A Study of Corrosion Control with Sodium Hexametaphosphate

Pallo, Peter E.

doi:10.1002/j.1551-8833.1946.tb17606.x

Cited by 6 publications

(5 citation statements)

References 3 publications

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“…There are very mixed results for the effect of flow velocity (see Eliassen et al (1956) and Pallo (1946) for a review). It is thought that two factors are dominant: increased flow provides more oxygen for the corrosion reaction, but it can also hasten the precipitation of a protective layer.…”

Section: Mixed Results Available On Effect Of Water Velocitymentioning

confidence: 99%

“…There is anecdotal evidence that phosphate inhibitors perform poorly at low flow or stagnant conditions (Rompre et al, 1999;Larson, 1957;Cohen, 1946;Hatch & Rice, 1945b;Hatch & Rice, 1940), and several studies found that phosphate inhibitors had no effect or actually increased iron corrosion under such conditions (McNeill & Edwards, 2000;Maddison & Gagnon, 1999;Rice, 1947;Pallo, 1946).…”

Section: Mixed Results Available On Effect Of Water Velocitymentioning

confidence: 99%

“…The original polyphosphate, known as sodium hexametaphosphate, glassy phosphate, or metaphosphate glass, had the approximate chemical formula Na 22 P 20 O 61 . Numerous studies found that polyphosphate could prevent corrosion and/or control red water (Facey & Smith, 1995;Williams, 1990;Huang, 1980;McCauley, 1960a;McCauley, 1960b;Hamilton & Flentje, 1958;Illig Jr., 1957;Larson, 1957;Uhlig et al, 1955;Lamb & Eliassen, 1954;Parham & Tod, 1953;Hatch, 1952;Raistrick, 1952;Barbee, 1947;Rice, 1947;Cohen, 1946;Pallo, 1946;Hatch & Rice, 1945a;Hatch & Rice, 1945b;Hatch & Rice, 1940). Corrosion prevention and red water control are in fact two very different phenomena, but this distinction was sometimes overlooked in these studies.…”

Section: Phosphate Inhibitors Play a Mixed Rolementioning

confidence: 99%

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IRON PIPE corrosion IN DISTRIBUTION SYSTEMS

McNeill¹,

Edwards²

2001

Journal AWWA

264

112

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This literature review summarizes the results of 100 years of corrosion studies, citing information from almost 300 peer‐reviewed articles to provide the water industry with an updated understanding of factors that influence the complex process of iron pipe corrosion. These factors include water quality and composition, disinfectant residuals, pipe age, scale formation, temperature, flow conditions, biological activity, and corrosion inhibitors. The authors review the reported role of these factors and highlight discrepancies in the literature. The article also discusses corrosion indexes that are intended to help control corrosion. In particular, it reiterates conclusions of prior studies regarding the Langelier index. Although this index continues to be widely used, it does not provide an effective means of controlling iron corrosion. Finally, a review of potential implications of existing and upcoming regulations, including the Lead and Copper Rule, the Disinfectants/Disinfection Byproducts Rule, and the Enhanced Surface Water Treatment Rule, for iron corrosion is also presented.

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Section: Mixed Results Available On Effect Of Water Velocitymentioning

confidence: 99%

Section: Mixed Results Available On Effect Of Water Velocitymentioning

confidence: 99%

Section: Phosphate Inhibitors Play a Mixed Rolementioning

confidence: 99%

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IRON PIPE corrosion IN DISTRIBUTION SYSTEMS

McNeill¹,

Edwards²

2001

Journal AWWA

264

112

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“…[4][5][6][7][8][9] However, there is anecdotal evidence that phosphate inhibitors perform poorly at low flow or stagnant conditions, 6,[10][11][12][13] and three studies found that phosphate inhibitors either had no effect or actually increased iron corrosion under such conditions. [14][15][16] Thus, the current study was undertaken to rigorously examine long-term phosphate performance in a variety of water qualities under stagnant conditions. These conditions simulate the worst case stagnation times that might be found in "dead-end" sections of a distribution system or in home plumbing.…”

Section: Introductionmentioning

confidence: 99%

Phosphate Inhibitors and Red Water in Stagnant Iron Pipes

McNeill

Edwards

2000

J. Environ. Eng.

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This four-year study evaluated the effect of phosphate inhibitors on the corrosion of iron pipes under extended stagnant water conditions. Study parameters included pH and alkalinity, age of the pipe, water stagnation time, and inhibitor type. For iron release, addition of phosphate inhibitors had no statistically significant effect (at 95% confidence) in two-thirds of the experiments. In the remaining experiments, addition of orthophosphate or zinc orthophosphate always increased iron concentration. Polyphosphate addition decreased iron release at only one water quality and increased it at other conditions. For weight loss, polyphosphate inhibitor dosing did not decrease the extent of scale buildup or overall weight loss. Orthophosphate dosing reduced overall weight loss at only one water quality condition; at all other conditions, the addition of orthophosphate had a detrimental effect.

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“…Inhibiting corrosion of iron and steel in water solutions by small additions of sodium polyphosphates, of which sodium metaphosphate is an example, has been described in the literature since 1940 (1)(2)(3)(4). Engineering applications have sometimes led to doubtful results (5)(6)(7). Laboratory tests show that high concentrations of metaphosphates increase corrosion (3), but smaller additions reduce attack, optimum effects being obtained in the presence of calcium ion (3), together with agitation or continuous flow of inhibited solution, and in presence of dissolved oxygen (4).…”

Section: Introductionmentioning

confidence: 99%

Effect of Oxygen, Chlorides, and Calcium Ion on Corrosion Inhibition of Iron by Polyphosphates

Uhlig¹,

Triadis²,

Stern³

1955

J. Electrochem. Soc.

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Data are presented showing that sodium polyphosphates are effective corrosion inhibitors for steel, provided the dissolved oxygen Concentration is above a critical minimum. Presence of calcium ion appreciably improves inhibition under all conditions. In solutions containing less than the critical amount of oxygen (1 ml/l), 60 ppm sodium polyphosphate accelerates corrosion. This is also true when 60 ppm Ca ++ is added to the polyphosphate solution, although the critical oxygen concentration is now about 0.15 ml/1.Sixty ppm sodium polyphosphate effectively inhibits against Cor~'osion in solutions containing up to 0.01% NaC1; above this concentration, passivity by dissolved oxygen is lost, and the inhibitor is no longer effective. However, the calcium complex continues to function to some extent even at high chloride ion concentrations.The foregoing corrosion data combined with polarization and potential studies indicate that sodium polyphosphates inhibit by favoring the passivation of steel by adsorbed oxygen. The hydrous FeO film normally present on iron presumably reacts with polyphosphate to form a soluble complex, permitting higher surface concentrations of oxygen for a given concentration in solution. Corrosion control under these circum~ stances is mixed, and pitting occurs in presence of chlorides. Calcium salt additions lead to formation on cathode areas of a diffusion barrier film of unknown structure containing both calcium and phosphorus. This film appreciably reduces the corrosion rate, with control of corrosion, however, remaining mixed. Reasons for the need of continuous flow and aeration in practical systems are discussed.

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A Study of Corrosion Control with Sodium Hexametaphosphate

Cited by 6 publications

References 3 publications

IRON PIPE corrosion IN DISTRIBUTION SYSTEMS

IRON PIPE corrosion IN DISTRIBUTION SYSTEMS

Phosphate Inhibitors and Red Water in Stagnant Iron Pipes

Effect of Oxygen, Chlorides, and Calcium Ion on Corrosion Inhibition of Iron by Polyphosphates

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