Aluminum Coated Type 2

OverviewALT2 ApplicationsDOT InformationSuccess StoriesResources

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

fully-perforated pipe

Project Spotlight: Santa Anita Industrial Park

By:  Pacific Corrugated Pipe Company A large tilt-up Industrial Park located in Rancho Cucamonga, California required two large, multi-barrel retention systems to support the storm water management plan for this property. Both systems utilized fully-perforated 60” diameter 16 gage 5” x 1” Aluminized Type 2 corrugated steel pipe. The first system was a smaller 3-barrel […]

underground detention system, stormwater retention, aluminized underground detention system

Project Spotlight: Thompson Middle School

By: Contech Engineered Solutions The Thompson Middle School expansion was required as the School District shifted from a three school configuration to two. Civil Engineering firm Rettler Corp identified three areas of the site that could be used to meet the required detention storage volume of 6.10 Ac-Ft. Three options were analyzed: ponds, underground concrete […]

underground detention storm drainage pipe stormwater drain pipe

Project Spotlight: Cornelius 100,000+ ft3 Detention System in Cornelius, North Carolina

By: Southeast Culvert, Inc The Watermark Luxury Condo development in Cornelius, North Carolina is another example of how early collaboration between the project engineer, developer, and drainage manufacturer can reduce a project’s cost. Initially designed with a concrete vault for the underground detention system and RCP for the stormdrain pipe, the developer JMR Construction approached […]

stormwater treatment and storage perforated aluminized steel detention and infiltration

Project Spotlight: Racetrac Blairs Bridge

By: Southeast Culvert In 2017, Racetrac Petroleum implemented a new company concept in Douglas County, GA known as a convenience stop (otherwise known as a truck stop). This site is located on Interstate 20 which runs from South Carolina to California. The sites are larger than  the traditional gas stations so the stormwater treatment and […]

Studies, Resources & Marketing Materials