It’s tough down there.

ALUMINIZED STEEL TYPE 2CORRUGATED STEEL PIPE

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Strength of steel, corrosionresistance of aluminumCorrugated Steel Pipe manu-factured from Aluminized SteelType 2 offers the corrosion resis-tance and surface characteristicsof aluminum with the strength andeconomy of Corrugated Steel Pipe.

The product is fabricated fromsteel coils that have been hot dipcoated in a bath of commerciallypure aluminum. The coating hasuniform thickness on both sides ofthe sheet, with a strong metallurgi-cal bond between the metals. TheAluminized Steel Type 2 materialmeets AASHTO specificationsM274 and ASTM A 929.

The coils are then fabricatedinto helically corrugated pipemeeting the requirements ofAASHTO specifications M36 andASTM A 760. Helically corrugatedsteel pipe has been a standardof the construction industry fordecades. Pipe is fabricated withlock seams or welded seamsdepending on the job requirements,and each pipe end can bereformed to provide at least twoannular corrugations.

Excellent barrier protectionAluminum forms a passive alumi-num oxide film that adds to theservice life by providing goodbarrier protection. This passive filmforms rapidly and maintains betterprotection over a wider environ-mental range than zinc reactionproduct films. The aluminum oxidepassive film is effective in both hardand soft water.

The passive oxide film willendure as long as the free alumi-num coating layer lasts. When thislayer is eventually penetrated, thereis an underlying hard, thick alumi-num-iron alloy layer that provides

further corrosion protectionplus some significant abrasionprotection.

Based on field studies of 42–43year installations, Aluminized SteelType 2 service life is estimated tobe 75 years minimum at 16 gagein the 5–9 pH and ≥1,500 ohm-cmresistivity ranges.

In some cases, the pH/resistivityranges may be extended somewhatas is the case in arid regions wheremoisture availability is generallya controlling factor, and satisfac-tory service life may be realizedat soil resistivities somewhatbelow the 1,500 ohm-cm lowerlimit. In wetter climates, satisfactoryservice life may be realized atsoil pH values below the 5.0lower limit when resistivities arerelatively high.

In general, however, environ-ments outside the recommendedpH/resistivity ranges should besubjected to additional testing tosee if conditions conducive toaccelerated corrosion actually exist.For example, low resistivity watersand soils may contain excessiveconcentrations of corrosive chlorideand sulfates salts. In addition, anydark or light gray, blue, or olive-colored clay constituents observedin a heterogeneous soil should be

isolated for pH measurement sincethese sometimes contain water-soluble heavy metal salts. Theseconstituents induce strong acidifi-cation necessitating the use of abituminous coating to ensurenormal soilside corrosion behavior.

Environments that are faroutside the recommended pH/resistivity ranges should beavoided, including acid minewater,seawater, estuary brackish water,and sanitary/industrial sewage.

Ideal for storm sewersAluminized Steel Type 2 corrugatedsteel pipe is an ideal material formunicipal storm sewers or any

The photomicrograph on the left shows how the thick alloy layer metallurgically bonds thealuminum coating to the steel base metal, as well as how the coating provides continuousprotection to the base metal. The same coating protection is provided to both sides of thesteel base metal.

Aluminized Steel Type 2 Pipe for added durability.

Standard specifications

1. AASHTO M274 (Alumi-nized Steel Type 2 material)and ASTM A 929.

2. AASHTO M36 and ASTMA 760 (conduit, pipe.)

3. AASHTO Standard BridgeDesign Specifications,Section 12 (structuraldesign) and ASTM A 796.

4. ASTM A 798 (installation).

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normal drainage project. Alumi-nized Steel Type 2 pipe offers adurable and economical alternateto reinforced concrete pipe. Fea-tures include light weight, longlengths, and joints that havepositive pull-apart resistance andthe ability to adjust to yieldingfoundations.

Pipe and pipe-arch areavailable in four corrugations(2 2/3" x 1/2", 3" x 1", 125mm x25mm, and Spiral Rib’s 3/4" x3/4" x 7 1/2" rib corrugation) andin all standard diameters and16 gage through 10 gage.

Long-term field testingBased on extensive data fromactual field installations datingback 43 years, Aluminized SteelType 2 is a superior product forstorm sewer and drainage projects.It has better corrosion resistancethan galvanized structures anddisplays better abrasion resistance.

Prior to 1953, Aluminized SteelType 2 and galvanized steelculverts were exposed in sitesacross the U.S. These sites repre-sented a variety of service condi-tions including farm field drainage,fresh water swamps, alkali soils,and erosive applications. Testinstallations were sampled aftereight years and again after 24years. Weight loss data analyzedat all sites indicate Aluminized SteelType 2 provided significant addi-tional corrosion resistance.

In addition to the carefulsampling and evaluation accom-plished during this 24-year pro-gram, simple visual inspectionrevealed that:

• The appearance of AluminizedSteel Type 2 was clearly superiorto that of conventional metalliccoating.

• The condition of AluminizedSteel Type 2 pipe inverts—a critical point in durabilitydesign—was excellent.

In 1952–53, an additional 135composite culverts of AluminizedSteel Type 2 and galvanized steelwere installed in 20 states. Basedon the current conditions of thepipes available, the data indicatesa minimum 75-year service life for16 gage Aluminized Steel Type 2pipe when installed in the recom-mended environment.

Independent studiesMany independent studies havebeen performed that confirmAK Steel Corporation’s long-termfield test.

rability.

This AluminizedSteel Type 2

corrugated steelpipe was installed

in 1953 inEl Dorado,

California. It wasinspected in 1982

and in 1995.Coupons were

removed in 1995for evaluation by

the AK SteelResearch Centerand CALTRANS.

This close-up view shows the AluminizedSteel Type 2 pipe installed in Garland,Maine, with the dark staining wiped awayto reveal the like-new underlying aluminum.

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AK Steel ResearchCenter’s corrosionengineers andMissouri D.O.T.material engineersinspect a 43-yearold AluminizedSteel Type 2 pipeinstallation. This isone of two culvertinstallations inCarter County,Missouri, installedin a series contain-ing half AluminizedSteel Type 2 pipeand half galvanizedsteel pipe.

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75 years minimum service life. And still counting.