INTRODUCTION
It was the intent of AS Inc. (ASI) to employ an independent third-party to test the corrosion inhibiting capabilities of their unique product, AS-8150, to substantiate actual field results. Puckorius & Associates, Inc. (P&A) was asked to submit a proposal for providing technical advice and for performing laboratory experiments to measure corrosion rates of carbon steel, copper and copper alloys under simulated open circulating evaporative cooling water conditions. P&A is an independent water management consulting firm which does not sell or endorse chemicals or equipment, and has many years experience in this type of evaluation.
SCOPE OF WORK
Objective
The objective of the project was to compare the corrosion inhibiting properties of the ASI product, with the orthophosphate ion (PO 4 3–) under similar operating conditions. No other water treatment chemical was to be included in the test.
Tasks
1. P&A was to assemble two identical recirculating test systems that included an Advantage Model ADPM-1-A Scale Monitor, see Photos 1 and 2.
Photo 1 – The AS-8150-treated System
Photo 2 – The PO 4-treated System
Task (continued)
2. We were to install in each system mild steel, copper, Admiralty Metal and 90:10 copper:nickel corrosion coupons as well as Linear Polarization probes (LPP) for continuous and “instantaneous” corrosion measurements, respectively.
3. At the end of the test the coupons were to be photographed and the weight loss determined for calculation of corrosion rates in mils per year (MPY) based on exposure time.
4. The data collected by the LPP was to be studied and processed into tables and graphs.
5. Conclusions were to be drawn from the data and a report provided.
Equipment
An eight port “corrosion rack” was added at the effluent end of each Advantage monitor. Both systems were cleaned of any residue, scale or corrosion products from a previous use. Then, in case there were any materials in the systems that would absorb any of the treatment chemicals, a solution of 25 mg/L of neat (as drummed) AS-8150 in deionized (DI) water at pH 9.0 was circulated over-night in the AS-8150 system. The same procedure was performed on the phosphate system with 10 mg/L PO 4 as PO 4. Both systems were thoroughly rinsed with DI water until all traces of the treatment chemicals were gone. These cleaning and “passivation” steps were done without the test specimens installed in the test rack.
A conventional “mild steel” (MS) corrosion coupon (alloy C1010) was installed in the top first position of each of the two eight-port corrosion racks in the circulating systems, plus one set of 3 MS “electrodes” or ‘tips” in Linear Polarization Probes (LPP) in each of the bottom first positions.
Two additional MS specimens have perforations with a series of holes to induce scale formation, one in each of the two Advantage scale and corrosion monitors. Each “scale” coupon also serves as a corrosion coupon.
Corrosion coupons of copper (CDA110), Admiralty brass (CDA443) and 90:10::Cu:Ni (CDA706) were installed in that order, left to right, in the remaining top ports of the corrosion racks, and electrodes ot the same metals in LPP’s were installed in the same order in the remaining six bottom ports. The coupons were to remain in the systems until the end of the test at which time they were to be removed, photographed and processed for weight loss and mil per year (MPY) calculations, the same term as obtained from the LP instrument.
Both systems contained 10 gallons (37.85 Liters) of Evergreen city water supplemented with::
to six times their normal content, as if the water had been concentrated by evaporation in a cooling tower, (except for the chloride, sodium and sulfate anions, which will be higher due to the salts used); see Columns A & B in Table III. The test water will tend to be slightly scale-forming. However, as with most waters, it also will have a tendency to be corrosive, particularly if scale or precipitation occurs, taking some of the calcium, alkalinity and phosphate out of solution.
One system was treated with 5 mL of 50% AS-8150 equivalent to 1.8 mg/L Sn as Sn, the other with 10 mg/L orthophosphate as PO 4 from disodium phosphate, a slightly alkaline salt. The pH was adjusted, as necessary, to between 8.0 and 8.5, which is near optimum for corrosion inhibition of carbon steel, copper and copper alloys.
Summarizing the components of the test systems:
The circulating systems each consisted of:
A treated test water sump with pump and electrical heating elements capable of heating the test water to 140 oF, with connecting hoses to and from the test units, containing a ball stop-valve.
An Advantage Model ADPM-1-A Scale Monitor consisting of:
A gpm flow meter,
Inlet and outlet thermocouples with digital displays,
A jacketed stainless steel tube containing heater and thermocouple for reading skin and water temperatures, with digital display,
A perforated carbon steel coupon to induce scale formation at the 140 °F system temperature.
An eight port 1 inch PVC corrosion rack containing four corrosion coupons and four LP corrosion probes, each with 3-electrode tips for linear polarization instantaneous corrosion readings,
Other Instrumentation
Two (2) percent-timers to control the temperature of the two sumps at 140 °F.
A Metal Samples Model MS1500L LPR Data Logger for collecting and storing corrosion readings from the probes. The recorder can be downloaded in Excel format to a computer and graphed.
A Myron L Model 6P combination pH, ORP temperature and conductivity meter,
A Hach Model 2010 Spectrophotometer,
An Oven, a desiccator and a 4-place balance for processing corrosion coupons.
Plus chemicals, reagents and equipment for processing corrosion coupons and for analyzing test water.