Explanation of Manufacturers Coatings

quired, by local safety regulations.

tank application. It contains a permanent dye and the

a. Install temporary plugs or other closures to cover

solids content is controlled in the range of 17-19 percent.

b. The EC 776 SR contains a dye which is soluble in

all openings except fuel inlet. Do not coat fuel inlet caps

fuel and fades out after vehicle operation. It also allows

or threads in fitting openings.

b. Apply Buna-N coating (table I and para 10) by fill-

a broader solids content range of 17-22 percent. The EC

776 SR coating can be used until stock is exhausted or if

and-drain or by slush coating. If fill-and-drain method is

the EC 776 R (TARCOM) coating is unavailable. As the

used, invert tank or agitate to assure coating of top

solids content increases, and the material is more

interior surfaces. In slush coating, fill about 20 percent of

viscous, coating application and thickness are affected.

tank capacity and manipulate tank for a sufficient time to

c. The PRC 1005 L coating is generally similar to

wet all surfaces. Assure that enough coating flows to

the specified 3M Company coatings. The solids content

both sides of baffles before slushing. This procedure is

is controlled in the 19-20 percent range and has soluble

not recommended for large capacity tanks which cannot

red dye.

be removed from the vehicle.

c. Remove temporary plugs and other closures and

d. When the coating material is reused, the solids

drain excess coating material which may be reused (see

content increases as a result of solvent evaporation.

para 10). When coating stream becomes broken during

The original viscosity can be restored by adding Methyl

draining, begin passing compressed air at about 10 psi

Isobutyl Ketone (MIBK) to readjust the solids content to

through tank. Continue passing air for approximately 3-5

the original range.

e. Procedures are outlined in paragraph 11 for

minutes after coating flow slows to occasional drops.

The air flow rate (cfm) should approximate one air

measuring the solids content and calculating the amount

change per minute during this operation, and also during

of solvent to add to restore the desired solids content

the curing operation.

and viscosity. Be sure to add solvent slowly to coating

d. Inspect to insure complete coverage. Recoat, if

while mixing.

necessary. The coating contains a red dye to aid

11. Measurements for Controlling Coating Solids

inspection.

Content. a. Measurement of solids content:

e. Move tank to curing location with a minimum

(1). Weigh container with cover (2 oz. ointment

of delay. If the curing location is remote from coating

can or similar lightweight container) to nearest milligram

location, temporarily cover tank openings to avoid

(0.001 gram) (w,) and record weight. It is preferred to

escape of solvent vapors into uncontrolled areas while

run three samples and average.

transporting.

(2). Spread a few grams of coating material

f. Cure coating by one of the following optional

over bottom and side interior surfaces of container, close

methods with minimum delay after coating:

cover immediately, and weight to nearest milligram

(1) Oven cure by baking tank at 250'F. : 5'F.

(W2).

for 1

(3). Remove cover and place both container and

hour, passing dry air through tank continuously at ap-

cover in air circulating oven at about 200'F.-225'F. After

proximately 10 psi.

approximately 10 minutes, remove from oven, replace

WARNING

cover, and cool. Weigh to nearest milligram (W3).

(4). Compute the solids content using the

Ovens shall comply with NFPA No. 86A,

following:

Standard for Ovens and Furnaces.

formula:

(2) Air cure at 70'F.-120'F. for 16-24 hours,

W3 - W1 x 100

% solids =

passing dry air through tank continuously at

W2 - W1

approximately 10 psi.

g. Upon completion of curing, check tank interior

where:

atmosphere with an explosimeter (para Sc). Reading

should indicate 10 percent (or less) of Lower Explosive

W1 = weight of container

Limit (LEL).

Cap all tank openings and repeat

W2= weight of container and wet coating

explosimeter readings after 12-24 hours. Meter reading

W3 = weight of container and dry coating

should be below 10 percent LEL.

b. Calculation of solvent to be added to restore

h. Reinstall fittings or plugs to cap all tank openings.

desired solids content:

i. Clean application equipment with methyl isobutyl

ketone before coating has set up or cured.

Gals of coating x DS - gals of coating - gals of solvent to

add where:

10. Explanation of Manufacturers Coatings (table 1).

KS = KNOWN % solids

a. The 3M Co. EC 776 R (TARCOM) and EC 776 SR

DS = Desired % solids

coatings are almost identical. EC 776 R (TARCOM)

coating is being specially manufactured for Army fuel