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TO 1-1-700 - Robins Air Force Base

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<strong>TO</strong> 1-1-<strong>700</strong><br />

below and adhere very poorly to metal structure having a surface<br />

temperature of 600 ºF (160 ºC) and below due to poor<br />

surface wetting properties at the time of the application. These<br />

problems can be eliminated by preheating the metal surfaces<br />

to which a sealant will be applied to a temperature of 600 ºF<br />

(160 ºC) or higher and/or heating the sealant to a temperature<br />

of 130 ºF ±10 ºF (54 ºC ±10 ºC) after application with hot air,<br />

infrared lamps, or some other approved method after allowing<br />

the sealant to stand for a minimum of 30 minutes at ambient<br />

temperature after it is applied to flash off its contained solvents.<br />

12.5.1.3 Sealants applied to metal surfaces having a surface<br />

temperature of 100 ºF (35 ºC) or greater will very likely have<br />

bubbles in the cured sealant film, commonly called “solvent<br />

pop,” due to too rapid evaporation of the solvents contained in<br />

the sealant. Cool the metal surface down to a temperature of<br />

90 ºF (32 ºC) or lower by wetting it down with water and then<br />

wiping the surface dry by some other approved method and/or<br />

relocate the equipment to which sealant is to be applied to an<br />

area having an ambient temperature of 90 ºF (32 ºC) or lower<br />

prior to applying sealant. Keep the equipment in this cooler<br />

condition for a minimum of 30 minutes to allow the contained<br />

solvents to flash off before relocating the equipment in a hotter<br />

area or applying heat to the sealant.<br />

12.5.1.4 Sometimes sealant must be applied in areas where<br />

other maintenance is being accomplished which leads to sealant<br />

smears in the area caused by walking on and/or dragging<br />

tools through sealant that is not completely cured. To minimize<br />

this problem, apply a polyurethane film over the uncured<br />

sealant after allowing a minimum of 30 minutes at ambient<br />

temperature after it is applied to flash off its contained solvents<br />

and permit the film to remain in place until the sealant<br />

has completely cured.<br />

12-20

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