8.7 Scaling IndicesThe saturation level (SL) of water in a mineral phase is a goodindicator of the potential for scaling due to that specific scalant.Saturation level is a ratio between the ion activity product (IAP) andthe thermodynamic solubility product (Ksp) of a specific compound inthat water. For example, when calcium carbonate (CaCO3) is thescalant SL is defined asSL Ca COsp=a ⋅ 23 2+ − aK(8.25)where a a Ca+ CO ⋅3 2− is the IAP of the two ions involved in the formationof CaCO3, that is, Ca2+ and CO32−.Ksp is a measure of ionic concentration when dissolved ions andundissolved ions are in equilibrium. When a saturated solution ofsparingly or slightly soluble salt is in contact with undissolved salt,equilibrium is established between the dissolved ions and theundissolved salt. In theory, this equilibrium condition is based uponan undisturbed water maintained at constant temperature andallowed to remain undisturbed for an infinite period of time.Water is therefore said to be undersaturated (SL value less than 1.0)if it can dissolve the scalant, that is, calcium carbonate in the presentexample. When water is at equilibrium, SL will be 1.0 by definition.Supersaturated water (SL value greater than 1.0) will precipitatecalcium carbonate from water if allowed to rest. As the saturationFIGURE 8.22 Fouled chiller unit. (Courtesy of Defence R&D, Canada-Atlantic)314 C h a p t e r 8 level increases beyond 1.0, the driving force for the precipitation ofcalcium carbonate increases.The following sections describe some indices that are used toindicate the tendency of given waters to deposit scales on metalsubstrates and by extension to predict the corrosivity of specific waters.Generally speaking, scales precipitated onto metal surfaces can provideprotection of the substrate from general corrosion. If on the other hand,the scales are defective and contain voids and/or cracks, they couldlead to localized corrosion. However, the assumption that water belowsaturation with respect to calcium carbonate is corrosive, whileoccasionally correct, is not always reliable.8.7.1 Langelier Saturation IndexThe Langelier saturation index (LSI) is probably the most widely used

indicator of a water scale potential. This index indicates the driving forcefor scale formation and growth in terms of pH as a master variable. Inorder to calculate the LSI, it is necessary to know the alkalinity (mg L−1 asCaCO3 or calcite), the calcium hardness (mg L−1 Ca2+ as CaCO3), the totaldissolved solids (mg L−1, TDS), the actual pH, and the temperature of thewater (°C). If TDS is unknown, but conductivity is, one can estimate mgL−1 TDS using a conversion table (Table 8.15). LSI is defined asLSI = pH − pHs(8.26)where pH is the measured water pHpHs is the pH at saturation in calcite or calcium carbonate andis defined as:pH (9.3 ) ( ) s = + A + B − C + D (8.27)A[Log (TDS) 1]10= 10−(8.28)B 13.12 Log ( C 273) 34.55 10= − × o + + (8.29)C Log10 (Ca as CaCO ) 0.423 = + −(8.30)D Log10 (alkalinity as CaCO3 ) =(8.31)As for the SL reasoning described earlier, the LSI indicates threesituations:• If LSI is negative: No potential to scale, the water will dissolveCaCO3.• If LSI is positive: Scale can form and CaCO3 precipitation mayoccur.• If LSI is close to zero: Borderline scale potential. Water qualityor changes in temperature, or evaporation could changethe index.C o r r o s i o n b y W a t e r 315Calculation example. Suppose the drinking water supplied to animalshas the following analysis:pH = 7.5TDS = 320 mg/LCalcium = 150 mg L−1 (or ppm) as CaCO3Alkalinity = 34 mg L−1 (or ppm) as CaCO3The LSI index is calculated at two temperatures, that is, 25°C (roomtemperature) and 82°C (cage wash cycle). The colder incoming water willwarm to room temperature in the manifolds. Residual water in the rack

manifold can be heated to 82°C when the rack is in the cage washer.LSI formula:LSI = pH − pHspHs = (9.3 + A + B) − (C + D)Conductivity(lS/cm)TDS(mg/L as CaCO3)1 0.4210.6 4.221.2 8.542.4 17.063.7 25.584.8 34.0106.0 42.5127.3 51.0148.5 59.5169.6 68.0190.8 76.5212.0 85.0410.0 170.0610.0 255.0812.0 340.01008.0 425.0TABLE 8.15 Conversion Table between the Conductivity of Natural Water andthe TDS It Contains316 C h a p t e r 8 where A = [Log10(TDS) − 1]/10 = 0.15B = −13.12 × Log10(°C + 273) + 34.55= 2.09 at 25°C and 1.09 at 82°CC = Log10(Ca2+ as CaCO3) − 0.4 = 1.78D = Log10(alkalinity as CaCO3) = 1.53Calculation at 25°C:pHs = (9.3 + 0.15 + 2.09) − (1.78 + 1.53) = 8.2LSI = 7.5 − 8.2 = − 0.7Hence no tendency to scaleCalculation at 82°C:pHs = (9.3 + 0.15 + 1.09) − (1.78 + 1.53) = 7.2LSI = 7.5 − 7.2 = + 0.3Hence slight tendency to scale8.7.2 Other IndicesThe Ryznar stability index (RSI) uses a correlation established between anempirical database of scale thickness observed in municipal water systemsand associated water chemistry data. As with the LSI, the RSI has its basisin the concept of saturation level. The RSI takes the following form:RSI = 2(pHs) − pHThe empirical correlation of the RSI can be summarized as follows:

• RSI < 6 the scale tendency increases as the index decreases• RSI > 7 the calcium carbonate formation probably does notlead to a protective corrosion inhibitor film• RSI > 8 mild steel corrosion becomes an increasing problemThe Puckorius scaling index (PSI) is based on the buffering capacityof the water, and the maximum quantity of precipitate that may formin bringing water to equilibrium. Water high in calcium, but low inalkalinity and buffering capacity can have a high calcite saturationlevel that increases the ion activity product. Such water might have ahigh tendency to form scale, but the scale itself might be of such a smallquantity as to be unobservable. The water has the driving force but notthe capacity and ability to maintain pH as precipitate matter forms.The PSI index is calculated in a manner similar to the RSI.Puckorius uses an equilibrium pH rather than the actual system pHC o r r o s i o n b y W a t e r 317to account for the buffering effects:PSI = 2 (pHs) − pHeqwhere pHs is still the pH at saturation in calcite or calcium carbonatepHeq = 1.465 × log10[Alkalinity] + 4.54[Alkalinity] = [HCO3−] + 2 [CO32−] + [OH−]The Larson-Skold index is based upon evaluation of in situ corrosionof mild steel lines transporting Great Lakes waters. Extrapolation toother waters than the Great Lakes, such as those of low alkalinity orextreme alkalinity, goes beyond the range of the original data. Theindex is the ratio of equivalents per million (epm) of sulfate (SO42−)and chloride (Cl−) to the epm of alkalinity in the form bicarbonateplus carbonate:Larson-Skold index (epm Cl epm SO4 )/ = − + 2−(epm HCO3 epm CO3 )− + 2−(8.32)The index has proven a useful tool in predicting the aggressivenessof once-through cooling waters. The Larson-Skold index might beinterpreted by the following guidelines:• Index < 0.8 chlorides and sulfate probably will not interferewith natural film formation.• 0.8 < index < 1.2 chlorides and sulfates may interfere withnatural film formation. Higher than desired corrosion ratesmight be anticipated.• Index > 1.2 the tendency toward high corrosion rates of alocal type should be expected as the index increases.The Stiff-Davis index attempts to overcome the shortcomings ofthe LSI with respect to waters with high total dissolved solids and

the impact of “common ion” effects on the scale formation drivingforce. Like the LSI, the Stiff-Davis index has its basis in the conceptof saturation level. The solubility product used to predict the pH atsaturation (pHs) for a water is empirically modified in the Stiff-Davis index. The Stiff-Davis index will predict that water is lessscale forming than the LSI calculated for the same water chemistryand conditions. The deviation between the indices increases withionic strength. Interpretation of the index is by the same scale as forthe LSI.The Oddo-Tomson index accounts for the impact of absolutepressure and partial pressure of carbon dioxide on the pH of water,and on the solubility of calcium carbonate [20]. This empirical modelalso incorporates corrections for the presence of two or three phases(water, gas, and oil). Interpretation of the index is by the same scale asfor the LSI and Stiff-Davis indices.318 C h a p t e r 8 8.8 Ion-Association ModelThe saturation indices discussed previously can be calculated based upontotal analytical values for all possible reactants. Ions in water, however, donot tend to exist totally as free ions [21]. Calcium, for example, may bepaired with sulfate, bicarbonate, carbonate, phosphate, and other species.Bound ions are not readily available for scale formation and such binding,or reduced availability of the reactants, decreases the effective ion-activityproduct. Saturation indices such as the LSI are based upon total analyticalvalues rather than free species primarily because of the intense calculationrequirements for determining the distribution of species in water.Speciation breakdown of all species in a given water requires numerouscomputer iterations to achieve the following [22]:• The verification of electroneutrality via a cation-anion balance,and balancing with an appropriate ion (e.g., sodium or potassiumfor cation-deficient waters; sulfate, chloride, or nitrate for aniondeficientwaters).• Estimating ionic strength; calculating and correcting activitycoefficients and dissociation constants for temperature;correcting alkalinity for noncarbonate alkalinity.• Iterative calculation of the distribution of species in the waterfrom dissociation constants. A partial listing of possible ionpairs is given in Table 8.16.• Verification of mass balance and adjustment of ion concentrationsto agree with analytical values.• Repeating the process until the desired resolution is achieved.• Calculation of saturation levels based upon free concentrationsof ions estimated using the ion-association model (ion pairing).The ion-association model has been used by major water treatmentcompanies since the early 1970s. When indices are used to establishoperating limits such as maximum concentration ratio or maximumpH, the differences between indices calculated using ion pairing can

have some serious economic significance. For example, experience ona system with high-TDS water may be translated to a system operatingwith a lower-TDS water. The high indices found acceptable in thehigh-TDS water may be unrealistic when translated to a water whereion pairing is less significant in reducing the apparent driving forcefor scale formation. Table 8.17 summarizes the impact of TDS uponLSI when it is calculated using total analytical values for calcium andalkalinity, and when it is calculated using the free calcium andcarbonate concentrations determined with an ion-association model.Indices based upon ion-association models provide a commondenominator for comparing results between systems. For example,calcite saturation level calculated using free calcium and carbonateC o r r o s i o n b y W a t e r 319ALUMINUM[Aluminum] = [Al3+] + [Al(OH)2+] + [Al(OH)2+] + [Al(OH)4−] + [AlF2+] + [AlF2+] +[AlF3] + [AlF4−] + [AlSO4+] + [Al(SO4)2−]BARIUM[Barium] = [Ba2+] + [BaSO4] + [BaHCO3+] + [BaCO3] + [Ba(OH)+]CALCIUM[Calcium] = [Ca2+] + [CaSO4] + [CaHCO3+] + [CaCO3] + [Ca(OH)+] + [CaHPO4] +[CaPO4−] + [CaH2PO4+]IRON[Iron] = [Fe2+] + [Fe3+] + [Fe(OH)+] + [Fe(OH)2+] + [Fe(OH)3−] + [FeHPO4+] +[FeHPO4] + [FeCl2+] + [FeCl2+] + [FeCl3] + [FeSO4] + [FeSO4+] +[FeH2PO4+] + [Fe(OH)2+] + [Fe(OH)3] + [Fe(OH)4−] + [Fe(OH)2] +[FeH2PO42+]MAGNESIUM[Magnesium] = [Mg2+] + [MgSO4] + [MgHCO3

+] + [MgCO3] + [Mg(OH)+] +[MgHPO4] + [MgPO4−] + [MgH2PO4+] + [MgF+]POTASSIUM[Potassium] = [K+] + [KSO4−] + [KHPO4−] + [KCl]SODIUM[Sodium] = [Na+] + [NaSO4−] + [Na2SO4] + [NaHCO3] + [NaCO3−] + [Na2CO3] +[NaCl] + [NaHPO4−]STRONTIUM[Strontium] = [Sr2+] + [SrSO4] + [SrHCO3+] + [SrCO3] + [Sr(OH)+]TABLE 8.16 Example of Ion Pairs Used to Estimate Free Ion ConcentrationsLSIWater Low TDS High TDS TDS Impact on LSIHigh chloride• No pairing 2.25 1.89 −0.36• With pairing 1.98 1.58 −0.40High sulfate• No pairing 2.24 1.81 −0.43• With pairing 1.93 1.07 −0.86FIGURE 8.17 Impact of Ion Pairing on the Langelier Scaling Index (LSI).320 C h a p t e r 8 concentrations has been used successfully as the basis for developingmodels which describe the minimum effective scale inhibitor dosagethat will maintain clean heat-transfer surfaces [23]. The followingcases illustrate some practical usage of the ion-association model.8.8.1 Limiting Halite Deposition in a WetHigh-Temperature Gas WellThere are several gas-well fields that produce hydrocarbon gasassociated with very high TDS connate waters. Classical oilfield scaleproblems (e.g., calcium carbonate, barium sulfate, and calciumsulfate) are minimal in these fields. Halite (NaCl), however, can beprecipitated to such an extent that production is lost in hours. As aresult, a bottom-hole fluid sample is retrieved from all new wells.Unstable components are “fixed” immediately after sampling, andpH is determined under pressure. A full ionic and physical analysis isalso carried out in the laboratory.Some of the analyses were run through an ion-association modelcomputer program to determine the susceptibility of the brine to haliteprecipitation. If a halite precipitation problem was predicted, the ionassociationmodel was run in a “mixing” mode to determine if mixing the

connate water with boiler feedwater would prevent the problem. Thisapproach has been used successfully to control salt deposition in the wellwith the composition outlined in Table 8.18. The ion-association modelevaluation of the bottom-hole chemistry indicated that the water wasslightly supersaturated with sodium chloride under the bottom-holeconditions of pressure and temperature. As the fluids cooled in the wellbore, the production of copious amounts of halite was predicted.Bottom Hole Connate Boiler Feed WaterTemperature (°C) 121 70Pressure (bars) 350 1pH (site) 4.26 9.10Density (kg/m3) 1.300 1.000TDS (mgl−1) 369,960 <20Dissolved CO2 (mgl−1) 223 <1H2S (gas phase) (mgl−1) 50 0H2S (aqueous phase) (mgl−1) <0.5 0Bicarbonate (mgl−1) 16 5.0Chloride(mgl−1) 228,485 0TABLE 8.18 Hot Gas-Well Water AnalysisC o r r o s i o n b y W a t e r 321Bottom Hole Connate Boiler Feed WaterSulfate (mgl−1) 320 0Phosphate (mgl−1) <1 0Borate (mgl−1) 175 0Organic acids <C6 (mgl−1) 12 <5Sodium (mgl−1) 104,780 <1Potassium (mgl−1) 1600 <1Calcium (mgl−1) 30,853 <1Magnesium (mgl−1) 2910 <1Barium (mgl−1) 120 <1Strontium (mgl−1) 1164 <1Total iron (mgl−1) 38.0 <0.01Lead (mgl−1) 5.1 <0.01Zinc (mgl−1) 3.6 <0.01TABLE 8.18 (continued)In this case, the ion-association model predicted that the connatewater would require a minimum dilution with boiler feedwater of15 percent to prevent halite precipitation (Fig. 8.23). The model alsopredicted that over-injection of dilution water would promote barite(barium sulfate) formation (Fig. 8.24). Although the well producedH2S at a concentration of 50 mg/L, the program did not predict theformation of iron sulfide because of the combination of low pH andhigh temperature. Boiler feedwater was injected into the bottom ofthe well using the downhole injection valve normally used forcorrosion inhibitor injection. Injection of dilution water at a rate of 25to 30 percent has allowed the well to produce successfully since startup.

Barite and iron sulfide precipitation have not been observed, andplugging with salt has not occurred.8.8.2 Identifying Acceptable OperatingRange for Ozonated Cooling SystemsIt has been well-established that ozone is an efficient microbiologicalcontrol agent in open recirculating cooling-water systems (coolingtowers). It has also been reported that commonly encountered scales havenot been observed in ozonated cooling systems under conditions wherescale would otherwise be expected. The water chemistry of 13 ozonated322 C h a p t e r 8 25 42 58 75 92 108 1251008367503317000.511.522.5Degree of saturationTemperature% InjectionFIGURE 8.23 Hot gas-well halite degree of saturation as a function oftemperature and reinjected boiler water (DownHole SAT).cooling systems was evaluated using an ion-association model. Eachsystem was treated solely with ozone on a continuous basis at the rate of0.05 to 0.2 mg/L based upon recirculating water flow rates [24].The saturation levels for common cooling-water scales werecalculated, including calcium carbonate, calcium sulfate, amorphoussilica, and magnesium hydroxide. Brucite saturation levels wereincluded because of the potential for magnesium silicate formation asa result of the adsorption of silica upon precipitating magnesiumhydroxide. Three categories of systems were encountered [24]:• Category 1: The theoretical chemistry of the concentratedwater was not scale-forming (i.e., undersaturated).• Category 2: The concentrated recirculating water would havea moderate to high calcium carbonate scale-forming tendency.Water chemistry observed in these systems was similar tothat in systems run successfully using traditional scaleinhibitors such as phosphonates.• Category 3: These systems demonstrated an extraordinarilyhigh-scale potential for at least calcium carbonate and brucite.

These systems operated with a recirculating water chemistryC o r r o s i o n b y W a t e r 32325 42 58 75 92 108 1251008367503317000.511.522.533.5Degree of saturationTemperature% InjectionFIGURE 8.24 Hot gas-well barite degree of saturation as a function oftemperature and reinjected boiler water.similar to that of a softener rather than of a cooling system. TheCategory 3 water chemistry was above the maximum saturationlevel for calcium carbonate for which traditional inhibitorssuch as phosphonates are able to inhibit scale formation.Table 8.19 outlines the theoretical versus actual water chemistryfor the 13 systems evaluated. Saturation levels for the theoretical andactual recirculating water chemistries are presented in Table 8.20. Acomparison of the predicted chemistries to observed systemcleanliness revealed the following:• Category 1 (recirculating water chemistry undersaturated).The systems did not show any scale formation.• Category 2 (conventional alkaline cooling system controlrange). Scale formation was observed in eight of the nineCategory 2 systems evaluated.• Category 3 (cooling tower as a softener). Deposit formationon heat-transfer surfaces was not observed in most of thesesystems.System Calcium Magnesium Silica(Category) T a Ab Dc T a Ab Dc T a Ab Dc System Cleanliness1 (1) 56 43 13 28 36 −8 40 52 −12 No scale observed2 (2) 80 60 20 88 38 50 24 20 4 Basin buildup3 (2) 238 288 −50 483 168 315 38 31 7 Heavy scale4 (2) 288 180 108 216 223 −7 66 48 18 Valve scale

5 (3) 392 245 147 238 320 −82 112 101 11 Condenser tube scale6 (3) 803 163 640 495 607 −112 162 143 19 No scale observed7 (3) 1464 200 1264 549 135 414 112 101 11 No scale observed8 (3) 800 168 632 480 78 402 280 78 202 No scale observed9 (3) 775 95 680 496 78 418 186 60 126 No scale observed10 (3) 3904 270 3634 3172 508 2664 3050 95 2995 Slight valve scale11 (3) 4170 188 3982 308 303 5 126 126 0 No scale observed12 (3) 3,660 800 2860 2623 2972 −349 6100 138 5962 No scale observed13 (3) 7930 68 7862 610 20 590 1952 85 1867 No scale observedTa = theoretical (ppm)Ab = actual (ppm)Dc = differencel (ppm)TABLE 8.19 Theoretical vs. Actual Recirculating Water Chemistry324System Calcite Brucite Silica(Category) T a Ab T a Ab T a Ab Observation1 (1) 0.03 0.02 <0.001 <0.001 0.20 0.25 No scale observed2 (2) 49 5.4 0.82 0.02 0.06 0.09 Basin buildup3 (2) 89 611 2.4 0.12 0.10 0.12 Heavy scale4 (2) 106 50 1.3 0.55 0.13 0.16 Valve scale5 (3) 240 72 3.0 0.46 0.21 0.35 Condenser tube scale6 (3) 540 51 5.3 0.73 0.35 0.49 No scale observed7 (3) 598 28 10 0.17 0.40 0.52 No scale observed8 (3) 794 26 53 0.06 0.10 0.33 No scale observed9 (3) 809 6.5 10 <0.01 0.22 0.27 No scale observed10 (3) 1198 62 7.4 0.36 0.31 0.35 Slight valve scale11 (3) 1670 74 4.6 0.36 0.22 0.44 No scale observed12 (3) 3420 37 254 0.59 1.31 0.55 No scale observed13 (3) 7634 65 7.6 0.14 1.74 0.10 No scale observedTa = theoretical (ppm)Ab = actual (ppm)TABLE 8.20 Theoretical vs. Actual Recirculating Water Saturation Level325326 C h a p t e r 8 The study revealed that calcium carbonate (calcite) scale formedmost readily on heat-transfer surfaces in systems operating in a calcitesaturation level range of 20 to 150 mg/L, the typical range forchemically treated cooling water. At much higher saturation levels, inexcess of 1000, calcite precipitated in the bulk water. Because of theoverwhelming high surface area of the precipitating crystals relativeto the metal surface in the system, continuing precipitation wouldlead to growth on crystals in the bulk water rather than on heattransfersurfaces. The presence of ozone in cooling systems did notappear to influence calcite precipitation and/or scale formation.8.8.3 Optimizing Calcium Phosphate Scale InhibitorDosage in a High-TDS Cooling SystemA major manufacturer of polymers for calcium phosphate scale

control in cooling systems has developed laboratory data on theminimum effective scale inhibitor (copolymer) dosage required toprevent calcium phosphate deposition over a broad range of calciumand phosphate concentrations, and a range of pH and temperatures.The data were developed using static tests, but have been observed tocorrelate well with the dosage requirements for the copolymer inoperating cooling systems. The data were developed using test waterswith relatively low levels of dissolved solids. Recommendations fromthe data were typically made as a function of calcium concentration,phosphate concentration, and pH. This database was used to projectthe treatment requirements for a utility cooling system that usedgeothermal brine for makeup water. An extremely high dosage (30 to35 mg/L) was recommended based upon the laboratory data [22].It was believed that much lower dosages would be required inthe actual cooling system because of the reduced availability ofcalcium anticipated in the high-TDS recirculating water. As a result, itwas believed that a model based upon dosage as a function of theion-association model saturation level for tricalcium phosphatewould be more appropriate, and accurate, than a simple lookup tableof dosage versus pH and analytical values for calcium and phosphate.Tricalcium phosphate saturation levels were calculated for each ofthe laboratory data points. Regression analysis was used to develop amodel for dosage as a function of saturation level and temperature.The model was used to predict the minimum effective dosage forthe system with the makeup and recirculating water chemistry foundin Table 8.21. A dosage in the range of 10 to 11 mg/L was predicted,rather than the 30 mg/L derived from the lookup tables. A dosageminimization study was conducted to determine the minimumeffective dosage. The system was initially treated with the copolymerat a dosage of 30 mg/L in the recirculating water. The dosage wasdecreased until deposition was observed. Failure was noted whenthe recirculating water concentration dropped below 10 mg/L,validating the ion–association-based dosage model.C o r r o s i o n b y W a t e r 327Water Analysis at 6.2 CyclesDeposition PotentialIndicators• Cations • Saturation LevelCalcium (as CaCO3) 1339 Calcite 38.8Magnesium (as CaCO3) 496 Aragonite 32.9Sodium (as Na) 1240 Silica 0.4• Anions Tricalcium phosphate 1074Chloride (as Cl) 620 Anhydrite 1.3Sulfate (as SO4) 3384 Gypsum 1.7Bicarbonate (as HCO3) 294 Fluorite 0.0Carbonate (as CO3) 36 Brucite <0.1

Silica (as SiO2) 62 • Simple IndicesParameters Langelier 1.99PH 8.40 Ryznar 4.41Temperature (°C) 36.7 Practical 4.201/2 Life (hours) 72 Larson-Skold 0.39Recommended Treatment100% Active Copolymer (mg/L) 10.53TABLE 8.21 Calcium Phosphate Inhibitor Dosage Optimization ExampleReferences1. Petroleum and Natural Gas industries—Materials for Use in H2S-ContainingEnvironments in Oil and Gas Production. NACE MR0175/ISO 15156. Houston,Tex.: NACE International, 2001.2. Koch GH, Brongers MPH, Thompson NG, Virmani YP, Payer JH. Corrosion Costsand Preventive Strategies in the United States. FHWA-RD-01-156. Springfield,Va.: National Technical Information Service, 2001.3. Kirmeyer GJ, Wagner I, Leroy P. Organizing corrosion control studies andimplementing corrosion control strategies. In: Internal Corrosion of WaterDistribution Systems. Denver, CO: American Water Works Association, 1996;487–540.4. Deterioration and inspection of water distribution systems: a best practice bythe national guide to sustainable municipal infrastructure. Deterioration andInspection of Water Distribution Systems. Issue No. 1.1. Ottawa, Canada: NationalResearch Council of Canada, 2003.5. Romanoff M. Underground Corrosion. Houston, Tex.: NACE International,1989.6. Makar JM, Kleiner Y. Maintaining Water Pipeline Integrity. NRCC-43986. Ottawa,Canada, National Research Council, 2001.7. Makar JM, Chagnon N. Inspecting Systems for Leaks, Pits, and Corrosion. AmericanWater Works Association. 1999; 91: 36–46.8. Davies M, Scott PJB. Guide to the Use of Materials in Waters. Houston, Tex.: NACEInternational, 2003.328 C h a p t e r 89. Roberge PR. Handbook of Corrosion Engineering. New York, N.Y.: McGraw-Hill,2000.10. Berry WE. Water corrosion. In: Van Delinder LS, Brasunas Ad, eds. CorrosionBasics. Houston, Tex.: NACE International, 1984; 149–76.11. Uhlig HH. Iron and steel. In: Uhlig HH, ed. The Corrosion Handbook. New York,N.Y.: John Wiley and Sons, 1948; 125–43.12. Hartt WH, Culberson CH, Smith SW. Calcareous deposits on metal surfaces inseawater—A critical review. Corrosion. 1984; 40: 609–18.13. Crovetto R, Murtagh E. Novel boiler condensate corrosion inhibitor with FDAapproval. CORROSION 2007, Paper #073. Houston, Tex.: NACE International,2007.14. Herro HM, Port RD. The NALCO Guide to Cooling Water Systems Failure Analysis.New York, N.Y.: McGraw-Hill, 1993.15. Syrett BC, Gorman JA. Cost of corrosion in the electric power industry—An

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