NBSIR 75-923

Corrosion of Metallic Piping on

Military Bases - A Survey

Paul Wencil Brown

and

James R. Clifton

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

November 1975

Final

Prepared for Office of the Chief of Engineers, U.S. Army

Washington, D. C. 20314

Directorate of Civil Engineering, U.S. Air Force

Washington, D. C. 20330

Naval Facilities Engineering Command, U.S. Navy

Alexandria, Va. 22332

NBSIR 75-923

CORROSION OF METALLIC PIPING ON

MILITARY BASES - A SURVEY

Paul Wencil Brown

and

James R. Clifton

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

November 1975

Final

Prepared for Office of the Chief of Engineers, U.S. Arnny

Washington, D. C. 20314

Directorate of Civil Engineering, U.S. Air Force

Washington, D. C. 20330

Naval Facilities Engineering Command, U.S. Navy

Alexandria, Va. 22332

U.S. DEPARTMENT OF COMMERCE, Rogers C.B. Morton, Secretary

James A. Baker, III, Under Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

TABLE OF CONTENTS

Page

ABSTRACT iv

1. INTRODUCTION 1

2. REVIEW OF THE CORROSION SURVEYS 1

3. WATER VARIABILITY 2

k. PIPING SYSTEMS k

h.l Potable Water Systems , k h.1,1 Corrosion Evaluation of Water Systems k h,2 Heat Distribution Systems 8 h.3 Cooling Systems 10

h .h Fire Protection Systems 11

U.5 Gas Lines 11

5, RECOMMENDATIONS AND CONCLUSIONS 12

6. REFERENCES ik

iii
ABSTRACT

The results of surveys of the extent of corrosion of metallic piping systems at

selected military installations have been analyzed. Potable water, fire protection, heat

distribution, cooling, and natural gas distribution systems are included in these surveys.

The corrosion evaluation techniques used in these surveys and the types of protection

applied are discussed. General recommendations regarding continuation and extension of

these surveys are given.

Keywords: Corrosion; corrosion control; metallic piping; nondestructive evaluation; survey;

water hardness.

iv
1 . INTRODUCTION

The corrosion of metallic piping systems is a nationwide problem resulting in interrupted

operations and expensive repairs. The costs associated with corrosion-related failures have

been estimated to be 22 billion dollars annually. The extent of piping corrosion problems

at military facilities, while likewise presumed to be high, has not been well identified.

This indicates the need to characterize the type and frequency of corrosion failures encountered at military facilities in order to more effectively evaluate and recommend

corrosion control procedures.

Accordingly, as part of an on-going corrosion survey program, the metallic piping systems

of selected Air Force installations have been inspected by Air Force personnel to determine

the extent of corrosion. Selected surveys have been reviewed and form the basis for the

present report in which the most common corrosion problems are identified and discussed.

Recommendations of methods to minimize the corrosion of piping systems and methods to improve

the corrosion inspections are also given.

This study was carried out with Tri-Service support.

2. REVIEW OF THE CORROSION SURVEYS

The corrosion surveys [l-ll], conducted by military personnel, were for the most part

limited to the following fluid transportation systems:

1) Potable water systems

2) Fire protection systems

3) Natural gas lines

h) Heat distribution systems

5) Cooling systems.

1
Corrosion problems in sewage disposal systems and in systems designed to carry liquid

fuel or highly corrosive materials were not considered. With the exception of natural gas

lines, both interior and exterior surfaces were examined for corrosion. The sites included

in this survey are:

1) Goodfellow AFB, Texas . .

2) McClellen AFB, California ,

'

3) Homestead AFB, Florida , .. . ^

h) Bobbins AFB, Georgia

5) Altus AFB, Oklahoma

6) Richards-Gebaur AFB, Missouri ,^ ,. ,

7) Elgin AFB, Florida : - - -. .^....-rj

8) Tinker AFB, Oklahoma ,

• .

,

9) Andrews AFB, Maryland

10) F.E. Warren AFB, Wyoming .. .;; . ..

11) Loring AFB, Maine. y,^.

The data analyzed in the following sections have been taken from these surveys.

3. WATER VARIABILITY ,

Water samples from the sites included in the survey were chemically analyzed. These

analyses revealed that the nature of the water varied from hard and scale-forming to soft

and corrosive. The range of the properties of the water is indicated in table 1. Hard

water contains dissolved alkaline materials such as calcium bicarbonate which may inhibit

but also tend to deposit on the interior walls of piping systems. Hard water is

usually obtained from wells and its high mineral content is the result of mineral extraction

during underground flow. Protective films of chalky rust, a mixture of calcium carbonate

and iron oxide, may be formed on ferrous piping transporting hard water in the presence of

calci\Jim bicarbonate if the CO^ content of the water is limited to the amount required for

its stabilization [12]. In this case, a very small pH rise will suffice to supersaturate

the water near the metal with calcium carbonate. However, protection is obtained only

2
if sufficient oxygen is available to oxidize ferrous compounds to the less soluble ferric

compounds. Solid material that precipitates at points remote from pipe walls does not form

an adhering protective coating. Soft water may also contain dissolved minerals, but their

concentrations are usually lower. Soft water is generally obtained from sources at or near the earth's

svirface and is corrosive due to the presence of carbonic acid. Carbonic acid may be formed

by the dissolution of atmospheric CO^ or from CO^ generated by rotting vegetation. Cascading

of such water is helpful in minimizing corrosion [l3]. Cascading allows COg gas to escape

shifting the following reaction to the right:

"2^03 HgO + CO^.

CaCO^ addition may or may not be of value in the treatment of aggressive water. The

Langlier saturation index [l^] is commonly used to characterize the aggressiveness of CO^

in water and its value indicates the difference between the initial pH value and that after

treatment with CaCO^. A negative value indicates the inability of water to develop a protective film.

TABLE 1

Range of Properties of Potable Water

at Military Facilities 1-11

Analysis Maximum Minimum

pH 9.9 6.6

Total Alkalinity^ '"^ 265 30

Ca Hardness^-"-^ 355 ^0

Total Hardness ^"""^ 205 ^5

Dissolved Solids 950 63

Conductivity (ymho/cm) 2300 I60

Langlier Index +2.3 -1.5

Dissolved Oxygen (ppm) 9.8 1.0

(1) Expressed as equivalent ppm CaCO^.

(2) Calculated from conductance reading.

3
k. PIPING SYSTEMS .

k.l Potable Water Systems " -> ' <: -

. i

The sites examined in this survey are geographically widely dispersed including various

soil and climatic conditions, fig\ire 1. The variabilities in the water supplied to these

sites may therefore be considered reasonably representative of those encountered at most

military installations within the continental U.S. • ' '

Radiography was the technique primarily employed in the evaluation of the severity of

both corrosion and scale formation in undisturbed building service water lines. In some

cases, however, excavations were carried out and then radiographic analyses performed. In

one instance, an electrical potential survey of a water main was performed [lO] because this

main had leaked in the past. The presence of corrosion cells was indicated by the variation

in measured potentials. Accordingly, a cathodic protection current requirement measurement

was made and indicated a very large protection current requirement of 230 amps. Failures of

this type may be expected when inadequate attention is directed toward factors such as soil

conditions. Soil resistivity measurements, also a part of this survey, were performed at

this base. Values as low as 1550 fi-om were measured, indicative of an environment in which

corrosion of an unprotected ferrous structure can be expected (table 2). Specifically, soil

resistivities less than 10,000 ^-cm are considered corrosive to steel, while those less than

5,000 fi-cm corrosive to cast iron [16-I7].

U.1.1 Corrosion Evaluation of Water Systems

TABLE 2 [15]

Soil Corrosivity vs Resistivity

Resistivity, fi-cm Corrosivity

Below 500 Very corrosive

500-100 Corrosive

1000-2000 Moderately corrosive

2000-10,000

Above 10,000

Mildly corrosive

Progressively less

corrosive
5
Soil resistivities along actual and proposed routes for underground metallic pipe

should be routinely measured. These measurements are useful in the location of low resistivity

areas, hot spots, to determine proper anode placement and in the estimation of external protective coating requirements for pipes. Soil resistivity measurements should he carried

out at different times throughout the year in order to take account of the soil moisture

content as this will affect protection current requirements. In addition, remeasurement

should be carried out on a routine basis. This is especially important in areas where a

build-up of hygroscopic electrolytes, such as deicing salts, may occur.

I

While numerous soil evaluation techniques exist [l8 ] , the measurement of soil resistivity

is the most widely used criterion in the assessment of soil corrosivity. Investigations

have both supported the value of this criterion [l9 ] and cautioned against its use [20-2L].

However, it is generally agreed that resistivity measurement provides the best single

indication of the corrosivity of soil. These measurements may be made in 2 ways. The Wenner

k probe method [22 ] involves the measiarement of the potential between 2 probes driven into

the ground. Current is supplied by an additional 2 probes. This technique allows the

meas\irements to be taken at the site without disturbing the soil. The soil box method [23]

requires obtaining a core sample from the soil and measuring its resistance directly. The

advantages of the Wenner method lie in its ease and speed. In addition, the resistance of a

large soil volume is measured thereby improving accuracy. The principal advantage of the

soil box method is that it is possible to intentionally vary the moisture content of the soil.

Although the Wenner method was used exclusively in the soil resistivity measurements included

in this s\irvey, the soil box method is of value in testing soils in areas where substantial

annual moisture variations occur.

In general, the water lines examined in this survey are in good condition having slight

to moderate amounts of pitting or scale. When evaluating the degree of scale deposition on

building service water lines, both hot and cold water lines should be examined in the fut\ire

inspections, particularly in areas where hard, untreated water is used. A greater degree of

scale build-up occurs in hot water lines and, especially in water heaters due to water

evaporation and CaCO^ precipitation. However, overall indications were that the levels of

water treatment were adequate. Radiographic, ultrasonic, or other appropriate corrosion

6
detection measurements should te carried out on a routine basis, preferably at representative

and fixed points, to determine the deterioration rates and hence the projected lifetimes of

these systems.

One technique upon which undue reliance seems to be placed is that of electrical

potential measurement. Measurements of this type, if properly conducted, may give information

as to the thermodynamic probability of corrosion taking place. These measurements, however,

provide no kinetic or corrosion rate information. The traditional assumption that a potential

of -O.85 volt between buried ferrous structure and a Cu-CuSO^^ electrode is indicative of

adequate cathodic protection is not necessarily valid. Voltage gradients, or the presence

of junction potentials may act to invalidate this assumption [2^+ ]

Linear polarization is a technique by which the dynamics of the corrosion process may

be readily determined [25-26]. This technique has the advantage of allowing in-situ corrosion

rate measurements. In addition, the instr\imentation may be remote from the corroding body.

An electrode may be inserted in the wall of a buried pipe either during installation or after

excavation. By establishing a test station at the ground surface after backfilling, corrosion

rate measiorements can be carried out on a routine basis. Disadvantages in this method lie

in the expense of the electrodes and instrumentation and in that it is not possible to

ascertain the type of corrosive attack, such as general, pitting, etc., by this technique.

Radiography probably provides the most powerful nondestructive evaluation technique

by which the extent of corrosion may be ascertained because it provides information both

as to the type and degree of deterioration. However, determination of the degree of

general corrosion is difficult unless a reference point of known thickness is available [27].

The major limitation of radiography lies in the requirement of access to both sides of the

structure undergoing inspection. Ultrasonics and eddy current techniques [28-29] may also be

used to detect wall thickness discontinuities and corrosion pitting and are well suited for

absolute thickness measurements. Although these techniques are not useful in the detection

of scale and sediment deposits, they are useful corrosion assessment techniques where access

is limited as in the building service lines.

7
h.2 Heat Distribution Systems

Of all systems included in this survey, heat distribution systems, due to their

complexity and their operation at elevated temperatures, are probably the most susceptible

to corrosion failure. The results of this survey indicate that a large part of this

vulnerability lies in the fact that, while the proper corrosion control measures exist, they

have either not been instituted or have been largely ignored.

The survey of the heat distribution systems consisted primarily of chemical analyses of

boiler water and condensate samples and the radiographic examination of the steam and condensate return lines. Analyses of boiler feed water and ultrasonic thickness measurements

were carried out in some cases. Radiographic examination of the steam lines of the boiler

systems included in this survey indicated them to be free of serious scale and pitting in

most instances. The corrosion observed in the condensate return lines, however, may be

characterized as moderate to severe. This indicates that the water treatment programs are

adequate to protect the steam lines but in most cases do not afford sufficient protection to

the condensate return systems. .in'

It was noted that improper procedures regarding the addition of meike-up water were

being followed at several of the sites. Water softening units were either being by-passed

or exhausted zeolite exchangers were not reactivated. In addition, de-aeration units were

found to be operating ineffectively. The introduction of oxygen and CO^ into boiling

systems may result in severe pitting and channeling in condensate return lines. The

addition of volatile inhibiting amines may be used to neutralize absorbed CO^. Care must

be taken in doing this, however, because these compounds tend to accelerate the corrosion of

any nonferrous metals present in the system. Furthermore, it is difficult to estimate the

concentration of these amines in the areas which are remote from the boiler. While there

are a number of proprietary corrosion inhibiting compounds marketed, their use is not

recommended. Uncertainties, as to their effectiveness and their compatibility with other

additives, combined with the inability to adjust the relative amounts of their constituents

weigh heavily against the use of proprietary inhibitors.

8
One instance was reported [5] where a ferrous condensate return line was replaced by

a section of continuous filament fiberglass reinforced plastic pipe. Apparently, the use of

this material is under consideration by the military for inclusion in the various service

manuals. However, further investigation may be warranted prior to the acceptance of this

material as a substitute for metallic pipe in boiler systems since degradation due to

inhibitor attack may result

Chemical analyses of both the boiler water and the condensate were carried out in most

cases. The extremes of these analyses are listed in table 3. The variability of the

analyses listed in this table and their deviations from recommended values [30 ] is indicative

of the inadequacy of the treatment programs. Generally, the pH of the condensate was lower

than that of the boiler water although in one boiler system it was actually higher. Substantial concentrations of dissolved solids, oxygen, and CO^ were observed. Although most steam

lines were reported to be scale free, dissolved solid precipitation was noted to have caused

sediment build-up and flow restriction in at least one system.

Boilers are also susceptible to corrosion when idle. If the dry lay up method is used,

sedimentary deposits, due to their tendency to retain moisture may, during off-season shut

down periods, lead to accelerated corrosion. Even proper drainage after shut down will not

alleviate this problem. The presence of condensed moisture droplets, because of incomplete

drying, may also result in pitting due to the introduction of oxygen or 00^ into the system

as the pressure is dropped. The inleakage of feed water to a dry boiler system may lead to

corrosion by a similar mechanism. Complete drying by the addition of a suitable drying

agent, such as quicklime, or the circulation of dry air under positive pressure is recommended |o 1 •

The wet lay up method, that is filling the boiler system with treated water, may be

used as well. However, deaerated water should be used to avoid pitting corrosion. Maintenance of proper pH through NaOH or Na^SO^ addition should be carried out by continuous feeding

as this will minimize concentration gradients and hence corrosion cells.

9
TABLE 3

Analyses of Boiler Water and Condensate

Analysis

Boiler Water

Max Min

Recommended

[30]

Condensate

Max Min

Recommended

[30]

pH 12 8 10.5-11.5 8.3 5.3 7.5-8.5

Ca Hardness*

(Mmho/cm)

120 0 min.

Dissolved Solids

(ppm)

10,000 765 1000-UoOO 780 2 min.

Dissolved Oxygen*

(ppm)

6.8 0 1 ppm 5.6 0 1 ppm

COg (ppm) min. 20 0 min.

Iron ( ppm

2.5 0 min.

*feed water

h . 3 Cooling Systems

The cooling systems survey was limited to radiographic analyses of cooling water lines

and chemical analyses of cooling water samples. The cooling systems at two of the sites were

not inspected and the examination of several of the others were rather restricted, apparently

because maintenance is carried out on a contract "basis.

: ' o.i

'

Radiographic analyses were carried out at six sites. These analyses indicated the

presence of slight to moderate amounts of scale with a small amount of pitting. Visual

inspection of the cooling lines revealed that moisture condensation had saturated the thermal

insulation in several cases. In addition to increasing the probability of corrosion since

cathodic protection cannot be applied to cooling lines, the presence of moisture will greatly

reduce thermal barrier effectiveness.

The chemical analyses of the cooling water revealed both the pH values and the concentrations of dissolved solids to be above acceptable limits in almost all instances. The

extremes of these analyses are listed in table h. Concentrations of dissolved solids and pH

values in the ranges indicated in table k are conducive both to scale formation and algae

growth. Scale formation and algae growth not only reduce cooling efficiency but may also

result in flow restriction or blockage. Fortunately, control of algae and scale is easily

IQ,
accomplished "by pH control. Maintaining pH values in the recommended, range along with the

addition of small amounts of algicide, sodium hexametaphosphate complexer and other inhibitors

should afford adequate control. The phosphate inhibitor will complex CaCO^ and also inhibit

corrosion if the proper concentration of dissolved solids is maintained. Other types of

corrosion inhibitors may be added to cooling systems although chromates should be avoided due

to their toxicity.

TABLE k

Analyses of Cooling Tower Water

Observed

Analysis Max Min Recommended

pH 9.1 8.1 6.5-7.5

Dissolved solids (ppm) 12000 l80 600-1000

Chromates (ppm) 30 0

k.h Fire Protection Systems

The condition of the fire protection systems appears to be comparable to that of the

potable water systems. However, the surveys of several of the sites indicated that build-up,

of substantial amounts of scale and sediment had occurred in the piping. This is a potentially serious problem since this could result in the clogging of sprinkler heads. Flow testing with flushing on a routine basis should be adequate to alleviate this condition. Sediment

build-up can present serious problems even beyond that of flow restriction. For example,

sediment build-up across dielectric joints may provide high conductivity paths across these

joints and thereby allow galvanic corrosion. The measurement of the electrical resistivities

across these joints should give a reasonable indication of the severity of the problem.

U. 5 Gas Lines

The gas lines inspected in this survey, when cathodically protected, were for the most

part in good condition. A section of a cast iron gas main at one of the sites was found to

be unprotected [8]. Cathodic protection was unfeasible in this instance because this section

11
of pipe was not electrically continuous. It was recommended by the survey team that the

economic feasibility of excavating this section, electrically connecting the joints, and

applying cathodic protection be investigated. After the expenses of remedial measures of

this type are evaluated against those of premature replacement, appropriate action should be

taken.

One line which was cathodically protected had failed [5]. This failure was attributed

to the presence of holidays in the pipe coating. Because the coating was poorly bonded to

the pipe, the presence of holidays allowed moisture to migrate into the areas between the

coating and the pipe wall. These areas were not cathodically protected, because the coating

was an electrical insulator, and a corrosion failure resulted.

Soil resistivity has an important impact on the degree of cathodic protection. Seasonal

moisture variations, for example, may cause a piping system to become either under- or

over-protected. Underprotection may lead to direct corrosion attack while overprotection

can result in coating damage. If excess potential is applied to a coated structure, free

hydrogen will be evolved. Hydrogen gas bubbles may coalesce and exert pressure sufficient

to cause disbonding and ruptxire of a coating. .. j ;

• < '.!:

The detection of holidays in buried pipe coatings should be carried out prior to the

initial backfilling and after any excavation as a matter of routine. In addition to visual

and electrical inspection for holidays per se, coating thickness and moisture content

detectors exist which may be used in the evaluation of coating quality and dvirability.

5. RECOMMENDATIONS AND CONCLUSIONS . i ^ u>

1) The surveys discussed in this report provide an excellent starting point for the

analysis of the type, frequency, and severity of the corrosion problems encountered. However,

greater specificity regarding materials used, age at failure, and failure characterization

would be helpful. . •.

2) A survey program of this type should be instituted and carried out on annual or

semi-annual basis.

12
3) Sufficient data should te collected and then be used to develop criteria to define

adequate performance levels for the various systems studied. Comparative analyses of protection system performance, piping system life prediction, and performance criteria for

materials selection may then be evaluated by consistent deterioration rate observation.

U) The inclusion of corrosion failure cost analyses, such as the Corrosion Costs

Survey, Chanute AFB [31], would also be of benefit in a survey program. Input of this type

would provide a basis for the prediction of funding and manpower requirements attributable

to each class of corrosion failure and would indicate areas in which additional research and

development shotild be carried out

13
6. REFERENCES

1. Corrosion Analysis Survey Report, Goodfellow AFB, Texas, December 1972.

2. Corrosion Analysis Survey Report, McClellen AFB, California, October 1973.

3. Corrosion Analysis Survey Report, Homestead AFB, Florida, November 1973.

k. Corrosion Analysis Survey Report, Rotbins AFB, Georgia, February-March 1973.

5. Corrosion Analysis Survey Report, Altus AFB, Oklahoma, August-September 1973.

6. Corrosion Analysis Survey Report, Richards-Gebaur AFB, Missouri, August-Sept ember 1973.

7. Corrosion Analysis Survey Report, Eglin AFB, Florida, January-February 197^.

8. Corrosion Analysis Survey Report, Tinker AFB, Oklahoma, October 1972.

9. Corrosion Analysis Survey Report, Andrews AFB, Maryland, January-February 1973.

10. Corrosion Analysis Survey Report, F. E. Warren AFB, Wyoming, July-August 1973.

11. Corrosion Analysis Survey Report, Loring AFB, Maine, May-June 1973.

12. U. R. Evans, The Corrosion and Oxidation of Metals , Edward Arnold, London I960, pp.

160-3.

13. E. L. Steatfield, J. Soc . Chem. Ind. 58, 313 (1939).

ih. M. Pourbaix, Lectures on Electrochemical Corrosion , Plenum Press, New York, 1973, p. 75-

15. A. W. Peabody in: NACE Basic Corrosion Course , 1971, pp. 5-17.
16. M. Romanoff, Jnl . AWWA 56 , 1129 (l96U).

17. J. H. Fitzgerald, Jnl. AWWA 60, 882 (1968).

18 . E. Escalante and W. P. Iverson, Unpublished research.

19. J. D. Palmer, Matls. Performance 13, hi (19T^).

20. E. Schaschl and E. A. Marsh, Materials Protection 2, h2k (1963).

21. N. D. Tomashov and Y. N. Mikhailovsky, Corrosion 15, T9t (1959).

22. F. Wenner, NBS Bull. 12, U69 (I9l6).

23. Soil Survey Manual, USDA Handbook 18, 31+3 (1951 ).

2k. J. J, Meany, Jr., Proc. 17th AnnuaJ. Underground Corrosion Short Course , Engr. Expt.

Station Bull. IO6, West Va. Univ., p. 596 (1972).

25. W. J. Schwerdtfeger, Materials Research and Stds. 10, 22 (1972).

26. R. L. Leroy, Corrosion 29, 272 (1973).

27. B. F. Peters, Matls. Evaluation 23, 129 (1965).

28. B. F. Peters, Engineering Journal 55, 20 (1972).

29. W. J. McGonnagle, Nondestructive Testing , Gordon & Beach, 1966, New York, p. 3^6.

30. Boiler-Water-Treatment Manual for Federal-Plant Operators Handbook 5» 1951, Bureau of

Mines, Dept. of Interior.

15
31. R. Heidersbach and W, Mikucki, Letter Report M-89 , Corrosion Costs Siirvey, Chanute AFB,

April 197^^.

USCOMM NBS Dr 16
NBS-114A >Hcv. 1.1 II

u s. OFPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. I'l Hl.l' A 1 K>,\ OK Kl I'OK 1 NO. NBSIR 7-.-'^:' '.

2. Cm)v 't Aci ( ssion No.

3. K( ( i|)i<.iil 's Af cession No.

4. 1 1 ri.i-: AND M l* 1 1 1 1. i:

Corrosion of Metallic Piping on Military Bases - A Survey

5« 1 'u t>l 1 c .1 1 1 on Diitt* November 1975

6. Ptrforminp Or>;.ini/ati<)n (..ode7. Atj lllOR(S)

Paul W. Brown and James R. Clifton

8. Pi-rforminK Orpan. Report No.

'9, i>i:ri-orminc; okc.ani/.a i ion .nami; and addkiiss

national bureau of standards

department of commerce

washington, o.c. 20234

10. Hro|ict/ 1 ask/ work unit No.

11. Contraci/Grant No.

12. Spon.'sorinc Orc.iniz.uiDn N'.imo .>nii ( ompk-tc AJi|rcs.>i (Street, City, State, ZIP)

Office of Chief of Engineers, U.S. Army

Directorate of Civil Engineering, U.S. Air Force

Naval Facilities Engineering Command, U.S. Navy

Washington, D.C.

13» lypt' of Kt'port & t^o r i oti Covered

Final

14. Sponboring Agency Code

15. SUPPLLMENTARY NOTtS

16. ABSTRACT (A 200-word or less (actual summary of most sigfiidcartt information. If document includes a sif^nificant bibliography or literature survey, mention it here.) The results of surveys of the extent of corrosion of metallic piping systems at selected

military installations have been analyzed. Potable water, fire protection, heat distribution, cooling, and natural gas distribution systems are included in these surveys.

The corrosion evaluation techniques used in these surveys and the types of protection

applied are discussed. General recommendations regarding continuation and extension

of these surveys are given.

17, KEY U'ORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons

)

Corrosion; corrosion control; metallic piping; nondestructive evaluation; survey;

vater hardness.

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