750 ppm good protection
1500 ppm excellent protection
2500 ppm excellent protection
Levels at and above 1500 ppm showed excellent protection
TEST #3 RESULTS- This test was performed to determine if the AS-8310 formulation without any of the Tin-based compound would provide any corrosion control. The Tin-based compound was replaced with water with all other ingredients at the same level. The results indicated that dosages up to 3500 ppm of the product did not provide any noticible mild steel corrosion protection but did suspend some of the “rust”. This is likely due to the dispersant in the formulation .Photos were taken and are shown in the appendix.
TEST # 4 RESULTS- This test involved the use of corrosion coupons, mild steel and copper in separate vessels. The dosage of AS-8310 the tin-based formulation was as used in tests #1 and #2. The dosage was 1500 ppm of product and the same test water and conditions as performed in the previous tests. The test results showed excellent corrosion protection with the corrosion rates of cleaned coupons calculated basedon the 30 day exposure:
Mild Steel 0.2 mpy (mls per year)
Copper 0.1 mpy
No localized or pitting was noted on either metal.
Photos show the coupons in the test vessels as well as before and after cleaning.
CONCLUSIONS- The results of this laboratory evaluation conclusively show that the tin-based corrosion inhibitor formulation AS-8310 will provide excellent mild steel and copper corrosion protection under typical closed cooling/chilled water system conditions.
The dosages that provide excellent mild steel and copper corrosion control were at 1500 ppm or higher of product .
We also wish to indicate that this type of basic laboratory screening tests usually requires higher dosages of inhibitor by 10-25% greater than would be experienced in actual systems..
Testing and report preparation by Paul Puckorius
APPENDIX- Photos of test results. (The page will take a few seconds to load. Please be patient.)
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