NATIONAL BUREAU OF STANDARDS REPORT

6658

REPORT ON FIELD PERFORMANCE OF BITUMINOUS PROTECTED METALS

by

W. C. CULLEN

P. F. WENDELL

W. A. HORTON

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

<2 The functions of the National Bureau of Standards are set forth in the Act of Congress, March

3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and

maintenance of the national standards of measurement and the provision of means and methods for making measurements consistent with these standards: the determination of physical constants and

properties of materials; the development of methods and instruments for testing materials, devices,

and structures; advisory services to government agencies on scientific and technical problems; in- vention and development of devices to serve special needs of the Government; and the development

of standard practices, codes, and specifications. The work includes basic and applied research,

development, engineering, instrumentation, testing, evaluation, calibration services, and various

consultation and information services. Research projects are also performed for other government

agencies when the work relates to and supplements the basic program of the Bureau or when the

Bureau’s unique competence is required. The scope of activities is suggested by the fisting of

divisions and sections on the inside of the back cover.

Publications

The results of the Bureau’s work take the form of either actual equipment and devices or published papers. These papers appear either in the Bureau’s own series of publications or in the journals

of professional and scientific societies. The Bureau itself publishes three periodicals available from

the Government Printing Office: The Journal of Research, published in four separate sections,

presents complete scientific and technical papers; the Technical News Bulletin presents summary

and preliminary reports on work in progress; and Basic Radio Propagation Predictions provides

data for determining the best frequencies to use for radio communications throughout the world.

There are also five series of nonperiodical publications: Monographs, Applied Mathematics Series,

Handbooks, Miscellaileous Publications, and Technical Notes. Information on the Bureau’s publications can be found in NBS Circular 460, Publications of the

National Bureau of Standards ($1.25) and its Supplement ($1.50), available from the Superintendent

of Documents, Government Printing Office, Washington 25, D.C.
NATIONAL BUREAU OF STANDARDS REPORT

MBS PROJECT MBS REPORT

1004-12-10443 5 February 1960 6658

REPORT ON FIELD PERFORMANCE OF BITUMINOUS PROTECTED METALS

by

W. C. Cullen

Floor, Roof and Wall Coverings Section

Building Technology Division

P. F. Wendell

Engineering Division, Military Construction

Office of the Chief of Engineers

W. A. Horton

New England Division, Corps of Engineers

U . S . Army

Sponsored by

Office of the Chief of Engineers

Department of the Air Force

Bureau of Yards and Docks

IMPORTANT NOTICE

NATIONAL BUREAU OF ST

intended for use within the

to additional evaluation and r listing of this Report, either

the Office of the Director, Na

however, by the Government

to reproduce additional copie

irogress accounting .documents Approved for public release by the mally published It is subjected

Director of the National Institute of

; ®n'

i

s

d obVaTn e d' i

n

Pw^it i n^Vrom

Standards and Technology (NIST) Such permission Is not needed, on October 9, 2015. prepared If that agency wishes

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

REPORT ON FIELD PERFORMANCE OF BITUMINOUS PROTECTED METALS

1. INTRODUCTION

Accelerated performance tests have been conducted on samples of bituminous

protected metals produced by three manufacturers on at least four occasions at

the National Bureau of Standards. Specimens of each material were subjected to

a number of laboratory tests which were designed to simulate on an accelerated

basis the various conditions to which these materials may be exposed. The

following tests were included in the laboratory program:

a) Accelerated Weathering Tests.

b) Low Temperature Impact at 0°F. and -30°F.

c) Salt-Spray Tests.

d) Abrasion Tests.

e) Outdoor Exposure Tests.

The results of each series of tests have been reported in detail to the

sponsoring agencies in the following National Bureau of Standards Reports:

a) NBS Report No. 1808 dated 12 August 1952.

b) NBS Report No. 4963 dated 14 December 1956.

c) NBS Report No. 5148 dated 5 February 1957.

d) NBS Report No. 6389 dated 30 April 1959.

As a result of these laboratory tests,, many data are available for the

performance of each material in a given test. It was recognized , however

,

that an accurate interpretation of these data, in terms of actual performance,

was lacking. Therefore, in order to obtain data on the actual field behavior,

a survey was conducted to investigate the performance of each material exposed

under various climatic conditions.

2. FIELD INSPECTIONS

The field inspections were made in November and December 1959 by an inspection team made up of three members representing:

a) Office of the Chief of Engineers, U.S. Army.

b) New England Division, Corps of Engineers, U.S. Army.

c) National Bureau of Standards.*

inspections in the New England Division only.

- 2 -

The inspections were made of various types of structures which employed

protected metals as roofing or siding or both, located at the following Air

Force Installations:

a) New England Division, Corps of Engineers, U. S. Army.

1) Otis A.F.B., Massachusetts.

2) Pease A.F.B., New Hampshire.

3) Westover A.F.B., Massachusetts.

4) Barnes A.F.B., Massachusetts.

5) Bradley A.F.B., Connecticut.

6) Hanscom A.F.B., Massachusetts.

b) Missouri River Division, Corps of Engineers, U. S. Army.

1) Ellsworth A.F.B., South Dakota.

2) Lincoln A.F.B., Nebraska.

3) Lowry A.F.B., Colorado.

4) Sioux A.F.B., Iowa.

5) Forbes A.F.B., Kansas.

6) McConnell A.F.B., Kansas.

7) Richards-Gebaur A.F.B., Missouri.

c) South Atlantic Division, Corps of Engineers, U. S. Army.

1) Hglin A.F.B., Florida.

2) Tyndall A.F.B., Florida.

3) McCoy A.F.B., Florida.

4) Patrick A.F.B., Florida.

The inspections consisted of a. critical examination of each structure

by each member of the team. A previously prepared check list was used to

insure uniformity during the inspections and an inspection form was com- pleted for each structure that was observed. A copy of the inspection form

is attached to this report. When sidings were involved, observations were

made of each exposure, including the upper courses, when facilities for such

inspections were available. In regard to the protected metals used as roofings, "on the roof" inspections were made by the team members. The team was usually accompanied by representatives of the Division and of the Base.

Information regarding the history, age, maintenance, etc., of each installation was supplied by the Base personnel.

- 3

-

3. RESULTS OF INSPECTIONS

Tables 1, 2 and 3 summarize the results of the performance of each

material as they were observed during the inspections. The tables do not,

of course, indicate the severity of the particular deficiencies which were

evident and ranged in degree from mild to severe. For example, a large

proportion of the sheets on a structure may show exposed felt, or exposed

metal, whereas on another structure, only a very small proportion of the

sheets exhibited these defects. However, they establish the trends as to

the types of defects noted and the frequency with which these defects

occurred on a specified material.

The ratings are a summation of the general appearance and performance of

the material on a particular installation. They bear out the general conclusion that protected metals, properly applied, perform adequately even though

individual installations may show a number of minor defects.

In addition to the structures presented in the tables, a number of

additional structures were observed that were not rated, since they were

either erected under the same contract as one that was rated or had been

painted a number of times for reasons not established.

4. DISCUSSION

4.1 Effectiveness of Protection.

If it is considered that the primary function of a protective system is

to prevent the deterioration of the base metal, the field observations

indicated that, in general, Galbestos, Plasteel and Steelbestos performed

adequately.

In many cases the materials which were located in areas subject to

impact (lower courses, doors, corners, etc.) were damaged to such an extent that the base metal was exposed. The Plasteel. material, apparently

is the most frequent offender in this area. It was evident that with this

material, a loss of adhesion between the metal and protecting system resulted

from an impact at a low temperature, and the metal was subsequently exposed

by a secondary force. It is doubtful whether this same condition would exist

if the impact had occurred at a higher temperature (70°F. and above). Of

course, once the base metal is exposed, prompt maintenance is required to

prevent early deterioration. It was also noted that when ice which accumulated

on horizontal surfaces (flashings) of Plasteel was shattered, the weather

coating under the ice was removed completely.

In regard to the loss of the weather coating from material utilizing a felt in the protective system (Galbestos and Steelbestos) , either from

abrasion, sticking of sheets prior to erection, etc., this defect did not

appear to have an immediate effect on the deterioration of the base metal

since some protection from the felt and adhesive was still available.

The use of a tape to protect the raw cut edges as called for in the

specifications appeared to be ineffective since the. tape rarely remained in

place. In addition, the inspections indicated that, except in areas under

severe salt exposure, additional protection for the raw cut edges was not

required.

Failures of the protective systems of Galbestos and Steelbestos were

observed at both factory and field bends, but, in the case of 'Plasteel, this

type of failure was evident only at field bends. The condition of head and

sill flashings of Plasteel (field bends) was such that continuous lengths of

exposed, corroded metal were observed. Factory bends which had cracked and

were recoated appeared to give adequate protection.

A number of instances were noted where patching material, used on Plasteel, was incompatible with the weather coating. Wherever this

material was used the coating had curled, exposing the bare metal.

4.2 Appearance

A primary reason for the poor appearance of Galbestos and Steelbestos

was the failure of the installer to recoat areas where the felt was exposed

during the separation of sheets which had stuck together because of failure

of the anti- stick compound. It was recognized, of course, that the exposed

areas were not readily apparent since the asphalt" saturated felts were black.

However, when exposed, the asbestos felt approached its characteristic white

color shortly (within one year) after erection, because of the rapid

weathering of the asphalt saturant.

The poor appearance of the Plasteel material was attributed to the

uneven loss of mica which occurred on the various sheets during the weathering

process. This condition did not affect the protecting qualities of the

coating, but resulted in a mottled appearance. It was also noted that with

Plasteel, the color of the patching material was not similar to that of the

weather coating after exposure which contributed to a poor appearance.

The number of painted protected metal sheet installations which were

observed during the survey indicated to the team a general dissatisfaction

with the black materials. Frequently, materials of all types which were

installed as little as 4 years had been painted at a considerable cost.

For example, two DC hangars, erected in 1954, were painted in 1958 at a cost of $20,000.
•

'
- 5

-

As a matter of interest, structures constructed of both painted and

unpainted galvanized sheets, in many cases exposed longer than those using

protected metal siding, were observed and were apparently giving satisfactory

service.

4.3 Fasteners

The protected metal sheets on the observed structures were fastened to

the framing members with either the screw- or stud-type fasteners, with few

exceptions. It was the opinion of the inspecting team that the screw-type

fastener gave the better performance. The following deficiencies were common

to the stud-type fasteners:

a) Sheets were not drawn as tightly as with the screw type.

b) Loose sheets were noted at the corner laps, apparently because of

failure to install studs of sufficient length.

c) A greater loss of adhesion of the protecting system to the metal in

the vicinity of the fasteners was more pronounced with the stud-type fasteners.

d) A number of missing caps were observed and, in some cases, broken

studs were evident after the structure was subjected to high winds.

e) The daubing of the stud- type fasteners frequently resulted in a poor appearance for the siding as a whole.

f) Several installations were noted where overtightening of screw- type

fasteners on Plasteel also resulted in loss of adhesion of the coating in

the vicinity of the fasteners. This appeared to be more more severe when

the material was installed during cold weather.

4.4 General Comments

It was observed that the most severe damage occurred on areas located

in the vicinity of doorways, entrances, loading docks, etc., and in the

lower courses (4 ft. and below) of the structure, regardless of the type of

protected sheet used. This condition was noted particularly on the lower courses of the large, sliding doors of the nose dock type structure where it was common practice to use power vehicles to open and close the sliding doors.

On DC hangars where the Plasteel material was selected for use, the

specifications called for the use of a zinc base sheet on the lower courses. However, zinc base sheets were intermixed with regular sheets throughout the

structure. It was assumed that this deficiency resulted from, the failure of

the manufacturer to properly identify the individual sheets as to their base.

5. CONCLUSIONS AND RE COMMENDAT'lONS

The following conclusions and recommendations are based on the field

examinations of protected metal installations described in this report:

1. In general , the performance of the protected metals which were

observed during the field survey tends to substantiate the validity of the

performance data which were obtained in the laboratory tests made at the

National Bureau of Standards.

2. The bituminous (black) protected metals, properly used and installed,

should provide adequate protection with little maintenance for a number of

years when appearance is not a major considerat ion.

3. The common deficiencies noted with each material were:

Plasteel - Exposed metal which resulted from poor resistance to

impact

.

Galbestos and Steelbestos - The loss of protecting weather coat

from abrasions, sticking of sheets to each other in

storage, etc., resulted in a general poor appearance

when the asphalt saturant weathered from, the asbestos felt.

4. Specifications should insure the complete coverage of all abraded or damaged areas, prior to acceptance or during the guarantee period, with a material which is similar in color and. compatible with the weather coating.

5. The manufacturer should be required to provide the means to prevent

the sheets from sticking to each other prior to erection.

6. Protected metal sheets should not be used at door jambs or on walls

within 4-5 feet of ground or platform levels.

7. The protection of raw cut edges should be mandatory in areas subject

to salt-air exposure.

8. Consideration should be given to the use of conventional metal flashing materials for all horizontal flashings at head and sill of openings.

9. When two types of sheets from one manufacturer are specified, such

as the zinc base or regular base sheet, the individual sheets should be

marked plainly for identification.
.

.
- 7

-

10. Self-tapping screw type fasteners provide a superior installation

of protected metal sheets and their exclusive use is recommended. If it is

necessary to permit stud-type fasteners, their use should be restricted to

materials which employ a felt in the protective system. Specifications should

also require the use of extra length studs where corner laps occur.

11. Specifications should be more emphatic in regard to the following

points

:

a) Discouragement of the use of field bends.

b) The precautions necessary to minimize cracking when making

field bends, and the need for immediate protection of both

factory and field bends if cracks or damage are evident.

c) Care during cold weather installation of Plasteel. This

might include a prohibition against the use of air wrenches

on screw type fasteners.

12. Anticipating the probability of future painting of the black sheets

because of the general dissatisfaction with the appearance of this material,

consideration should be given to the use of painted galvanized sheets on an optional basis.

13. The proposed specification change calling for a guarantee against

defects for a one year period is very desirable. However, careful inspection

and correction of defects just prior to acceptance should also be stressed.

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.
Date Temp

.

°F.

Date erected Location Building

Material: Galbestos Steelbestos Plasteel Color

Corrugated V-Beam Other

Fasteners: Stud Screw

Atmosphere: Chemical Salt Other

Exposure: Siding Roofing

Weather Coating: Hard & Brittle Soft & Pliable _____ Blistering

Checking Pinholes Spalling

Describe :

Cracking: Valleys Crests Bends _____ Surface

Thru Surface Av. Width

Extent

Loss of Adhesion to Metal: General _____ At Fasteners _____ At damaged

areas Comment

Corrosion Pinholes Edges Damaged Areas _____ Other

Creep Describe ___

Patching : Pliable Hard Tight Loose

Fasteners: Tight Loose N. Washer _____ Covered Rusty

Remark s

General Appearance: Good Fair Poor Mottled Loss of

Mica Exposed Felt Exposed Metal Spot patching

Around doors Near Ground

Comments

Interior Insulation: Type Wainscot General Appearance:

Photos: No. Showing

Remarks

:

ILS. DEPARTMENT OF COMMERCE

Frederick H. Mueller, Secretary NATIONAL BUREAU OF STANDARDS

A. V. Amin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its major laboratories in Washington, D.C., and

Boulder, Colorado, is suggested in the following listing of the divisions and sections engaged in technical work.

In general, each section carries out specialized research, development, and engineering in the field indicated by

its title. A brief description of the activities, and of the resultant publications, appears on the inside of the front cover. WASHINGTON, D.C.

Electricity and Electronics. Resistance and Reactance. Electron Devices. Electrical Instruments. Magnetic Measurements. Dielectrics. Engineering Electronics. Electronic Instrumentation. Electrochemistry.

Optics and Metrology. Photometry and Colorimetry. Photographic Technology. Length. Engineering

Metrology.

Heat. Temperature Physics. Thermodynamics. Cryogenic Physics. Rheology. Molecular Kinetics. Free

Radicals Research. Atomic and Radiation Physics. Spectroscopy. Radiometry. Mass Spectrometry. Solid Stale Physics. Electron Physics. Atomic Physics. Neutron Physics. Radiation Theory. Radioactivity. X-rays. High

Energy Radiation. Nucleonic Instrumentation. Radiological Equipment.

Chemistry. Organic Coatings. Surface Chemistry. Organic Chemistry. Analytical Chemistry. Inorganic

Chemistry. Electrodeposition. Molecular Structure and Properties of Gases. Physical Chemistry. Thermochemistry. Spectrochemistry. Pure Substances.

Mechanics, Sound. Mechanical Instruments. Fluid Mechanics. Engineering Mechanics. Mass and Scale. Capacity, Density, and Fluid Meters. Combustion Controls.

Organic and Fibrous Materials. Rubber. Textiles. Paper. Leather. Testing and Specifications. Poly- mer Structure. Plastics. Dental Research. MetaUurgy. Thermal Metallurgy. Chemical Metallurgy. Mechanical Metallurgy. Corrosion. Metal

Physics.

Mineral Products. Engineering Ceramics. Glass. Refractories. Enameled Metals. Constitution and Microstructure.

Building Technology. Structural Engineering. Fire Protection. Air Conditioning, Heating, and Refrigeration. Floor, Roof, and Wall Coverings. Codes and Safely Standards. Heat Transfer. Concreting Materials.

Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Mathematical Physics.

Data Processing Systems. SEAC Engineering Group. Components and Techniques. Digital Circuitry.

Digital Systems. Analog Systems. Application Engineering.

• Office of Basic Instrumentation. « Office of Weights, and Measures. BOULDER, COLORADO

Cryogenic Engineering. Cryogenic Equipment. Cryogenic Processes. Properties of Materials. Gas Liquefaction. Radio Propagation Physics. Upper Atmosphere Research. Ionospheric Research. Regular Propagation

Services. Sun-Earth Relationships. VHF Research. Radio Warning Services. Airglow and Aurora. .Radio

Astronomy and Arctic Propagation.

Radio Propagation Engineering. Data Reduction Instrumentation. Modulation Research. Radio Noise. Tropospheric Measurements. Tropospheric Analysis. Propagation Obstacles Engineering. Radio-Metcorology. Lower Atmosphere Physics.

Radio Standards. High Frequency Electrical Standards. Radio Broadcast Service. High Frequency Impedance Standards. Electronic Calibration Center. Microwave Physics. Microwave Circuit Standards. Radio Communication and Systems. Low Frequency and Very Low Frequency Research. High Fre- quency and Very High Frequency Research. Ullru High Frequency and Super High Frequency Research. Modulation Research. Antenna Research. Navigation Systems. Systems Analysis. Field Operations.