TECHNICAL IFEORI.A.TION ON BUILDING MA.TERIALS

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NOR USE IN THE DESIGN ON LOU-COST HOUSING

THE NATIONAL BTJREAU OF STANDARDS

UNITED STATE'S DPPAP.nffNT OF COMMERCE

UASHINGTON, D. Co

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ALUJ/IINIM PAINTS

This is chiefly a digest of a -ng^r ''Sorne Observations on Aluminum

Paints" "pre-oarei by P, H. Ualher and E, F. Hickson, and published by ner- mission of the Director, Bureau of Standards, Derartment of Coiimerce.,

Uashington, D, C, in "Chemical and Metallurgical Engineering", Mol, 31»

No, IS, November 3> 192^. The paner and this digest discuss various tests

made by the Bureau to determine how and when aluminum paints may be used

satisfactorilyo

The following TiBM's contain additional infonnation relative to paint

pigments, oil paints, and water paints?

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"Paint Pigments - White"

"Paint Pigments - Black, Red, and Lakes"

"Paint Pigments - Yellow, Brown, Blue, Green, and Bronze"

"Federal Specification Paint Pigments and Mixing

Formulas"

"Federal Snec ificaticn Ready-Mixed Paints, Semipaste

Paints and Mixing Formulas"

"Preparation of Paints from Paste and Dry Pigments"

"Preparation of Paints from Semiraste Paints, Thinning

Ready-Mixed Paints, and Preparation of Water Pa.ints"

Paint is "a mixture of pigment with vehicle intended to be spread in thin

coats on surfaces for decoration or protection, or both."

^Quoted from "Standard Definitions of Terms Relating to Paint Specifications", American Society for Testing Materials, A. S. T, M. Standards

(1933), t)p. 735-739.

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Federal Specifications are specifications adopted "by the Federal Specifications Executive Committee and approved hy tho Director of Procurement,

Treasury Department, for use of all d.epartraents and establishments of

the Government*^

Durability cf Aluminum Paint

To determine the durability cf aluminum paints as corrroared with red

lead linseed oil paint, the Bureau of Standards began a series of exposure

tests cn six metal panols in llcvember 1920. The aluminum paints used

were prenared by hand, stirring 15 and 30 percent aluminum pewder (by weight

of paint) in boiled linseed oil and spar varnish*

Formulas used in preparing the paints, manner of application and ex~ pesure, and results cf tests are given in Table I (page 3)0

Aluminum Paint Mixing Formulas

Tests conducted by the Bureau and subsequent experiences indicate that,

while an aluminum paint having a vehicle composed entirely of boiled linseed oil applied on metal panels in a hcrizcntal position was mere durable

on an outside exposure than paints containing an equal quantity of aluminum

powder in a vehicle composed of two-thirds boiled linseed oil and one-third

spar varnish, some aluminum paints frequently showe i. tendencies to run and

sag when applied to vertical surfaces*

Aluminum paint s prcduced from formulas given in Table II (page 4) were found to be suitable for painting vertical surfaces. Paints made from formulas given in Table III (page 4) preved to be unsatisfactory when applied to

smooth, vertical iron plates, although they possessed suitable brushing

consistencies.

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Copies of all Federal Specifications mentioned in this digest may be

obtained from Superintendent of Documents, Government Printing Office,

Washington, D, C, (Price 5 cents each).

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! TABLE I

Results of Exposure Tests Comparing Alumin'am and Bed Le ad Paints^

Paint : iNumher

: of

: Coats

Condition of Paint after

Tyce Ingredients Amount : 3 1/2 years eioposurCf

Aluminum Aluminum Powder2

Boiled Linseed 0il3

3 l‘/^lhs, : 1 gal , :

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r-l

CM Practically -gone,

Good condition.

Excellent condition.

Red Lead Dry Red Lead^

Raw Linseed Oil^

Turpentine^

Drier 3

20 Ihs, : 5 pts, : 2 ' gills : 2 gills :

: 1

; 2

:* 3

Practically gone.

Faded (nearly white) apd

chalking, h\it in good condition.

Faded (nearly white) and

chalking, hut in excellent

condition*

Aluminum Aliaminum Powder

Boiled Linseed 0il3

Spar Varnish“

3 1/2 Ihs. : 2/3 gal. . : 1/3 gal, :

: 1

: 2

: 3

Practically gone.

Rust streaks showed throu^,

fair condition, needed re- paint ing.

Excellent condition.

Red Lead Dry Red Lead^

Raw Linseed Oil^

Turpentine^"

DrierT

20 Ihs, ' : 5 pts, : 2 gills : 2 gills :

: 1

: 2

: 3

Practically gone.

Chalking and faded, hut in

good condition.

Chalking and faded, hut in

excellent condition.

Aluminum Aluminum Pcwder2

Spar Varnish^

1 1/3 Ihs. : 1 gal ,. :

: 1

: 2

3

Gone,

Considerahle rust; poor

condi tion.

Rust streaks showing; fair

condition.

Red Lead Dry Red Lead‘d

Raw Linseed Oil^

Turpentine^

Drier^

20 Ihs. : 5 pts. : 2 gills : 2 gills :

: 1

: 2

: 3

Prac ticallj'- gone, hut better

than the alumi num paint.

Chalking and fading, hut

in good condition.

Chalking and fading, hut in

excellent condition.

^The paints uere applied "by "briashing on one side of clean, horizontal steel

panels measuring l/U”xlS”x2U" , The first coat of red lead was applied to the left

’ half of the panel and the first coat of aluminum to the right half, • The second coat

Was applied to the upper two-thirds of the resuective area in each case, and the

I last coat to the upper third. The first coats were applied Oct, 26, 1920, the

‘ second coats Oct^ 23, 1920, and the third coats on IJov, 1, I92 O, The painted

' panels, after drj’ing in the laheratory, were exposed on Nov, 1920, facing

' South at an angle of '45*^, on the roof of the Chemistry Building, National Bureau

of Standards, Tvs.shington , D, C,

^Eederal Suecificaticn TT-A-H 76 ''A-luminum-Powder; (Eor) Paints (Alur.inumBron ze -F owde r )

,

3 Eod&ral Spec iflotion “Oil,* Boiled."

j ^Federal Suecificaticn TT-R-I9I "Bed Lead; Dry and Paste-In-Oil,"

j! ^Federal Specification JJJ-0-336 "Oil; Linseed, Paw,"

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I ^Federal Specification LLL-T-791a "Turpentine; (For) Paint, Type I,"

^Federal Specification TT-D- 65 I "Drier; Paint, Liquid,"

i “Federal Specification TT-V-121a "Varnish; Spar, Water-Resisting, II
TABLE II

Aluminum Paint Formulas Suitable Eor Vertical Surfaces^

Fo. 1 , 2 l"bs. Aluminum Powder, polished‘s

1 gal. Vehicle consisting -of

^0 parts Bodied Linseed Oil^

6 " Liquid Paint Drier^

3^ " Mineral Spirits5

No. 2

2 l"bs. Aluminum Powder, polished^

1 gal. Mixing Varnish for Aluminum

Paint

No. 3 No. U

2 l"bs. Aluminum Powder, polished‘s , 2 l"bs. Aluminum Powder, polished^

1 gal, "Bronzing Liquid"? 1 gal. Vehicle consisting of:

2/3 Mixing Varnish for Aluminum

. Paint°

1/3 Boiled Linseed Oil^

TABLE III

Aluminum Paint Formulas Providing Suitable Brushin,^ Consistencies^ No, 1

2 l"bs. Aluminum Powder, polished^

1 gal. Vehicle consisting of:

90 parts Raw Linseed Oil^^

10 " Liquid Paint Drier^

No. 2

2 l"bs. Aluminum Powder, polished^

1 gal. Vehicle consisting of:

SO parts Raw Linseed Oil^®

10 " Mixing Varnish for

Aluminum paint®

10 " Liquid Paint Drier^

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0 • 2 l"bs. Aluminum Powder, polished^ 2 l"b-s. Aluminum Powder, polished^

1 gal. Vehicle consist^Pg of; 1 gal. Boiled Linseed Oil^

1/3 Mixing Varnish for

Aluminum Paint°

2/3 Boiled Linseed Oil^

^These paints posfiess good 'brushing consistencies, which when applied to

vertical metal plates gave firm, uniform, smooth films free from running, stireaking, or sagging,

“^Eederal Specification TT-A-U 76 '’Aluminum-Powder; (for) Paints (AluminumB ren ze-Powder ) .

’’ ^Eaw linseed oil JJJ-0-336 heated to 295°C for three hours,

federal Specification TT-D-651 "Drier; Paint, Liquid,"

^Pc^ral Specificatien TT-T-29I "Thinner; Paint, Volatile Mineral Spirits,"

^Federal Specification TT-V-81 "Varnish; Mixing (For) AluminuiUr-Paint."

^Commercial san|)le of a "brittle rosin varnish not siiita'ble for out door use,

^Federal Specification JJJ-0-331 "Oil; Linseed, Boiled,"

^These paints possess suitable "brushing consistencies, "but proved to "be unsatisfactory when applied to smooth vertical i^Jon plates,

^^ederal Specification JJJ->0-336 "Oil;. Linked, Raw,"

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Conclusions and Hecomiendations

Leafing Prouertics ; Federal Specification TT-A-lJ-76 "Aluminuoi-Powder

;

(For) paints (Aluminum-Bronze-Powder) ” states "Tlie powder shall have good

•leafing’^ pro-rerties and a paint made hy mi:cing with a suitable vehicle

in the proportion of two pounds of alumin:am powder to one gallon of ve- hicle shall give a free flowing, smooth continuous coating," It is reasonable to suppose that this metallic top layer or coating protects the

perishable paint vehicle from the sunlight,, .

As the desirable leafing properties of alumlnun powders, )T;ixed in

various paint liquids, develop rapidly and gradually diminish in readynixed paints, it is recommended that aluminum paint be mi.xed on the job

and only in such quantities as will be used the same day, because mixed

aluminum paints kept in closed packages for various lengths of time may

produce gases and burst the packages.

Durable Outside Aluminum Paints : An aluminum paint containing from 25 to

30 percent of aluminum powder in a vehicle composed of boiled linseed oil, or a mixture of boiled linseed oil and mixing varnish will prove to be a

durable outside paint when applied in three coats. Two coats of these

paints will give good service. One coat alone is not recommended,

A paint containing Ip percent aluminum powder in mixing varnish does

not equal, for outdoor durability, one containing approximately twice as much powder in a mixed vehicle of mixing varnish and boiled linseed oil.

This is also true of one, two, or three-coat work.

Aluminum paint containing boiled linseed oil without any varnish

proved to be more durable for outside use, under test conditions, than a paint containing an equal amount of the same aluminum powder in a vehicle

of two- thirds boiled linseed oil and one- third mixing varnish,

Recommended Outside Alu.min-am Paints ; For outdoor exposures including vertical surfaces, Formulas I'Tos. 1, 2, and 4 given in Table II (page 4) arc recommended. Paints produced from. Formulas Dos. 1 and 4 will probably be

more durable than paint made from Formula ITo, 2 which contains straight

alumimim paint mixing varnish. One gallon of average mixing varnish for

aluminum paint will wei^ about seven and one-half pounds, and with two

pounds of aluminum powder, the paint will weig)i about 8,0 pounds to the

gallon and contain about 21 percent of pigment by wei^xt.

Aluminum paint for outdoor exposure, possessing extreme durability,

nay be made by using as much as two and one-half pounds of aluminum powder

^"Leafing is the terra used when a continuous brilliant film forms

over the entire free surface of a mixture of aluminum powder in a suitable

liquid, within one minute after cessation of stirring the mixture,"

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to one gallon of liqtiid, provided the paint is still of good hnishing con- sistency withoTit the addition of turpentine or mineral snirits, A gallon

of this naint will weigh ahont 2*9 pounds, and contain ahont 25 percent

of pigment hy weight. The present day trend for exterior al-uminnm naints,

is to use two pmmds of aluminum powder or paste to one gallon of a s:'m- thetic resinous type spar varnish, particularly of the straight phenclform.aldehyde type.

Tests indicate that the use of raw or hoilcd linseed oil alone, as the liquid in aluminum paints for painting vertical surfaces is not advisable, as such uaints, esrecially those containing raw oil, do not form

a continous film hut exhibit marked running, streaking, and sagging tendencies. Although the streak;/ defect seemed to be lessened slightly by

increasing the amount of powder in the oil vehicle, exueriments show that even though the powder content be increase^d to three and one-half pounds

to one gallon of boiled linseed oil, the paint still produces a somewhat

streaky appearance on vertical surfaces. This same formula, however, gives a very durable paint on outdoor horizontal surface s.

In using aluminum paint for the protection of exterior steel structures, it is recomm-cnde d that the first or priming coat on bare steel, should

be other than aluminum paint. A rust-inhibitive primer such as red lead

paint, basic lead chromate or zinc chromate paint, etc,, is recomended

next to the bare steel. Over this primer the aluminum paint may be applied.

Aluminum Paints For Or dinary Interior Use ; Jor ordinary interior rise, one and one-half to two pounds, or more of aluminum powder mixed with either

one gallon of mixing varnish for aluminum uaint, or one gallon of a mixture

of two volumes of the mixing varnish and one volune of tumentine or mineral

spirits, will give a quick-drying serviceable paint.

Aluminum Faint for Radiators ; Two or more pounds of aluminum powder mixed

with one gallon of equal volumes of mixing varnish and turpentine will

produce a good radiator paint.

Aluminum Paint For Surfaces Subject To Su luhi de Fumes ; In tests conducted

by the Bureau, a paint composed of two to two and one-half pounds of polished aluminum powder in one gallon of mixing varnish for aluminum paint (a com- mercial sample free from lead, but containing cobalt) showed no discoloration when exposed to sulphide fumes. Substitution of boiled linseed oil,

containing 0,12 percent lead, for the mixing varnish in this paint showed

appreciable darkening in hydrogen suluhide

,

Aluminum B ron ze Powder versus Other Metal Powder Pigments ; As bronze

powder pigments other than alumin^ira, such as "couper bronze" and "pale

gold bronze", have hi^or specific gravities, about twice as iiroch pigment

should be used to moke satisfactory brushing paints as is required for

aluminum bronze powder.

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