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Aluminum Coated Type 2

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OverviewALT2 ApplicationsDOT InformationSuccess StoriesResources

Aluminum Coated Type 2

 

corrugated steel pipe detention system large volume detention systemAluminum Coated Type 2 (AASHTO M274, ASTM A929) is a pure aluminum coating (no more than 0.35 percent silicon). It is produced with a coating weight of 305 g/m² (1 oz/ft²) of surface (total both sides) to provide a coating thickness of 48 µm (0.0019 in.) on each surface. The aluminum coated type 2 (ALT2) is the most widely used supplemental coating for CSP. “Aluminum is a reactive metal, but it develops a passive aluminum oxide coating or film that protects it from corrosion in many environments.” This film is quite stable in neutral and many acid solutions but is attacked by alkalies greater than a pH of 9. From a corrosion standpoint, aluminum has an advantage over galvanized in lower pH and in soft water conditions due to the formation of the oxide film. The coatings are essentially equal under abrasion and in waters where the zinc oxide film forms rapidly.

Aluminum coated type 2 CSP has been installed at thousands of sites over the past 50 years and many of these sites have been and are still being monitored for performance. Recent AK Steel research has indicated that 14 gage ALT2 CSP can achieve a 100-year service life when the environmental conditions have a pH of 5 to 9 and a resistivity greater than 1500 ohm-cm.

For more information download our Pipe Selection Guide found here.

DOT Information

The below is a map of the states that currently accept ALT2 coated pipe and plate in their specs.

Success Stories

stormwater management

John Rolfe Square – 2017 Retention/ Detention Project of the Year

By: Lane Enterprises, Inc. Lane Enterprises, Inc. are the recipients of the 2017 Retention/Detention Project of the Year award for their work at John Rolfe ... Read more
galvanized steel pipe

Project Spotlight : Highway 160 Interchange

by Pacific Corrugated Pipe   Galvanized steel pipe was used to create isolation casings for bridge foundations on a project in Antioch, California in 2014. ... Read more
buried bridge

Project Spotlight: North Carolina State Veterans Home Culvert

By: Big R Bridge Constructed in 2011, this is the longest single span box culvert of any material in North America. This was also the ... Read more

Studies, Resources & Marketing Materials

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