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Aluminum Coated Type 2

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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

2023 Project of the Year – Rehabilitation Winner: Union Pacific Bridge Replacement

By: Lane Enterprises, Inc.   Railway timber trestles were extensively used in the 19th century, making up from 1 to 3 percent of the total ... Read more

2023 Project of the Year – ALT2 Winner: Lincoln South Beltway

By: Metal Culverts, Inc The idea of a beltway around south Lincoln, Nebraska began in the 1960’s.  Due to funding and planning issues, the project ... Read more

2023 Project of the Year – Galvanized Winner: 90″ CSP Vertical Monopole Casings

By: TrueNorth Steel TrueNorth Steel was contacted about an application in which three vertical monopoles, approximately 50 feet in length, were being constructed in northern ... Read more

Studies, Resources & Marketing Materials

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