MOISTURE RETARDERS
Polykraft & Polysurlyn

BELOW ARE DEFINITIONS ACCORDING TO THE ASTM C1729 STANDARDS FOR
ALUMINUM JACKETING FOR INSULATION

MOISTURE RETARDER (also known as moister barrier): layer of plastic film or other material
applied to the inner side of metal jacketing to inhibit jacket corrosion by interfering with the
formation of a galvanic cell between the dissimilar metal of the pipe and jacket or by preventing crevice corrosion.

POLYKRAFT: multilayer composite film used as a moisture retarder on metal jacketing consisting of at least one layer of minimum 40 LB kraft paper and one or more layers of plastic film, usually polyethylene at a minimum thickness of 1.5 mils.

POLYSURLYN: a multilayer film used as a moisture retarder on metal jacketing
consisting of at least one layer of acid copolymer, surlyn and one or more layers of
other polymers, usually polyethylene.

The above moisture retarders can be applied to aluminum, stainless, AZ 60 galvalume, galvanized and aluminized steel. The intended purpose of applying a moisture retarder is to provide
additional protection and prevent the migration of moisture to the metal. It acts as a mechanical, moisture and electrical barrier between the insulation and the metal to help prevent corrosion of the interior surface to the metal jacketing.