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QUESTIONS

AND ANSWERS

Advanced Stabilized AlkalinePhosphate (ASAP) CoolingWater Treatment Program

Increased legislation concerningheavy metals continues to limit thechoices for good cooling watertreatment programs. Additionally,

personnel safety is a top priority forindustry. With these concerns inmind, Nalco has developed the

Advanced Stabilized AlkalinePhosphate (ASAP) program.

What is the ASAP program?

ASAP is Nalcos next generationAlkaline Phosphate program thathas been optimized for hightemperature and long HoldingTime Index (HTI) applications. Ithelps protect open recirculatingcooling water systems fromcorrosion and scale by utilizingNalcos state-of-the-art HighStress Polymer and a new dual

function corrosion inhibitor.

Where should ASAP be used?

The ASAP program is an excel-lent alternative for plants thathave environmental limitationson heavy metal and phosphatedischarge. In most cases, the levelof phosphates in this programwill not be constrained byenvironmental discharge limits.

The ASAP program is the pro-gram of choice for plants desiringfewer foulants in their recircu-lating cooling water systems.The program requirements of4 to 8 ppm phosphate are signifi-cantly less than the 10 to 17 ppmphosphate requirements for astabilized phosphate program.

Additionally, lower circulatingphosphate residuals mean lowerphosphate going to blowdown,resulting in a reduced load towaste water treatment.

The ASAP program is designedto reduce or eliminate the need tofeed acid. The program param-eters take advantage of a towersnatural cycling up of alkalinity.

How does the ASAP program

work?

The program contains several

corrosion inhibitors for mild steeland yellow metal corrosionprotection. In addition, state-of-the-art High Stress Polymer(HSP) technology is used forcontrol of scale and deposits.The program also contains a dualfunction organic phosphate for

mild steel localized corrosionprotection and the stabilizationof calcium carbonate at hightemperatures.

Two types of phosphate, ortho-phosphate and polyphosphate,provide the corrosion protectionfor mild steel. Orthophosphatehas been known as an anodicinhibitor which combines withiron at the anode to form ahighly insoluble iron phosphateprecipitate. In addition, ortho-phosphate is thought to promotepassivation through the forma-tion of a passive gamma ironoxide (Fe

2O

3) film. Both of the

mechanisms provide a protectivefilm at the anode and preventpitting and/or localized corrosion.

(Continued on Reverse Side)

Figure 1 Diagram of a corrosion cell

SM

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Cathodic protection is providedby two mechanisms, both ofwhich require at least 25 ppmcalcium in the recirculatingwater. At the cathode, hydroxylions are released from the reac-tion of oxygen and electrons.

The result is a localized high pHat the cathodic metal surface(see Figure 1). Both the neworganic phosphate inhibitorand polyphosphate combinewith calcium in the water andlocally precipitate at the high-pHcathodic sites. The principalcorrosion inhibition mechanismfor the ASAP program is cathodi-cally controlled.

The purpose of the polymer is to

maintain the phosphate corrosioninhibitors in a soluble form in therecirculation water and prevent

bulk precipitation. Using themost advanced polymer tech-nology ensures excellent programcontrol at the most economicalcost. An azole is included in theASAP program for yellow metalcorrosion protection.

How important is pH control?

The ASAP program is designedto run at higher alkalinities (pH).Both pH and alkalinity areimportant parameters for theproper operation of the program.Being in the correct pH range isoften more important than theproper alkalinity.

Use of this program can eliminateor significantly reduce the needfor acid feed.

What are the calcium limitations

of the program?

The minimum calcium level is50 ppm for good corrosionprotection. Calcium levels of upto 1200 ppm can be achieved

before uncontrollable calciumphosphate precipitation mayoccur.

What can I do if I have high iron

in my makeup water?

Control of iron is very importantwith any phosphate-containingprogram. Uncontrolled, ironphosphate deposition will resultin reduced heat transfer andpotentially underdeposit corrosion.

The ASAP program incorporatesthe most efficient and technologi-cally advanced polymer (HSP)able to tolerate iron. Additionalpolymer feed (over the normalprogram recommendations)typically results in improvedperformance and iron control. Noadditional products are needed.

What effect does temperature

have on this program?The ASAP program has shown, inpractice, the ability to handletemperatures similar to alkaline-zinc programs.

The polymer portion of theprogram has raised the break-point for cooling water calciumphosphate dispersants. The pro-gram provides reliable operationin bulk water temperatures to160F, or on exchangers withmetal skin temperatures of 180F.

How can I be assured the

program is working effectively?

Monitoring and control areimportant aspects of any coolingwater program. As part of themonitoring program, the ASAPprogram incorporates depositmonitors, corraters and corrosioncoupons to continually evaluatedeposit control and corrosion.

Proper control of product feedcan ensure the success of anyprogram. TRASAR Technologycan be incorporated into theASAP program. TRASAR pro-vides on-line measurement andcontrol of product feed.

How can I find out more about the

program as it applies to my

particular system?

The needs of your plant areunique due to the diversity ofdesign and equipment. Nalcooffers several choices for coolingwater treatment programs. YourNalco representative can deter-mine the proper program to meetyour plants particular needs and

work with you to help implementa program that provides the bestresults.

Registered Trademarks of Nalco Chemical Company 1999 Nalco Chemical Company

All Rights Reserved Printed in U.S.A. 10-99 Bulletin 427