ASI 502 100% RTV Silicone Sealant, Black, 2.8 oz Squeeze Tube

Black ASI 502 is ASI’s High Performance 100% RTV Silicone in black: a one-part acetoxy silicone that cures in air to a durable, waterproof rubber. Choose black when the seal sits against black or dark surfaces, such as powder-coated frames, dark trim, trailer seams and appliance housings, or when a clear bead would show the joint behind it. The 2.8 oz squeeze tube needs no caulking gun.

Key features

• Black, 100% acetoxy RTV silicone; ASI says it is solvent-free, so it will not shrink or crack
• Rated for interior and exterior use, with resistance to UV degradation and weathering; passed 10,000 hours of QUV testing (ASTM G154)
• -70°F to 400°F service, with intermittent exposure up to 450°F
• Non-slump on vertical and overhead joints; 25% joint movement (ASTM C920 Class 25)
• Cured properties: 25 Shore A, 264 psi tensile strength, 500% elongation
• UL Recognized and meets MIL 46106B Type 1, per ASI

Where to use it

ASI’s list includes sealing trailers, sheet metal, ductwork, HVAC, formed-in-place gaskets, appliance manufacturing and refrigeration units. In practice, black 502 suits seams on trailers and truck bodies, bedding a light or fixture against a dark panel, forming a gasket on a cover plate, or weather-sealing a dark metal enclosure.

How to use

1. Clean metal and trim with 100% isopropyl alcohol or acetone, removing oil and old sealant. Avoid petroleum-based solvents.
2. Apply between -35°F and 150°F. For a formed-in-place gasket, run one continuous, unbroken bead.
3. Tool the bead or assemble the parts within about 10 minutes, before the skin forms.
4. Allow about 24 hours per 1/8″ bead at 70°F and 50% RH. ASI notes that confined joints, such as gasket flanges, take longer.
5. Test strength and adhesion on day 7, when ASI says maximum strength has developed.

Compatibility and cautions

ASI 502 is an acetoxy silicone, and ASI notes it is corrosive to sensitive metals when confined. Do not use it on circuit boards or around sensitive metal parts in enclosed spaces; that is the job for neutral-cure ASI 388. ASI also says not to use 502 on porous surfaces such as concrete, mortar or brick, it is not paintable, and plastics should be tested first. It gives off a vinegar odor while curing, so work outdoors or with good ventilation; the SDS does not classify it as hazardous under GHS. Documents: technical documents.

Choosing between ASI 502 colors and related sealants

The same formula comes in clear and white squeeze tubes, and as a clear 10.2 oz cartridge for long runs. For wiring and electronics use ASI 388 electronic grade silicone. Building or resealing a tank? Black ASI 502 is not aquarium-rated; use ASI 509 black aquarium silicone instead.