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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

agricultural water control canal

2022 Project of the Year Winner – Aluminized: Florida Canal Water Control

By: Metal Culverts, Inc. Florida agricultural producers have always relied on larger quantities of water for aid in the production of their various commodities.  Producers ... Read more
low profile structural plate arch

2022 Project of the Year Winner – Service Life: RT 828 VA

By: Contech Engineered Solutions This low profile structural plate arch is located in Rockingham County, Virginia. It was constructed in 1979 as a replacement of ... Read more
perforated retention system

2022 Project of the Year Winner – Retention & Detention: Steelpointe

By: Lane Enterprises, Inc Steelpointe is a 37 acre mixed housing development on the former industrial site of Phoenix Iron Works, located in Phoenixville, Pennsylvania, ... Read more

Studies, Resources & Marketing Materials

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